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EFFECTS OF VARIOUS PLANTING PRACTICES ON YIELDS,
AND GROWTH AND DEVELOPMENT OF SOYBEANS

(GLYCINE MAX L. MERRILL) IN MICHIGAN

 

By

David Warren Merck

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

Master of Science

Department of Crop and Soil Science

1980

)1)

’J
., 1‘

(:/7(7CW

ABSTRACT

EFFECTS OF VARIOUS PLANTING PRACTICES ON YIELDS,
AND GROWTH AND DEVELOPMENT OF SOYBEANS
(GLYCINE MAX L. MERRILL) IN MICHIGAN

 

BY

David Warren Merck

The effects of various cultural practices on yield, and growth

and development of soybeans (Glycine max L. Merrill) were studied at

 

two Michigan locations in 1978 and 1979.

Yields were generally reduced with later planting dates. However,
earlier than normal dates for northern locations responded with
little if any yield advantage.

Row widths of 25 and Si cm yielded significantly more than 76 cm
widths. However, yield responses to width were somewhat inconclusive
since plant densities in each width varied by year.

Of four cultivars tested both years, yield differences were
of a much smaller magnitude than those of planting date and row width.
Over years and locations 'Hodgson (78)' yielded the most followed
by 'Corsoy', 'SRF 200' and 'Evans'. 'Nebsoy,’ grown only in 1979,
appeared tolerant to late summer drought.

There were several yield interactions. Measurements were
recorded for developmental stages, photosynthetically active radiation,

agronomic characteristics and yield components.

 

ACKNOWLEDGMENTS

Special thanks are due my parents for their encouragement and
support. I want to express my sincere appreciation to my major
professor, Dr. Taylor J. Johnston for his guidance and constructive
criticism throughout my studies. It has been a real joy to work with
him. Also deserving of thanks are Dr. Zane R. Helsel, Dr. Charles
E. Cress, and Dr. Anton Lang as members of my Guidance Committee
for their invaluable assistance. The financial support of the
Michigan Soybean Committee has been much appreciated in enabling
me to complete this project. Mr. Coridon Webster at the Crop Science
farm has repeatedly rendered willing and much appreciated assistance.
And the unusual cooPeration and assistance of Mr. Edward Burns as
owner of sites of my work for two years have also been much appreciated.

But superseding these deserved earthly acknowledgements are
the praise, honor and glory which must go to my God and King for
creating the very materials for my study, for granting gifts and
abilities to undertake the work, for graciously bestowing strength,
patience and endurance for completion of the task, and above all

for saving my soul, an act of mercy above all others.

ii

TABLE OF CONTENTS

Page

List of Tables . . . . . . . . . . . . . . . . . iv
List of Figures. . . . . . . . . . . . . . . . . ix

Introduction. . .7 . . . . . . . . . . . . . . . 1
Literature Review . . . . . . . . . . . . . . . . 4
Materials and Methods. . . . . . . . . . . . . . . 12
Results and Discussion . . . . . . . . . . . . . . 28
I. Grain Yields . . . . . . . . . . . . . . . 28

A. 1978 . . . . . . . ._ . . . . . . . . . 28

B. 1979 . . . . . . . . . . . . . . . . . 51

II. Growth and Development Factors . . . . . . . . . 75

A. Developmental Stages and Periods. . . . . . . . 7S

1. 1978 . . . . . . . . . . . . . . . . 75

2. 1979 . . . . . . . . . . . . . . . 82

B. Vegetative DevelOpment . . . . . . . . 93
1. Percentage Emergence and Initial Stand. . . . . 93
2. Numbers of Mainstem Nodes and Growth . . . . . 101
3. Numbers of Branches and Nodes on Branches Per Plant 110
4. Leaf Area . . . . . . . . . . . 116
5. Penetration of Photosynthetically Active Radiation

(PAR). . . . . . . . . . . . . . . . 118
6. Mature Plant Height . . . . . . . . . . . 127
7. Plant Lodging . . . . . . . . . . . . . 136
8. Internode Length . . . . . . . . . . . . 153
C. Reproductive Development . . . . . . . . . . 155
1. Pod Numbers. . . . . . . . . . . . . . 155
2. Seed Numbers . . . . . . . . . . . . . 162
3. Seed Weights . . . . . . . . . . . . . 164
4. Percentages of Whole Plant Yield and Other Responses
of Evenly-Divided One-Third Sections of Sample
Plants . . . . . . . . . . . . . . . 168
5. Height and Number of the Lowest Mainstem Node to
Which Was Attached a Pod or Pod-Bearing Branch . . 177
6. Productive Nodes and Mainstem Lengths, and Related
Measurements . . . . . . . . . . . . . 185
III. Planting Systems . . . . . . . . . . . . . 189
Summary and Conclusions . . . . . . . . . . . . . . 191

Appendix . . . . . . . . . . . . . . . . . . . 195
Bibliography. . . . . . . . . . . . . . . . . . 214

iii

Table

1.

10.

LIST OF TABLES

Ideal, components of yield sample plant numbers and
spacings (cm) for the 1978 Chesaning location by row
width (cm) and plant density. . . . . . . . . .

Plant numbers and spacings (cm) for ideal, components of
yield samples from the 1979 Chesaning location by row width
(cm) and plant density. . . . . . . . . . . . .

Effects of planting date, row'width, and cultivar on soybean
yields (ql/ha) at both 1978 locations averaged over all
other factors. . . . . . . . . . . . . . .

Soybean yields (ql/ha) at the 1978 Chesaning location as
influenced by planting date and row width, averaged over
cultivar and plant density. . . . . . . . . . . .

The effect of planting date and row width upon 1978 soybean
yields (ql/ha) averaged over location, plant density and
cul t ivar C O O O O O O O O C O O O O O O 0

Influence of planting date, row width, and plant density
upon 1978 soybean yields (ql/ha), averaged over all
cultivars, at the Carleton location. . . . . . . .

The effect of planting date and plant density upon 1978
soybean yields (ql/ha) averaged over row width, cultivar
and location. . . . . . . . . . . . . . .

Soybean yields (ql/ha) at the 1978 Carleton location as
influenced by planting date and cultivar, averaged over row
width.and plant density. . . . . . . . . . . . .

Soybean yields (ql/ha) at the 1978 Chesaning location as
influenced by planting date and cultivar, averaged over row
width and plant density. . . . . . . . . . . . .

The influence of planting date and cultivar upon 1978

soybean yields (ql/ha) averaged over location, row width,
and plant density. . . . . . . . . . . . . . .

iv

Page

25

25

29

33

34

37

39

41

42

43

Table Page

11. The effects of row width and cultivar upon 1978 soybean yields
(ql/ha) averaged over plant density and planting date, at the
Chesaning location. . . . . . . . . . . . . . . 47

12. Plant density and cultivar effects upon 1978 soybean yields
(ql/ha) averaged over row width.and planting date, at the
Chesaning location. . . . . . . . . . . . . . . 50

13. Effects of planting date, row width and cultivar on soybean
yields (ql/ha) at both 1979 locations averaged over all other
factors. . . . . . . . . . . . . . . . . . . 52

14. Planting date and cultivar effects on 1979 soybean yields
(ql/ha) averaged over row width and plant density at the
Dundee location. . . . . . . . . . . . . . . . 62

15. Soybean yields (ql/ha) at the 1979 Chesaning location as
influenced by planting date and cultivar (SRF 250 excluded),
averaged over row width.and plant density. . . . . . . 63

16. Soybean yields (ql/ha) at the 1979 Dundee location as
influenced by row width and cultivar, averaged over planting
date and plant density. . . . . . . . . . . . . . 69

17. Row width and cultivar effects upon 1979 soybean yields
(ql/ha) averaged over location and planting date. . . . . 70

18. Effects of planting date, row width and cultivar on soybean
yields (ql/ha) for both years averaged over locations and
all other factors. . . . . . . . . . . . . . . 73

19. The influence of cultivar and row width on 1979 maturity
dates (days after September 1) at the Dundee location,
averaged over planting date. . . . . . . . . . . . 88

20. Effects of planting date, row width, plant density and
cultivar on initial plant stand (plants/ha) averaged over
all other factors for both locations in 1978 and 1979. . . 96

21. Vegetative growth expressed in mainstem nodes above the
cotyledonary nodes at various developmental stages in 1978 for
the Chesaning and Carleton locations as affected by planting
date and cultivar, and averaged over plant density and
row width. . . . . . . . . . . . . . . . . . 102

22. Vegetative growth rate expressed as increase of mainstem
nodes above the cotyledonary nodes per day between various
developmental stages in 1978 for both locations as affected
by planting date and cultivar, and averaged over plant
density and row width. . . . . . . . . . . . . . 105

Table . Page

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

Influence of planting date, row width, plant density and
cultivar upon total nodes per plant and upon percentage
branch nodes of total plant nodes for the 1978 and 1979
Chesaning locations, averaged over all other factors. . . 115

Plant lodging as influenced by planting date, row width

(25, 51 and 76 cm) and cultivar at the 1978 Carleton

location, averaged over plant density (1 - all plants

upright, 5 - all plants prostrate). . . . . . . . . 137

Plant lodging as influenced by planting date, row width,

plant density, and cultivar at all the 1978 and 1979

locations, averaged over all other factors (1 - all plants
upright, 5 - all plants prostrate). . . . . . . . . 138

Influence of planting date, row width (25, 51 and 76 cm),
and cultivar upon plant lodging at both 1979 locations
(1 - all plants upright, 5 = all plants prostrate). . . . 149

Total pods per node, per plant and per land area (m2) as
influenced by planting date, row width, plant density and
cultivar at the 1978 and 1979 Chesaning locations, averaged

over all other factors. . . . . . . . . . . . . 156

Branch pods per branch node, per plant and per land area (m2),
and branch pod percentage of total pods as influenced by
planting date, row width, plant density and cultivar at the

1978 and 1979 Chesaning locations, averaged over all other
factors. . . . . . . . . . . . . . . . . . 159

Influence of planting date, row width, plant density and
cultivar upon mainstem pods per mainstem node, per plant and

per land area (m2) at the 1978 and 1979 Chesaning locations,
averaged over all other factors. . . . . . . . . . 161

Number of seeds per pod, per node, per plant and per land

area (m2) as influenced by planting date, row width, plant
density and cultivar at the 1978 and 1979 locations, averaged
over all other factors. . . . . . . . . . . . . 163

Weight of 100 seeds (3) as influenced by planting date, row
width, plant density, and cultivar at the 1978 Chesaning

location and at both 1979 locations, averaged over all other
factors. . . . . . . . . . . . . . . . . . 165

Influence of planting date, row width and cultivar upon
percentage branch nodes, percentage mainstem pods, percentage
branch pods and percentage total pods associated with evenly
divided bottom, middle and top (B, M and T) plant sections

at the 1979 Chesaning location, averaged over all other

factors. . . . . . . . . . . . . . . . . . 172

vi

Table Page

33. Seed weight/node (g), seed weight/pod (g), and percentage
of branches associated with evenly divided bottom, middle,
and top (B, M and T) plant sections as influenced by
planting date, row width, and cultivar at the 1979 Chesaning
location, averaged over all other factors. . . . . . . 173

34. Influence of planting date, row width and cultivar upon
branch pods/branch node, mainstem pods/mainstem node and
overall pods/node associated with evenly divided bottom,
middle and top (B, M and T) sample plant sections at the
1979 Chesaning location, averaged over all other factors. . 175

35. Influence of planting date, row width, plant density, and
cultivar upon the height(cm) and nodal number of the lowest
mainstem node bearing either a pod or a pod-bearing branch
at the 1978 and 1979 Chesaning locations. . . . . . . 178

36. Productive mainstem length (cm/plant) (PML), productive
mainstem node numbers/plant (PMN), productive mainstem
internode lengths (cm) (PMIL) and nonproductive mainstem
internode lengths (cm) (NPMIL) as influenced by planting
date, row width, plant density and cultivar at the 1978 and
1979 Chesaning locations, averaged over all other factors. . 186

37. Mainstem pods/productive mainstem node (MP/PMN), seed number
loverall productive node (SN/OPN) and seed weight (g/overall
productive node) (SW/OPN) as influenced by planting date,
row width, plant density and cultivar at the 1978 and 1979
Chesaning locations, averaged over all other factors. . . 188

38. Influence of planting systems composed of different
planting dates, row widths and cultivars upon yield (ql/ha),
lodging and height of the lowest mainstem node tO‘which is
attached a pod or pod-bearing branch (cm), averaged over
year, location and.plant density (where applicable). . . . 190

A1. Phytophthora root rot damage (percentage of plants affected)
at the 1979 Chesaning location (includes only those plots
with.someoinfestation). . . . . . . . . . . . 195

A2. Component sample grain yields (g/pod, g/node, g/plant and
) at the 1978 and 1979 Chesaning locations as influenced
by planting date, row width, cultivar and plant density,
averaged over all other factors. . . . . . . . . . 196

A3. Temperature (degrees Celsius) at sites near the 1978 and 1979
Chesaning (St. Charles), 1978 Carleton (Willis), and 1979
Dundee (Adrian) research locations. . . . . . . . 197

A4. Key for component of yield raw date Tables A5, A6 and A7. . 198

vii

Table Page

A5. Raw data for 1978 Chesaning components of yield including
whole plant measurements. . . . . . . . . . . . 199

A6. Raw data for 1979 Chesaning yield components including
whole plant measurements. . . . . . . . . . 205

A7. Raw data for 1979 Chesaning yield components including
measurements for one-third plant sections. . . . . . . 208

A8. Analyses of variance of soybean yields (ql/ha) for both
1978 locations as influenced by replication (R), planting
date (D), row width (W), plant density (P) and cultivar (C). 210

A9. Analysis of variance of soybean yields (ql/ha) for the
combined 1978 locations as influenced by location (L),
replication (R), planting date (D), row width (W), plant
density (P), and cultivar (C). . . . . . . . . . . 211

A10. Analyses of variance of soybean yields (ql/ha) for both
1979 locations as influenced by replication (R), planting
date (D), row width (W) and cultivar (C). . . . . . . 212

All. Analysis of variance of soybean yields (ql/ha) for the
combined 1979 locations as influenced by location (L),
replication (R), planting date (D), row Width (W) and
cultivar (C). . . . . . . . . . . . . 213

viii

 

LIST OF FIGURES

Figure

l.

10.

Association of developmental growth stages of four soybean
cultivars with planting date and seasonal rainfall data taken
near the Chesaning location in 1978. . . . . . . . .

Association of developmental growth stages of four soybean
cultivars with planting date and seasonal rainfall data
taken near the Carleton location in 1978. . . . .

Association of developmental growth stages of eight soybean
cultivars with.planting date and seasonal rainfall data
taken.near the Chesaning location in 1979. . . . . . .

Association of developmental growth stages of eight soybean
cultivars with planting date and seasonal rainfall data
taken near the Dundee location in 1979. . . . . . . .

Ground level and mid-canopy penetration of photosynthetically
active radiation (PAR) as influenced by cultivar and planting
date, averaged over row width at the 1979 Chesaning location.

Ground level and mid-canopy penetration of photosynthetically
active radiation (PAR) as influenced by cultivar and row
width, averaged over planting date at the 1979 Chesaning
location. . . . . . . . . . . . . . . . . .

The influence of plant density, planting date and cultivar
upon mature plant height (cm) at the 1978 Chesaning location,
averaged over cultivar. . . . . . . . . . . . .

Influence of cultivar upon mature plant height (cm) at the
1979 Dundee, Chesaning and combined locations, averaged over
row'width and planting date. . . . . . . . . . .

Mature plant height (cm) in 1979 as influenced by planting
date and cultivar; averaged over location and row width. .

Plant lodging as influenced by row width.and planting date at

both 1978 locations, averaged over cultivar and plant density
(1 . all plants upright, 5 - all plants prostrate). . . .

ix

Page

76

77

83

84

122

. 124

130

132

134

140

 

 

Figure ”Page

'11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

Influence of row width and cultivar upon plant lodging at both
1978 locations, averaged over plant density and planting date
(1 - plant upright, 5 - all plants prostrate). . . . . . 141

Plant lodging as influenced by planting date and cultivar
at both 1978 locations, averaged over row width and plant
density (1 - all plants upright, 5 = all plants prostrate). . 142

Influence of cultivar and plant density upon plant lodging at

the 1978 Chesaning and combined locations, averaged over row
width and planting date (1 = all plants upright, 5 - all plants
prostrate). . . . . . . . . . . . . . . . . . 144

Plant lodging as influenced by row width and planting date
at both 1979 locations, averaged over cultivar (1 - all plants
upright, 5 - all plants prostrate). . . . . . . . . . 146

Influence of planting date and cultivar upon plant lodging at
both 1979 locations, averaged over row width (1 = all plants
upright, 5 - all plants prostrate). . . . . . . . . . 147

Plant lodging as influenced by cultivar and row width at the
1979 Dundee location, averaged over planting date (1 - all
plants upright, 5 = all plants prostrate). . . . . . . 150

Influence of planting date and cultivar upon early and final
plant lodging at the 1979 Dundee location, averaged over row
width (1 - all plants upright, 5 - all plants prostrate). . 152

Influence of cultivar upon percentages of sample whole plant
seed yields produced by one-third plant sections at the 1979
Chesaning location, averaged over all other factors. . . . 169

Percentages of sample whole plant seed yields produced by
one-third plant sections as influenced by row width at the
1979 Chesaning location, averaged over all other factors. . 170

Influence of cultivar and planting date upon the height of

the lowest mainstem node bearing either a pod or pod-bearing
branch at the 1978 Chesaning location, averaged over row

width and plant density. . . . . . . . . . . . . 181

Nodal number of the lowest mainstem node bearing either a

pod or pod-bearing branch as influenced by row width and

plant density at the 1978 Chesaning location, averaged over
planting date and cultivar. . . . . . . . . . . . 182

Nedal number of the lowest mainstem node bearing either a

pod or pod-bearing branch as influenced by planting date and
cultivar at the 1979 Chesaning location, averaged over

row width. . . . . . . . . . . . . . . . . . 183

INTRODUCTION

During the last few decades the agricultural production of soybeans
has risen to a level of primary, world-wide significance. In the state
of Michigan, there has been a dramatic increase in cropland planted to
soybeans to the 1978 level of 324,000 hectares, an increase of 362 per-
cent since 1960. This rapid rise in production is continuing with the
1979 soybean cropping area estimated in excess of 364,000 hectares
in Michigan. At present the soybean crop in the state is second only
to that of corn among the grain crops.

This sizeable committment of cropland resources to the soybean
crop highlights the importance of developing methods to maximize yield
from these resources. Such a maximization is critical not only for
the obvious and basic economic reasons, but also for the more philo-
sophical and moral reason of being a good steward of the resources
devoted to production of a primary world food crop.

It is commonly known that the reproductive capacity of a plant,
or community of plants, is dependent upon many factors. These factors
may be categorized as either micro-factors or macro-factors. Micro-
factors having a direct relationship to reproductive capacity would
include such metabolic factors as photosynthesis, respiration,
nitrogen metabolism, and water relations, and also plant growth and
development factors such as vegetative growth, flowering and senescence.
On a macro level are factors which may influence the micro—factors
just mentioned. In soybean production, macro-factors include the

1

2
various standard crop production practices, some of which are
characteristically associated with the planting of the crop. Selection
of the particular cultivar to be planted is critical, for each
cultivar possesses different inherent expressions of the micro—factors.
The spatial arrangement of plants in a monocrop community will have
profound effects upon the micro-factors through varying intraspecific
competition for raw materials. In the row—crop production of soybeans,
both row width and overall plant density contribute to the final spatial
arrangement. The nature of the growing season will also affect the
micro-factors, especially those related to plant growth and development.
Planting date directly determines the portion of the growing season
utilized by the crop.

Each of the above planting practices not only may have potentially
profound effects upon final reproductive yield, but also have the
additional advantage of being manipulated without significant invest-
ments of time, money (with the possible exception of spatial arrangement
factors), and energy resources.

The effects of the various planting practices are not individually
independent. There is a composite effect from various combinations of
these practices. Also, different combinations of planting practices
may produce varying responses under diverse conditions. Hence, a
systems approach would be a more realistic way to determine the
Optimal set of planting practices. Such systems approaches have been
utilized in other states in the past, but little information was
available for the rather unique environmental conditions of Michigan.
This study involved such a systems approach in which combinations

of various levels of planting practices were analyzed with two

3
objectives in view. The first was to obtain preliminary indications
of the individual planting practices and overall planting systems
which result in maximum economic yield under typical Michigan growing
conditions. The second objective was to explore in a preliminary
fashion some growth and development factors, especially as they
related to the variability in yield resulting from these different

combinations of planting practices.

 

LITERATURE REVIEW

The concept of a systems approach to soybean production has
gained increasing acceptability in recent years and has been investi—
gated by several researchers.

One systems approach composed of production practices specifi-
cally related to planting has been investigated in Ohio by Ryder and
Bierlein (33). Planting practices in this system included plant
density, row width, planting date and cultivar. There have been other
uses of the systems approach in soybean production including one
investigation into a system for production of soybeans on sloping
land (45).

In general, delays in planting of soybeans beyond the optimal
period for a given location or cultivar, have resulted in reductions in
grain yields (l6, 19, 33). The later the planting date beyond the opti-
mum period, the larger the yield reduction has been. In northern areas
of the U.S., soybeans generally have not responded favorably to
extremely early plantings in contrast to corn (16). The early plantings
have often resulted in reduced stands, slow early growth and serious
weed competition (19). Soybeans appear to be sensitive to the cool
soil temperatures present at very early planting dates, and the soil
temperature should be at least 10°-12° C before planting begins (23).

Crop yields are known to be related to both the total assimila-

tion and nutrient uptake during the growing season, and also to the way

4

5
this material is partitioned between harvestable storage structures and
the rest of the plant. When differentiation of the reproductive struc-
tures is an alternative to vegetative growth, as is the case with
indeterminate soybeans, the timing of the transition to reproductive
growth has been reported to be a factor in determining the number of
reproductive structures, the competitive ability of these structures
in accumulating reserves, and ultimately the overall yield (17).
Planting date is a critical factor in the timing of this transition.

In the northern latitudes, longer photoperiods generally delay
flowering of most adapted cultivars (8, 26). Cooler temperatures also
delay flowering in an additive fashion with photoperiod. Effects of
cool spring temperatures on flowering predominated with plantings
early in the season while photoperiod predominated in later plantings
according to Major, et a1. (26). In a study in the California Imperial
Valley, the maturity date was delayed relatively little by successive
delays in planting (1). However, in the northern U.S., a three-day
delay in planting on the average results in a one-day delay in maturity
(16).

Later planting dates tend to result in better emergence (49).
In research done at Urbana, Illinois, it was found that on the average,
maximum plant height was attained by the first planting date (May 1).
However, this same study also concluded that lodging was greater with
later planting dates (29). Other Midwest data have indicated that
medium planting dates respond with the greatest plant height and that
more lodging occurs with early dates (4).

Although in the southern U.S., narrow row widths have given

little yield advantage (19, 23), the increased yields from row widths

6
which are narrower than traditional row widths have been widely
documented in the north (5, 6, 7, 16, 21, 22, 23, 30, 33, 36, 39, 44,
46). The optimal row width is less well established and may be depen-
dent upon cultivar, length of the growing season and soil fertility.
Some work done in Indiana, Iowa, Ohio and Illinois has indicated that
highest yields occurred at 53 cm row widths, and that yield reductions
occurred at widths of 36 and 18 cm (19). However, a classic study by
Wiggans in New York indicated that, in general, decreasing row width
increased yield all the way down.to 20 cm widths (46).

Narrower rows tend to have a higher leaf area index (LAI)
earlier in the season than do wide rows (18). As a result, natural
weed control tends to be more effective in narrow rows due to earlier
shading (13, 16). With narrow row widths, there appears to be more
water infiltration and less soil loss, but Hartwig and Pendleton
reported no width effect on evapotranspiration (16). A critical factor
with narrow rows appears to be maintaining a low enough seeding rate to
avoid potential lodging problems which might negate the yield advantage
(3, 4, 5). Lodging is less of a problem at later planting dates.
Narrow row widths have had yield advantages at all planting dates but
the percentage increase appears to rise as planting date is delayed
(6, 16, 33). In one study, narrow rows also tended to yield better in
relation to wide rows during poor growing seasons when plants remained
short (33).

The effects of varied plant densities upon soybean yields have
usually been negligible except at extremes toward very high or very low
(4, 7, 13, 18, 22, 25, 46). In some instances higher densities have

resulted in higher yields (16, 33) while in other instances in Iowa

7

and Minnesota, yields have decreased (39, 44).

High plant densities have been shown to reduce the harvest
index of some crops (36). Research with corn has indicated that plant
height increased to an optimum density and then decreased at higher
densities. Evidently a point was reached where the stimulation of
elongation was negated by shading effects, although this point varied
by cultivar (9). This response of corn perhaps explains reports of
variable responses of soybean plant heights to plant density (18, 25,
44, 47). The general increase in plant height often observed with
increased plant densities has been closely related to another density
response of increased early lodging (4, 7, l3, 16, 25, 31, 44, 47).
Early lodging has been observed to decrease yield, and in Indiana,
the R5 stage was the most critical for yield reductions (43, 48)
resulting from early lodging. Other observed responses to increased
plant densities have included decreased branching, fewer seeds and pods
per plant, decreased seed weight per plant, greater height of the
lowest pod-bearing mainstem node, fewer seeds per branch pod, increased
LAI, reduced number of days to 95% (daily basis) solar radiation inter-
ception from the date of emergence, decreased stem diameter, and
increased number of pods per land area (m2) (7, 13, 18, 22, 25, 36, 37,
44, 47). Individual seed weight was usually little affected by density.

The concept of spatial arrangement of soybean plants is actually
a combination of row width and plant density. Theoretically the highest
yield should come from equidistant spacings (16). However, the need for
mechanical weed control often dictates wider row spacings. It has
generally been recommended that narrow row widths should be planted

with more plants per land area for maximum yield than wider rows

8

(16, 19, 23). However, work in central Illinois indicated that a
rate of 37.5 viable seeds per m2 was near optimal for all three row
widths tested and for most cultivars (5). Wiggans (46), on the other
hand, in earlier work indicated that the optimal spacing and plant
density should be determined for each individual cultivar. Plant
density responses provide a tremendous capability for soybean plants
to compensate for different densities.

Two major concerns when considering cultivar selection are
maturity groups and varying plant morphology. The responses of culti-
vars with early or late maturities for a given location may be varied.
Embryos of early maturing cultivars have been found to be more suscep-
tible to imbibitional chilling injury than have late cultivars. This
response may be due to the fact that seeds of early maturity cultivars
generally mature during warmer periods of the year and are therefore
not hardened to cold (2). Maximum yields have usually been obtained
from highly-productive, adapted late-maturing cultivars for a given
location (6, 16). Early maturing cultivars have usually been less
sensitive to photoperiod than late maturing cultivars (8, 26). There-
fore, as planting date has been delayed, the period from planting to
flowering has tended to be reduced more for later cultivars than earlier
ones. The reverse was true for the flowering to maturity period in
California and Illinois (1, 29). Research by Osler and Cartter (29) in
Illinois has indicated that early cultivars responded with their
greatest yields when planted at a medium planting date (May 15) while
late maturing cultivars yielded best when planted early (May 1). Early
cultivars also tended to decrease in height more rapidly as planting
date was delayed and tended to produce pods at lower plant levels in

one study (16).

9

Early maturing cultivars tended to be more responsive to
narrow rows in Illinois, Wisconsin and Minnesota (5, 6, 7). However,
at Wisconsin, the later cultivar yielded the most at every row width
treatment. Generally, the optimum plant density has been shown to be
less for late, tall, large leaf cultivar types than for earlier and
shorter types (16).

Considering morphological characteristics, attempts have been
made to find common yield components with significant correlations with
yield. In one study involving 237 strains, of the five factors of
percent of abortive seed, weight of 100 seeds, number of nodes per
plant, number of pods per node and number of seeds per pod, only the
first two had significant correlations with grain yield (42). In
studying the morphology of the above-ground plant portions, an obvious
factor is that of penetration of light into the canopy. wahua and
Miller, utilizing various levels of shading, reported significant
decreases in yield and number of pods per plant with increased shading
(40). Increasing light intensity by use of lights or reflectors at the
lower portions of plants caused increased yields, especially of the
bottom and middle plant portions. Also increased were numbers of seeds,
nodes, pods, branches, pods per node, seeds per pod,rate of apparent
photosynthesis and oil content. Protein content and seed size were
reduced (21, 38). These results tend to indicate that light levels at
the lower canopy level are a limiting factor to yield. In an attempt
to determine the contribution of leaves at various plant areas, a
defoliation experiment was conducted by Johnston et al. (20). Defolia-
tion of the middle plant leaves caused the greatest yield reduction

while that of the top portion was second and of the bottom portion was

10
last in reducing yield. In related studies in Iowa (14) the highest
abortion levels of flowers and pods were found to occur on branches and
on lower mainstem nodes.

In an attempt to better utilize the incoming light, various
plant morphologies have been tested. In general, thin-line cultivars
have tended to do best in narrow rows, while branching, medium to
late cultivars have generally proven best if wide rows are used,
especially at later planting dates (33). Iowa results have indicated
that most light interception occurred at the periphery of soybean
canopies, and that many lower leaves in a closed canopy did not receive
optimal radiation levels (34). In an attempt to allow'more light pene-
tration, narrow leaflet plant types have been designed. However, thus
far no consistent yield advantage has been observed for the narrow
leaflet cultivars, even when comparison was made with near isogenic
lines with broad leaflets (15, 16, 18). This was true even though more
light penetrated into the narrow leaflet cultivar canopies, compared to
those with broad leaflets.

In addition to providing energy for photosynthesis, other
aspects of radiation may influence patterns of growth and development.
One possible example is that of a phytochrome regulated branching
response, since the relative ratio of far red to red radiation increases
rapidly from the top of the canOpy down to the soil surface. However,
such a response is still somewhat speculative (28).

Canopy morphology also may affect more than just light distribu-
tion. The patterns of leaf distribution may also influence air circula-
tion, canopy roughness and hence the efficiency of eddy turbulence.

These factors in turn affect C0 ’HZO vapor and heat transfer so that

2

11
canopy structure may influence the microclimate of plants (24).

Noticeable environmental effects upon soybean plants highlight
the need for repetition of experiments across locations and years.
Warrington (41) found that a constant day/night temperature cycle of
23°/23° C resulted in significantly higher plant heights and mainstem
leaf numbers. Increasing differences in this cycle resulted in higher
leaf, stem and root dry weights, and higher specific leaf weights (41).
Limited soil moisture has been found to reduce plant height, the size
of the assimilating leaf area, and the size and number of potential
storage sites for produced dry matter (27). However, the effects of
moisture stress have been found to be very dependent on the stage of
plant development. .A shortage of water during pod-fill has reduced
yields more than one during flowering (16). Using a greenhouse tech-
nique, it has been possible to a limited degree to identify cultivars
which are either drought resistant or susceptible (35). In one analysis
at Urbana, Illinois, it was possible to account for 68% of the variation
of soybean yields from 1909 to 1957 utilizing precipitation and maximum
daily temperature figures for the site (32). These results reinforce
the importance of environmental factors.

Growth stage differences, noted earlier in relation to date of
planting, may also help explain certain plant yield responses. A
Kentucky study has indicated that the length of the effective grain
filling period was positively associated with yield (11). In another
study, there was no association between yield and the number of days
between any two vegetative stages. However, the period from the R.4 to
R7 stages was most highly correlated with growth. Longer periods of pod

development (RZ-R4) tended to be associated with lower yields (10).

 

MATERIALS AND METHODS

A field study investigating various systems of planting
practices for soybeans was conducted during the 1978 and 1979 growing
seasons at two locations each year. The two locations were selected
from the two major soybean producing areas in Michigan, the south-
eastern portion of the lower peninsula and the Saginaw Valley area.
The Saginaw Valley location was essentially identical both years
while the southeastern location was at two distinctly separate sites

during the two growing seasons.

I. 1978 Growing Season

Both locations were planted in a 3 X 3 X 2 X 4 factorially
arranged classical split, split plot design with three replications.
The 72 treatments consisted of 3 planting dates, 3 row widths, 2
intended plant densities and 4 cultivars. The first split involved
planting dates and the second split reflected row width. Equally-
spaced planting dates varied by location. Row widths of 24, 51 and
76 cm were planted in 2 intended plant densities of 344,000 (low) and
474,000 (high) plants per hectare. Of the 4 cultivars planted, 3 were
selected as commonly-used, well-adapted representatives of 3 different
maturity groups. 'Evans' was selected from Group 0, 'Hodgson' from
Group I, and 'Corsoy' from Group II. In addition to these 3 cultivars,
a Group II narrow-leaf cultivar, 'SRF 200,’ was selected. Standard

warm germination tests utilizing 200 seeds from each cultivar yielded

12

13

the following results: 'Corsoy' -- 90 percent, 'Evans'-- 84 percent,
'Hodgson' - 90 percent, and 'SRF 200' -- 96 percent. However, the
seed amounts planted were not adjusted by these germination test
figures.

Planting was accomplished with a 1949 Model G Allis Chalmers
tractor Specially adapted for planting small plots. The planting
adaptation consisted of a ground—driven, belt metering device, a
simple two-way divider, and two John Deere rolling disk planter units
with depth bands. Depth of planting was slightly varied on differing
planting dates due to changing field conditions. Final plot lengths
were all 5.0 m. Plot widths were 3.0 m for 76 cm rows (4 rows planted);
and 2.5 m for both 51 cm rows (5 rows planted) and 25 cm rows (10 rows
planted). An alley of 1.5 m was left between rows of plots. The 76
cm row width plots were planted with the 2 planter units 76 cm apart.
The 25 cm row width plots were planted by first planting two 76 cm
rows and then shifting the planting vehicle over 25 cm for two
additional passes. A total of six passes were made. Only 10 rows
instead of 12 were planted because seeds for the outer row were
caught and not planted on 2 passes. In planting the 51 cm row width
plots, 1 planter unit was removed; and the other was center-spaced
and adjusted so that all seed from the divider entered it. By making
2.5 rounds, 5, 51 cm rows resulted. One exception to the previous
procedure was that the 51 cm plots for the first planting date at the
Saginaw Valley location were hand-planted using a V—belt Planet Junior
planter

During the growing season, essentially complete weed control was

achieved through the combined use of herbicides, mechanical cultivation,

 

14

and hand weeding.

Mechanical harvesting was accomplished with a Hege small plot
research combine. In instances where hand harvesting was necessary,
the Hege combine was utilized as a stationary threshing unit. All
seed harvested was dried in a forced air drier to a 7.22 moisture
level and recorded in grams per plot. Subsequently, yields were
converted to quintals per hectare on a 13% moisture basis. Yields
were statistically analyzed using the standard analysis of variance
technique. At the southeastern location, eight plot yield values

were estimated using the standard missing plot statistical procedure.

A. Location One

 

The southeastern location was near Carleton, Michigan. The
previous crop was soybeans, and the soil type was a Hoytville clay
loam (Mollie Ochraqualf, illitic, mesic) with a zero percent slope.
An application of 450 kg/ha of 6-24-24 analysis fertilizer was made
in the spring prior to planting. Averages of soil samples taken on
August 3 in open areas between plots indicated a pH of 6.7, 158 kg of

Bray P extractable P/ha, and 94 kg of K/ha. A pre-plant incorporated

1
herbicide application was made of pendimethalin (1-2 kg/ ha) and
metribuzin (0.4 kg/ha). Primary tillage was accomplished with two
passes of a vibra-shank tillage tool, and a rotary tillage tool was
used for secondary tillage. The entire plot area received secondary
tillage before the first planting date. The second planting date area
received another secondary tillage operation before it was planted,

but the third planting date area received no additional secondary

tillage due to unavailability of equipment.

15

Planting dates were May 25 (first date), June 12 (second date -
51 cm plots only due to inclement weather), June 15 (second date - 25
and 76 cm plots), and July 7 (third date). Initial emergence of the
first planting date areas was irregular due to dry soil conditions.
Rainfall was more than adequate untileuly 1, and thereafter was
severely limited until late August. Greater drought effects were
not realized due to the exceptional water-holding capacity of the
soil. Some scattered root rot symptoms were observed early in the
season but readings were not taken. The 25 and 51 cm plots of the
first planting date in the first replication were harvested on
September 30. Inclement weather delayed further harvest until
October 12 when the remaining plots of the first planting date were
harvested. A killing frost the morning of October 8 hastened the
maturity of green plants of the third planting date of 'Corsoy' and
'SRF 200.‘ Plots of the second and third planting dates were hand-
harvested, due to the shortness of the plants, on October 21.
Harvested portions were 4 m long and two rows wide for 76 and 51 cm
rows, and three rows wide and 3 m long for 25 cm rows. All harvest
samples were taken from the middle of the plots where there were
enclosing border plants during the growing season. Shorter harvested
portions for 25 cm rows were used due to unevenness of stand in those

plots.

B. Location Two

 

The Saginaw Valley location was near Chesaning, Michigan. The
previous crop was corn, and the soil type was a combination of Parkhill

loam (Mollie Haplaquept, mixed, nonacid, mesic) and Macomb sandy loam

 

 

 

 

 

 

 

 

16

(Aquollic Hapladalf, mixed, mesic) with a zero percent slope. An
application of 330 kg/ha of 6-24-24 analysis fertilizer was made in
the spring prior to planting. Averages of soil samples taken on
August 4 in open areas between plots indicated a pH of 7.1, 36 kg

of Bray P extractable P/ha, 139 kg of K/ha, and 18 parts per million

1
of 0.1N, HCl extractable Mn. A preemergence herbicide application
was made of alachlor (2.2 kg/ha) and linuron (0.8 kg/ha). Some
chemical damage did appear on plots of the first two planting dates
which was evidently the result of too shallow planting before the
preemergence application was made. A chemical rating for the plots
of the first two planting dates was made using the following scale:
5 - moderate damage, 3 3 light damage, and 1 - no damage (Table A.S ).
Due to a heavy yellow nutsedge (Cyperus esculentus L.) infestation,
2 applications of bentazon of 1.75 l/ha each were made over the
whole plot area, one each.on June 22 and July 6. Some bronzing
of leaves on plants of the first date in the first replication did
occur as the result of too high an herbicide rate during the initial
application. Primary tillage was accomplished with a moldboard plow,
and a combination of field cultivator and harrow was used for
secondary tillage. The entire plot area received secondary tillage
before the first planting date. The second and third planting date
areas received another secondary tillage operation just prior to.
planting.

Planting dates were May 8 (first date - 25 and 76 cm plots
only due to inclement weather), May 10 (first date - 51 cm plots),
May 23 (second date) and June 7 (third date). Due to cool, wet

weather conditions, emergence of plants in the first planting date

17
plots was delayed until May 21. Rainfall was adequate in June, but
was somewhat limiting in July and August. Some scattered root rot
symptoms were observed early in the season but readings were not taken.
In mid-July, apparent mild manganese deficiency symptoms appeared on
lower leaves in the first planting date plots in the first replication,
second planting date plots in the second replication, and adjacent
plots. The plants appeared to grow out of this deficiency. The
'SRF 200' cultivar evidenced a lower level of visual deficiency symptoms
than did the other cultivars. On July 28, considerable early lodging
was observed in first and second planting date plots, evidently the
result of a windstorm. The 'Corsoy' cultivar was observed to be
particularly susceptible to lodging at this time, as were all varieties
in the 51 and 76 cm rows and the high plant densities. All plots were
harvested on October 10, with the harvested row lengths all being 4 m.
Harvested portions included two 76 cm rows, three 51 cm rows, and five
25 cm rows from the middle of the plots where there were enclosing

border plants during the growing season.

11. 1979 Growing Season

Both locations were planted in a 3 X 3 X 8 factorially arranged
classical split plot design with 3 replications. The 72 treatments
consisted of 3 planting dates, 3 row widths, and 7 cultivars, with 1
cultivar at 2 intended plant densities. Main plots consisted of all
9 possible combinations of planting date and row width. Equally-spaced
planting dates varied by location, and row widths of 25, 51, and 76 cm

were planted as in the previous season.

18

The 4 basic cultivars planted in 1978, 'Corsoy,' 'Evans,‘
'Hodgson 78,‘ and 'SRF 200,‘ were again used, but each row width -
planting date treatment was planted at only one intended plant
density. In 1979 'Hodgson 78' was planted instead of 'Hodgson.'

In addition to the above four cultivars, 'Beeson,’ 'Nebsoy' and

'SRF 250,‘ all taturity'(koup II cultivars were planted at the same
intended plant density. 'Nebsoy' was also planted at 1.5 times the
standard intended plant density. The standard intended plant densities
were based upon the average recommended density for each row width.
They were 460,000 plants/ha for 25 cm row widths, 321,570 plants/ha

for 51 cm row widths, and 302,630 plants/ha for 76 cm row widths.

The within-row spacings were 11.5, 16.4,and,2331plants/m of row

for 25, 51 and 76 cm row widths, respectively. Actual seed numbers
planted were adjusted upward by 10 percent, and again adjusted upward
to account for varietal differences in standard warm germination

tests. These germination tests, utilizing 200 seeds from each cultivar,
yielded the following results: 'Corsoy' - 90 percent, 'Evans' -

90 percent, 'Hodgson 78' - 95 percent, 'SRF 200' - 90 percent,

'Beeson' - 88 percent, 'Nebsoy' - 90 percent, and 'SRF 250' - 94
percent.

Planting was accomplished with the same basic planting unit
with minor modifications. Depth of planting was slightly varied on
different planting dates due to changing field conditions. The third
planting date plots at the southeastern location were planted
unusually deep (6.3 - 7.6 cm) due to a dry, sandy seedbed. Emergence
was delayed by 2-3 days as a result. Final plot lengths were all

5 m with alleys of 1.5 m left between rows of plots. Plots were 4,

19

4, and 8 rows wide for 76, 51, and 25 cm.rows, respectively. The

76 cm row width plots were planted in the same manner as in 1978.

The 51 cm row width plots were planted by 1 round—trip of the planting
vehicle with the 2 planter units spaced 51 cm apart and offwcenter.
The 25 cm row width plots were planted using the.previously mentioned
51 cm spaced planter units. Due to the.off-center arrangement, it was
possible to plant all eight 25 cm rows without running the tractor
(planter) wheels on previously planted rows.

Essentially complete weed control was again maintained, and the
harvesting methods and statistical analysis remained the same as in
1978 except that harvested seed was dried to a 6,6 percent moisture
level. At the Saginaw Valley location, 2 plot yield values were

estimated using the standard missing plot statistical procedure.

A. Location One

 

The southeastern location was near Dundee, Michigan. The
previous crop was corn and the soil type was a combination of Metamora
sandy loam (Udollic Ochraqualf, mixed, mesic) and Brookston silty clay
loam (Typic Argiaquoll, mixed, mesic) with a zero percent slope.

An application of 224 kg/ha of 3-17—40 analysis fertilizer
with 2 percent Mn was made during the previous fall. Soil samples

taken before planting indicated a pH of 6.7, 75 kg of Bray P extrac—

1
table P/ha, and 269 kg of K/ha. A prerplant incorporated application
was made of trifluralin (0.8 kg/ha) and chloramiben (2.2 kg/ha).
Primary tillage was accomplished with a mold—board plow, and secondary
tillage prior to the first planting date was accomplished with a

combination of one disking operation and two spring—tooth harrow --

spike-tooth harrow operations. The second planting date area

20

received another secondary tillage operation with a small spring-tooth
harrow before it was planted, but the third planting date area
received no additional secondary tillage due to adequate seedbed
condition.

Planting dates were May 15, June 2, and June 19. The month of
June was extremely dry, but from early July until early September
rainfall was nearly optimal, if not excessive at times. Like June,
the month of September was also a very dry month. Early lodging
was apparent in the first planting date area by July 25. By August 1,
the first planting date area was heavily lodged and the second
planting date area was beginning to lodge. A severe storm occurred
on August 23 which virtually levelled plants in the first two planting
date areas and caused heavy lodging of plants in the third planting
date area. Only some of the 'SRF 250' plots in the third planting
date area remained standing at an acceptable level. On September 20,
the 'Evans' plots in the first planting date area were hand harvested
due to the early maturity of these plants in relation to the others.
On October 22, all remaining plots were mechanically harvested with
the harvested row lengths all being 3.5 m. Harvested areas included
two 76 cm rows, two 51 cm rows, and four 25 cm rows from the middle
of the plots where there were enclosing border plants during the

growing season.

B. Location Two

 

The Saginaw Valley location was in the same field near
Chesaning, Michigan, as was the 1978 study. The exact location was

shifted a few feet east of the previous year's site in an attempt to

21

obtain a more uniform soil type. This effort was successful and the
soil type was uniformly Parkhill loam (Mollic Haplaquept, mixed, non-
acid, mesic) with a zero percent slope. The previous crop was soybeans.
Soil samples taken in the spring indicated a pH of 7.5, 27 kg of Bray
P1 extractable P/ha, 126 kg of K/ha, and 11 parts per million of 0.1N
HCl extractable Mn. An application of 450 kg/ha of 16-24-24 analysis
fertilizer was subsequently made on May 15. A pre-plant incorporated
herbicide application was made of trifluralin (0.7 kg/ha) and chlora-
miben ( 2.2 kgfha). Primary tillage was accomplished with a moldboard
plow, and a combination of one vibra-shank operation and two spike-
tooth harrow -- cultipacker operations was used for secondary tillage
prior to the first planting date. No additional secondary tillage
was utilized on subsequent planting date areas due to adequate seedbed
conditions.

Planting dates were May 17, May 30, and June 13. The month of
June was very dry. Adequate rainfall was received during early July,
but rainfall became quite limiting in late July. Dry conditions
interrupted only by widely scattered light showers prevailed for the
remainder of the growing season. A root rot subsequently identified
as phytophthora root rot (Phytophthora megasperma var. ggjgg) appeared
in early July, and especially devastated the 'SRF 250' plots. As a
result, the 'SRF 250' cultivar was not included in the final statistical
analysis. Other cultivars, especially 'Corsoy,' experienced some
limited infestation. Readings on all plots based upon the estimated
percentage of infected plants were taken (Table A1 ). In contrast
to 1978, very few manganese deficiency symptoms were noted during

this growing season. A light frost caused slight damage to the top

22

leaves of plants of some third planting date plots on September 22.

No killing frosts were experienced. Approximately one half of the
first planting date plots were harvested on October 2 before rain
interrupted harvest. The rest of the first planting date plots and a
few second and third planting date plots were harvested on October 15.
The harvest was interrupted by equipment failure. On October 25 the
remaining plots were harvested. The harvested row lengths were all

4 m. Harvested areas included two 76 cm rows, two 51 cm rows, and

four 25 cm rows from the middle of the plots where there were enclosing

border plants during the growing season.

III. Morphological Development

 

Dates when plants in the.various treatments achieved certain
developmental stages were noted each year. Emergence dates for each
planting date were.recorded when plants began to appear above the soil
5, R1 and R5

Caviness (12), were recorded by date and cultivar, averaged across plant

surface. In 1978, V stage dates, as defined by Fehr and

density and row width. Approximate vegetative growth stages at R1

and R were also recorded. In 1979, R stage dates only were recorded,

5 1
but were.noted for each.individual plot. Maturity readings each year
were based upon harvest maturity rather than physiological maturity.
Harvest maturity was defined as the stage when essentially all pods
had turned brown and were dry~enoughito permit thorough threshing.
Due to wet weather throughout September and into October during the
1978 season, maturity readings, again recorded by date and cultivar,
and averaged across plant density and row width, reflected dates when

the plants were actually ready to harvest. Due to interspersed

showers, the relationships of the various treatment maturity readings

23
were somewhat distorted. In 1979, essentially no rainfall interrupted
maturity until early October. Maturities, again recorded for each
plot, which occurred later than this time were projected to dates when
they would have occurred if rain had not interrupted the normal drying
process. Therefore, relationships between treatments were more precise.
All plots were actually ready for harvest by October 15 except for the
third planting date, 'Beeson' plots.

Final estimated plant density figures for each plot were obtained
soon after emergence from.two 1.83 m samples taken, 1 each, from a pair
of interior rows planted during the same trip by the planting vehicle
where applicable. Selection of these particular rows allowed for seed
divider fluctuations. Sample areas from the selected rows were repre-
sentative areas in the plots and were essentially directly across from
one another.

Final lodging readings, using a scale of l = totally erect to
5 - lying prostrate, were gathered on each plot prior to harvest.
Early lodging readings were taken in similar fashion on first and
second planting date plots at the Dundee location on August 1, 1979.

Average final plant height for each plot was measured at the
Carleton location in 1978 and both locations in 1979 by sighting
across the plot portions to be harvested with an upright measuring
stick. Final plant height measures for each plot at the Chesaning
location in 1978 were obtained by averaging measurements taken from

yield component plant samples to be described later.

IV. Yield Components

 

Seed size was estimated by randomly selecting and weighing a

100 seed lot from each plot for each location and year except for the

24
1978 Carleton study where no seed size information was obtained. For
the 1978 Chesaning study, 100 seed lots were randomly selected from
seed obtained from yield component plant samples to be described
later. For both 1979 studies, 100 seed lots were randomly obtained
from the seed harvested for basic yield measurements.

During both the 1978 and 1979 growing seasons, mature plant
samples were obtained from each plot at the Chesaning location, except
for the 'SRF 250' plots in 1979, and were broken down into basic
components of yield. Plant numbers and regular spacings for each
plant density and row width treatment, reflecting estimated overall
average final plant density, were used to construct an ideal, regularly-
spaced sampling ruler. The sampling ruler was used to select a one-
third meter sample from a row to be harvested in each plot. Samples
were selected which most nearly conformed to the ideal plant number
and spacing on the sampling ruler (Tables 1 and 2). After drying,
data from whole plants were collected from the above samples for the
number and height (cm) of the lowest podded node, number of mainstem
nodes and pods, number of branch nodes and pods, branch numbers, and
seed yield (gm), in addition to components mentioned earlier. In
1979, an additional procedure was added for the 'Hodgson 78,'

'SRF 200,‘ and 'Beeson' plot samples. Sample plants were divided

into thirds by counting mainstem nodes and dividing by three. The
bottom third and then the middle third received any extra nodes above
the greatest figure divisible by three. The same components mentioned
above were measured for each plant third and then whole plant averages
were obtained by combining the figures for the thirds. These basic

component figures were then used to derive other component figures.

25

Table 1. Ideal, components of yield sample plant numbers and spacings
(cm) for the 1978 Chesaning location by row width (cm) and
plant density.

 

 

 

 

Row Width Plant Density
Low High
Number Spacing Number Spacing
51 f7 5 5.66 7 4.29
76 $0 8 3.78 10 2.87

 

Table 2. Plant numbers and spacings (cm) for ideal, components of
yield samples from the 1979 Chesaning location by row width
(cm) and plant density.

 

 

 

 

Row Width Plant Density
Regular 1.5 Regular
Number Spacing Number Spacing
25 4 8.42 5 5.61
51 5 5.90 7 3.93
76 7 4.21 10 2.80

 

In 1979, photosynthetically active radiation (PAR) was measured
for each plot at the Chesaning location. Full sunlight readings at
mid-canopy and ground levels were taken at three representative sample
sites per plot in the areas to be harvested. A hand-held light meter
(Lambda Instruments, Model LI-185) and a one meter long, line quantum
sensor (Lambda Instruments, Model LI—19IS) were used to obtain PAR
readings. A cover was utilized to reduce the sensor length to 76 cm
when measuring 76 cm rows in order to insure readings over whole row
widths, since the sensor was inserted perpendicularly to the rows.

The readings obtained were converted to percentages of direct sunlight

26

based upon readings in full sunlight over bare soil, obtained for
each eight-plot sequence. For all readings obtained, the sensor was
held as nearly level horizontally as possible. Readings were taken
between 11:45 AM and 2:25 PM EDT over all 3 replications. Plots in
the first planting date were measured on August 15 at approximately
the R5 growth stage, using 'SRF 200' as the reference cultivar. The
second and third planting date plots were measured on August 30 and
31. Plants in the second planting date plots were several days past
the R5 growth stage and the third planting date plots were one or
two days past the R.5 growth stage, again using the 'SRF 200' cultivar
for reference. When the second planting date plot readings were
obtained, the 'Evans' cultivar had already begun to exhibit leaf~
turn which probably resulted in some increase in the percentage of
direct sunlight figures.

In an attempt to identify reasons for cultivar differences in
PAR measurements, limited leaf area determinations were made on
August 30 and 31 utilizing border-row plant samples obtained in the
same manner as were yield component plant samples, described earlier.
Although less satisfactory, border rows were utilized to avoid, as
much as possible, disruption of the canopy of plot areas to be har-
vested for yield measurements. Determinations were derived from
all the first planting date plots of 'Corsoy,' 'Hodgson 78,'
'SRF 200,‘ and 'Nebsoy' (regular plant density) cultivars. Since
advanced maturity made determinations of leaf area for 'Evans' in
the first planting impossible, determinations were also obtained for
second planting date plots of 'Evans' and 'SRF 200' cultivars with

'SRF 200' plots included for approximate comparison. Cumulative

27
leaf area readings were obtained for all leaves of one representative
sample plant using a leaf area meter (Lambda Instruments, Model LI-300).
These leaves were then weighed as were the leaves from the remaining
sample plants, and average leaf area figures per plant were calculated
on a direct proportion basis. Average per-plant leaf area figures
were then multiplied by the number of plants per squared meter,
obtained from the ideal figures used in sampling in order to derive

a leaf area index (LAI).

RESULTS AND DISCUSSION

1. Grain Yields

 

A. ‘1918

The average soybean yield at the Chesaning location was 25.51
ql/ha, or 24.9% greater than the 20.43 ql/ha yield at the Carleton
location (Table 3). Some of this difference may be explained by the
drought conditions experienced at the Carleton location, although rain-
fall was also subnormal during much of the growing season at the
Chesaning location. Rainfall data were not recorded at the actual
locations, but rainfall records were available for nearby sites,

The later planting dates cOupled with later dry soil conditions
at the Carleton location also apparently contributed to the yield
reduction.

It should be mentioned that the third replication at the
Chesaning location was clearly divided into two different soil types,
Parkhill loam and Macomb sandy loam, which did respond differently.

The more droughty Macomb sandy loam did respond with lower yield levels.
Although all three replications are included in the results and
discussion, it should be remembered that this unplanned source of
variability did exist.

The main effects of planting date, row width and cultivar all
significantly (0.01, 0.001, 0.001, respectively) affected yields at

the Carleton location, while only row width and cultivar significantly

28

29

Table 3. Effects of planting date, row width, and cultivar on
soybean yields (ql/ha) at both 1978 locations averaged
over all other factors.

 

 

 

 

 

0.05

Treatments Location _
Carleton Chesaning x
Plantinngate
lst 23.57 26.32 .24.95
2nd 20.88 26.04 23.46
3rd 16.83 24.16 20.50
LSD 0.05. 3.11 n.s 1.70
Row Width (cm)
10" 25 22.52 26.66 24.59
36" 51 21.60 26.35 23.98
30" 76 17.15 23.50 20.33
LSD 0.05 2.33 1.16 1.23
Cultivar
Corsoy 20.67 26.02 23.35
Evans 18.69 23.86 21.28
Hodgson 21.66 25.41 23.54
SRF 200 20.68 26.74 23.71
LSD 1.05 0.80 0.65

 

30
(0.001, 0.001, respectively) affected yield at the Chesaning
location. When locations were combined in 1978, yields were also
affected by planting date, row width and cultivar at significant
levels (0.001, 0.001, 0.001, respectively). Plant density main
effects were not significant in any instance although low density
yields tended to be slightly greater than those at high density.
Unless otherwise indicated, all future treatment effects and
interactions discussed may be considered to be at least significant
at the five percent level.

Planting date effects were much more pronounced at the Carleton
location than at the Chesaning location (Tablei3). At the Carleton
location, first date yields were 12.9% greater than those of the
second date (not significant), and second date yields were 24.1%
greater than third date yields. The first date yields were also
40.0% greater than the third date yields, indicating profound effects
of delayed planting date upon yield at this location. The yield
reduction between dates 2 and 3 was 4.05 ql/ha, or 50.6% larger than
the yield reduction of 2.69 ql/ha between dates 1 and 2. Although
not significant, Chesaning location yield responses to the different
planting dates followed a similar, though lesser, trend of greater
yield reductions with further delays in planting.

The much smaller response to planting date at the Chesaning
location may be attributed to several factors. The first planting
date at the more northerly Chesaning location was May 8, or 17 days
before the first planting date at the Carleton location. An earlier
planting date normally results in colder soil temperatures. This

negative temperature effect was indicated by the 13 day period for

31

emergence of the first planting date at the Chesaning location, as
compared to a 5 day period for emergence of the first planting date
at the Carleton location. This delayed emergence, coupled with more
unfavorable growing conditions after emergence, helps to explain the
lack of advantage of the first planting date over the second. Another
factor explaining the lesser response to planting date at the Chesaning
location is that of interval between planting dates. The intervals
between the first and second, and second and third planting dates were
21 and 23 days, respectively, at the Carleton location while at the
Chesaning location they were only 15 and 15 days, respectively. These
longer intervals, coupled with a later first planting date at the
Carleton location, caused the second and third planting dates to
occur relatively much later in the growing season. The resulting
marked reduction in growing season length, shorter daylengths, and
greater exposure to late season dry periods at critical growth stages
would all provide explanation for the larger planting date effects
on yield which resulted at the Carleton location.

The effect of row width upon yield is also presented in Table13
which shows a trend of increasing yield reduction with increasing
row width. Yield differences between 25 and 51 cm row widths were
not significant for either location or for the combined averages.
As with planting date, yield response to row width was much greater
at the Carleton location than at the Chesaning location. Yields
from 25 cm row widths were 4.3% greater than those from 51 cm row
widths, and yields from.51 cm row widths were 25.9% greater than
those from 76 cm widths at the Carleton location with 25 cm row

widths producing 31.3% higher yields than 76 cm row widths. However,

32

at the Chesaning location plants in 25 cm rows produced only 1.2%
higher yields than those in 51 cm rows, and plants in 51 cm rows
produced only 12.1% higher yields than those in 76 cm rows, with
plants in 25 cm rows producing only 13.4% higher yields than those
in 76 cm rows. However, it should be noted that the row width x
location interaction was not significant.

The similarity of the degree of row width response to that of
planting date between the two locations suggests the possibility that
the row width effects on yield are related to those of planting date.
The row width x planting date interaction was indeed significant for
the Chesaning location and the combined averages, but not significant
for the Carleton location (Tables ziand 5). At the Chesaning loca-
tion, the first planting date evidenced a much greater response to
row width than did the second date. The third planting date resulted
in a much greater response to 51 cm row widths over 76 on row widths
than did the second date. However, the 25 cm row width response was
surprisingly less than the 51 cm row width reSponse for the third
date. It should be noted that differences between the 25 and 51 cm
row widths were not significant for all dates, and that the difference
_ between 51 and 76 cm row widths was also not significant for the
second date.

The row width within planting date response for the Carleton
location, although not significant, was very similar to that of the
Chesaning location with a much greater row width response at the first
and third planting dates than at the second date. This similar
response was surprising if row width responses were indeed related

to planting date, since the first planting date at the Carleton

33

 

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34

 

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35

location came after the second planting date at the Chesaning location,
and the second and third Carleton planting dates were much later than
the third Chesaning planting date. The row width.within planting date
response for the combined locations was therefore understandably
significant since the individual location responses were similar.
However, it would seem that such a combined response has little meaning
since the planting dates at the two locations were so different.

The planting date within row width response, derived from the
same significant Chesaning row width x planting date interaction, was
also of interest. There was a much greater decline in yield exper~
ienced with later planting dates at the 25 cm row width, than at the
51 cm width; At the 76 cm row width, the first planting date surpris—
ingly responded with a lower yield than that from the second planting
date, but the third planting date experienced a fairly large yield
reduction in comparison to the second date. The only significant
planting date within row width comparison was that between the first
and third planting dates at the 25 cm row width. Although not signi—
ficant, the planting date within row width response at the Carleton
location furnished some additional notes of interest. There, the
response to planting date was greater for the 51 than for the 25 on
row widths. Also of interest was the fact that at the 76 cm row
width, the first planting date yield was again slightly lower than
that of the second date, and the third planting date yield was
extremely low.

Although the row width.x planting date interaction was not
significant at the Carleton location, the three-way interaction

between row width, planting date and plant density was significant

36

(Table 5), suggesting that at least at this location, plant density
was also a factor which should be considered when dealing with.row
width and planting date. At both densities, the 25 cm row width
response was much greater between the first and second planting dates
than between the second and third dates. The 76 cm row width response
was the reverse, revealing a much greater response between the second
and third dates than between the first and second. However, at the
51 cm row width, the low density response was much greater between
the second and third dates than between the first and second, while
the high density response was the reverse. This would seem to suggest
that the response to planting dates occurs earlier for narrow row~
widths and later for wide row widths. Or, possibly from the opposite
perspective, due to more equidistant spatial arrangement and resulting
light reception benefits, narrow rows evidenced less yield reduction
at later planting dates while wide rows evidenced more yield reduction.
It would also seem to suggest that negative planting date responses
occur earlier at wider row widths if plant density is increased. These
relationships were not apparent in the same three-way interaction at
the Chesaning location. However, they were apparent in the combined
three-way interaction. Neither of these last two interactions was
significant. The difference in the two location responses was supported
by a significant location x planting date x row width x plant density
interaction. The widely differing planting dates at the two locations
probably explain this response.

Row width responses within plant density and planting date from
the significant Carleton three—way interaction were similar to those

observed in the simple row width x planting date interaction. The only

 

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37

 

 

 

 

 

 

 

 

 

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38
items of special interest were the occurrence of a lower yield at
25 cm row widths than at 51 cm row widths for the low density, second
planting date and the high density, first planting date treatments.

No definite trends could be observed for plant density responses
within row width and planting date at the Carleton location (Table 5).
However, it is worthy of note that, while overall averages for low
density were higher than those for high density, six of the nine
applicable comparisons indicated superior yield responses from the
high density. This superior high density response was true for all
three row widths at the third planting date. A comparison with the
same Chesaning three-way interaction (not significant) suggests that
the higher plant density indeed had a clear advantage with the third
. planting date, while plants in the lower plant density generally
performed better with the first two dates.

The above observation is further supported by the significant
planting date x plant density interaction for the combined means as
shown in Table 7. The low density out-yielded the high density with
both the first and second planting dates, but the reverse was true for
the third planting date. Or, if this interaction is viewed from a
planting date within plant density perspective, the low density
.responded negatively to later planting dates in a more pronounced
manner than did the high density. Although the importance of planting
date comparisons when combining means for both locations would be
somewhat questionable due to different planting dates at the two
locations, it does seem that a definite trend was occurring.

'Evans,' as expected for a Group 0 cultivar, was significantly

lower yielding than the other three cultivars at both locations and

Table 7. The effect of planting date and plant density upon 1978 soy-
bean yields (ql/ha) averaged over row width, cultivar and
location.

 

 

 

 

 

 

Planting Plant Density (plants/ha) % Difference
—-3§-'i9-— 344,000 (Low) 474,000 (High) Low > High
lst 25.39 24.50 3.63
2nd 23.73 23.19 2.33
3rd 20.21 20.77 —2.70

‘Z'Differences

lst > 2nd 7.00 5.65

2nd > 3rd 17.42 11.65

lst > 3rd 25.63 17.96

LSD 0 05 - Plant density within planting date - .80

Same or different density across date - 1.79

 

in the combined response as shown in Table 3. The average response

for 'Corsoy"was.always slightly, although not signifiCantly,~lower 1
than the 'SRF 200' yield response. At the Chesaning location, 'Hodgson,'
as expected for a Group-I cultivar, responded at a level between that

of the Group 0 'Evans' and the Group II 'Corsoy' and 'SRF 200' cultivars.
'Hodgson's' response was significantly lower than that of the 'SRF 200'
cultivar. However, at the Carleton location, the Group I 'Hodgson'
cultivar reaponded at a higher level than did the Group II cultivars.
This unexpected result might possibly be attributed to greater drought
resistance, superior inherent yield potential, or the arrival of rain-
fall during the critical growth periods in a manner favoring the
'Hodgson' cultivar. This varying response by location is supported

by a significant location by cultivar interaction. Combined means

in Table 3 indicated that 'SRF 200' had the highest yield response,

followed in order by 'Hodgson,' 'Corsoy,' and 'Evans.‘ It should be

40
noted that the differences between yield means for the 'Hodgson,'
'Corsoy' and 'SRF 200' cultivars at the Carleton location and for
the combined locations were all not significant.

The occurrence of significant planting date x cultivar inter-
actions for the individual location means (Tables Sand 9) and for
the means combined over locations (TablelO) indicates that cultivar
plays an important role in response of plants to different planting
dates. In all instances, the 'SRF 200' cultivar responded with the
greatest percentage overall yield reduction from later dates of
planting. It also experienced the greatest percentage yield reduction
from the first to second dates, and from the second to third dates in
all instances except at the Carleton location where 'Evans' responded
with a larger percentage yield reduction from the first to second
dates. All cultivars except 'Evans,' in all instances, responded
with fairly large overall planting date responses, with much larger
yield reductions between the second and third dates, than between
the first and second dates. This uniform response in all but 'Evans'
may possibly be attributed to the restriction of a shortened growing
season upon medium to full season cultivars, combined with dry con-
ditions later in the growing season when late plantings had more of
the critical growth stages yet to complete. At the Carleton location,
the Group I 'Hodgson' cultivar responded with a much smaller per-
centage overall yield reduction relative to the two Group II cultivars,
as would normally be expected of a shorter season cultivar. This
response may in part explain why 'Hodgson' yields were greater than
those of 'Corsoy' and 'SRF 200' at the Carleton location. However,

at the Chesaning location the percentage overall yield reduction for

41

 

 

 

 

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42

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43

 

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44

the 'Hodgson' cultivar was much nearer that of the 'SRF 200'
cultivar, and was in fact greater than that of the 'Corsoy' cultivar.
This change in the relative response of 'Hodgson' from the Carleton
to the Chesaning location may, in part, be attributed to the fact
that growing season length was a less critical factor at the Chesan-
ing location where planting dates were much earlier, and more closely
spaced. These planting date effects were evidenced by the much
smaller percentage overall yield reductions at the later Chesaning
planting dates compared to those at the Carleton location. Other
factors such as rainfall during critical growth periods, timing of
which varies by cultivar, may aid in explaining the unusual 'Hodgson'
response.

The response of the early 'Evans' cultivar to planting date
varied even more widely by location. At Chesaning, yields of the
'Evans' cultivar surprisingly increased slightly at later planting
dates with a greater percentage increase between the first and second
dates than between the second and third. None of the planting date
comparisons for Evans was significant, yet reasons for the reversed
trend are not readily obvious. Since 'Evans' is a very short season
cultivar, and since all the planting dates at Chesaning were relatively
early, the length of growing season for even the last planting date
should not have been a factor in yield response. It may also have
been true that, due to the short growing season of 'Evans,' late
season dry conditions did not occur until after a large portion of
the critical growth periods had passed. One possible explanation for
the reversed response is that the first planting dates occurred too

early in the season, and premature flower induction resulted with

45

concurrent restriction of vegetative growth. This premature flower
induction of course would have been the result of the too early
presence of inducing short daylengths for the early planting date
plants. This was apparently not the case with 'Evans' for flowering
occurred on July 1, just one day prior to flowering of the Group I
'Hodgson' cultivar and three days prior to flowering of the Group II,
'SRF 200' cultivar. The July 1 flowering date was also several days
past the longest daylength day in the year. Another possible explan-
ation for the reversed trend is that 'Evans' was less cold tolerant
than the other cultivars, but there is no direct evidence supporting
this possibility. Rather than being less cold tolerant, it may also
have been true that more of the 'Evans' vegetative growth period
occurred during the periods of colder temperatures which resulted in
smaller plant size. The plausibility of any of the above explanations
is somewhat supported by the fact that at the more southerly Carleton
location, with relatively much later planting dates and therefore
comparatively warmer conditions at those dates, the yield of the
'Evans' cultivar responded with a more normal decrease at later
planting dates. Unexplained is the reason for the much greater
percentage yield reduction between the first and second dates, than
that between the second and third dates at the Carleton location for
'Evans.' This is the reverse of the response trend of the other
cultivars, and perhaps again may be explained by critical rains
received at different relative growth periods of the cultivars. It
should be noted that the location x planting date x cultivar inter—

action was not significant. However, the location x planting date

46
x row width x cultivar interaction was significant, and will be
discussed later.

The row width x cultivar interaction at the Chesaning location
was also significant although just barely (Table11). All cultivars
responded with uniform percentage yield increases at row widths of
51 over 76 cm. However, the early maturing cultivars, 'Evans' and
'Hodgson,' actually yielded more at the 51 «nu row width than at the
25 cm row width. This response of these early cultivars may, in part,
be related to the earlier observation that the narrow row widths
responded with much greater yield reductions between the first and
second planting dates, than between the second and third. The
Group II cultivars, 'Corsoy' and 'SRF 200' both responded with higher
yields at the 25 cm row width than at the 51 cm width. 'SRF 200,‘ the
narrow leaf cultivar, showed the greatest response to 25 over 51 cm
widths, and therefore showed the greatest percentage overall increase
in yield from narrow rows. This response at Chesaning would seem to
indicate a greater advantage to a narrow leaf morphology at narrow
rows due to greater light penetration. However, at the Carleton
location, where this cultivar x row width interaction was strongly
not significant, an almost opposite response was evident, with the
'SRF 200' cultivar evidencing the least yield increase at 25 over
51 cm row widths. This opposite response may suggest that, given
the drier conditions at the Carleton location, environmental effects
at least partly masked the assumed light use efficiency advantages of
narrower row widths.

Of note is the lack of a significant location x cultivar x row

width interaction. However, as noted before, the location x planting

47

 

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48

date x row width x cultivar interaction was barely significant. This
interaction provides several observations of interest. At the Chesaning
location, the second planting date uniformly had much lower percentage
response to row width across all cultivars than did the other two dates.
The Carleton location also evidenced the same trend across all culti-
vars. At the Chesaning location, the first and third planting dates
responded in fairly similar fashion uniformly across cultivars, while
at the Carleton location, the third planting date evidenced a much
higher percentage response to row width than the first date, in a fairly
uniform fashion across all cultivars. At the Chesaning location, both
the 'Corsoy' and 'SRF 200' cultivars evidenced decreased response
between 25 and 51 cm row widths at the later planting dates. In fact,
the 51 cm row widths yielded more than the 25 cm row widths at the
third planting date for these two cultivars. Surprisingly, the
reverse trend was evident for these two cultivars at the Carleton
location with the greatest response of 25 over 51 cm row widths at
the third planting date. The 'Evans' and 'Hodgson' cultivars
responded to row width at a much higher level at the Carleton location
than they did at the Chesaning location, in a fairly uniform manner
across all planting dates.

Both locations, in fairly uniform fashion, evidenced much higher
yield reductions for the narrower row widths than for the 76 cm row

widths between the first and second planting dates. In fact, the 76 cm

49
row width showed yield increases at the second date over the first
date in a uniform fashion across all cultivars. However, there were
marked location differences in the row width response between the
second and third planting dates as might be expected, since planting
dates varied so greatly between locations. At the Carleton location,
the 76 cm row width showed a much greater response than did the narrower
row widths for the third over the second planting date for all cul-
tivars. Response to the third over the second planting date at the
Chesaning location was much more varied, with 51 cm row widths sur-
prisingly evidencing less response than did either the 25 or 76 cm
row widths for the 'Corsoy' and 'SRF 200' cultivars. The 'Evans' and
'Hodgson' cultivars responded in the above comparison in a manner
similar to that of all the cultivars at the Carleton location,
although to a lesser degree.

Another interaction involving cultivars, which was barely sig-
nificant, was the plant density x cultivar interaction at the Chesan-
ing location (TablelZ). The early maturing cultivars, 'Evans' and
'Hodgson,' responded with slightly higher yields at the high, rather
than the low plant density. This result was not surprising since
shorter season cultivars tend to be smaller plants when mature. The
'Corsoy' and 'SRF 200' cultivars had higher yields at the low, rather
than the high plant density, which would be expected for a long
season cultivar. Only the difference between the low and high density
yields for the 'SRF 200' cultivar was significant. Surprisingly, at
the Carleton location where the cultivar x plant density interaction
was not significant, the 'Evans' and 'SRF 200' cultivars were reversed

in their response to plant density, compared to that occurring at the

50

 

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51

Chesaning location. The location x cultivar x plant density interaction
was significant in support of this result. It is possible that these
responses might reflect varying cultivar response to the drought at

the Carleton location.

B. 1979

 

Table.l3shows that the average soybean yield at the Dundee location
was 37.14 ql/ha, or 46.8 percent greater than the 25.30 ql/ha yield at
the Chesaning location. This marked difference in yield may be
attributed to the drier conditions experienced at the Chesaning
location and to the near optimal rainfall received during much of the
growing season at the Dundee location. Although rainfall data were
not recorded at the actual locations, rainfall records were available
for nearby sitesr In comparison with 1978 Chesaning average
yields, the 1979 Chesaning average yields were only 0.8 percent lower.
The average yields at the southeastern locations, although from dif-
ferent locations each year, switched from a level much lower than
that at the Chesaning location in 1978 to a level much higher in
1979 (Tables 3 and 13) .

The main effects of planting date, row width and cultivar all
significantly affected yields at both the Dundee (0.001, 0.001,

0.001, respectively) and Chesaning (0.001, 0.05, 0.001, respectively)
locations; and also for the combined 1979 yield means (0.001, 0.001,
0.001, respectively). All future treatment effects and interactions
referenced without comment upon their significance may be assumed to

be at least significant at the five percent level.

52

 

Table 13. Effects of planting date, row width and cultivar on soybean
yields (ql/ha) at both 1979 locations averaged over all
other factors.

Treatments Location

 

 

(With SRF 200)

Dundee

Chesaning
(Without.SRF 250)

X

(Without SRF 250)

 

PlantipgfiDate

lst
2nd
3rd

LSD0.05

Row Widths (cm)

25
51
76

LSD0.05

Cultivar*

Corsoy
Evans
Hodgson 78
SRF 200
Beeson
Nebsoy
(Regular Density)
Nebsoy
(1.5 Density)
SRF 250

LSD0.05

*Means within column followed by the same letters are not significantly

40.89
37.58
32.94

2.03

38.67
38.93
33.82

2.03

40.87
36.90
39.83
38.26
34.11

35.98

35.22
35.94

1.70

('DU‘NON

D.

on.

26.71
27.15
22.03

1.81

24.50
26.85
24.54

1.81

24.70
25.37
25.54
24.59
23.45

27.30

26.13

1.08

b
a
a

b

a

9

different at the 0.05 level of probability by LSD.

b
b

 

34.00
32.53
27.38

1.38

31.67
33.10
29.14

1.38

32.79
31.13
32.68
31.42
28.78

31.64

30.67

1.03

O‘NU‘N

 

53 O MAIC

Overall planting date effects were slightly more pronounced at the
Dundee location than at the Chesaning location, as indicated in TabLe13 .
At the Dundee location, first planting date yields were 8.8% higher
than those of the second date, and second date yields were 14.1% higher
than those of the third date. The first date yields were also 24.1%
higher than those of the third date. Yield reduction between the
second and third dates was 4.64 ql/ha or 40.2% larger than the yield
reduction of 3.31 ql/ha between the first two dates.

First planting date yields at the Chesaning location were
surprisingly 1.6% less than those of the second date (not significant)
and as would more normally be expected, second planting date yields
were 23.2% higher than those of the third planting date. The first
date yields were also 21.2% higher than those of the third date.

The yield difference between the first and second dates was only

.44 ql/ha, and the yield reduction between the second and third dates
was 5.12 ql/ha. The absence of a negative planting date response
between the first two planting dates at the Chesaning location cor-
relates with the small 1978 negative response (compare Tables 23 and

13 ). It is interesting to note that yield reduction between the second
and third dates at the Chesaning location (23.2%) nearly equalled that
between the first and third dates at the Dundee location (24.1%).

Comparison of planting date effects between locations was more
meaningful in 1979 than in 1978, because actual planting dates were
more nearly parallel. Planting date intervals at the Dundee location
were slightly longer than those at the Chesaning location. The
Dundee first, second and third planting dates were two days earlier,
and three and six days later, respectively, than those at the Che-

saning location. The slightly longer planting date intervals at the

54

Dundee location aid in explaining the slightly larger overall planting
date effects there, compared to the Chesaning location. The planting
date x location interaction was significant.

Before discussing the row width main effects upon yield, a basic
change in the 1979 experimental design must be noted. Instead of
maintaining two uniform intended plant densities across all row widths,
as was done in 1978, a single intended plant density reflected the
standard recommended seeding rate for each row width. Therefore, each
row width was planted with its own unique intended plant density.
Another change in the 1979 procedure was the adjustment of the actual
seed rates planted upward from the intended plant densities by adding
an additional 10 percent to all rates, and then by adjusting to 100
percent viable seed using the standard warm germination test results.
This resulted in actual seeding rates which were considerably larger
than the intended plant densities.

A comparison of the actual seeding rates in 1978 and 1979 reveals
the following differences. In 1978, the uniform, actually seeded
plant densities were 344,000 (Low) and 474,000 (High) plants/ha.

In 1979, 25 cm row width actual seeding rates in plants/ha were
533,000 for 'Hodgson 78'; 575,000 for 'Beeson'; 538,000 for 'SRF 250';
and 562,000 for 'Corsoy,' 'Evans,' 'SRF 200,’ and 'Nebsoy' (Regular
Density). These actual seeding rates for 25 cm row widths were on
the average 17.4% higher than the high actual seeding rate in 1978.
Actual seeding rates in plants/ha for the 51 cm row widths were
373,000 for 'Hodgson 78'; 403,000 for 'Beeson'; 377,000 for 'SRF

250'; and 394,000 for 'Corsoy,' 'Evans,' 'SRF 200,‘ and 'Nebsoy'

(Regular Density). These actual seeding rates for 51 cm row widths

55
were on the average 13m3% higher than the 1978 low actual seeding rate,
and 17.8% less than the high actual seeding rate in 1978. And 1979 actual
seeding rates in plants/ha for the 76 cm row widths were 350,000 for
'Hodgson 78'; 378,000 for 'Beeson'; 354,000 for 'SRF 250'; and 370,000
for 'Corsoy,' 'Evans,' 'SRF 200,‘ and 'Nebsoy' (Regular Density). These
actual seeding rates for 76 cm row widths were on the average 6.4% higher
than the 1978 low actual seeding rate, and 22.8% less than the 1978 high
actual seeding rate.

The 1978 high actual seeding rate was 37.8% higher than the low
actual seeding rate. However, the 1979 actual seeding rate in 25 cm rows
was 42.7 and 52.0% higher than the actual seeding rates for 51 and 76 cm
rows, respectively. The above comparisons, coupled with the fact that
'Nebsoy' was also planted at an actual seeding rate 1.5 times greater than
the rates given above in 1979, reveal that plant density variations of
greater magnitude than those in 1978 were an inherent part of the row width
treatment, even though plant density was not a separate factor in the fac-
torial design. Any analysis of row width response in 1979 must therefore
take this variation in plant density into consideration, and direct come
parison of 1978 and 1979 row width responses would be of somewhat less-
ened significance due to the design differences between years. Refer-
ence to signficant 1978 plant density interactions may, however, provide
some assistance in evaluating 1979 row width response.

In 1979, plants in 51 cm rows outyielded those in 76 cm rows at both
locations. Yields for 25 cm rows were less than those for 51 cm rows,
although significantly so only at Chesaning (Table L3). At the Chesaning
location, the 51 cm row width response was 9.4 and 9.6% greater than that
of the 76 and 25 cm widths, respectively. In fact, the 25 on row width

yield was slightly lower than that of the 76 cm row width. At the Dundee

 

56

location, the 51 on row width response was 15.1 and 0.7% greater than that
of the 76 and 25 cm widths, respectively. The combined averages showed a
51 cm row Width response which was significantly 13.6 and 4.5% greater than
that of the 76 and 25 cm widths, respectively. The much larger intended
plant density at the 25 cm row width.over the other two row widths is a
possible explanation of its lower yield compared to the 51 cm width. It
would appear that plant densities at the 25 cm row width were higher than
the optimal level, especially at the drier Chesaning location.

Some comparison with the 1978 row width response can be made by sep-
arating out the response of the four cultivars grown in 1978 from the 1979
data. The separate 1979 average row width response of 'Corsoy,' 'Evans,'
'Hodgson 78,' and 'SRF 200' at the Dundee location was 41.48, 40.99, and
34.72 ql/ha at the 25, 51, and 76 cm row widths, respectively. Although
the 25 cm width response was only 0.5% greater than that of the 51 cm width,
it was greater rather than less than that of the 51 cm width. This trend,
similar to that in 1978, would be expected at the Dundee location where
rainfall was optimal for most of the growing season. This slightly
smaller response to 25 over 51 cm row widths in 1979 could possibly be
explained by increased lodging from the higher plant density. However,
the separate 1979 row width resPonse for the same four cultivars at the
Chesaning location was 36.87, 39.28 and 35.60 ql/ha at the 25, 51 and 76
cm row widths, respectively. Although the 25 cm row width response was
not less than that of the 76 cm row width, as it was when all cultivars
were included; yet the 51 cm row width response was still 6.5% greater
than that of the 25 cm row width. This relative 25 cm row width
response, so different from that in 1978, would again appear to be
the result of a higher plant density in the drier Chesaning environ—

ment. This suggested climatic factor is supported by a signficant

 

 

57

location x row width interaction. It is also of interest that
percentage yield increases for the 51 over 76 cm row widths at both
locations were somewhat higher when the above four cultivars were
separated, and were at levels more nearly approximating those in 1978.

Although, in contrast to 1978, no planting date x row width
interactions were significant in 1979, the location x planting date
x row width interaction was significant. This interaction including
location contrasts with 1978 results when the locations responded
similarly in the planting date by row width interaction. Some obser-
vations from this three-way interaction are as follows. At both loca-
tions, yields at the 25 cm row width were lower than those at the 51 cm
width for two of the three planting dates. However, at the Chesaning
location, a positive 25 over 51 cm width response occurred for the
second date, while at the Carleton location it occurred for the first
date. These varying positive responses may have been the result of
rainfall at different critical times during the growing season of the
applicable planting dates which negated the high plant density effect
upon 25 cm row width yields. Of interest is the fact that 25 cm row
width yields were lower than those for 51 cm rows for the third
planting date at the Chesaning location in both 1978 and 1979. This
would seem to suggest that perhaps 25 cm row widths do not have an
advantage over 51 cm widths for the later planting dates used at the
more northerly Cheasaning location.

Only for the first planting date was the percentage yield
increase of 51 over 76 cm row widths greater at the Chesaning location
than at the Dundee site. Surprisingly, the second planting date at
Dundee and the first date at Chesaning responded with the greatest

percentage yield increase for 51 over 76 cm rows. In the previous

58

year at the Carleton location this response was smallest at the
second planting date. Perhaps climatic conditions plus the varying
planting dates would help explain this reversal. The 51 over 76 cm
width percentage yield response at Chesaning was the least at the
second planting date as it was in 1978. However, the same response
at the third planting date was not nearly as large in 1978 which may
have been due to the dry conditions in the very last portion of the
growing season.

Except for the 25 cm row width at the Dundee location, there was
a greater percentage yield reduction for date three over date two, than
for date two over date one at each row width. First date yields were
actually lower than those of the second date for the 25 and 76 cm row
widths at the Chesaning location, and for the 51 cm width at the
Dundee location. The above Dundee response for 51 cm rows is very
difficult to explain in contrast to the positive 25 and 76 cm row
width responses. The dramatic yield increase from first to second
planting dates for the 25 on row width at the Chesaning location may
possibly be the result of June dry weather effects upon the higher
25 cm plant density. The even more dramatic yield reduction from the
second to third planting date at the 25 cm row width may again have
been a response of higher plant density to late season dry weather.
The increased yield from the first to second planting date for the
76 cm row width at the Chesaning location is also difficult to
explain, but it is of interest that the same response occurred in
1978 at both locations. This similarity in response over years would
seem to indicate some significant disadvantage of 76 cm row widths at

early planting dates.

59

There are a few further observations about the significant
location x row width x planting date interaction regarding the per-
centage increase in yields at the well-watered Dundee location over
the dry Chesaning location for the nine row width - planting date
combination means. There appeared to be a general trend of greater
percentage response of 25 over 51 and 76 cm row widths. This response
would be expected since 25 cm row widths were at higher plant densities
and thus more susceptible to the dry conditions at the Chesaning
location. However, the 25 cm row width response for the second
planting date was much less than that of the other dates, apparently
due to more optimal moisture levels for the second planting date at
the Chesaning location.

The location x cultivar interaction was significant for obvious
reasons. The cultivar main effects were nearly reversed at the two
1979 locations (Table 13) which would seem to indicate different
inherent genetic capabilities to adapt to the divergent environments
at those locations. Also, it is possible that critical rainfall at
different relative portions of the growing period could be reaponsible
for some of this effect.

The 'Beeson' cultivar yields were significantly lower than all
others except for those of the 'Nebsoy' (1.5 Density) at the Dundee
location. This response may have been due to the fact that 'Beeson'
has a very long growing season and the month of September was dry.
This possible explanation is supported by the fact that the 'SRF 250'.
cultivar, which has a growing season approximately as long as that of
'Beeson,' yielded sixth out of eight cultivars at the Dundee location.

Of interest is the fact that the four highest yielding cultivars at

60

the moist Dundee location were the same as the four cultivars grown

in 1978, with 'Corsoy' first, 'Hodgson 78' second, 'SRF 200' third, and
'Evans' fourth. The significantly lower yield of the 'SRF 200' cultivar
when compared to 'Corsoy' is difficult to explain. The 'SRF 200' cultivar
Aalso yielded at a lower level than did 'Corsoy' at the drier Chesaning
location (difference not signficant), but both surprisingly ranked 1
much lower overall at sixth and fifth places, respectively, out of

seven cultivars. The yield decreases of these two cultivars at the
Chesaning location in relation to the other cultivars may in part be
explained by lower relative genetic ability to perform under drought
conditions, and also perhaps by dry periods during critical stages of
their growth. 'Evans' and 'Hodgson 78' were consistent performers over
locations with 'Evans' ranking fourth at both sites, and 'Hodgson 78'
ranked second and third at the Dundee and Chesaning locations, respec-
tively. This consistent performance of these two shorter growing

season cultivars may be due in part to the fact that the late season

dry periods did not affect them as adversely as they did longer season
cultivars. The strong performance of the 'Hodgson' cultivar especially
may be also attributed to inherent genetic capability to resist drought
conditions, as supported by its strong performance at the dry, 1978
Carleton location. The reversed relative response of the 'Nebsoy'
cultivar at the two intended plant densities also suggests inherent
genetic ability to resist drought conditiOns, especially in the light

of the fact that it is a Group II cultivar as were 'Corsoy' and 'SRF
200,‘ and yet performed in an opposite manner. At the moist Dundee
location, 'Nebsoy' (Regular Density)and 'Nebsoy' (1.5 Density) were
ranked fifth and seventh, respectively, out of eight cultivars while

at the drier Chesaning location, they were ranked first and second,

61

respectively, out of seven cultivars. This reversed response might
also suggest inherent lack of capability to maximize yield under
optimal moisture conditions.

Due to the variant response between locations, the meaningfulness
of the combined cultivar means is somewhat questionable (Table 13).
'Corsoy' had the highest overall yield in 1979 followed closely by
'Hodgson 78' (difference not sigtificant). These two cultivars had
significantly higher combined yields than all other cultivars, and only
the lowest yielding 'Beeson' varied significantly in yield among the
remaining cultivars.

The planting date x cultivar interaction was significant at both
locations (Tables 14 andlS), but the combined interaction was not
significant, suggesting differences in response between locations.
However, the location x planting date x cultivar interaction was also
not significant. Significant comparisons were much more prevalent at
the moist Dundee location than at the Chesaning location where lower
moisture levels evidently masked much of the interaction response. At
the Chesaning location, the only significant cultivar within planting
date comparisons were found in the first date, with the exception of
the comparisons of 'Evans,' 'Nebsoy' (Regular Density) and 'Nebsoy'
(1.5 Density) with 'Beeson' in the second planting date. This response
would seem to suggest that the inherent potential yield differences
between cultivars are most fully expressed when they are planted
earlier, and have the longest portion of the growing season in which
to produce their yield. Although significant differences were not so
restricted, this same trend was noted at the 1979 Dundee location, and

also at the 1978 Chesaning location. Strangely, this trend was not

 

62

on.N I eueo mnnuneae emonoe ne>nuanu unenewmao no eaem

 

 

 

 

Nm.n 1 some manuamna ensues na>Nunao uno.ooms

Ne.on mm.N oa.N ms.sm om.mm mo.mm onN new
Assamese n.nv

sw.QN no.nN on.m mm.om No.6N sn.mm somsmz
Azuneneo neanwemv

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23 A 2: 3 3 lac! INqu 23
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63

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one eueo wnnnnean mo oeonenaunn me nonueooa waneeenu mnon eon ne Aen\aov eoaenm neenxom .mn eases

64

evident at the 1978 Carleton location, perhaps because the extremely
dry weather there masked effects of an extended growing season resulting
from earlier planting dates.

Also of interest at the Chesaning location is the fact that dif-
ferences between the first two planting dates within cultivars are all
not significant while differences between the last two planting dates
within cultivars are all significant. All but two cultivars, 'Hodgson
78' and 'Nebsoy' (Regular Density), had first planting date yields
which were lower than those for the second date. Also with the two
variant cultivars above, a much higher percentage yield reduction
occurred between the second and third dates than between the first and
second. These observations would seem to suggest that uniformly for
all cultivars tested, little if any advantage resulted from the first
planting date over the second at the northern location. This would
again seem to strongly imply the influence of climatic factors. This
above trend was not uniformly true at the southern Dundee location
where 'SRF 200,‘ 'SRF 250,‘ and 'Beeson' actually experienced larger
percentage yield reductions between the first and second planting
dates, than between the second and third. Also, in general, percentage
yield differences between the first and second dates, and the second and
third dates did not vary as widely for each cultivar at the Dundee
location as they did at the Chesaning location.

Of the two cultivars which responded with higher yields at the
first planting date than the second at the Chesaning location, 'Nebsoy'
(Regular Density) had the highest percentage yield reduction between
the first and second dates. In contrast, 'Nebsoy' (1.5 Density) had

the second highest percentage yield increase between the first and

65
second planting dates; and a smaller percentage yield reduction
between the second and third dates, than that resulting with 'Nebsoy'
(Regular Density). The above contrast between the two 'Nebsoy' plant
densities would seem to indicate that the higher population was at a
greater disadvantage at the first planting for some unknown reason.
It would also seem to indicate that the higher population does not
result in as great a yield reduction from later planting dates as does
the regular population for this cultivar. This proposed explanation is
borne up by the treatment means for the two plant densities in which
the 'Nebsoy' (Regular Density) responded with significantly higher
yields than 'Nebsoy' (1.5 Density) at the first planting date. At
the second planting date the higher plant density yield approached
that of the regular density, and at the third planting date the
'Nebsoy' (Regular Density) yield was actually surpassed by that of
the higher density, although the difference was not significant.

This observed trend is not totally supported by the applicable
means at the Dundee location. In fact, the 'Nebsoy' (1.5 Density)
actually experienced a greater yield reduction between the second
and third dates than did 'Nebsoy' (Regular Density). However, the
above plant density trend at the Chesaning location does correspond
with trends observed at both locations in 1978. It may be that the
opposing 1979 Dundee location response was indeed the result of the
extremely late dry period in September which may have caused much
greater yield reductions for third date high plant densities in
comparison to the second planting date than those experienced at
other locations and years where the dry weather ammeearlier in the

season, during July and August.

66

A few more observations regarding the cultivar x planting date
interactions are as follows. The 'SRF 200' cultivar did not show the
consistently higher percentage yield reductions in comparison with the
other cultivars at later planting dates as it did so uniformly in 1978.
This may have been due to different 1979 climatic conditions. At the
Chesaning location, the four cultivars grown in 1978 responded in
similar fashion in 1979 between the second and third planting dates.
The longer season cultivars 'Corsoy' and 'SRF 200' did experience some-
what higher percentage yield reductions between those dates than did the
shorter season, 'Evans' and 'Hodgson 78' cultivars. This trend would,
as in 1978, seem to be explained by the restrictions of a shortened
growing season upon full season cultivars. However, no such trend was
obvious between the first and second planting dates, nor was it true
with the late maturing 'Beeson' cultivar which evidenced a much smaller
planting date reaponse.

The 1979 Dundee location results also failed to support the above
planting date-yield response trend. Of the four cultivars grown in
1978, the early maturing cultivars 'Evans' and 'Hodgson 78' actually
had noticeably larger overall percentage yield reductions between the
first and third planting dates, and also between the second and third
dates, than did the longer season 'Corsoy' and 'SRF 200' cultivars.
Also of note is the fact that the shorter season cultivars had much
larger percentage yield reductions between the second and third planting
dates than between the first and second. All of the Group II cultivars
responded in the opposite fashion, except 'Nebsoy' and 'Corsoy.'
Although percentage yield reductions were not greater between the first

and second dates than between second and third dates for the 'Corsoy'

67
cultivar, the two values were nearly equal. This unusual Dundee
location result may be partly explained by several facts: First,
since planting dates were earlier than in 1978 at the southern location
and since they were nearly the same as those at the northern Chesaning
location, it stands to reason that length of growing season would be
less critical at the southern location for the same Group II cultivars,
than it would be at the northern location. This, coupled with the fact
that dry periods occurred earlier at the northern location, would seem
to indicate that, perhaps, climatic factors, especially rainfall, were
more responsible for planting date response at the southern location.
This would also help explain the exceptions of the 'Corsoy' and
'Nebsoy' cultivars at the Dundee location. One last observation at
the Dundee location is that the 'SRF 250' cultivar had a very small
relative response to planting date. This may be possibly explained
by critical rainfall times, and also perhaps by inherent adaptability
to varying growing season lengths.

A final cultivar x planting date interaction observation of
interest at the Chesaning location was the response of the 'Evans'
cultivar between the first and second planting dates. Between these
two dates, yield increased in a noticeable, although not significant
manner. This response in part parallels that observed for this
cultivar at the 1978 Chesaning location, and may again be the result
of less cold tolerance than that possessed by the other cultivars.

This explanation is supported by the fact that this reverse response
occurred both years at the northern location, and was most apparent

between the first and second planting dates.

68

The cultivar x row width interactions were also significant at
the Dundee location, and for the combined locations (Tables 16 and 17).
All cultivars in both interactions consistently responded much less, and
sometimes negatively, to going from 51 to 25 cm row widths, than from
76 to 51 on row widths. This, coupled with the fact that the 'Nebsoy'
(1.5 Density) cultivar had a markedly greater percentage yield reduction
in going from 51 to 25 cm widths than did 'Nebsoy' (Regular Density) or
any other cultivar, would strongly support the explanation that the
reduced 25 cm row width response was largely due to the effects of the
much greater plant density at that row width. Also, since 'Nebsoy' was
the only cultivar at the Dundee location responding with a yield decrease
at 25 over 51 cm widths, with the exception of a similar although
lesser 'Corsoy' response, it would seem that 'Nebsoy' inherently does
not respond as favorably to the narrower, 25 cm row widths. Perhaps
this is due to the structure of the 'Nebsoy' plants. However, the
unique 'Nebsoy' response may also be explained by a greater inherent
sensitivity to the higher plant densities present at the 25 cm row
width.

Surprisingly, the wide leaf 'Beeson' cultivar responded with the
highest percentage yield increase at 25 over 51 cm row widths at the
Dundee location. It, however, also responded with the lowest percentage
yield increase at 51 over 76 cm widths both at the Dundee location and
with the combined locations, with the exception of the 'SRF 250' culti-
var at the Dundee location. The latter response would normally be
that expected for a wide leaf cultivar, but the first response might
possibly be due to inherently greater adaptability to the increased

plant competition from the higher densities at the 25 cm width.

 

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70

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71

The 1978 Chesaning location trend of greater row width responses
from longer versus shorter season cultivars was not consistently
evident at the 1979 Dundee location. Rather, the Dundee location
response was more similar to the 1978 Carleton location cultivar x row
width interaction, which was not significant. The long season, 'Corsoy'
cultivar did respond with the largest percentage yield increases at
the 51 over the 76 cm row widths both at the Dundee location, and with
the combined locations. However, a negative response resulted when
going from 51 to 25 cm row widths. And surprisingly, the narrow leaf
cultivars, 'SRF 200' and 'SRF 250,‘ had the lowest percentage yield
increases for 51 over 76 cm row widths at the Dundee location, with
the exception of 'Beeson.‘ This low row width response for 'SRF 200'
was repeated when two locations were combined. This response is
especially surprising because it might be expected that a narrow leaf
morphology would have an advantage at narrower rows due to better light
penetration, as appeared to happen at the 1978 Chesaning location.
However, the heavy early lodging at the Dundee location may help
explain this lack of advantage for the narrow leaf cultivars.

These explanations might also be partially supported by the
cultivar x row width interaction at the Chesaning location which was
not significant. Here, early lodging was not so severe and the
percentage yield increase Of'SRF 200' at 51 over 76 cm widths was
fairly equal to that of the other cultivars. However, a greater
percentage yield reduction was experienced by 'SRF 200' in comparison
with the other three cultivars also grown in 1978, at 25 over 51 cm
row widths. This higher reduction was also evident in the 1979

combined interaction where only 'Nebsoy' had a higher percentage

72
reduction in yield. One possible explanation for this negative row
width response is a greater sensitivity to the higher plant densities
at the 25 cm width. However, a similar response relative to the other
cultivars was also evident for the strongly not significant interaction
at the 1978 Carleton location, where plant density did not vary by row
width. Here, as noted before, perhaps the drought conditions produced
competition effects similar to those resulting from increased plant
density.

The cultivar x row width x location interaction was not signifi-
cant. Also, the row width x cultivar x planting date x location inter-
action was not significant in 1979 as it had been in 1978.

In conclusion of this discussion of grain yield response, brief
mention should be made of the combined treatment means for the two
growing seasons listed in Table 18. Statistical comparison of these
means is not possible due to the different experimental designs used
each year. However, it is interesting to note that the first planting
date uniformly yielded more than the second date, although the percentage
yield reduction of 5.3% resulting with the second date was much
smaller than that resulting from the second date to the third which
was 17.0%. Overall 25 on row width yields were actually slightly less
than those of the 51 cm row widths, which seems to indicate that even
when plant densities were uniform across row widths, the significance
of increased yields of 25 over 51 cm row widths was negligible. Also
apparent was the fact that 51 cm row widths consistently resulted in
higher yields than did 76 cm widths, with 51 cm width yields averaging

15.4% higher than those of 76 cm widths.

73

Table 18. Effects of planting date, row width and cultivar on
soybean yields (ql/ha) for both years averaged over

locations and all other factors.

 

Treatments

 

PlantingfiDate

lst
2nd
3rd

LSD0.05

Row Width (cm)

 

25
51
76

LSD0.05

Cultivar

Corsoy
Evans

Hod gson (78)
SRF 200
Beeson

Nebsoy

(Regular Density)

Nebsoy
(1.5 Density)

LSD0.05

1978

24.95
23.46
20.50

1.70

24.59
23.98
20.33

1.23

0.65

Year

_J£!Ei_

34.00
32.53
27.38

1.38

31.67
33.10
29.14

1.38

32.79
31.13
32.68
31.42
28.78
31.64

30.67

1.03

Overall x

 

29.48
28.00
23.94

28.13
28.54
24.74

28.07
26.21
28.11
27.57

 

74

Surprisingly, of the four cultivars grown both years, the
'Hodgson(78)‘cultivar responded with higher yields than any other,
although the difference from the overall 'Corsoy' yield was slight.
This response of a shorter season cultivar over longer season cultivars
would suggest inherently higher yield potential and/or greater adap-
tability to the wide range of environmental conditions occurring at
the different locations and years. 'SRF 200' yielded at slightly
lower levels than 'Corsoy,' and, as would be expected, the shortest
season 'Evans' cultivar had noticeably smaller yields. However, the
'Hodgson(78)'yield was only 7.2% higher than that of 'Evans' which
would suggest that, on the average, differences between superior

cultivars are not as important as other planting practices.

75

II. GROWTH AND DEVELOPMENT FACTORS

A. Developmental Stages and Periods

 

1. 1978

No statistical analysis was possible for developmental stages
because readings were taken only from representative field plots of
each planting date and cultivar treatment combination, rather than from
each field plot included in the experiment. Planting date differences
for the various developmental stages were reduced as later stages were
achieved. For each of the three planting dates all cultivars were
planted the same day (Figures 1 and2 ). There was a consistent trend
of subsequent developmental stages occurring earlier for the maturity
Group 0 or I cultivars than for the maturity Group II cultivars. Stages
for the Group I 'Hodgson' cultivar normally occurred at the same time
or later than those for the Group 0 'Evans.' One interesting exception
was the earlier flowering of 'Hodgson' at the third planting date at the
Chesaning location (Figure 1). However, subsequent to this, the R5 and
maturity stages followed those of 'Evans.' Another interesting obser-
vation at the Carleton location was that the 'Hodgson' maturity date
at the second planting date preceded that of 'Corsoy' by only one day.
Flowering of the 'SRF 200' cultivar tended to precede that of 'Corsoy,'
but the R.5 stage of 'SRF 200' followed that of 'Corsoy.' Maturity of
'Corsoy' followed that of 'SRF 200' with earlier planting dates, but
the reverse was true with later dates at Carleton. This would seem to
indicate the possibility of greater daylength sensitivity in 'Corsoy'
than in 'SRF 200' to decreasing daylength for later planting dates.
Also of interest is the fact that, in spite of a relatively longer

growing season at later dates for 'SRF 200,' this cultivar experienced

the greatest percentage yield reduction with later planting dates.

76

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78

At the Chesaning location where planting date intervals were short-
er, the variability of cultivar responses for flowering and R5 stages
remained fairly constant across planting dates, while for maturity, cul-
tivar differences appeared to decrease at later dates. However, at the
Carleton location where much larger planting date intervals occurred and
where the planting dates were much later, the variability of cultivar
responses decreased rapidly at later planting dates for flowering and R5
stages while it remained fairly constant, if not greater, for maturity at
later dates. The above flowering response might be due to the fact that
at earlier planting dates, unique cultivar photoperiodic responses were
fully expressed as daylength gradually shortened below critical levels
for floral initiation; while at the very late planting dates, daylengths
were so much shorter than critical levels for all cultivars that when
adequate vegetative development had occurred, the cultivars all tended
to flower at once.

Figure 1 indicates the major factor that time of emergence was
at the Chesaning location. The period between emergence of plants in
dates one and two was quite short due to delayed emergence of the first
date, while the period between emergence of the second and third dates
was quite a bit longer due to a somewhat longer emergence time for
seedlings in the third planting date. This, as noted before, aids in
explaining the small response between the first and second dates at the
Chesaning location. Since planting to emergence periods were so variable,
all growing season periods will begin with emergence, rather than planting.

The average growing season lengths (E — M) at the Chesaning

location were 125, 122, and 113 days for the first, second and third

planting dates, respectively. The E - M periods at the Carleton

79
location were shorter, due to delayed planting and were 114, 108, and
98 days, respectively. Drought effects were probably also reflected
here. One interesting exception was that for 'Hodgson,' the E - M
period for the first date at Carleton was only three days less than
for the equivalent second date at Chesaning. The E - M period for the
second date of 'Hodgson' at Carleton (111 days), planted June 15, was
actually four days longer than for the third date at Chesaning planted
June 7 (107 days). This surprising response of 'Hodgson' under the
droughty conditions at Carleton may help explain its superior yield
performance. This correlates well with yields at the two locations
(Table 3).

The average period from emergence to V (E - V5) was about 28

5
days and was fairly constant across planting dates and locations.

This would seem to indicate genetic control relatively unaffected by
the environment for timing of this vegetative development of the plant.
The average decrease in the period from V5 to flowering (V5 - R1) was
quite marked with later planting dates as would be expected. The V5 -
R1 periods were much shorter at the Carleton than at the Chesaning
locations in a manner similar to the E - M periods. This varying

V5 - R1 period response at the two locations might be due, in part,

to shorter daylength periods at the southern location, and therefore

to earlier inducement of flowering. Also, it must be remembered that
planting dates were much later at Carleton. Reduced yields at later
planting dates would therefore appear to be partly the result of

reduced vegetative growth available to support reproduction altough

some vegetative growth did continue after flowering.

80

Cultivars within planting dates maintained a fairly uniform
ranking of VS - R1 period lengths, with 'Corsoy' having the longest
period, followed by 'SRF 200,' 'Hodgson' and 'Evans.' One exception
at the Chesaning location was that 'Hodgson's' VS - R1 period went
from a length greater than that of 'Evans' at date one, to a length
less than that of 'Evans' at date three, which for 'Hodgson' was a
reduction of 64% from date one to date three. This may help to explain
why 'Hodgson's' percentage yield response between the first and third
planting dates at the Chesaning location was larger than that of
'Corsoy' and nearly equal to that of 'SRF 200.‘

Within the period between flowering and maturity (R1 - M), the
R5 to maturity (R5 - M) period showed relatively little decline,
and in fact increased at times with later planting dates. However,
the flowering to R5 (R1 - R5) period showed a marked reduction with
delayed planting. Of special interest is the fact that the length
of the RS - M period was relatively uniform for both locations where

there were radically different planting dates and environmental

conditions. This, as with the E - V period, would seem to indicate

5
genetic control of the timing of this portion of podfill somewhat
independently of environment.

Cultivars maintained a fairly uniform ranking in length of the
R1 - R5 period with that of 'SRF 200' the longest, then 'Hodgson,'
'Evans,' and 'Corsoy,' in descending order. The only exceptions to
this ranking caveat the Chesaning location, third date where 'Hodgson'
exceeded 'SRF 200,' and at the Carleton location, first date where

'Corsoy' exceeded 'Evans.' The small R1 - R5 period for 'Corsoy'

81

5 l

'SRF 200,' coupled with its second ranking V5 - R1 period length ex-

plains why this cultivar had the longest E - R5 period of the cultivars.

At the Chesaning location, the average R5

actually increased with later planting dates (Figure 1). This response

was balanced by its long V — R period. The long R1 - R.5 period for

— M period length

may be possibly attributed to late season rains which did not benefit
and extend this period for the first date. Also, the cooler, cloudy
fall weather probably delayed maturity somewhat for later dates. At

the Carleton location (Figure 2 ). the average R - M period length

5
was longer for the second than for the first planting date, but shorter
for the third over second date with the third date length nearly equal
to that of the first date. This variable response was, again, perhaps
due to late season rains which did not benefit or extend the first
date R5 - M period, coupled with a killing frost which shortened this
period for 'Corsoy' and 'SRF 200' in the third date.

Ranking of cultivars within planting dates fluctuated widely
for R.5 - M period lengths, especially between locations. Ranking at
the Chesaning location was fairly uniform and logical, with 'Corsoy'
always having the longest period, 'SRF 200' the second longest, and
'Evans' and 'Hodgson' the shortest, with some switching around of the
last two. The long R5 - M period for 'Corsoy' explains why, although
it was earlier than 'SRF 200' in achieving R , it was equal with or
later than 'SRF 200' in achieving maturity.

The widely varying cultivar within planting date ranking for the
R5 - M period lengths at the Carleton location were also probably due
to critical rainfall at different developmental stages. At the first

82

planting date, the R5 - M periods of the earlier maturing cultivars
neared or were greater than that of 'Corsoy' in length, and 'SRF 200'
lagged behind. By the second date, Group 0 'Evans' was lagging behind
while 'Hodgson' still had the longest period length, and 'SRF 200' had
tied 'Corsoy' at a length near the 'Hodgson' level. Finally, by the
third planting date, a ranking more normally expected was observed
with the longer season cultivars having longer lengths than the shorter
season cultivars, even though a killing frost cut short this period for
the longer season cultivars.

Although statistical analysis of these developmental periods was
not possible, correlations between the various periods and yield were
computed for the combined locations by assigning the applicable plant-
ing date-cultivar treatment combination mean to each plot. The P - R5
correlation was 0.69 (P represents planting date). Other periods with
5 ' R1’ R1 ' RS’

E - M, v5 - R5, v5 - M, and R1 - M.

correlations greater than 0.50 were P - E, V P - V

5’

P - R P - M, E - R

1, E - R

1’ 5’
2. 1979

'Flowering and maturity dates were recorded on a per plot basis
during this growing season so that full statistical analyses of these
stages and the resulting periods were possible. However, V5 and R.5
stages were not recorded. Again, each of the three planting dates
were uniform for all 8 cultivars at each location, although actual
planting dates did vary by location, as indicated by Figures 3 and 4.

There was a fairly consistent trend for subsequent developmental

stages to occur earlier for the maturity Group 0 or I cultivars than

for the Group II cultivars. Of the four cultivars planted in 1978,

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83

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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85

Group I 'Hodgson' and Group 0 'Evans' alternated in the timing of
flowering, but 'Hodgson' always matured after 'Evans.' 'SRF 200'
consistently flowered after the earlier maturing cultivars but before
'Corsoy' as in 1978. However, in 1979, 'SRF 200' consistently matured
after 'Corsoy' while in 1978, it matured before 'Corsoy' at earlier
planting dates. Even though planting dates were later at Chesaning
in 1979, than in 1978, the maturity dates for these two cultivars
occurred earlier. It should be noted that yields were reversed in
1979 between these two cultivars which would seem to suggest that, in
this case, the longer 'SRF 200‘.growing season did not give it an advan-
tage in yield, and in fact may have in some way been an indication of
detrimental effects.

The added cultivars for 1979, 'Beeson' and 'SRF 250' generally
responded in a manner normally expected for late Group II cultivars.
Flowering and maturity for these cultivars generally occurred later
than for 'SRF 200' and 'Corsoy' although for all three dates at the
Chesaning location, 'SRF 200' matured after these two cultivars.
Also, for the third planting date at the Chesaning location, both
'SRF 200' and 'Corsoy' flowered after 'Beeson.' One interesting
observation regarding the new, 'Nebsoy' cultivar was that it tended
to flower much earlier than the other Group II cultivars, sometimes
as soon as the early maturing cultivars. In fact, for the first
planting date at the Chesaning location, both 'Nebsoy' plant
densities actually flowered one day before 'Evans.' This early
flowering response of 'Nebsoy' may aid in explaining why its yields

were higher than those of the other Group II cultivars at Chesaning,

86

while the reverse was true at Dundee in 1979. This early flowering
response would appear to have been especially beneficial when dry
conditions were experienced in the latter half of the growing season
as was thchase at the Chesaning location. The fact that 'Nebsoy'
yields were so high at the Chesaning location coupled with the fact
that the early maturing (and flowering) cultivars also responded
with high yields would tend to support this benefit of early flowering.
'Nebsoy' did mature at times more nearly approximating maturity dates
for the other Group II cultivars. At the Chesaning location, 'Nebsoy'
maturity dates tended to fall in between those of the pairs of
'Corsoy' and 'SRF 200,' and of 'Beeson' and 'SRF 250.‘ At the
Carleton location, maturity dates were always earlier than those of
the other Group II cultivars with the exception of 'Corsoy' at the
first planting date. This response might tend to indicate some
reasons for the poor relative yield response here. Perhaps, due to
the earlier flowering date, this cultivar was unable to extend its
growing season in response to optimal growing conditions as readily
as could other Group II cultivars. These facts would seem to indicate
that 'Nebsoy' would be better adapted for dry conditions, but is
unable to take advantage of optimal growing conditions such as those
experienced under irrigation. No apparent difference occurred in
flowering and maturity dates between the two plant densities used
for 'Nebsoy.‘

The planting date x cultivar interactions for flowering and
maturity were significant at both locations. At the Chesaning

location, the variability of cultivar responses within planting dates

87
remained fairly constant for both flowering and maturity stages; while
at Dundee, variability decreased with later planting dates. This
different location response may in part be attributed to slightly
later planting dates two and three at the Dundee over the Chesaning
location, coupled with slightly shorter daylengths at the southern
location.

Surprisingly, flowering and maturity dates were also signifi-
cantly different for the different row widths at the Chesaning
location. Plants in narrower rows flowered later and matured earlier
than those in wide rows. However, differences were all less than one
day which would appear to indicate little effect upon yield. At the
Dundee location, row width differences were not significant for
flowering or maturity, but there was a strangely reversed trend of
narrower rows maturing later than wide rows. This location difference
is difficult to explain since yield responses to row width tended to
be more pronounced at the southern location. However, the row width
x cultivar interaction in Table 19 was surprisingly significant for
maturity at Dundee. 'Evans' responded with later maturity at wider
row widths while 'SRF 200,' 'Beeson,' and both 'Nebsoy' densities
responded in an opposite manner. The other three cultivars gave
mixed responses.

Emergence at Chesaning required less time at the later dates,
which probably reflected rising soil temperatures. The same effect
was true at the Dundee location, except that emergence was somewhat
delayed for the third date by deep planting in dry soil conditions.

Due to the variability of the emergence periods, growing season

88

Table 19. The influence of cultivar and row width on 1979 maturity

dates (days after September 1) at the Dundee location,
averaged over planting date.

 

 

Same or different cultivar across row width - 1.47

 

Cultivar Row Width (cm)
.22.. _51_ _z_6_ 5:
Corsoy 33.8 33.6 33.7 33.7
Evans 22.2 22.4 23.4 22.7
Hodgson 78 27.4 29.7 28.4 28.5
SRF 200 38.6 38.4 37.8 38.3
Beeson 37.8 37.8 37.1 37.6
Nebsoy (Regular Density) 34.1 33.2 32.8 33.4
Nebsoy (1.5 Density) 33.9 33.1 33.0 33.3
SRF 250 37.7 36.6 36.7 37.0
i 33.2 33.1 32.9
LSD0.05 - Cultivar within row width - 1.20

 

89
periods will all begin with emergence, rather than planting.

The average growing season lengths (E - M) for the first,
second and third planting dates were 128, 117, and 106 days,
respectively, at the Dundee location, and 123, 115, and 108 days,
respectively at Chesaning. Although the first date at Dundee was
before the first planting date at Chesaning, maturity occurred later
at Dundee. Also of note is that the second date at Dundee had a
slightly longer E - M period than the same date at Chesaning, even
though it was planted later. These observations would seem to suggest
that the optimal rainfall amounts at Dundee were an overriding factor
over shortened daylengths in extending the E - M period length beyond
those at Chesaning. However, the third date E - M period was shorter
at Dundee than at Chesaning. This probably reflects the fact that
emergence of the third date was eight days later at Dundee, and also
later in the growing season when planting date effects on yield were
more pronounced. The dry period late in the growing season at Dundee
may also explain the shorter third date E - M period in relation to
that at Chesaning. The longer average E - M periods at the Dundee
location in comparison with those at Chesaning were even more pro-
nounced when periods for the four cultivars grown in 1978 were seg-
regated out. First, second, and third planting date periods were
125, 115, and 105 days, respectively, at Dundee, and 119, 111, and
104, respectively, at Chesaning. Here, even the third date E - M
period was longer at Dundee. This reversed response of the third
date when the four cultivars were segregated was due to the earlier

maturity date of 'Nebsoy' in relation to the other Group II cultivars

90
at Dundee, but not at Chesaning.

Although V stages were not recorded in 1979, since the E - V

5
period lengths seemed fairly fixed and independent of location and

5

planting dates in 1978, it might be proper to assume that most of
the E - R1 period length trends reflected changes in the V5 - R1

portion in 1979. Cultivar variations of the E - R1 period within
planting dates paralleled flowering dates noted earlier. Even though
E - M periods at Dundee were generally longer than at Chesaning, the
E - R1 periods were consistently shorter at Dundee than at Chesaning,
although not in so pronounced a manner as in 1978. This would again
seem to indicate the effects of the shorter daylengths upon flowering
at the southern location, especially since planting dates at the two
locations corresponded closely.

At the Chesaning location, with one exception, cultivars

responded with greatly reduced E - R periods at the second over the

1
first date, while for the second and third dates they were nearly
identical. This latter response is difficult to explain, since it
runs contrary to that which would normally be expected of a photo-
periodically regulated response. Flowerfing of the third date may
possibly have been delayed due to the June dry weather, which perhaps
would have had greater delaying effect upon the smaller third date
plants than the larger ones of the second date. The effect of a
limiting "ripeness to flower" period does not seem to be present

here since shorter E - R1 periods occurred at the same location in

1978 and at the Dundee location both years. 'Nebsoy' was an inter-

esting exception to the above trend in that its E - R periods were

1

91

nearly uniform for the first and second dates, and then were noticeably
reduced for the third date. This response again may have been due to
timing of dry weather periods and to the fact that this Group II culti-
var had an unusual flowering response.

At the Dundee location, E - R1 periods again were shortened
with later dates, although decreases here were more uniform between
the first and second, and second and third planting dates. However,
except for 'Beeson,' decreases were greater between the first and
second dates, than between the second and third. Of interest is the
fact that 'Nebsoy' did not exhibit the opposite response seen at
Chesaning. This change probably indicated either different clima-
tological conditions or the effect of the shortened photoperiod at
the southern location. One last observation is that the overall
decreases in E - R1 period lengths with later planting dates were
much larger at the Dundee location than at Chesaning.

The R5 - M period length was fairly constant over dates and
locations in 1978, and therefore it again might be proper to assume

that a great deal of the differences in the R - M period lengths

1

were due to changes in the lengths of the R - R portions in 1979.

1 5

R1 - M periods were consistently much longer at the Dundee location
than at Chesaning, in a manner opposite to the lengths of E - R1
periods. This accounts for the longer overall E - M periods at
Dundee, and indicates that the increased E - M periods may have been
due to increased periods of flowering and podset, and perhaps also

of podfill in response to optimal rainfall in the second half of

the growing season. As will be seen later, seed size was larger

92
at Dundee. When seed size was divided into overall plot yields,
it also appeared that seed numbers were greater at Dundee.

At both locations, the overall R - M periods decreased less

1

between the first and second dates, than between the second and third,
in fairly uniform fashion for all cultivars. This, as would be expec-

ted, was the opposite of the trend for the E - R period, and probably

1

reflected greater end of the season pressures upon the last planting
date maturity. The ranking of cultivars within planting dates at
both locations was fairly similar with 'SRF 200' always the longest,
'Evans' the shortest, and the other cultivars closely grouped in
between. 0f the four cultivars grown in 1978, the ranking was
consistently 'SRF 200' the longest, then 'Hodgson 78,' 'Corsoy' and
'Evans' in descending order. Note that 'Corsoy' and 'Evans' switched

positions from those indicated in 1978. Although the R - M period

1

was fairly short for 'Corsoy,' its long E - R period again balanced

1

out its growing season as in 1978.
Although fewer periods were divided in 1978, it was possible to

compute correlations of the E - M, E - R1, and R - M periods to

1

yield. The only correlation over 0.50 was that of the R - M period

1

which was 0.62. This correlation would seem to indicate the importance

of the total reproductive period to yield.

93

B. Vegetative Development

 

1. Percentage Emergence and Initial Stand
A. 1978

In 1978, since seed quantities planted were not adjusted by
warm germination tests for each cultivar, the percentage emergence
figures were adjusted so that they reflected percentage emergence of
viable seed planted, rather than of desired stand. warm germination
tests were evidently fairly accurate for the Chesaning location, as the
above adjustment resulted in cultivar differences being not significant.

Emergence percentages were a little higher at the Chesaning than
at the Carleton location. This was somewhat surprising since soil
temperatures are normally cooler when the Chesaning plots were
planted. At both locations and with the combined figures, differences
were significant for planting date, row width, and plant density. At
the Carleton location, significant differences for cultivar were
present along with a significant row width x plant density x cultivar
interaction.

At both locations, the percentage emergence of the second date

was surprisingly a little lower than that of the first date, especially
given that the first date took much longer to emerge at Chesaning.
As would more normally be expected, emergence for the third planting
date was much higher than that for dates one and two. The location
x planting date interaction was not significant.

Surprisingly, at both locations a uniform trend of higher per-

centage emergence at narrower row widths was observed. Differences

94

between 25 and 51 cm widths were much greater than those between 51

and 76 cm widths. The row width x location interaction was not sig-
nificant. However, the row width x planting date x location interaction
was significant. Most noticeable in this interaction was the fact that
the percentage emergence was lower for the second date than the first
for the 25 and 76 cm row widths at the Chesaning location and for the

51 cm width at the Carleton location. Also at the Carleton location,
emergence for the second date, 56 cm width was less than that for

the second date, 76 cm width.

At both locations, percentage emergence was significantly higher
for the low density than for the high.

Although adjustments for warm germination tests were made, a
significant cultivar difference occurred at the Carleton location.

The significant difference was a much higher percentage emergence for
'Corsoy' than for the other cultivars.

A significant interaction between plant density and cultivar
appeared when results were combined for both locations, although this
interaction was not significant for the individual locations. The
major observation from this interaction was that the high density of
'Corsoy' emerged better than the low density, while the reverse was
true for the other cultivars.

One last significant interaction in 1978 was that of row width
x plant density x cultivar at the Carleton location, and also with the
combined figures for both.locations. Most prominent in both the
Carleton, and combined location interactions is the observation that
the high density of both 'Corsoy' and 'Evans' at the 25 cm row width
had a noticeably higher percentage emergence than the low density.

The reverse trend was generally true for other cultivars and row widths.

95

Initial plant stands which represent expanded field samples are
indicated in Table 20. The higher stands for the third date in con-
junction with the earlier observation that the high density treatment
responded with higher yields than the low for all row widths of the
third date (including the yet higher stand, 25 cm row widths) further
reinforce the observation that higher plant densities were more bene-
ficial to yield at later planting dates. Also of interest is the
fact that with the average row width stands, 25 cm rows had stands
which were 8.3 and 9.8% greater than those of the 51 and 76 cm widths,
respectively. These higher stands at the 25 cm row width may partially
explain why 25 cm width yields were not much higher than 51 cm widths,
given the dry weather during the growing season. Mainly due to the
failure to adjust actual number of seed planted based on the warm
germination tests, quite noticeable differences appeared in the
initial stands of the various cultivars. Since 'Evans' normally
produces a fairly small plant in comparison to the other cultivars,
it may well be that by having the lowest plant density, this cultivar
was placed at even greater disadvantage than its shorter growing
season would normally cause. Also of interest is the fact that
'SRF 200' responded with the highest yields at Chesaning while also
having the highest stand there.

The 1978 high plant density treatment was originally intended
to have 37.8% more plants per unit area than the low density treatment.
However, due to the wide fluctuations in the treatments noted above,
much greater variation occurred. An extreme example at the Carleton
location was the stands of the third date, high density, 25 cm 'Corsoy'

cultivar and of the first date, low density, 76 cm 'Evans' cultivar

96

 

 

 

 

 

Table 20 . Effects of planting date, row width, plant density and cultivar on initial plant stand
(plants/ha) averaged over all other factors for both locations in 1978 and 1979.
Treatments 1978 Locations 1979 Locations
Dundee Chesaning 2
- (with (Without) (Without)
Carleton Chesaning i 82! 250 SR! 250) SR! 250)
Planting Date
1st 386,154 400,780 393,467 367,186 417,244 396,221
2nd 384,933 391,486 388,209 423,950 400,416 414,547
3rd 410,946 433,395 422,170 445,768 454,780 450,605
1.500 05 20,658 20,658 14,607 28,052 25,594 18,557
Row Widths (cm)
25 417,399 432,050 424,724 535,941 556,961 546,964
51 383,463 401,029 392,246 367,637 373,244 373,458
76 381,171 392,582 386,876 333,327 342,235 340,952
1.500 05 18,490 18,490 13,074 28,052 25,594 18,557
Plant Density (plants/ha)
344,000 (Low) 338,946 353.314 346,130 --- ——-- ---
474,000 (High) 449,076 463,793 456,435 --- --- ---
1.800.05 14,409 14,409 10,189 ----- --- ----
Cultivar
Corsoy 419,857 417,299 418,578 418,723 407,230 412,977
Evans 358,397 386,370 372,383 384,291 404,162 394,227
Hodgson (78) 385,971 397,399 391,685 384,025 369,402 376,713
SRF 200 411,818 433,146 422,482 380,901 373,320 377,110
Beeson --- --—- --- 319,752 354,907 337,329
Nebsoy --- -—-- --- 426,169 426,173 426,171
(Regular Density)
Nebsoy --—- ..... --- 603,522 633,834 618,678
(1.5 Density)
SRF 250 -—- ---—- --- 381,028 --- -—-
LSD 20,378 20,378 14,409 42,783 39,035 29,178

0.05

 

97

which were 588,425 and 243,981 plants/ha, respectively. In this

case, the high density treatment had 141% more plants per unit area
than the low density treatment. If density treatments were averaged
in the above example, the third date, 25 cm 'Corsoy' cultivar still
had 487,962 plants/ha to the 288,232 plants/ha for the first date,

76 cm 'Evans' cultivar, or 69.3% more plants/ha. The above examples
illustrate the large stand fluctuations which occurred. These may.
have been part of the reason why plant density yield differences

were not significant, and also why some of the observed responses,
which were either unexplained or attributed to other treatment factors,

actually occurred.

B. 1979

Since seed quantities planted were adjusted by warm germination
tests for each cultivar, percentage emergence figures reflected the
percentage emergence of the desired plant stand.

Emergence percentages were again a little higher at the Chesaning
than at the southern location. At both locations and for the combined
figures, differences were significant for planting date and cultivar.
Chesaning and combined figures also revealed significant differences
for row width, and a significant planting date x row width inter-
action.

At Chesaning, the percentage emergence for the second datewas
again a little lower than that of the first date, as was the case at
both locations in 1978. The third date had a much higher percentage
emergence than the first and second as would normally be expected.

The Dundee location showed a more consistent response of increasing

98

emergence percentages at later dates with a larger difference between
dates one and two, than between dates two and three. The location x
planting date interaction was significant. As in 1978, plants in
narrower rows emerged better than those hiwider rows, with larger
differences between 25 and 51 cm row widths than between 51 and 76 cm
widths. This was significant for Chesaning and combined figures but
not for Dundee alone.

At the Chesaning location, the planting date x row width inter-
action was significant, as was also the same interaction for the
combined locations. For both of the above interactions, narrow rows
responded, as previously noted, with higher emergence than wide rows
for the first date. The same response was present for the second date,
except that 76 cm widths emerged slightly better than did 51 cm widths.
However, at the third date a totally reversed and consistent response
occurred with wide rows emerging better than narrow rows. This last
response might possibly have been the result of the greater ability
of 76 cm rows to push thorugh a dry crust which existed to some degree
at the later dry June date. The same interaction at Dundee, although
not significant, responded in a similar fashion. The low emergence
figure for first date, 76 cm widths at Chesaning may perhaps give a
clue for explaining the lower yield response of the first over the
second date for 76 cm rows.

The combined planting date x row width interaction also con-
sistently responded with increased emergence percentage at later dates
for all row widths. However, at Chesaning, this response consistently
occurred only for the 76 cm widths. At the 25 cm row widths, the

first date surprisingly emerged better than the third date, and the

99

second date was poorest. At the 51 cm width, the first date emerged
slightly better than the second date, while the third emerged best.
These last two observations account for the overall lower emergence
figure for the second date versus the first at this location.

As was true at the 1978 Carleton location, significant cultivar
differences occurred at both 1979 locations although the seed planted
was adjusted by warm germination tests. Because of the above'adjustment
prior to planting, initial cultivar stands listed in Table 20 also
reflect relative emergence, so both will be discussed together. At
both locations, 'Nebsoy' exhibited the highest percentage emergence.

At Dundee, emergence of the 1.5 density treatment was noticeably

lower than that of the regular density which was similar to plant
density response in 1978, and initial stand was 1.42 times that of the
regular density. At Chesaning, emergence percentages of the two
densities of 'Nebsoy' were nearly equal and the initial stand of the

1.5 density was 1.49 times that of the regular density. 'Corsoy'

had the next highest emergence, followed by 'Evans,' 'Hodgson 78,'

'SRF 200' and 'Beeson.' At Dundee, 'SRF 250' had a percentage emergence
between that of 'SRF 200' and 'Beeson.' 'Beeson' responded with
noticeably lower emergence which corresponded with visibly poor seed
quality at planting time. Although the warm germination test for this
cultivar was 882, the average emergence percentage of actual seed
planted was only 752 while the same figure for the regular density of
'Nebsoy' was 962 in comparison with a 902 warm germination test. The
poor response of 'Beeson' may have resulted not only in fewer plants/ha,
but also in lowered seedling vigor which might explain the poor yield

performance of this cultivar in 1979.

100

Consideration of 1979 initial plant stands in Table 20 indicates
that planting date effects were even more pronounced than the year
before. Differences were especially pronounced at Dundee where the
third date had 21.4% more plants than did the first date. Due to the
design of the experiment, row width differences were expected. However,
due to the higher percentage emergence of 25 cm widths over other widths,
the 25 cm widths had average stands which were 46.5 and 60.42 greater
than those of the 51 and 76 cm widths, respectively. This is somewhat
larger than the 42.7 and 52.0% figures originally intended.

An extreme example of the large fluctuations in intitial stand
can be found at Dundee where the initial stands of the third date,

25 cm 'Hodgson 78' cultivar and the first date, 76 cm 'Beeson' cultivar
were 592,167 and 245,431 plants/ha respectively. The first treatment
combination had 141% more plants per unit area than the second, and,
although some of these differences may be the result of sampling error,
there still exists strong reason to believe that differing plant stands

had some effects on the final yield.

101

2. Numbers of Mainstem Nodes and Growth

 

The number of mainstem nodes above the cotylendonary nodes were

recorded by field observations for the R and R stages at both

1 5

locations for each planting date and cultivar treatment combination,
averaged across the other treatments in 1978. The final numbers of
mainstem nodes at maturity were also recorded from the component of
yield samples from each plot at the Chesaning location in both 1978

and 1979. Applicable 1978 results are recorded by planting date.and
Cultivar'in Table 21..7The Chesaning figures-for matureplants averaged
over‘row~width.ahd plant‘density, nicely matched those obtained earlier
by field observations.

The ordering of cultivars within planting dates in Table 21
remained fairly constant at each developmental stage, with the Group II
cultivars possessing more nodes at each stage than the earlier
maturing cultivars, 'Evans' and 'Hodgson.' In all but one case,
'Hodgson' had more or an equal number of nodes than 'Evans.' At
the R and M stages, 'Corsoy' had more than or an equal number of

1

nodes than 'SRF 200,' but this trend was reversed at the R5 stage.

This last reversed observation was probably the result of the longer
R1 to R5 periods of 'SRF 200.‘

At Chesaning, numbers of nodes of cultivars across dates at
the R1 stage remained fairly constant although there was a trend for
'Corsoy' to have fewer nodes at later dates. At the Carleton

location, dates two and three were the same (5.5) and were both less

than date one (6.8) at the R stage. This uniform flowering

1

response at the late planting dates would seem to support the concept

of "ripeness to flower" in which a plant must reach a certain stage

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103

of development before flowering may occur. If the ratio of mature to
immature leaves is the critical factor in "ripeness to flower," then

the number of mainstem nodes with mature leaves would provide a good

indicator of this factor.

There was a noticeable decrease in mainstem nodes as planting was
delayed for all cultivars at the R5 stage. This result would seem to
indicate that reproductive development at this stage was proceeding
independently of vegetative development. However, the maturity figures
for the Chesaning location indicated that by the end of the growing
season, the difference which existed between dates at R5 had largely
disappeared. Node numbers for dates one and two were identical, and
those for date three were only slightly less than those for other dates.

The information in Table 21 not only provides a record of node
numbers at each stage, but also provides data on the nature of the
vegetative development of the soybean plants in relation to their
reproductive development. The most important trend observed was that
of greater delay in vegetative development with later planting date.
Essentially no vegetative development occurred after R5 in the first
date. However, increasingly larger amounts of development occurred
after R5 in the succeeding dates. The increasing percentage of nodes
at R1/R5 at Carleton in a manner similar to that at Chesaning sug-
gests that the same vegetative developmental response to delayed
planting date was also occurring there. The yields resulting from
later planting dates, therefore, may possibly have been not so much
affected by decreased final vegetative development, as by delayed

vegetative development which caused a smaller portion of the final

104

plant to be available to support early reproductive functions, and
also which caused more partitioning of assimilate for vegetative
development later in the season. Other effects which “might be
expected as a result with later planting date would be decreased
seed and pod numbers, and perhaps decreased seed size. As will be
seen later, only seed size was consistently reduced at later dates.

By combining the developmental periods discussed earlier and
the node development above, growth rate data was obtained reflecting
nodal growth per day, and is presented in Table 22. The growth rate
for the E - R1 period at Chesaning generally tended to increase at
later planting dates, although some cultivar fluctuations occurred.
This response was logical since the shortened growing season resulting
from later planting date would hasten the plant to reach the "ripeness
to flower" vegetative stage so that reproductive development could
commence. The E - R1 growth rates remained fairly constant at
Carleton with later dates which would seen to suggest that the
drought conditions there slowed growth even at this stage of vege-
tative development of plants planted late. This difference from the
Chesaning results would aid in explaining the very short mature plants
of the second and third dates at Carleton.

Another observation of interest is that the E - R1 growth rates
for the first date, 'Evans' and 'Hodgson' plants were quite slow in
comparison with the other cultivars and dates at Chesaning. This
may help explain why 'Evans' yielded less at the first date than the

second here.

 

105

 

 

 

 

 

 

 

 

 

 

 

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106

The R1 - R5 growth rates decreased quite rapidly with later
planting dates at both locations. However, the reduction at the
Carleton location was much greater, which again probably reflected
drought conditions there and resulted in the very short third date
plants. The decrease in R1 - 5 growth rates at both locations with
later planting dates would suggest that the priorities of the par-
titioning of assimilate shifted increasingly to the reproductive
processes during the period as planting dates‘iflfi delayed. This
reduction was pronounced enough that with the E - R5 growth rates,
the increasing rates of the E - R1 portion with later dates were
negated.

A final observation of great interest was that, although E - R5
rates decreased with later dates, E - M rates remained essentially
constant across all planting dates and cultivars. This observation
would seem to suggest that, although vegetative growth rates varied
at different periods of the growing season for different reasons, in
the end the plants were pacing themselves so that the season-long
vegetative development directly reflected the length of growing
season available. Unfortunately, since component samples were not
obtained at Carleton, corroborating evidence was not available. It
may be that the drought conditions there would have altered the
constant E — M rate observed at Chesaning.

Since mature plant samples from each plot at the 1978 and 1979
Chesaning location were measured for average mainstem node numbers,
statistical analysis of the results was possible. For both years,

significant differences occurred for planting date and cultivar.

In 1978, average mainstem nodes per plant were 14.79, 14.61 and

107
13.57, while in 1979 they were 15.88,.15.75 and 14.51 for the first,
second and third planting dates, respectively. Surprisingly, although
overall yields were slightly lower in 1979, mainstem node numbers were
slightly higher. A consistent trend occurred each year with the second
date plants having only a slightly smaller node number than those of the
first, while the third date plants had an average of about one node less
than those of the other two dates. This result closely paralleled that
of yield.

Before discussing cultivar differences, it is necessary to note
that due to the small size of the yield component samples, area grain
yields extended from sample plants did not correlate as closely with
overall plot yields as might have been desired. This correlation was
only 0.53 in 1978 and 0.44 in 1979. As a result, some trends for yields
from the samples also varied from the overall plot yields discussed
earlier. The trend most consistently altered was that of cultivar,
although other treatment trends were also affected. Therefore, data
obtained from the component samples will be briefly discussed, but
little attempt will be made to correlate these results with overall
plot yields when extended sample yield trends do not closely coincide.
Sample yields on a per plant and per squared meter basis, as influenced
by the main treatments, are provided in Table.A2for further reference.

Average mainstem node numbers for the 1978 cultivars of 'Corsoy,'

'Evans,' 'Hodgson’ and 'SRF 200' were 15.40, 12.94, 13.67 and 15.27,

respectively. For the 1979 cultivars of 'Corsoy, 'Evans, 'Hodgson
78,' 'SRF 200,' 'Beeson,' 'Nebsoy' (Regular Density) and 'Nebsoy'
(1.5 Density) node numbers were 15.04, 13.91, 14.72,17.04, 16.92,

and 14.18 respectively. As would normally be expected, long season

108
cultivars tended to have more mainstem nodes than those adapted to
shorter seasons.

Row width differences in 1978 were also significant and closely
reflected yield. There was an interesting trend of 15.30, 14.17, and
13.49 mainstem nodes for 25, 51 and 76 cm row widths, respectively.

It may be that the plants in narrower rows produced more nodes because
they were less crowded, and therefore did not have to grow upward so
fast in competition for light. Row width responses in 1979 varied very
little which would support the above supposition, since higher plant
densities at narrower row widths probably negated the reduced crowding
effect. The increased node numbers in 1978 at narrower row widths
provided additional sites for reproductive growth and may partly
account for the increased yields at those widths.

Although row width differences in 1979 were not significant, the
planting date x row width interaction was significant. Node numbers
were higher at the second dates over the first for the 25 and 76 cm
widths. Node numbers were higher for the 51 cm widths than for the
25 and 76 cm widths for the first and third dates. These trends almost
exactly parallel those of overall plot yield figures which would seem
to indicate some relationship here, although the overall correlation
between yield and mainstem node numbers was low (0.17).

Plant density differences were also significant in 1978 with
an average of 15.06 nodes at low densities and 13.58 nodes at high
densities. This response further supports the concept that increased
competition, eSpecially competition for light, caused decreased node
numbers as the plants were forced to grow upward more rapidly. The

nodal response of narrow row widths at the higher 1979 densities is

109

also further supported.

The planting date x plant density interaction was also signifi-
cant in 1978. The major observation of interest was that the second
date had slightly more nodes than the first date at low density, while
the high density had a consistent downward trend from the first through
third dates.

Before leaving this section it should be noted that the correla-
tion between mainstem nodes and overall plot yield was much higher in

1978 (0.51) than in 1979 (0.17). The 1978 correlation was significant.

110

3. Numbers of Branches and Nodes on Branches Per Plant

 

Since significant treatments and interactions were the same for
number of branches and of nodes on branches per plant, and since these
two developmental components were similar in response, they are dis-
cussed here together. All future references to branch number or to.
number of branch nodes should be understood to reflect per plant
values. Row width and cultivar differences were significant both years.
In 1978, branches per plant were 1.34, 0.96 and 0.77 and numbers of
branch nodes per plant were 4.36, 2.69, and 1.91 for 25, 51 and 76 cm
row widths, respectively. This response would be expected where plant
densities were uniform across row widths since 25 cm width plants were
more evenly spaced, and therefore, more likely to branch. The
increased number of branches and therefore of branch nodes available
at narrower row widths provided additional sites for reproductive
growth, and perhaps account for the similar yield response in 1978.
The especially high plant density of the 25 cm widths in 1979 was
reflected in the branch.numbers of 0.92, 1.66 and 1.56, and in the
number of branch nodes of 2.24, 4.39, and 4.26 for row widths
of 25, 51 and 76 cm, respectively. The reduced numbers for 25 cm
rows in 1979 again may have accounted for some of the yield reduction
experienced, although the increased number of plants available would in
a more moist year perhaps have made up for this decreased number.

Cultivar influences in 1978 upon branch number were 1.19, 1.04,
1.33, and 0.53; and upon branch node numbers were 3.49, 2.67, 4.14
and 1.65 for 'Corsoy,' 'Evans,' 'Hodgson' and 'SRF 200,' respectively.
In 1979 the same figures were 1.50, 1.41, 2.09, 1.67, 1.74, 1.03, and
0.23; and 4.28, 3.76., 5.67, 4.14, 4.36, 2.68 and 0.53 for 'Corsoy,'

'Evans,' 'Hodgson 78,' 'SRF 200,' 'Beeson,' 'Nebsoy' (Regular Density) and

111

'Nebsoy' (1.5 Density), respectively. Observations of interest in-
cluded the consistently superior branching response of the 'Hodgson(78)'
cultivar although it was a shorter season cultivar. Perhaps this
branching characteristic aids in explaining the consistent overall
yielding ability of this cultivar. 'SRF 200' indicated a much lower
relative branching response in 1978 than in 1979. This may have been
due in part to the fact that overall plant density of this cultivar
was 16% higher in 1978 than in 1979, and also was relatively higher
than the other cultivars in 1978 while the opposite was essentially
true in 1979. Although 'Nebsoy' branched less than the other cultivars
at the regular density, effects at the increased density were quite
marked to almost no branching at all. Perhaps this branching character
along with the overall structure of the plant provide some clues to the
observed superior yield performance in dry conditions.

From this point, the significant branching responses of the
two growing seasons were quite different. During the 1979 season,
planting date responses were significantly different. Number of branches
were 1.43, 1.20 and 1.52, while number of branch nodes were 4.03, 3.14
and 3.72 for the first, second and third dates, respectively. Sur-
prisingly, the second date which had the highest overall plot yield
and sample yield, had the lowest amount of branching which would seem
to indicate that this factor in itself was not critical for yield.
Also of interest is the fact that emergence was also lowest for the
second date which would seem to warrant more branching. As would be
expected, there were fewer nodes per branch for the third dates.
The 1978 response, which was not significant, showed a decrease in

branching at later planting dates.

112

The 1979 planting date x row width interaction was also sig-
nificant. First date plants had the most branches with the third and
second dates following in decreasing order for the 51 and 76 cm widths.
However, the 25 cm widths responded with consistently more branches at
later planting dates. First and third date plants had more branches
in 51 than 76 cm widths, and the least branches in 25 cm widths.
However, second date plants had consistently more branches at wider
row widths. Branch nodes had similar responses except that 25 cm
widths had more nodes at the first over the second date, and the
76 cm widths had more nodes at the second over the third date.

In 1978, plant density responses were significant as expected
with 1.41 and 0.64 branches, and 4.35 and 1.63 branch nodes per plant
at the low and high densities, respectively. Responses here high-
light the high level of adaptability of the soybean plant to varying
plant densities.

In 1978, the row width x plant density interaction was also
significant. For both branch numbers and nodes there was a consis-
tently decreasing trend from low density, 25 cm widths to high
density, 76 cm widths, with the size of decreases diminishing in the
same manner.

Another significant interaction in 1978 was between cultivar
and planting date. The branch number and nodes of the longer season
cultivars, 'Corsoy' and 'SRF 200' decreased in the order of the
second, first and third dates while for the shorter season 'Evans'
and Hodgson' cultivars, the order was the first, third and second
dates; and the first, second and third dates respectively. The

'Evans' response was very simdlar to that of 'Hodgson.' However,

113

the opposite response of the other two cultivars suggests that branch
numbers and nodes were not only a function of plant density and avail-
able growing season length, but also of the arrival of rainfall and
other climatic factors in relation to the unique genome of each cul-
tivar, since responses appeared to be grouped by maturity class.

The last significant interaction for branch numbers and nodes
was the three-way interaction in 1979 between row width, planting
date and cultivar. This interaction was characterized by fairly
random fluctuations which probably were due to the small number of
sample plants represented by each mean, but also perhaps due to the
various combinations of the factors mentioned above. However, some
general trends and notes of interest did appear. The 'Hodgson 78'
cultivar within planting dates and row widths tended to have the most
branches and branch nodes followed in varying order by 'Beeson,'
'Corsoy,' and 'SRF 200'; with 'Evans' and 'Nebsoy' usually having
the least. 'Hodgson's' largest branching advantage over other cul-
tivars tended to be at 25 cm row widths in which plant densities were
quite high. Within cultivar and planting date, 25 cm widths tended
to uniformly have less branching than the other widths, with some
exceptions. The most noteable exception was with 'SRF 200' in the
third date where 25 cm widths had the most branching followed by the
51 and 76 cm widths in decreasing order. The most consistent ordering
of row width responses within cultivar and planting date occurred at
the first planting date for both branch numbers and nodes where
differences appeared to be related to maturity groups, as noted before.
'Nebsoy' plants in 25 cm widths (1.5 Density) had no branching at

any planting dates.

114

Total nodes per plant were calculated and analyzed along with
the percentage of total plant nodes found on branches. The influences
of the main treatments on these factors are recorded in Table 23. In
1978, row width, plant density and cultivar responses were all sig-
nificantly different for both factors. The row width x plant density
and planting date x cultivar interactions were also significant. In
1979, planting date, row width and cultivar responses were all signifi-
cantly different for both factors, and the planting date x row width
x cultivar interaction for percentage of total plant nodes found on
branches was also significant. Total nodes per plant in 1978 increased
from 15.41 to 19.66 as row width was changed from 76 to 25 cm. The
percent nodes on branches was 11.3 and 18.7 for 76 and 25 cm rows,
respectively. The reverse trend occurred in 1979 with total nodes
and percent branch nodes both significantly decreasing as rows became

more narrow .

115

Table 23. Influence of planting date, row width, plant density and cultivar upon total nodes
per plant and upon percentage.branch nodes of total plant nodes for the 1978 and
1979 Chesaning.locations, averaged over all other factors.

 

Treatments . _ Year

1978 1979
Total NodeslPlant 2 Branch Nodes Total NodesZPlant z Brangh Nodes

 

Planting Date

1st 18.50 17.2 19.91 18.5
2nd 17.49 13.6 18.89 15.4
3rd 15.93 13.3 18.23 18.6
LSD 0.05 n.s. n.s. 0.77 2.5

Row Width (on)

25 19.66 18.7 17.59 11.3
51 16.86 14.1 19.93 20.6
76 15.41 11.3 19.50 20.6
LSDO.05 1.15 3.0 0.77 2.5
Plant Densigy
Low 19.41 19.8 --- --
filth 15 .21 9 .6 -.... ..--
LSDO.05 0.79 2.1 --- ....
Cultivar
Corsoy 18.89 16.0 19.32 20.8
Evans 15.61 15.2 17.67 20.2
Hodgson 78 17.82 19.7 20.40 26.9
SR! 200 16.92 7.9 21.18 18.4
Beeson —-—- -- 21.28 19.8
Nebsoy -- --- 18.53 13.1
(Regular Density)
Nebsoy -- --- 14.70 3.5
(1.5 Density)
LSD 1.12 2.9 1.23 4.0

0.05

 

116
4. Leaf Area

A limited number of leaf area readings were obtained from border
row plants in an attempt to explain cultivar light reading responses.
'SRF 200,' 'Corsoy,' 'Hodgson 78,' 'Nebsoy' (Regular Density) and
'Beeson' plots in the first planting date were measured with respective
responses of leaf area per plant (cm2/plant) being 1544, 1580, 1992,
2082, and 2481. Cultivar differences were significant. Although some
difference in cultivar responses to border row conditions may have
occurred due to branching, the above results seemed to be representative
of the cultivar differences within the canopy at the time measurements
were made. Since cultivar values were averaged over row widths, the
leaf area per land area means (LAI) were in exact proportion to leaf
area per plant means. 'Beeson' had the most leaf area as would be
expected for a wide-leaf cultivar. 'Nebsoy' and then 'Hodgson 78' had
intermediate values, with 'Corsoy' and then 'SRF 200' having the least
leaf areas. It was surprising that the early maturing 'Hodgson 78'
cultivar had more leaf area than did two Group II cultivars. However,
its superior branching character may have been expressed to a larger
degree in border row conditions.

Because 'Evans' in the first date had already begun final
maturation with leaf senescence and some abscission, leaf area per
plant measures were also recorded for the second date plots of this
cultivar along with those of 'SRF 200' for reference. Results were
1306 and 1922 cm2 for 'Evans' and 'SRF 200,' respectively. Although
the value of 'Evans' was quite low in comparison to 'SRF 200,' it
should be noted that the leaves of the second date plots were also

just beginning to senesce, and some leaves may have already fully

117

senesced and abscissed. This explanation is supported by the fact
that second date values for the 'SRF 200' cultivar were much higher
than the first date values, which would seem to indicate that perhaps
some leaves of the first date plants had already senesced and abscissed.

Row width differences were also significant for the first date
measurements. Measures for 25, 51 and 76 cm widths were 2,299, 1,795,
and 1,713 cmz, respectively, for leaf area per plant and 10.78, 5.99,
and 5.35, respectively, for LAI using within canopy extrapolation
factors. It would appear that more leaf area was produced in narrower
row widths. However, because these plants were border row plants, the
row width treatments were effective only on one side, and essentially
no competition effect was present on the other side. Therefore,
extrapolated LAI measures above, based upon average densities within

the canopy, were not true measures.

118

5. Penetration of Photosynthetically Active Radiation (PAR)

 

It would be expected that closely related to leaf area measures
would be those for photosynthetically active radiation. All subsequent
readings are an expression of photosynthetically active radiation (PAR)
penetrating the crop canopy as a percentage of total PAR striking a bare
soil surface at a distance from the crop canopy. Readings were taken
only in 1979 at both ground level and mid-canopy heights within the
plant canopy for all plots at the Chesaning location. Means of PAR
readings at mid-canopy were about three times greater than those at
ground level. Both levels had significant row width and cultivar
differences, as well as significant planting date x cultivar and row
width x cultivar interactions. Planting date differences were not
significant which would seem to suggest that by the R5 developmental
stage, plants had reached a fairly uniform level of light absorption
regardless of planting date. If planting date yield differences were
not due in part to differences in PAR penetration, they would most
likely be a function of the length of time of exposure to total PAR
(i.e. length of growing season) rather than the level of penetration
of the canopy at any one developmental stage. Such exposure differences
would occur due to shorter daylengths and less growing days for later
planting dates than for earlier ones.

PAR readings for 25, 51 and 76 cm row widths were 3.28, 3.39
and 7.11, respectively, at ground level and 9.01, 12.32, and 18.72,
respectively, at mid-canopy. At both canopy levels, 76 cm width
readings were approximately double those of 25 cm widths. However,
the 51 cm reading was only 3.4% higher than that of the 25 cm widths

at ground level; while at mid-canopy, the 51 over 25 cm row width

119

reading was 36.7% higher. Apparently, at ground levels, plants in

20 cm rows had grown together so densely that there was no significant
difference between 25 and 51 cm widths, while at mid-canopy level the
51 cm wide rows were still somewhat more separated. It would appear
that the overall yield trend was more closely correlated to that of
the gmund level PAR since 51 cm row widths actually yielded slightly
more than 25 cm rows.

When the percentages of mid-canopy light which reached the
ground level were calculated, no significant differences occurred
between row width means. This would seem to suggest that the amount
of PAR interception (or reflection) by the lower half of the plant
canopy was a proportional response to the amount of PAR penetrating
the top half. Perhaps leaf senescense at lower canopy levels would
partly account for this proportional response. However, arithmetic
differences between PAR readings for the two levels revealed sig-
nificantly different row width means which were 5.73, 8.93, and 11.61
for 25, 51 and 76 cm widths, respectively. These means were note-
worthy in that the smaller PAR readings at narrower row widths
decreased less from mid-canopy to ground level than the larger readings
at wider widths. However, since the differences between the two
canopy level readings were direct percentages of the total PAR
available above the canopy, higher percentages of the total PAR
available were evidently absorbed (or reflected) in the lower half
of the canopy with wide row spacings. It would seem that the lower
leaves of wider row canopies would also not senesce as rapidly as
the canopy increased in height, and that perhaps more reproductive

growth would occur on the lower portions of the plants.

120

PAR means by cultivar at ground level and mid-canopy were as
follows: 'Nebsoy' at 1.5 Density (1.56, 5.99), 'Nebsoy' at Regular
Density (2.18, 6.54), 'Beeson' (2.74, 8.21), 'SRF 200' (4.05, 12.37),
'Hodgson 78' (5.87, 16.51), 'Corsoy' (6.25, 18.72) and 'Evans' (9.50,
25.11). The ranking of cultivars remained the same at both canopy
levels. It would be expected that the early maturing cultivars,
'Evans' and 'Hodgson 78,' would allow the most PAR to pass through
their respective canopies, since early maturing cultivars do not have
as long a period to develop vegetatively. However, the fact that
'Corsoy' had a higher PAR reading than the narrow-leaf 'SRF 200'
cultivar was somewhat surprising. This response was somewhat explained
by the previous observation that the second date, 'SRF 200' plots had
more leaf area per unit land area than did first date, 'Corsoy' plots.
In a preliminary fashion, this PAR and leaf area response would seem
to indicate that possession of a more lanceolate leaf shape was no
guarantee of reduced leaf area or of greater PAR penetration in every
case. It is also interesting to note that 'Corsoy' yields were
slightly higher than those of 'SRF 200,' as was also initial stand.
'Beeson,' as expected for a wide leaf cultivar with a large leaf area,
had quite low PAR readings. However, it is interesting that 'Nebsoy'
had lower PAR readings than 'Beeson' while the first date leaf area
response was reversed. Either the loss by 'Nebsoy' of more leaves
due to senescence and abscission than by 'Beeson' between the times
of PAH readings and leaf area readings, or some other factor such as
differing morphological arrangement of leaves might explain this
reversed response. The two 'Nebsoy' plant densities responded in the

expected manner with the higher density having lower PAR readings.

121

As with the row width treatment, when the percentages of mid-
canopy light which reached the ground level were calculated and
analyzed, no significant differences between cultivar means occurred.
This again would suggest that for the various cultivars, the amount of
PAR interception by the lower half of the plant canopy was a propor—
tional response to the amount of PAR penetrating the top half.
Analysis of the simple differences between PAR readings at the two
canopy levels revealed significant differences between cultivar
means. The means for these differences were 4.43, 4.36, 5.47, 8.32,
10.64, 12.47 and 15.61 for 'Nebsoy' (1.5 Density), 'Nebsoy' (Regular
Density), 'Beeson,' 'SRF 200,' 'Hodgson 78,' 'Corsoy' and 'Evans,'
respectively. With the exception of the two plant densities of
'Nebsoy,’ the order above was the same as for the PAR readings at
each level. This response would suggest that since higher per-
centages of the total PAR available were evidently intercepted by
the lower half of the canopy of cultivars with large values above,
these same cultivars may have responded with more reproductive
production on the lower portion of the crop plants. The reversed
order of the two 'Nebsoy' plant densities indicated that more of
the total available PAR was intercepted in the lower half of the
canopy at the higher versus the lower density, even though less
total PAR actually penetrated this far. This response may have
been due to the presence of more plants in the canopy resulting
in more leaves per land area in the lower half of the canopy.

The significant cultivar x planting date interactions for PAR
readings at both levels are portrayed in FigureES. Cultivar within

planting date responses followed basically the same trend as the

1 OF TOTAL PAR AVAILABLE

122

32-

30..
28..

26 D Hid-canopy
2“ I Ground Level
— .1 1 Date One

2 Date No
3 Date Three

22.;

20.1

18.-J

14..

 

 

12

10..

 

 

 

 

 

 

 

 

 

 

 

 

        

 

 

 

 

 

 

123

  

   

    

 

       

 

I I
b

123 123

I'T_E

123

     

123

 

123

Go rsoy Eva na Hod gson 3115' 200 Beeson Nebsoy Nebsoy
78 ( Regular (1 . 5

Density) Density)
CULTIVAR
Figures . Ground level and aid-canopy penetration of photosynthetically active radiation (PAR)

as influenced by cultivar and planting date, averaged over row width at the 1979
Chesaning location.

123

overall cultivar response with some minor exceptions. However,
planting date within cultivar responses fluctuated widely with no
consistent trend. This response perhaps aids in explaining why over-
all planting date responses were not significant. Also, the varying
trends would seem to suggest that foliage growth was to some extent
dependent upon climatic conditions at the various times of development
of the differing cultivars and dates. Planting date within cultivar
response trends were similar for readings at both levels except for
the 'Beeson' and 'Nebsoy' (1.5 Density) cultivars. The second date
plots of both 'Nebsoy' densities responded in an unusual manner with
the ground level readings having about one-half the value of those of
the mid-canopy, instead of the more normal one-third comparison.

The cultivar x row width interactions for PAR readings at both
levels, and also for simple differences of the two readings were
significant. These interactions are displayed in Figure6 . Cultivar
within row width responses generally agreed with those of overall
cultivar means except that the ground level readings for 'Nebsoy'
(Regular Density) were lower than those of the higher 'Nebsoy'
density in 25 cm row widths. Mid-canopy readings were consistently
higher for wider row widths than for more narrow rows. The ground
level readings and difference values generally responded in
similar fashion.

Since it would be expected that PAR and leaf area measurements
would be related, the applicable PAR measures were segregated out.
Ground level readings were 5.47, 5.65, 2.42, 2.60, and 1.11; and

mid-canopy readings were 16.67, 16.84, 9.44, 8.58, and 7.24 for the

I 01" TOTAL PAR AVAILABLE

32 q
30 q
28 ..
26
21
22
20 -
18 ..
16 J
1:. -

1'2 _,

 

 

124

[:1 Mid-canopy

I Ground Level

N 25 c-

1 11 51 c.
'-‘ U 76 ca

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NM" NM"

  

 

N M W N M H N H H
Corsoy Evans Hodgson Beeson Nebsoy Nebsoy
78 (Regular (1.5
Density) Density)

 

CULT! VAR

Figure 6. Ground level and aid-canopy penetration of photosynthetically active radiation
(PAR) as influenced by cultivar and row width. averaged over planting date at the
1979 Chesaning location.

125

first date plots of 'Corsoy,' 'Hodgson 78,' 'SRF 200,' 'Beeson,'
and 'Nebsoy' (Regular Density), respectively. Also, ground level
readings were 12.78 and 3.73; and mid-canopy readings were 29.64 and
11.09 for second date plots of 'Evans' and 'SRF 200,' respectively.
The second date PAR readings correlated significantly with LAI
measurements at a level of 0.60 for ground level readings and of
0.66 for mid-canopy readings. However, similar correlations for
the first date readings with many more degrees of freedom evidenced
no significance. This lack of correlation was evidently due to the
fact that PAR readings for the first date plots were recorded 15 days
before leaf area measures were recorded, while for the second date
plots both readings were recorded at the same time. As noted before,
'SRF 200,' plants in the first planting date had evidently experienced
significant leaf abscission by the time leaf area readings were
recorded. Also 'Hodgson 78' PAR readings indicated that the unusual-
ly large leaf area values may have resulted from full expression of
this cultivar's branching character by the border plants sampled,
while PAR readings were within the canopy. The PAR readings of
the 'Nebsoy' cultivar appeared to reSpond in a manner somewhat
unique from the other cultivars. It appeared that most of the
PAR was intercepted by the initial thick layer of leaves at the
very top level of the canopy, and that only a small amount of leaf
area existed below this level. Visual inspection reinforced this
observation. 'Beeson' also appeared to reSpond somewhat similarly,
although to a lesser degree.

By deleting the 'SRF‘ cultivar from the above first date

correlation, the resulting correlations more nearly approached

126

significant levels, even though.degrees of freedom were decreased.

When 'Hodgson 78' readings were also deleted, the mid-canopy readings
correlated with LAI readings at a significant level, with a correlation
of 0.56. This was true even though.degrees of freedom were reduced.
However, correlations using ground level readings were not significant.
When the 'Nebsoy' cultivar readings were also deleted, leaving only

the 'Corsoy' and 'Beeson' cultivars, the same correlation using mid-
canopy readings jumped to 0.71 and was even more significant, even
though degrees of freedom were reduced to very low levels. Again,
correlations with ground level readings were not significant.

The above responses seem to indicate, in conjunction with
significant second date correlations, that the time period between
readings plus the use of border row plants and divergent cultivars
were the primary factors for the lack of overall significant cor-
relations between PAR readings and LAI readings for the first date
plots sampled. There is reason to believe that the correlation between
these two factors under more favorable circumstances would have been
fairly high. It should also be noted that there were no significant

correlations between the PAR readings and overall yield.

127

6. Mature Plant Height

 

a. 1978

Mature plants at the dry Carleton location averaged about three—
fourths the height of plants at Chesaning. Apparently, the different
climatic conditions in conjunction with the different measuring
techniques at each location were responsible for the fact that there
was only one significant response, that of cultivar, common to both
locations. The cultivar response at Chesaning was 87.7, 69.9, 77.6,
and 85.1 cm while at Carleton it was 62.0, 53.5, 58.3 and 65.8 cm
for 'Corsoy,' 'Evans,' 'Hodgson,' and 'SRF 200,' respectively. As
would be expected, the shorter season cultivars had shortened plants.
The reversed response of 'Corsoy' and 'SRF 200' may have been due to
more resistance to drought effects upon vegetative growth in the
'SRF 200' cultivar. It also may have been due to stem elongation
in the 'Corsoy' cultivar subsequent to fairly heavy lodging which
characterized this cultivar at the Chesaning location. In the
significantly different combined cultivar responses, 'SRF 200' was
slightly taller than 'Corsoy.' The location x cultivar interaction
was significant.

Planting date means were significantly different at the Carleton
location, but the Chesaning means were not. The longer planting date
intervals plus drought effects at Carleton probably accounted for this
significant planting date x location interaction. The Carleton
means for the first, second and third planting dates were 76.6,

58.3 and 44.8 cm, respectively. The significantly different planting
date means were 79.6, 71.1, and 59.3 cm for the first, second and

third dates for the combined locations, respectively. The late

128

planting dates responded with much shorter plants at the Carleton
location which was probably also due to later season drought. Normal
mechanical harvesting of these plants would have been very difficult.

The planting date x cultivar interaction was also significant
at the Carleton location, but at Chesaning this interaction was not
quite significant at the 52 level. Means for both.interactions are
recorded on Figures 1 and 2. One observation of special interest at
Chesaning was the fact that second date plants of 'Evans' and 'Hodgson'
were actually taller than those of the first planting date. This
response again reinforced earlier observations that these cultivars
appeared to respond more slowly vegetatively with the colder first
planting. According to the final yield figures, first date 'Evans'
plants never fully recovered from this apparent slow initial growth
while 'Hodgson' did to some extent, perhaps due to its superior
branching ability. The combined planting date x cultivar interaction
was also significant.

Means for height as influenced by plant density were significantly
different at Chesaning but not at Carleton. Drought effects and
uneven emergence may have masked differences here. Plant heights
at Chesaning averaged 81.8 cm at low density and 78.4 cm at high
density. This response was somewhat surprising since it would have
been expected that the more closely clustered, high density plants
would have been taller. Perhaps lack of soil moisture was an over-
riding factor here, especially for final vegetative growth later in
the season. The plant density means for the combined locations were
also significantly different with values of 70.8 and 69.2 cm for

the low and high densities, respectively. The location x plant

129

density interaction was also significant.

The three-way planting date x row width x plant density inter-
action at Chesaning was significant, and is portrayed in Figure 7.
Only in the instance of the third date, 76 cm row widths was the high
density mean greater than that of the low density. Row width within
planting date and density responses showed a general trend of shorter
plants at wider row widths with three noticeable exceptions. The
second date, low density plants were much taller in the 76 cm width
over the other two row widths. Also, the 76 cm width plants were
slightly taller than those of the 51 cm widths at dates two and three
of the high density treatment. Planting date within row width and
plant density response consistentlyindicated shorter plants at later
dates with one major exception. At both plant densities, the first
date, 76 cm width plants were shorter than those of the second date.
This closely corresponds with the yield response observed both years
at three locations and suggests some vegetative growth disadvantage
for early plantings at this width.

The combined planting date x row width and location x planting
date x row width x cultivar interactions were also significant.
However, due to the lack of significant interactions at either
location and also, due to the widely varying planting dates, the
meaningfulness of these interactions was probably negligible.

Mature plant height had a correlation of 0.56 at Chesaning
and 0.60 at Carleton with overall yield. It was also interesting
to note that the correlation with overall yield was greater than
that with the yields of the sample from which the height readings

were taken at Chesaning, which was 0.45. At Chesaning the number

130

I (N) 25 c.
E] (n) 51 c-
I (u) 76 .-

Date 2

 

 

 

 

 

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m w m w m w m m m

Aluv 5mm: 3 uuP—Zz .

HIGH PLANT DENSI‘H

W PLANT DENSITY

The influence of plant density. planting date and cultivar upon nature plant height

(CI) at the 1978 Gleaaning location. averaged over cultivar.

Figure 7.

131

of mainstem nodes had a correlation with plant height of 0.74.

b. 1979

Plant heights in 1979 at the Chesaning location were 9.2%
greater than those at the same location in 1978. This difference
may have been due in part to the different measuring techniques.
Dundee plant heights were 17.42 higher than those at Chesaning due
to greater rainfall and the vining effects from heavy lodging at
Dundee.

The responses of the two locations were much more similar than
in 1978. At both locations and with the combined locations the
planting date and cultivar means varied significantly, and the
planting date x cultivar interactions were also significant.

Plant heights were 108.5, 111.5 and 88.3 cm at Dundee; 93.3,
89.5 and 79.8 cm at Chesaning; and combined averages were 101.3,
101.1 and 84.4 cm for the first, second, and third dates, respect-
ively. Second date plants were taller than those of the first
date at Dundee while the reverse was true at Chesaning. However,
the order of yield responses to planting date was just the opposite
at the two dates. The planting date x location interaction was
significant.

Cultivar responses are shown in Figure 3. 'SRF 200' plants
were always tallest with 'Corsoy' and 'Beeson' next in plant
height. Of interest is the fact that 'Evans' plant height was
greater than that of 'Hodgson 78,' and 'SRF 250' appeared to be
the shortest cultivar at Dundee. At both locations, the higher

density 'Nebsoy' plants were taller than those at regular density,

- Dundee

D Chesaning

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Hodgson SRF 200 Beeson Nebsoy Nebsoy SRF 250
(1 . 5

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Corsoy

(Regular

78

Density)

Density)

CULT! VA“

Influence of cultivar upon nature plant height (ca) at the 1979 Dundee. Chesaning and cowined

locations, averaged over row width and planting data.

Figure 8 .

133

but the difference was much.greater at Dundee. The fact that the
higher density was taller at both locations may have been due in
part to the postulated drought resistance of 'Nebsoy,’ and the
greater difference at Dundee would probably be the expected response
where rainfall was adequate. The cultivar x location interaction was
significant.

The planting date x cultivar interactions for the two locations
were presented in Figures 3 and 4, while the same interaction for the
combined locations is presented in Figure 9. At Chesaning, a con-
sistent trend of decreasing height with later planting dates was
observed for all cultivars. At Dundee, second date plant heights were
greater than those for the first date for all cultivars but 'Nebsoy'
(Regular). 'SRF 200' was the tallest cultivar at both locations
except for the third date in Chesaning where 'Beeson' was taller.
'Evans' was always shorter than 'Hodgson 78' at Chesaning, but at
Dundee, there was a trend from 'Evans' being shorter than 'Hodgson 78'
at date one to 'Evans' being 8.4% taller at date three. The higher
'Nebsoy' density plants were almost always taller than those at
regular density at Chesaning. The high density plants of 'Nebsoy'
were unusually taller than the regular densitygflants for the second
date at Dundee. Both 'Nebsoy' and 'SRF 200' tended to be fairly
short in comparison to the other Group II cultivars.

The location x row width interaction was also signficant,
even though row width means at the individual locations were not
significantly different. At Chesaning, there was a consistent
trend toward greater plant heights at wider row widths, while at

Dundee, the same trend was observed between plants of the 51 and 76 cm

I nu. One

 

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78 (Regular

Evans

Corsoy

Density)

Density)

CULTIVAR

Mature plant height (cu) in 1979 as influenced by planting date and cultivar.
averaged over location and row width.

Figure 9.

135

row widths, but those of the 25 cm widths were taller than those at
the other two widths.

At Chesaning, mature plant height had the following correlations:
0.64 for emergence to flowering period, 0.51 for flowering to maturity
period, 0.71 for total growing season length, and 0.51 for lodging but
only 0.34 for yield. At Dundee, plant height correlations were 0.47
for emergence to flowering period, 0.60 for flowering to maturity
period, 0.61 for total growing season length, and 0.47 for yield.
Similar correlations for the combined locations were as follows: only
.0.19 for the emergence to flowering period, 0.68 for the flowering
to maturity period, 0.61 for the total growing season length, 0.70

for lodging, and 0.66 for yield.

136

7. Plant Lodging
a. 1978

Little lodging occurred at the Carleton location in 1978,
probably due to drought-shortened plants. However, the significantly
different treatment responses and significant interactions were nearly
the same at both locations. At both locations and in the combined
analysis, treatment means for planting date, row width and cultivar
were significantly different. Also significant were the planting date
x row width, planting date x cultivar, and row width x cultivar inter-
actions. In addition to the above, the planting date x row width
x cultivar interaction was significant at Carleton (Table 24). At
Chesaning and with the combined analysis, plant density means were
significantly different, and the cultivar x plant density interactions
were significant. Main treatment means are presented in Table 25.

With the analysis for the combined locations, the row width x plant
density interaction was also barely significant along with numerous
location interactions.

At both locations, the second date plants lodged more extensively
than those of the first as well as of the third date. A consistent
row width trend occurred at both locations with the wider widths having
more lodging. However, the difference between 51 and 76 cm widths
was much larger than that between 25 and 51 cm row widths. At both
locations, high plant densities lodged more extensively than low
densities, as would be expected. The taller, later maturing cultivars,
'Corsoy' and 'SRF 200,' lodged more than did the early maturing 'Evans'
and 'Hodgson.' 'Hodgson' lodged more than did 'Evans' at both loca—

tions. At Carleton, 'SRF 200' lodged slightly more than did 'Corsoy'

137

 

 

 

 

 

 

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139

while the reverse was true at Chesaning. These cultivar lodging
responses closely paralleled those of plant height. All location
interactions with the main treatments were significant.

Because Carleton lodging means were so low, little reference
will be made to them in the narrative and the results may be observed
in the applicable tables and figures. The significant row width x
planting date interaction at Chesaning, portrayed in FigurelO, showed
a trend of more lodging at wider row widths within each planting date.
Lodging of the 25 and 51 cm row widths showed steady decreases with
later planting dates, while lodging of the 76 row widths went up
dramatically from first to second dates, and then down even further
to a third date level below that of the first. The Carleton inter-
action also revealed this sharp second date increase for 76 cm widths.

At Chesaning the significant cultivar x row width interaction
revealed a consistent rise in lodging at wider row widths for each
cultivar (Figure 11). At each row width, 'Corsoy' lodged the most,
followed by 'SRF 200,' then 'Hodgson' and 'Evans.' The 76 cm widths
of 'Evans' lodged slightly more than the corresponding width of
'Hodgson.' Figure 12 indicates the significant planting date x
cultivar interactions. The early maturing cultivars lodged most
at date two, followed by dates one and three in that order. This
response corresponded with plant height for these cultivars. How-
ever, the Group II cultivars responded with decreased lodging at
later dates, as would more normally be expected. The order of
cultivars within dates generally remained the same as above, except

that the second date 'Evans' plants lodged more than did the second

LODGING RATINGS

2.3..

2.2-

2.1

2.0

1.9

1.8

1.7

1.6-

1.5-

1.4-

1.3

10L

1.1-

 

1.0J

 

140

[:1 Chesaning

 

 

 

   

 

 

 

 

 

 

 

 

  

 

'-
N'll W N 14 W N 11 W
Date 1 Date 2 'Date 3

 

Figure 10. Plant lodging as influenced by row

width and planting date at both 1978
locations, averaged over cultivar and
plant density (1 . all plants upright,
5 . all plants prostrate).

LUDGI NG RATINGS

2.6

2.5

2.4

2.3

2.2

2.1

2.0

1.9

1.8

1.7

1.6

1.5

1.3

1.2

1.1

1.0

141

Chesaning

Carleton

25 cm
31 cm
76 cm

:::z:z 'II [:1

 

 

 

 

 

 

 

 

 

 

 

 

 

   

N 1i W N Bi W N bi W N ll W

Corsoy Evans Hodgson SRF 200
CULTIVAR

Figure 11. Influence of row width and cultivar upon plant
lodging at both 1978 locations. averaged over plant
density and planting date (1 - plants upright,

5 - all plants prostrate).

LODGING RATINGS

' 1.2.4

2.6 .

2.5 a

2.34
2.2 ..
2.1 ..
2.0 .
1.9 _
1.8..
1.67
1.6J
1.5 .
1.4. 1

1.3 4

1.1 d

142

 

 

 

 

 

 

 

 

 

 

 

 

1.0 J

 

._—
[:1 Chesaning
I Carleton
1 Date One
2 Date Two
3 Date Three
H
— —
l 2 3 l 2 3 l 2 3 I. 2 3
Corsoy Evans Hodgson SRF 200
CULTIVAR

Figure 12. Plant lodging as influenced by planting
date and cultivar at both 1978 locations.
averaged over row width and plant density
(1 - all plants upright. 5 - all plants
prostrate).

143

date 'Hodgson' plants. The significant plant density x cultivar inter-
action at the Chesaning location is portrayed in Figure 13. All culti-
vars lodged more at the high than the low density. Within each density
'Corsoy' always lodged more than 'SRF 200' and 'SRF 200' always lodged
more than the other two cultivars. However, 'Evans' lodged less than
'Hodgson' at low density and slightly more than 'Hodgson' at high
density. This reversed response was somewhat reflected in the plant
height response.

Lodging had a correlation of 0.51 with plant height at Chesaning
but no significant correlation existed with yield. No correlations
with lodging were above 0.50 at Carleton or with the combined location

means a

b. 1979

Almost complete lodging occurred at Dundee in 1979 in comparison
to almost none at Carleton in 1978. The significantly different
treatment responses and significant interactions were nearly the same
at both locations, even though lodging levels were quite different.
Planting date, row width and cultivar means were all significantly
different at both locations and for the combined locations. The
planting date x row width, planting date x cultivar, and planting
date x row width x cultivar interactions were also significant for
the above analyses. The location interactions with all the above
treatments and interactions were also significant in the combined
location analysis. At Dundee, the row width x cultivar interaction
was significant.

Main treatment means are presented in Table 25. Lodging

responses to planting date closely reflected plant heights at the

 
    

     
 

    

      

 

 

     
 

 

  

 

 

     

 

144

 
    

 

              
 

   

 

  

 

 

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Figure 13.

Influence of cultivar and plant density

upon plant lodging at the 1978 Chesaning
and combined locations, averaged over row

width and planting date (1 - all plants
upright, S - all plants prostrate).

14S

respective locations. At Dundee, the second date lodged more than did
the first or third as in 1978. However, at Chesaning, the first date
lodged more than the other two. At both locations, the 51 cm row
widths lodged less than the 76 cm widths, as in 1978. However, the

25 cm widths lodged more than the 76 cm widths, probably due to the
high plant density at the 25 cm width. This response may aid in
explaining the reduced 25 cm row width yields in comparison to those
of 51 cm widths in 1979. As in 1978, 'Corsoy' lodged slightly more
than 'SRF 200' at Chesaning while the reverse was true at the southern
location. 'Evans' lodged more than 'Hodgson 78' at Dundee which
correlated with its higher plant height there. 'SRF 250' lodged

least at Dundee followed by 'Nebsoy’ (Regular Density). 'Nebsoy'
(Regular Density) lodged the least in Chesaning.

The significant row width x planting date interactions in
Figure 14 reveals the following departures from the main treatment
trends noted above. The 25 cm widths at Dundee responded consistently
with decreased lodging at later planting dates. Also at Dundee, the
25 cm widths lodged more than the other two only at the first planting
date, where 76 cm widths also lodged less than did 51 cm widths. At
Chesaning, 25 cm widths lodged less than 76 cm widths at the third
date.

The significant planting date x cultivar interactions are
presented in Figure 15. At Dundee, there was a fairly consistent trend
of reduced lodging at later planting dates except for the 'Evans,'
'Hodgson 78' and 'Nebsoy' (1.5 Density) cultivars where the second

date plants lodged the most.

LODGING RATINGS

4.9..
4.6-
4.3
4.0..
3.7-
3.4.,
3.1..
2.8..
2.5_
2.2 ..
1.9 -

1.6

1.3 -

1.0 -

 

146

Dundee

Chesaning

 

25 cm
51 cm
76 cm

I
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.............

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............

 

   

 

ll 14 W N PI W N )1 W
Date 1 Date 2 Date 3

Figure 14. Plant lodging as influenced by row
width and planting date at both 1979
locations, averaged over cultivar
(l - all plants upright, 5 - all plants
prostrate).

147

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148

Widely varying responses occurred in the significant row
width x planting date x cultivar interactions at both locations
(Table 26) and in the significant cultivar x row width interaction at
Chesaning (Figure 16).

At Chesaning, lodging had a correlation of 0.51 with plant
height, but no significant correlation with yield occurred. The same
correlation with plant height at Dundee was 0.69 and again there was
no significant correlation with yield. When locations were combined,
lodging had the following noteable correlations: 0.59 with the
flowering to maturity period, 0.58 with 100 seed weight, and 0.70
with plant height.

In 1979, early lodging readings were also recorded for the
first and second dates at the Dundee location on August 1. Date two
had lodged significantly less than date one with ratings of 2.13 and
2.92, respectively, as would have been expected since readings were
not taken at the same developmental stage for each date. Cultivar
means were also significantly different. They were 3.52, 3.09, 2,85,
1.46, 1.87, 2.56, 3.79 and 1.06 for 'Corsoy,' 'Evans,' 'Hodgson 78,'
'SRF 200,' 'Beeson,' 'Nebsoy' (Regular Density), 'Nebsoy' (1.5
Density) and 'SRF 250,‘ respectively. For the same cultivars above
in respective order, the differences between early and final lodging
ratings were 1.23, 1.34, 1.62, 3.44, 2.96, 1.78, 1.03 and 3.44 and the
percentages of final ratings represented by early lodging ratings
were 73.9, 69.6, 63.8, 29.8, 38.6, 59.1, 78.8 and 23.6. 'Corsoy,'
the two 'Nebsoy' densities, and the early maturing cultivars had

the highest early lodging ratings. They also experienced the

149

 

 

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(Regular

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Density)

CULTIVAR

Plant lodging as influenced by cultivar and row width at the l979 Dundee location. averaged over

Figure 16 .

planting date (l - all plants upright. 5 - all plants prostrate).

151

highest percentages of the final lodging at this time. The higher
'Nebsoy' density had much.more early lodging than did the regular
density, and the two 'SRF' cultivars evidenced noticeably low amounts
of early lodging.

The significant planting date by cultivar interactions for

both early and final lodging at Dundee are presented in Figure 17.

152

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153

8. Internode length

 

By combining mainstem nodes and plant height, it was possible
to calculate and analyze mainstem internode lengths. In 1978 planting
date means were not significantly different but those for row width,
plant density and cultivar were. The row width response was 5.31,
5.64 and 5.91 cm for 25, 51 and 76 cm widths, respectively. This
response seems to indicate that plants in closer proximity to one
another as in 76 over 25 cm widths, tend to have greater stem elongation
between nodes. This is further supported by the plant density response
where the low and high densities had internode lengths of 5.45 and
5.79 cm, respectively. Cultivar responses were 5.74, 5.43, 5.71, and
5.60 cm for 'Corsoy,' 'Evans,' 'Hodgson' and 'SRF 200,' respectively.
Internode lengths for 'Hodgson' were quite high in comparison with
the longer season 'Corsoy' and 'SRF 200.‘ The planting date x cultivar
interaction was also significant in 1978.

In 1979, planting date, row width and cultivar responses were
all significant. The planting date response was 5.92, 5.70 and
5.52 cm for the first, second and third dates, respectively. Row
width responses for 25, 51 and 76 cm widths were 5.64, 5.63, and 5.86,
reapectively. Internode lengths for 25 cm widths were not less than
those for 51 cm widths, probably because higher plant densities at
the 25 cm widths offset the more equidistant plant spacings at that
row width. Cultivar responses were 6.00, 5.76, 5.82, 5.60, 5.44,
5.32 and 6.04 cm for 'Corsoy,' 'Evans,' 'Hodgson 78,' 'SRF 200,'
'Beeson,' 'Nebsoy' (Regular Density)and 'Nebsoy' (1.5 Density),

respectively. The effects of plant density were here apparent since

154
internodes for 'Nebsoy' (Regular Density) were shortest and for
'Nebsoy' (1.5 Density) were longest of the cultivar treatments. No
interactions were significant in 1979 and no correlations were of

interest either year.

155

C. Reproductive Development

 

All reproductive development measurements, except some 100 see
weights, were derived from the yield component samples obtained from
the 1978 and 1979 Chesaning locations. As noted before, the sample
yields did not correlate very highly with overall plot yields. There-
fore, only significant main treatments results and a few significant
interactions of interest will be discussed. In some cases, signif-
icantly different main treatment means will not be mentioned in the
narrative, but may be determined from the applicable tables. All
correlations listed were significant and above 0.50. A correlation
listed one year and not the next for the same measurement may be
assumed to have been below 0.50 the year for which it was not listed.
Any further analyses may be derived by utilizing the raw data presented
in Tables A5, A5 and A7. The main treatment, sample yield means are

included in Table A2 for reference.

1. Pod Numbers

 

Pod numbers per plant, presented in Table 27, surprisingly
were not significantly different for planting dates either year.
This would seem to indicate that within the range of planting dates
used, the plants tended to produce essentially the same number of
total pods, and that yield differences for planting dates were due
to other factors. Row width means for pods per plant were signifi-
cantly different both years, but the trend was reversed in 1979 from
that in 1978. Plant density responses for pods per plant in 1978
were also significantly different. This density response perhaps
helps explain the reversed 1979 row width response, since plant

densities were higher at the narrower widths. Significant cultivar

156

 

 

 

 

 

 

 

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157

mean differences for pods per plant hoth.years are.also presented in
Table 27. 'SRF 200' tended to have lower pod numbers, as also did
'Beeson‘ which perhaps was an indication of greater potential yield
reductions with adverse pod filling conditions. In 1978, the row
width.x plant density interaction was also significant and responded
with trends consistent with.those.of the main.treatments.

Pod number per Plant correlations in 1978 were 0.83 with.total
nodes per plant, 0,89 with.yields per plant derived from the samples,
0.58 with.mainstem nodes per plant, 0.80 with branch.nodes per plant,
and 0.75 with.branch_number per Plant. In 1979 pod numbers per plant
had correlations of 0.81 with.yields per plant derived from the samples,
0.64 with.total nodes per plant, 0.72 with.branch.nodes per plant and
0.63 with branch number per plant.

Table 27 also reveals that pods per plant node responded in a
manner similar to that of pods per plant, except for some.cultivar
differences, evidently due to varying numbers of nodes characterizing
individual cultivars. Planting date differences were significant
and indicated more pods per node at later dates, evidently due to '
the fact that, although.pod numbers varied little, node numbers
decreased with later dates. The planting date x cultivar interaction
was also significant in 1978. In.1979, pods per overall plant node
had a correlation of 0.51 with total days in the.growing season.

When pod numbers per plant were extended to pod number per
land area sz) using the forced sample spacings, only row width-
and cultivar means were significantly different (Table 27). Plant
density mean differences in 1978 were.negated in this manner so that

they were no longer significant. Of special interest is the fact

158
that the row width response of pods per land area was the opposite of
that for pods per plant which.reflected the different plant densities
which were at each width. The rankings of cultivars varied only
slightly from those for pods per plant.

Total plant pods were also separated into branch and mainstem
pods. Table 28 presents treatment means for branch pods per plant node,
per plant and per land area (m2), and also for the percentages of total
pods being pods on branches. Planting date differences were not sig-
nificant for any of the above measurements except percentage of branch
pods in 1979, when the percentage was lowest for the second date. Row
width response again tended to be reversed in 1979 and 1978. Branch
pods per land area were still less at the 25 cm row width.in 1979 than
at the other widths which would seem to indicate that the higher
plant densities at this width had more influence upon branch pod numbers
than upon total pod numbers. In 1978, the row width x plant density,
planting date x cultivar and row width x cultivar interactions were
significant for branch pods per plant and per land area (m2), and
also for percentage branch pods. The planting date x row width x plant
density x cultivar interaction for percentage branch.pods was also
significant in 1978. In 1979, the planting date x row width x cul-
tivar interaction was significant for all four of the branch pod
measurements. In addition to the above, the planting date x cultivar
and row width x cultivar interactions were significant for branch
pods per branch node, and the planting date x cultivar interaction
was significant for percentage branch pods.

Branch pods per plant had correlations of 0.75 with sample

yields per plant, 0.86 with total nodes per plant, 0.95 with branch

159?

 

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160

nodes per plant, and 0.90 with branch number per plant in 1978. In
1979 correlations were 0.62 with sample yields per plant, 0.65 with
total nodes per plant, 0.85 with branch nodes per plant, 0.75 with
branch number per plant, 0.57 with mid-canopy PAR readings, and 0.56
with the difference between mid-canopy and ground level PAR readings.
There were no interesting correlations above 0.50 for branch.pods per
branch node in 1978, and those in 1979 were similar to those for branch
pods per plant.

Table 29 presents the main treatment means for mainstem pods
per mainstem node, per plant and per land area (m2). All main treatment
means were significantly different. Planting date responses for all
three measurements were similar both years. The first date had the
least mainstem pods for all measurements. The second date plants had
more mainstem pods per plant and per land area (m2) than did those of
the third date, but the reverse was true for mainstem pods per mainstem
node. This indicates that plants in the second data had more total
nodes on mainstems. In 1979 the reversed row width response between
mainstem pods per plant and mainstem pods per land area (m2) indicated
that the high density influences at 25 cm row widths were not as severe
upon mainstem pod numbers as upon branch pod numbers where this
reversal did not completely take place. In 1978, the planting date
x cultivar interaction was significant for all three mainstem pod
measurements.

Mainstem pods per plant had correlations of 0.78 with sample
yields per plant, 0.59 with.total nodes per plant, and 0.59 with main-
stem nodes per palnt in 1978. In 1978 the correlations were 0.79 with

sample yields per plant and 0.52 with total nodes per plant.

16].

 

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162

2. Seed Numbers

 

Main treatment means for seeds per pod, per node, per plant and
per land area (m2) are presented in Table 30. Seed numbers were highest
at the second date for the four measurements where significant. This
response along with that for pod numbers may aid in explaining why
yields were higher at the second date than at the first in 1979. The
same reversed row width response occurred between 1978 and 1979 as
occurred with pods. Of special interest is the fact that seeds per
pod were much higher for 'SRF 200‘ than for the other cultivars which
may have balanced the low pod numbers for this cultivar. Seeds per
node in 1978 and seeds per plant and per land area (m2) in 1979 were
highest for 'SRF 200' also. The planting date x plant density inter-
action was significant for seeds per pod in 1978. Also in 1978, the
planting date x cultivar interaction was significant for seeds per
node, the planting date x row width x cultivar interaction was signifi-
cant for seeds per land area (m2), and the row width x plant density
and planting date x row width x cultivar interactions were significant
for seeds per plant.

The 1978 correlations with seeds per plant were 0.96 with
sample yields per plant, 0.83 with total nodes per plant, 0.69 with
mainstem nodes per plant, 0.74 with branch nodes per plant, 0.91 with
total pods per plant, 0.83 with mainstem pods per plant, 0.72 with
branch pods per plant, and 0.66 with number of branches per plant.

In 1979 the correlations were 0.91 with sample yields per plant,
'0,67 with'total nodes per plant, 0.64 with‘branch nodes per plant,
R0.84 with total pods per.plant, 0.82 with mainstem’pods per plant,

0.64 with branch pods per plant and 0.59 with branch.numbers per plant.

1623

 

 

 

 

 

 

 

 

 

 

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164

3. Seed Weights

 

Weights of randomly selected 100 seed samples (g) were recorded
for the 1978 Chesaning location, and for both 1979 locations. The 100
seed weights were 2.28 g lower at the 1979 Chesaning location than at
the 1978 Chesaning location for the four cultivars grown both years.
This general response would seem to indicate that conditions during
podfill were more unfavorable in 1979 than in 1978. The main treatment
means are listed in Table 31.

As would be expected, 100 seed weights decreased with later
planting dates, but there was little difference between dates one and
two. This response would seem to indicate that podfilling was not
seriously restricted until the growing season was noticeably shortened.
However, it may also be true that due to unfavorable early season con-
ditions, the first date response was not as large as it might have been.
Row width differences were significant only at Dundee in 1979. The
25 cm widths had slightly lighter seed than did the 51 cm widths,
perhaps due to the higher plant density at the 25 on row width. This
explanation is reinforced by the fact that the 1978 Chesaning plant
density response was one of heavier seed at lower densities. Although
'SRF 200' tended to have more seeds per pod, it also tended to have
lighter seed than did 'Corsoy, 'Evans' or 'Hodgson(78)'. 'Beeson'
tended to have quite heavy seed in comparison to the other cultivars
which would tend to disprove the earlier premise that 'Beeson's'
reduced Yields were due to the late season dry period in 1979, although
it is not possible to determine what the relative 100 seed weights
would have been if the September dry period had not occurred in 1979.

However, at the drier 1979 Chesaning location, 'Beeson' was 12.4%

165

 

 

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166

heavier than the second ranking ‘Hodgson 78' cultivar, while at

the more moist Dundee location it was only 7.92 heavier which would
seem to indicate that podfilling factors were not the primary cause
for the poor 'Beeson' yield response.

At the 1978 Chesaning location, the planting date x cultivar
and planting date x row width x cultivar interactions were significant,
while at the 1979 Dundee location the planting date x cultivar inter-
action was also significant. When the two 1979 locations were combined
in one analysis, the location x row width, location x cultivar, planting
date x cultivar, and planting date x row width x cultivar interactions
were significant.

Weights of 100 seed samples had correlations of 0.60 with total
days of growing season and 0.55 with the flowering to maturity period
at the 1979 Chesaning location. At the 1979 Dundee location, there
was one correlation equal to or over 0.50 which was 0.50 with the
flowering to maturity period. When the two 1979 locations were
combined, correlations were 0.62 with overall plot yield, 0.54 with
total growing season days, 0.67 with the period from flowering to
maturity, 0.60 with mature plant height and 0.58 with lodging.

As noted before, Table A2 contains the main treatment means
for sample grain yields in grams per plant and per land area (m2) for
the 1978 and 1979 Chesaning locations. Table AZ also contains sample
grain weights for the same locations expressed in grams per pod and
per node. The weight per pod tended to remain constant for the first
two planting dates and then decreased sharply between the second and

third. Weights per node were greatest for the second date. The

167

reversed row width trend between 1978 and 1979 was again observed for
weight per node. Weight per pod was not significantly different for the
two plant densities in 1978, but low density weight per node was higher
than that at the high.density. 0f the four cultivars grown both years,
'SRF 200' had the.highest seed weight per pod both years, but had the lbwest
weight per node in 1979. This latter 1979 response may help explain
the poor overall yield of 'SRF 200' for that year. In 1978 for the
seed weight per pod, the planting date x plant density, planting date
x cultivar, planting date x plant density x cultivar and planting date
x row width x plant density x cultivar interactions were all significant.
The planting date x row width.and planting date x cultivar interactions
were also significant for seed weight per node in 1978 as was the row
width x cultivar interaction in 1979.

In 1978, seed weight per pod had a correlation of 0.83 with
seed number per pod. In 1979 it had correlations of 0.54 with 100
seed weight, 0.56 with mature plant height, 0.54 with mainstem nodes
per plant, 0.74 with seed number per pod, 0.59 with total growing season
days, and 0.59 with the period from flowering to maturity. In 1978,
seed weight per node had correlations of 0.86 with seed number per
node, 0.58 with seed number per plant, 0.63 with total pods per node,
0.61 with mainstem pods per plant and 0.65 with mainstem pods per
mainstem node. Correlations of 0.85 with seed number per node, 0.70
with mainstem pods per plant, 0.75 with seed number per plant, 0.62 with
overall pods per plant, 0.64 with mainstem pods per mainstem node, and
0.63 with total pods per node were computed for seed weight per node

in 1979.

168

4. Percentages of Whole Plant Yield and Other Responses
of Evenly—Divided One-Third Sections of Sample Plants

 

Yield component plant samples from the 1979 Chesaning location
were subdivided into three equal sections (bottom, middle and top) for
the 'Hodgson 78,' 'SRF 200' and 'Beeson' cultivars. Divisions were
not only across mainstems but also across any branch passing through
a plane perpendicular to the mainstem axis. For counts of branch
numbers, branches were considered to be associated with a particular
section if attached to the mainstem of that section. However, branch
pods and nodes from detached branch sections were included with the
plant portion with which they were found.

Percentage yield responses of each section in comparison with
whole plant grain yields are portrayed for cultivars in Figure 18 and
for row widths in Figure 19. Cultivar differences were significant
for all three plant portions. 'Hodgson 78' plants produced the highest
percentage yield in the bottom plant portions followed by 'SRF 200'
and 'Beeson' plants. This order is the same as that observed for the
difference in PAR penetration at mid-canopy and ground level for these
cultivars with 'Hodgson' having the highest percentage PAR intercepted -
between the two reading levels. It might be that the greater PAR
levels at low canopy heights may have contributed to these higher
percentage yield responses of the bottom plant portions. 'SRF 200'
plants had lower percentage responses for the middle portions and
higher percentage responses for the top portions than did the other
two cultivars. This may have been due partly to lower branching

levels with the 'SRF 200' cultivar.

1 OF TOTAL SEED WEIGHT/PLANT

7O

60

50

40

 

169

§§ Bottom

 

 

 

 

.....

.....

.....
.....
.....

......

......

......

.....

......

.....

.....

.....

.....

.....

 

 

 

 

 

Hodgson SRF 200

78 CULTIVAR

Figure 18. Influence of cultivar upon percentages
of sample whole plant seed yields produced
by one-third plant sections at the 1979
Chesaning location, averaged over all
other factors.

2 OF TOTAL SEED WEIGHT/PLANT

70

60

50

40

30

20

10

 

.....
......
......
......
.....

......

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.....
.....

.....

 

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Figure 19 -

25

170

 

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us
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51

.....

ROW WIDTH (cm)

 

 

.....

......
......

.....

 

Bottom

Percentages of sample whole plant seed

yields produced by one-third plant sections
as influenced by row width at the 1979

Chesaning location, averaged over all other
factors.

171

Row width percentage yield responses were significantly
different only for the bottom plant portions (Figure 19). Bottom
portions had increasing percentage yield responses with increasing
row widths. Row width responses paralleled PAR penetration readings
in the same manner as did cultivar responses.

Percentages of whole plant totals are listed for each plant
portion in Tables 32and 33 for branch nodes, mainstem pods, branch
pods, total pods and branch numbers, as influenced by the main treat-
ment. Percentages of mainstem nodes in each plant third were not
included, since equal plant divisions were based upon mainstem nodes.
Essentially all row width percentage responses were not significantly
different nor were the top portion planting date responses. Second
date plants tended to have higher percentages of branches, branch nodes
and pods associated with bottom plant portions than did the other two
dates. 'Hodgson 78' had a higher percentage of mainstem and total
pods associated with bottom plant portions than did the other two
cultivars, and 'SRF 200' was second which may aid in explaining the
percentage yield response for these cultivars. 'Hodgson 78' had lower
percentage responses of branch nodes and pods associated with bottom
plant portions than did 'SRF 200,' but the percentage of total pod
responses indicated that branch pods were a relatively small fraction
of the total. 'SRF 200' also had a lower percentage response of
mainstem pods associated with middle portions and a higher response
with top portions than did the other cultivars which may aid in
explaining its variant percentage yield response for these plant

portions.

1I72

 

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174

Table 33 also contains main treatment responses of seed weights
(g/node) and seed weights (g/pod) for the three plant portions. Bottom
portions tended to have higher weights at wider row widths and with
the 'Hodgson 78' cultivar versus the other cultivars, while 'SRF 200'
top portions tended to have higher weights than the other cultivars.
These responses again parallel yield responses.

Branch pods per branch node, mainstem pods per mainstem node and
overall pods per overall node main treatment responses of plant thirds
are listed in Table 34 . Again, responses for bottom portions tended
to be higher for wider row widths and for the 'Hodgson 78' cultivar
compared to other cultivars.

The planting date x cultivar interaction was significant for
percentages of branch pods associated with the bottom and middle
portions, for percentages of branches associated with the middle
portion, and for branch pods per branch node for the middle portion.
The planting date x row width interaction was also significant for
percentages of branches associated with the middle portion, and the
planting date x row width x cultivar interaction was significant for
the branch pods per branch node characterizing the middle plant portion.

Some correlations of interest for the percentage of seed yields
associated with each plant portion are as follows. Correlations for
percentage of plant seed yields associated with the bottom plant
portion were -0.59 with the height of the lowest mainstem node to
which a pod or pod-bearing branch was attached, -0.66 with the number
of the lowest mainstem node to which was attached a pod or pod-
bearing branch, 0.87 with mainstem pods associated with the bottom

portion, 0.71 with branch pods associated with the bottom portion,

175

 

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176

0.88 with percentage of plant mainstem pods associated with the bottom
portion, 0.52 with overall pods per plant, 0.60 with mainstem pods per
mainstem node, 0.57 with branch pods per branch node, and 0.62 with
overall pods per overall node.

Correlations for percentages of seed yields associated with
the middle plant portion were 0.80 with percentage of plant mainstem
pods associated with the middle portion and -0.69 with percentage of
mainstem pods associated with the top portion.

Finally, correlations for percentages of seed yields associated
with the top plant portion were -0.50 with mainstem pods associated
with the bottom portion, —0.52 with seed weights associated with the
bottom portion, -0.61 with mainstem pods associated with the middle
portion, -0.52 with seed weights associated with the middle portion,
-0.68 with percentage of plant mainstem pods associated with the
middle portion and 0.85 with percentage of mainstem pods associated

with the top portion.

 

177

 

5. Height and Number of the Lowest Mainstem Node to
Which was Attached a Pod or Pod-Bearing Branch

 

A factor of particular interest in avoiding harvest losses is the
height and also the number (counting up from the ground level) of the
lowest mainstem node to which.is attached a reproductive structure, or
reproductive supporting structure, since mechanical harvesting neces-
sitates the severing of the mainstem at a small distance above the
ground surface. These measurements were recorded using the yield
component samples from the 1978 and 1979 Chesaning locations. Table 35
contains the main treatment responses for the height and number of this
critical mainstem.node both years.

Planting date responses were significantly different for the
number of this lowest reproductive mainstem node, but not for its
height. This would possibly suggest that planting date differences
affected most directly the nodes which supported reproduction, rather
than the height of that production of reproductive structures. For
both years, the number of this critical node dropped with later
planting dates as might be expected, since later date plants were
shorter and had fewer total mainstem nodes available for reproduction.

Row width responses were significantly different for the
height of the lowest reproductive mainstem node both years, but
were significantly different for the nodal number of this node only
in 1979. In 1978, heights increased with wider row widths. This
was true even though PAR levels were higher in the lower canopy of
wider row widths which might have been expected to have resulted in
lower padding, since percentages of plant yields were higher for

bottom portions of plants in wide rows. The row width height response

 

1J78

 

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179

for 1978 would seem to suggest that the nearer proximity of plants to
one another in the wider row widths was the dominant factor in this
response. The 1979 node height response to varied row widths was
similar between the 51 and 76 cm widths, but the 25 cm width had a
much higher height which was evidently a response to the higher plant
densities at that width. The 1978 plant density responses evidenced
a similar trend of increased height and nodal number of the critical
node at higher plant densities.

Cultivar responses were significantly different for both height
and nodal number of the lowest reproductive mainstem node in both
years. Longer season cultivars tended to have greater heights and
longer nodal numbers than the shorter season cultivars. This may
partly be the result of the fact that plant heights of shorter
season cultivars were shorter also. 'SRF 200' consistently had
larger heights and nodal numbers than did 'Corsoy' both years, even
though 'SRF 200' plants were shorter than those of 'Corsoy' in 1978.
'Nebsoy' (Regular Density) means were lower than those for 'SRF 200'
and 'Beeson' in 1979, but the 1.5 density treatment of 'Nebsoy'
resulted in means well above those of any other cultivar. The
cultivar responses would seem to indicate that these traits may be
both genetically inherent and also modulated by the proximity of
neighboring plants. Another note of interest is that when the
1979 responses of four cultivars grown in 1978 were segregated out,
the average height of the lowest reproductive support mainstem node
was less in 1979 (13.48 cm) than in 1978 (14.96 cm) even though
plants were taller in 1979 than in 1978. ‘The reverse was true for

annual averages of the nodal number means for those four cultivars

 

180

with the 1979 average value (4.84) slightly higher than that in
1978 (4.60).

In 1978, the cultivar x planting date interaction for height
of the lowest reproductive mainstem node was significant and is
graphically portrayed in Figure 20. The trends of planting date
responses were the same for all cultivars, but 'Hodgson' and 'SRF
200' appeared to vary relatively little at different dates in
comparison to 'Corsoy' and 'Evans.' The plant density x row width
interaction for nodal number was also significant in 1978 and is
portrayed in Figure 21. One interesting observation is that the
nodal number for the high plant density was higher at 25 cm row widths
than at 51 cm widths.

The 1979 cultivar x planting date interaction in Figure 22
for nodal number was also significant, and revealed widely varying
planting date responses for the cultivars.

Correlations for nodal height in 1978 were -0.55 with branch
nodes per plant, -0.55 with branch pods per plant, -0.59 with number
of branches per plant, -0.60 with overall pods per plant, -0.60 with
mainstem pods per mainstem node, and -0.55 with overall pods per
overall node. In 1979 correlations were -0.50 with mid-canopy PAR
readings, -0.61 with branch nodes per plant, -0.54 with mainstem
pods per plant, -0.69 with branch pods per phant, -0.58 with number
of branches per plant, -0.50 with seed yields per sample plant, -0.54
with seed number per plant, -0.67 with overall pods per plant, -0.64
with mainstem pods per mainstem node, -0.67 with branch pods per
branch node, —0.55 with overall pods per overall node, -0.68 with

percent branch nodes of total nodes, -0.71 with percent branch pods

 

181

Date One
Two
- Date Three

U

 

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1.3 :53:

Evans

CULTIVAR

Influence of cultivar and planting date upon the
height of. the lowest mainstem node bearing either a
location. averaged over row width and plant density.

pod or pod-bearing branch at the 1978 Chesaning

Figure 20.

NODAL NUMBER

 

 

182

B High Density

I Low Density

 

 

 

 

 

 

 

51

ROW WIDTH (cm)

Figure 21. Nbdal number of the lowest mainstem
node bearing either a pod or pod-bearing
branch as influenced by row width and
plant density at the 1978 Chesaning
location, averaged over planting date and
cultivar.

 

. DateOne

I Date Three

183

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Density)

CULTIVAI

Nodal number of the lowest mainstel node bearing either a pod or pod-bearing

Figure 22.

branch as influenced by planting date and cultivar at the 1979 Chesaning location.

averaged over row width.

 

184

of total pods, and -O.50 with the simple difference between the mid-
canopy and ground level PAR readings.

Correlations for nodal number in 1978 were -0,89 with height of
the lowest mainstem node to which.was attached a pod or pod-bearing
branch, -0.57 with mainstem pods per mainstem node, -0.53 with overall
pods per overall node and -0.54 with percent branch nodes of total
nodes. And the nodal number correlations in 1979 were -O.58 with
mid-canopy PAR readings, 0.89 with nodal height of the lowest mainstem
node to which was attached a pod or pod-bearing branch, -0.53 with
branch nodes per plant, -O.68 with branch pods per plant, -0.50 with
number of branches per plant, -0.61 with overall pods per plant, -0.67
with mainstem pods per mainstem node, -0.70 with branch pods per branch
node, -O.61 with overall pods per overall node, -0.63 with percent
branch nodes of total nodes, -0.70 with percent branch pods of total
pods, 0.50 with total growing season length and -0.59 with the simple

difference between mid-canopy and ground level PAR readings.

 

185

6. Productive Nodes and Mainstem Lengths, and
Related Measurements

By subtracting the height and nodal number measurements of the
lowest mainstem node to which.was attached either a pod or podwbearing
branch from the total plant height, and from the total mainstem and
overall nodes per plant, respectively, it was possible to obtain the
length of portion of the mainstem directly supporting reproduction'
(productive mainstem) and the number of mainstem and overall nodes
above the nonproductive bottom nodes (productive nodes). Thus, these
measurements were actually vegetative in nature, but dependent upon
the reproductive response of the plant.

Table 35 lists the main treatment responses of productive main-
stem lengths and of number of productive mainstem nodes per plant for'
both years. The planting date x cultivar and planting date x row
width x cultivar interactions were significant both years for pro-
ductive mainstem lengths. The planting date x row width.and planting
date x cultivar interactions were significant for productive mainstem
nodes in 1978. Correlations for productive mainstem lengths in 1978
were 0.76 with mainstem nodes per plant, 0.71 with.mainstem pods per
plant, 0.72 with seed yields per sample plant, 0.68 with.seed numbers
per pod, 0.66 with.overall pods per plant, 0.64 with overall nodes
per plant and 0.62 with overall plot yield. In 1979 correlations for
productive mainstem lengths were 0.55 with.mainstem nodes per plant,
0.62 with seed yields per sample plant, 0.62 with overall nodes per
plant, 0.61 with productive overall nodes per plant, 0.71 with.pro-
ductive mainstem nodes per plant and —O.52 with.plants per land area

(m2). Productive mainstem nodes per plant in 1978 had correlations

 

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187

of -0.54 with height of the lowest reproductive support mainstem

' node, 0.71 with branch nodes per plant, 0.76 with mainstem pods per
plant, 0.65 with branch pods per plant, 0.67 with number of branches
per plant, 0.87 with seed yields per sample plant, 0.84 with seed
numbers per plant, 0.84 with overall pods per plant and 0.79 with
productive mainstem 1ength.per plant. In 1979 correlations were 0.56
with the height of the lowest reproductive support mainstem node, 0.67
with branch nodes per plant, 0.64 with mainstem pods per plant, 0.51
with branch pods per plant, 0.62 with number of branches per plant,
0.77 with seed yields per sample plant, 0.77 with seed number per
plant, 0.66 with overall pods per plant, -0.56 with plants per land
area (m2) and 0.71 with productive mainstem length per plant.

The main treatment responses of other related measurements are
listed in Tables 36 and 37. These include internode length of the
productive and nonproductive mainstem portions, mainstem pods per
productive mainstem node, seed number per productive overall node,
and seed weight per productive node. The planting date x cultivar
interaction was significant for all five above measurements in 1978.
However, in 1979 the row width x cultivar interaction was significant
only for seed numbers and seed weight per productive overall node.
Internode lengths of the productive mainstem portions had almost no
correlations over 0.50 while the internode length of the nonproductive

mainstem portion had many correlations over 0.50, most of them negative.

 

1138

 

 

 

 

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189

III. Planting Systems

This experiment was not only designed to test responses to
individual planting practices, but also to compare responses to
complete planting systems. Since plant density yield responses in
1978 were not significantly different, the density response was
averaged for 1978 means in computing overall responses. Responses
of 36 planting systems averaged over both years are presented in
Table-33 in.order of yield from highest to lowest. Overallresponses
to the planting systems of lodging (four locations) and height of
the lowest mainstem node bearing a pod or pod-bearing branch (two
locations) are also included. The first planting system ('Corsoy,'
Date 1, 25 cm rows) responded with yields which were 54.02 greater
than those of the lowest yielding system ('Evans,' Date 3, 76 cm rows),
indicating the significant differences which can occur with a systems

concept.

190

Table 38. Influence of planting systems composed of different planting
dates, row widths and cultivars upon yield (ql/ha),lodging and
height of the lowest mainstem node to which is attached a pod or
pod-bearing branch (cm), averaged over year, location and plant
density (where applicable).

 

 

 

Plantinglpate Row Width (cm), Cultivar Yield Lodging Nodal Height
1 25 Corsoy 32.90 3.01 16.7
1 25 Hodgson (78) 32.77 2.51 9.9
1 51 SRF 200 32.34 2.46 17.6
1 51 Corsoy 32.06 2.48 13.7
1 25 SRF 200 31.88 2.44 18.8
2 51 Hodgson (78) 31.67 2.10 10.3
1 51 Hodgson (78) 31.63 1.95 10.3
2 51 Corsoy 31.39 2.37 14.6
1 25 Evans 30.25 2.11 15.6
2 25 Hodgson (78) 29.74 2.13 10.3
2 25 Corsoy 29.71 2.37 13.8
1 51 Evans 29.11 1.83 9.8
2 25 SRF 200 28.91 2.41 18.0
2 51 SRF 200 28.67 2.19 20.2
2 51 Evans 27.89 2.02 11.1
2 25 Evans 27.66 2.13 11.4
1 76 SRF 200 27.39 2.83 21.5
1 76 Hodgson (78) 27.20 2.07 12.9
1 76 Corsoy 27.04 '2.69 18.7
2 76 SRF 200 26.98 2.56 20.1
2 76 Hodgson (78) 26.93 2.34 12.3
3 25 Hodgson (78) 26.11 1.73 11.8
2 76 Corsoy 26.08 2.90 14.2
3 25 Corsoy 26.04 2.06 15.2
3 51 Hodgson (78) 25.49 1.65 11.3
3 51 Evans 25.47 1.99 9.8
2 76 Evans 25.33 2.36 14.2
3 51 Corsoy 25.23 1.99 11.9
3 25 SRF 200 25.20 1.93 18.3
3 51 SRF 200 25.13 2.01 17.4
1 76 Evans 24.48 2.00 13.3
3 25 Evans 24.33 2.01 10.1
3 76 Corsoy 22.15 2.32 14.4
3 76 SRF 200 21.60 2.19 17.9
3 76 Hodgson (78) 21.45 1.95 13.0
3 76 Evans 21.36 2.05 12.5

 

 

SUMMARY AND CONCLUSIONS

The effects on soybeans of planting date, row width, plant
density and cultivar were studied at two locations in 1978 near
Carleton and Chesaning, Michigan. In 1979, the effects of planting
date, row width and cultivar were studied at two Michigan locations

near Chesaning and Dundee.

I-.Y_ie_12

Overall planting date responses indicated that late dates of
planting resulted in reduced yields. However, there were also indi-
cations that planting dates prior to normal dates for the northern
locations responded with little if any yield advantage.

Overall row width yield responses were somewhat inconclusive
since plant densities in each width varied by year. However, 25 and
51 on row widths responded with definite yield advantages over 76 cm
widths. 'Hodgson (78)' responded with the highest yields over all
years and locations followed closely by 'Corsoy,' and then by 'SRF
200' and 'Evans.' In 1979, 'Nebsoy' (Regular Density) yields were
third highest behind those of 'Corsoy' and 'Hodgson (78)' while yields
of 'Nebsoy' (1.5 Density) and 'Beeson' were lowest of the seven
cultivars tested at both locations. 'Nebsoy' and 'Hodgson (78)'
gave some indications of resistance to moisture stress.

There were no significant plant density responses in 1978.

191

. r,
.\_J
g)

 

192

Planting date x cultivar interactions were significant at all
locations. In 1978, the planting date x row width x plant density
interaction at Carleton, and the planting date x row width, row width
x cultivar, and plant density x cultivar interactions at Chesaning
were significant. In 1979 the row width x cultivar interaction at
the Dundee location was significant. The 76 cm row widths generally
responded with lower yields at the first than at the second planting
date while other row widths did not show this response. 'Evans' also
yielded less at the first than at the second planting date at both

northern locations.

II. Growth and Development

 

Within the testing locations, there were significant cultivar
responses at theSZ level for maturity and flowering dates, percentage
emergence, mainstem and branch nodes per plant, total nodes per plant,
number of branches per plant, leaf area, photosynthetically active
radiation (PAR), mature plant height, lodging, mainstem.internode
length, mainstem and branch pods per node and per plant, mainstem
and branch pods per land area (m2), percentage branch pods of total
pods per plant, total pods per node and per plant, total pods per land
area (m2), number of seeds per pod and per node, number of seeds per
plant and per land area (m2), weights of 100 seeds, sample grain weight
per pod and per node, sample grain weight per plant and per land area
(m2), percentage bottom plant portion yields of total plant yields,
percentage middle plant portion yields of total plant yields, per-
centage top plant portion yields of total plant yields, height and

nodal number of the lowest mainstem node bearing a pod or pod-bearing

 

193
branch, and productive mainstem length.and nodes.

There were at least some significant planting date responses
for all of the above measurements except leaf area (not measured),
PAR, total pods per plant and per land area (m2), branch pods per
node and per plant, branch nodes per land area (m2), the percentage
yields of all three plant portions, and height of the lowest mainstem
node bearing either a pod or a pod—bearing branch.

There were at least some significant row width responses for
all of the measurements under cultivar except maturity dates, mature
plant height, number of seeds per pod and percentage yields of total
plant yields for the middle and top plant portions.

Plant density responses were significantly different in at least
some cases for all of the measurements listed under cultivar except
maturity and flowering dates (not measured statistically in 1978),
total nodes per plant, leaf area (not measured), PAR (not measured),
total pods per land area (m2), number of seeds per pod and per land
area (m2), sample grain weight per pod and per land area (m2), and
percentage yields of total plant yields for all three plant portions
(not measured).

There were significant main treatment effects for other related
measurements. There were also numerous interactions between main

treatment effects for the growth and development measurements.

III. Conclusions

 

The following tentative conclusions may be drawn from this

experiment:

 

194

1. Delays in planting soybeans after mid—May in the Monroe
County area and after late May in the Saginaw County area resulted
in significantly decreased yield. The later the planting date was
beyond the above times, the greater the yield reduction which resulted.

2. Plants in row widths of 25 and 51 cm yielded more than those
in 76 cm rows, but little if any yield advantage of 25 cm row widths
was realized in comparison with 51 cm widths. Due to the weed control
problems encountered with 25 cm.widths, 51 cm widths would appear
advisable. More research should be conducted on row width yield
responses utilizing uniform plant densities for all row widths before
conclusions regarding the response of 25 and 51 cm row widths in
Michigan are finalized.

3. Overall cultivar yield differences for the four cultivars
tested both years were of a much.smaller magnitude than were those of
planting date and row width. However, 'Hodgson (78)' responded with
consistently high yields across a wide variety of environmental
conditions. 'Nebsoy' also appeared to have some tolerance to late

summer drought.

APPENDIX

 

195

Table A1 . Phytophthora root rot damage (percentage of plants affected)
at the 1979 Chesaning location (includes only those plots with
some infestation).

 

Replication Planting Date Row Width (mm) Cultivar Z Damage

 

l lst 25 SRF 250 15
2 lst 25 SRF 250 1
3 lst 25 SRF 250 17
l lst 51 SRF 250 40
2 lst 51 SRF 250 20
3 lst 51 SRF 250 20
1 lat 76 Corsoy 5
l lst 76 SRF 250 20
2 lst 76 SRF 250 6
3 lst 76 SRF 250 4
2 2nd 25 Corsoy 5
1 2nd 25 SRF 250 25
2 2nd 25 SRF 250 15
3 2nd 25 SRF 250 10
1 2nd 51 Corsoy l
2 2nd 51 Corsoy 2
1 2nd 51 SRF 250 60
2 2nd 51 SRF 250 10
3 2nd 51 SRF 250 40
1 2nd 76 Corsoy 8
2 2nd 76 Corsoy 5
3 2nd 76 Corsoy 10
1 2nd 76 SRF 250 50
2 2nd 76 SRF 250 35
3 2nd 76 SRF 250 7
1 3rd 25 Corsoy 1
2 3rd 25 Corsoy 3
1 3rd 25 SRF 200 l
1 3rd 25 Beeson 1
1 3rd 25 SRF 250 20
2 3rd 25 SRF 250 20
1 3rd - 51 Corsoy 2
2 3rd 51 Corsoy 3
1 3rd 51 SRF 250 7
2 3rd 51 SRF 250 12
3 3rd 51 SRF 250 5
1 3rd 76 Corsoy 5
2 3rd 76 Corsoy l
2 3rd 76 Evans 1
1 3rd 76 SRF 250 30
2 3rd 76 SRF 250 l
3 3rd 76 SRF 250 4

 

 

1965

 

 

 

 

 

x52» 2

 

 

 

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197

Table A 3. Temperature (degrees Celsius) at sites near the 1978 and 1979
Chesaning (St. Charles), 1978 Carleton (Willis), and 1979 Dundee
(Adrian) research locations.

 

Year Site Reading Month
May June July, August Septmber

 

 

1978 St. Charles Average Maximum 22.9 27.6 29.0 29.1 26.1

Average Minimum 9.3 12.6 14.7 14.8 11.8
Average 16.1 20.1 21:8 21.9 18.9
1978 Willis Average Maximum 21.0 25.7 29.0 28.1 26.9
Average Minimum. 8.6 12.3 16.6 13.2 10.9
Average 14.8 19.0 22.8 20.6 18.9
Departure from
Normal 007 - 007 002 - 001 202
1979 St. Charles Average Maximum 21.5 27.2 28.7 26.4 26.1
Average Minimum 8.4 13.3 14.5 13.8 10.1
Average 15.0 20.2 21.6 20.2 18.1
1979 Adrian Average Maximum 20.3 26.5 27.2 25.4 23.8
Average Minimum 6.2 11.8 13.6 12.8 8.6
Average 13.2 19.2 20.4 19.1 16.2

Departure from
Normal - 1.5 - 1.3 - 2.1 2.4 - 1.1

 

198
Table A4 . Key for component of yield raw data Tables A5 , A5 and.A7 .

Treatment Codes

 

 

 

1978 1979
lst Digit--Planting Date lst Digit--Planting Date
lst-1 lst--l
2nd-2 2nd--2
3rd-3 3rd-3
2nd Digit-—Row Width (cm) 2nd Digit-Row Width (cm)
25--1 25-1
51-2 51--2
76--3 76-3
3rd Digit-—Plant Density 3rd Digit--Cultivar
Low--l Corsoy--l
High--2 Evans--2
Hodgson 78--3
4th Digit-~Cultivar SRF 200--4
Beeson--5
Corsoy-l Nebsoy-6
Evans-~2
(Regular Density)
Hodgson-3
SRF 200__4 Nebsoy--7
(1.5 Density)
SRF 200-8

Abbreviations for Column Headingg:

TMC--Treatment codes

PLHT-Mature plant height

LNH-Height of lowest mainstem node to which is attached a pod or
pod-bearing branch

LNN--Nodal number of lowest mainstem node to which is attached a pod or
pod-bearing branch

MN--Mainstem nodes per plant

BN--Branch nodes per plant

MP--Mainstem pods per plant

BP--Branch pods per plant

BNRr-Number of branches per plant

SW-Seed weight per plant

100 SW-Weight of 100 seeds

CHEMD--Chemical damage ratings

If any of the above abbreviations are followed by a dash and a
number, the number has the following meaning:

Bottom plant portion-l
Middle plant portion-2
Top plant portion-3

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0o.n 00.nn 0~.n 00.nu 00.0 n N~.n 00.nh mama
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00.n 0o.a~ 00.~ 00.o~ 00.o n ¢¢.NN 0o.m0n aqua
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nn.o 00.N~ No.0 an.n~ nn.n n s¢.o nn.nn «nun
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5.55 65.6 66.6 65.5 65.55 66.5 66.55 66.5 6 65.55 66.66 5555
5.55 56.6 66.5 66.5 66.65 66.5 66.55 66.6 6 65.55 65.56 5555
6.55 56.6 65.6 66.5 66.55 66.5 65.55 66.5 6 56.55 65.55 5555
6.55 66.6 65.6 66.5 66.65 66.5 65.55 65.6 . 6 66.55 66.65 5555
5.55 65.6 66.6 65.5 66.55 65.5 65.65 66.6 6 56.65 65.66 5555
5.65 66.6 65.6 66.6 66.55 65.6 65.55 66.6 6 55.65 65.56 5555
6.65 56.6 56.6 55.5 55.65 56.5. 55.65 66.6 6 65.65 55.55 6555
5.65 65.6 66.5 55.5 56.65 66.5 56.65 55.6 6 56.55 65.56 6555
5.65 66.6 55.6 55.6 66.65 65.6 66.55 55.6 6 66.65 55.55 6555
6.65 66.6 55.6 66.6 55.65 65.6 65.55 66.6 6 65.55 65.66 5555
5.65 66.5 56.6 55.5 65.65 65.5 55.55 55.5 6 65.55 55.65 5555
6.65 65.6 56.6 66.5 66.65 65.5 55.55 56.5 6 65.55 65.65 5555
5.55 66.6 56.6 55.5 66.65 66.5 65.65 55.5 6 55.55 66.66 5555
6.65 66.5 65.5 55.5 55.65 65.5 66.55 65.5 6 66.65 56.66 5555
6.65 56.5 55.5 55.6 55.55 65.5 56.55 66.5 6 66.6 65.56 5555
6.55 55.5 66.5 66.5 56.65 55.5 65.55 66.5 6 65.65 66.55 5555
6.65 66.5 66.5 66.6 56.55 55.6 66.65 55.6 6 66.55 65.65 5555
6.65 56.6 55.5 66.6 56.55 55.6 66.65 65.6 6 66.55 55.56 5555
6.65 66.6 65.6 56.6 65.65 56.6 66.55 65.6 6 66.65 56.55 6555
6.55 55.6 66.6 66.6 55.65 66.6 65.55 65.6 6 66.65 56.66 6555
6.55 55.5 66.6 66.6 55.65 66.6 65.65 65.6 6 66.65 56.56 6555
6.55 66.6 66.6 66.5 65.55 66.5 66.55 66.6 6 65.65 66.56 .5555
6.65 65.6 65.6 66.6 65.65 55.6 55.55 66.5 6 66.55 55.55 5555
6.55 55.6 65.6 55.6 66.55 55.6 55.65 66.6 6 66.55 65.66 5555
6.55 66.6 65.5 65.5 65.55 66.5 55.65 66.5 6 66.5 66.56 5555
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6.65 66.6 66.6 66.5 66.65 65.5 66.55 66.5 6 65.6 66.66 5555
6.55 66.6 66.5 65.6 66.55 66.5 65.55 65.5 6 65.6 66.66 5555
6.55 66.6 66.5 66.6 66.55 66.5 65.65 66.6 6 65.65 66.65 5555
5.65 65.6 65.5 66.6 66.55 66.5 66.65 66.6 6 65.55 66.66 5555
6.65 55.6 66.6 66.6 66.55 66.5 66.65 66.5 6 66.6 66.66 5555
mmzwmm .mm mam mm mm. mm. mm. mam. n=m=u mam. . 9:45 mam

4.3.88 n < 3...;

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5.6.3306 6 < 0563.

 

205

Table A 6 . Raw data for 1979 Chesaning yield components including whole
plant measurements.

 

 

rang ELK LNN m. 133. by. .122 BNR aw. PLHT 19.9.
g in) _§_W_
111 12.55 5.50 15.75 3.50 21.25 4.50 1.50 9.04 37 16.1
111 21.00 6.50 16.00 1.50 20.00 1.75 0.50 5.99 39 15.7
111 15.98 5.00 14.25 1.50 18.50 1.25 0.75 4.93 38 15.7
112 17.10 5.50 13.75 0.00 20.50 0.00 0.00 5.98 30 16.1
112 22.50 5.75 14.50 2.00 16.00 0.50 0.75 4.75 33 15.0
112 17.88 6.00 14.50 0.50 20.50 0.25 0.25 5.63 33 15.6
116 27.13 8.25 16.75 0.00 16.50 0.00 0.00 5.47 38 17.8
116 38.70 7.75 14.00 0.00 11.75 0.00 0.00 4.12 37 16.6
116 12.85 5.50 17.50 4.00 24.50 2.00 1.75 7.50 33 17.0
117 26.14 7.60 14.80 0.00 13.60 0.00 0.00 4.99 32 17.0
117 29.50 7.80 15.80 0.00 17.80 0.00 0.00 5.02 36- 15.9
117 33.04 8.20 14.80 0.00 8.40 0.00 0.00 3.20 36 17.9
121 11.68 4.80 17.40 6.20 28.60 6.80 1.80 9.97 37 15.4
121 10.94 4.80 16.40 4.60 29.20 6.40 2.00 11.29 40 16.8
121 12.24 4.80 17.00 8.20 25.00 9.60 2.00 9.34 39 15.3
122 9.14 4.20 13.40 4.20 19.00 4.20 1.60 6.04 32 16.7
122 6.40 3.00 15.20 8.80 24.40 9.60 2.80 10.92 34 16.3
122 8.72 3.80 13.60 3.40 17.20 3.00 1.20 6.27 32 16.3
126 4.96 3.40 16.80 7.40 20.80 4.80 2.40 10.32 35 17.4
126 23.84 7.20 17.80 1.60 21.20 0.20 0.80 8.46 36 17.8
126 14.42 5.20 17.00 4.80 24.80 2.00 1.80 10.23 36 17.4
127 22.01 5.43 13.00 2.29 12.57 1.14 0.86 5.19 36 18.0
127 23.96 6.86 15.57 1.29 18.57 0.43 0.57 9.94 39 18.1
127 20.76 5.71 13.43 0.57 15.29 0.29 0.29 6.29 38 18.0
131 12.00 4.86 14.57 4.57 21.71 6.29 1.71 9.17 34 15.1
131 19.19 6.00 15.86 2.71 19.43 2.29 1.14 7.08 39 16.9
131 17.03 6.00 14.00 1.86 14.86 2.00 1.00 5.99 39 15.8
132 7.70 3.43 14.29 5.43 24.57 7.00 2.00 10.74 32 17.0
132 6.73 3.29 14.29 5.00 26.29 4.86 1.71 10.10 32 16.5
132 8.31 3.71 12.86 5.71 18.57 7.71 2.00 7.95 34 16.2
136 10.73 4.43 14.43 4.29 21.71 3.00 1.29 9.68 34 17.3
136 14.80 5.14 16.29 3.43 25.00 2.57 1.29 9.54 37 18.0
136 9.19 4.71 17.00 4.29 24.57 3.14 1.57 11.07 37 17.4
137 22.89 5.60 13.60 0.70 15.60 0.70 0.20 3.52 35 18.2
137 20.60 5.50 13.40 0.20 9.80 0.00 0.10 3.61 38 18.0
137 23.35 6.10 13.90 1.50 15.00 0.80 0.70 5.28 35 16.9
211 16.23 5.25 15.75 4.00 25.00 4.00 1.50 9.01 36 14.6
211 13.38 5.00 14.75 3.25 21.25 3.75 1.25 8.17 37 15.7
211 10.38 4.25 14.75 2.75 19.00 2.75 1.25 9.09 37 15.4
212 18.05 6.00 14.50 0.00 18.75 0.00 0.00 6.98 32 15.2
212 12.83 5.00 14.25 1.00 18.50 0.50 0.50 6.71 31 16.2
212 10.08 4.25 16.00 4.25 20.00 2.75 1.50 7.20 34 16.2
216 25.75 7.50 15.25 0.00 15.75 0.00 0.00 5.24 34 16.0
216 19.88 7.00 17.25 2.50 24.75 1.00 1.00 9.48 35 16.7
216 15.25 6.50 17.25 1.25 22.25 0.25 0.50 6.64 35 15.8

Table A 6 (cont'd.).

IMC

217
217
217
221
221
221
222
222
222
226
226
226
227
227
227
231
231
231
232
232
232
236
236
236
237
237
237
311
311
311
312
312
312
316
316
316
317
317
317
321
321
321
322
322
322
326
326
326

LNH

16.84
29.00
30.98
11.58
12.56
11.94

9.76

8.90

7.90
12.88
19.06
20.96
14.37
18.31
23.43

8.17

9.53

9.87

6.73
10.27
13.86
16.41
13.44
17.66
18.85
22.39
22.43
11.68
19.85
21.88

8.33
15.80
12.93
20.08
15.00
20.23
15.40
17.60
33.12

8.38
14.16
11.40
10.20
10.46
11.26

8.58
13.94
14.42

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15.00
15.00
15.80
14.80
15.40
15.80
13.20
14.00
15.20
16.20
15.60
16.60
14.14
16.14
15.14
15.43
15.86
16.71
14.43
13.57
12.71
16.43
16.43
15.86
14.70
13.90
13.10
15.00
11.25
14.25
13.25
13.50
13.00
14.25
15.25
14.00
13.60
13.80
12.40
14.40
16.00
12.40
13.60
13.80
14.20
15.80
14.20
15.20

a!
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206

19.40
16.40
15.20
19.40
24.00
24.60
21.60
21.80
25.60
22.00
22.60
28.60
16.71
20.00
18.29
25.14
27.29
30.29
23.29
19.14
18.43
27.71
22.86
21.71
19.20
16.20
13.40
25.75

8.00
20.50
19.50
20.75
20.75
19.00
22.50
17.00
17.80
16.20

8.40
22.60
25.20
19.80
20.80
20.40
20.20
25.60
20.60
23.20

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6.84
5.73
5.13
7.06
9.38
7.54
7.80
8.22
10.58
8.38
7.97
9.84
6.31
7.62
7.10
10.29
10.84
11.36
9.99
7.03
6.41
11.54
8.46
8.37
7.54
5.76
4.62
7.47
1.41
4.36
7.10
5.72
4.74
5.33
5.80
2.21
4.43
4.19
1.47
8.59
7.31
5.80
6.01
7.28
6.12

8.16 '

6.77
6.51

36

13.9

F‘h‘F‘F‘h‘h‘h‘h‘h‘t:t;t;t:

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NNOONI-‘Nwl-‘mowo

Table A 6 (cont'd.).

TMC

327
327
327
331
331
331
332
332
332
336
336
336
337
337
337

LNH

19.80
20.46
24.60
10.49
16.90
13.97
12.13
14.87
12.56
16.43
23.59
13.94
18.40
22.58
18.76

LNN

o o
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IE

13.29
14.86
14.00
14.14
14.00
14.14
13.00
13.43
13.57
13.86
14.86
16.14
12.70
13.00
13.90

6
Z

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bul-‘J-‘momomLflJ-‘QNNOO

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207

|%

17.14
22.29
18.71
24.29
24.57
22.00
20.00
20.29
20.43
20.43
20.71
28.00
17.60
15.80
20.80

.32

0.00
0.00
0.14
10.14
4.57
2.71
4.43
4.00
3.43
1.14
0.00
4.57
2.30
0.10
0.20

BNR

OOHNOOHHNHI—‘NOOO
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OOONONO‘NOJ-‘H‘OL‘OC

$1

Ulb-l-‘on-‘Na‘a‘owmmbmb

o o. to. 00 no a o
mVNO‘ONHmNI-‘U‘Lflomm
a‘mNH‘DNOHNNUWGO‘H

 

PLHT 100
gin! _Sj~_1_
28 18.0
32 14.2
30 13.0
28 13.0
37 13.1
36 13.6
28 13.3
34 15.2
31 13.8
28 14.2
33 13.4
30 14.0
31 18.0
33 13.9
32 13.8

 

Raw data for 1979 Chesaning yield components including measurements for one—third plant sections.

Table A‘7.

 

100 SU

in

PLHT

MP-2 BP-2 BNR—Z SH-Z HN-3 BN-3 HP-3 BP-3 ENE-3 SH-3

BP-l BNR—l SH-l HN-Z BN—Z

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...-

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209

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Table A8.

IOW‘Width (W), plant density (P) and cultivar (C).

210

Analyses of variance of soybean yields (ql/ha) for both
1978 locations as influenced by replication (R), planting date (D),

 

Source

R

D

Error 1
W

wa
Error 2
P

DxP

wxP
DxWxP

C

DxC
NRC
waxc
PxC
DxPxC
WXPxC
DXWxPxC
Error 3

In
H‘

...;

GGWNGGU§NNHN9N§NN

H

12
126

Carleton Location

 

Mean Square

 

72.70
828.86
45.08
593.37
80.94
41.02
4.21
15.00
1.93
25.43
83.44
22.84
1.92
8.34
11.64
5.84
11.08
5.30
7.15

__F.'__

1.61

18.39**

14.47***

1.97

0.59
2.10
0.27
3.56**

11.67***

3.20**
0.27
1.17
1.63
0.82
1.55
0.74

Chesaning Location

 

 

Mean Square F

352.10 10.53*
99.64 2.98
33.44

217.94 21.43***
33.94 3.34*
10.17
5.10 1.17
12.26 2.80
1.75 0.40
2.03 0.46
81.02 18.54***
19.11 4.37***
9.11 2.08*
6.57 1.50
11.42 2.61*
4.59 1.05
4.28 0.98
4.16 0.95
4.37

*** Denotes significance at the 0.001 probability level.
** Denotes significance at the 0.01 probability level.
* Denotes significance at the 0.05 probability level.

 

Table A9.

 

Analysis of variance of soybean yields (ql/ha) for the

combined 1978 locations as influenced by location (L),
replication (R), planting date (D), row width (W), plant
density (P), and cultivar (C).

 

 

Source ‘df Mean Square F

L 1 2788.07 71.01***
R(L) 4 212.40 5.41*

D 2 740.00 18.85***
LxD 2 188.51 4.80*
Error 1 8 39.26

W 2 764.37 29.86***
wa 2 46.94 1.83
DxW 4 85.84 3.35*
LxDXW 4 29.04 1.13
Error 2 24 25.59

P 1 9.29 1.61
LxP l 0.02 0.004
DxP 2 20.55 3.57*
LxDxP 2 6.70 1.16
wxp 2 1.19 0.21
LxWXP 2 2.48 0.43
waxr 4 9.74 1.69
LxDxWXP 4 17.72 3.08*

C 3 139.29 24.18***
LxC 3 25.17 4.37**
DxC 6 34.01 5.90***
LxDxC 6 7.95 1.38
WXC 6 2.36 0.41
waxc 6 8.67 1.51
waxc 12 4.90 0.85
PxC 3 5.25 0.91
LxPxC 3 17.81 3.09*
DxPxC 6 4.70 0.82
LxDXPxC 6 5.73 1.00
WXPxC 6 9.87 1.71
LxWXPxC 6 5.49 0.95
DXWxPxC 12 5.59 0.97
LxwaxPxC 12 3.86 0.67
LxDxWXC 12 10.01 1.74*
Error 3 252 5.76

*** Denotes significance at the 0.001 probability level
** Denotes significance at the 0.01 probability level
* Denotes significance at the 0.05 probability level

 

212

Table A10. Analyses of variance of soybean yields (ql/ha) for
both 1979 locations as influenced by replication (R), planting
date (D), row width (W) and cultivar (C).

 

ChesaninggLocation Dundee Location

 

 

 

 

Source g§_ Mean Square F Mean Square F

R 2 1.28 0.06 7.40 0.22

D 2 508.77 22.14*** 1147.64 34.66***
W 2 114.20 4.97* 596.88 18.03***
wa 4 49.86 2.17 67.12 2.03
Error 1 16 22.98 33.11

C 6 40.58 10.39*** 146.92 14.68***
DxC 12 8.46 2.17* 21.21 2.12*
WXC 12 6.25 1.60 20.08 2.01*
waxc 24 4.73 1.21 11.68 1.17
Error 2 108 3.91 10.01

*** Denotes significance at the 0.001 probability level.
* Denotes significance at the 0.05 probability level.

 

 

213

Table A11. Analysis of variance of soybean yields (ql/ha) for
the combined 1979 locations as influenced by location (L),
replication (R), planting date (D), row width (W) and
cultivar (C).

 

 

Source d£_ Mean Square F

L 1 13636.78 471.31***
R(L) 4 3.89 0.13

D 2 1524.23 52.68***
LxD 2 155.28 5.37**
W 2 505.32 17.46***
LxW 2 212.27 7.34**
DXW 4 11.27 0.39
LxDxW 4 99.86 3.45*
Error 1 32 28.93

C 6 99.13 13.51***
LxC 6 105.49 l4.38***
DxC 12 11.68 1.59
LxDxC 12 12.16 1.66
WxC 12 19.78 2.70**
LxWxC 12 5.08 0.69
DxWxC 24 11.04 1.50
LxDxWxC 24 7.21 0.98
Error 2 216 7.34

*** Denotes significance at the 0.001 probability level.
** Denotes significance at the 0.01 probability level.
* Denotes significance at the 0.05 probability level.

 

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