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THESIS

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27645,)

 

 

LIBRARY

Michigan State
University

 

 

 

This is to certify that the

thesis entitled

EFFECT OF ROW SPACING, HYBRID SELECTION, POPULATION,
AND PLANTING DATE ON CORN (Zea maxs L.) GRAIN AND
SILAGE PRODUCTION IN MICHIGAN

presented by

William D. Widdicombe

has been accepted towards fulfillment
of the requirements for

M.S. Crop and Soil Sciences

Jegree in

 

 

 

Date l77//3//QY)

0-7639 MS U is an Affirmative Action/Equal Opportunity Institution

PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINES return on or before date due.
MAY BE RECALLED with earlier due date if requested.

 

DATE DUE

DATE DUE

DATE DUE

 

OCT 2 1 2001

 

'n no 'A‘l
—6U 90 v;-

 

 

 

Mg! 2 2005

 

 

 

 

 

 

 

 

 

11/00 chiRClDateDtnpas-p.“

 

 

EFFECT OF ROW SPACING, HYBRID SELECTION, POPULATION,
AND PLANTING DATE ON CORN (Zea mays L.) GRAIN AND SILAGE
PRODUCTION IN MICHIGAN

By

William D. Widdicombe

A THESIS

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

MASTERS OF SCIENCE
Department of Crop and Soil Sciences

2000

ABSTRACT

EFFECT OF ROW SPACING, HYBRID SELECTION, POPULATION,
AND PLANTING DATE ON CORN (Zea mays L.) GRAIN AND SILAGE
PRODUCTION IN MICHIGAN

By

William D. Widdicombe

In recent years, Michigan corn growers have been interested in producing corn (Zea mays
L.) in row widths narrower than 30-inches. Corn producers questioned whether hybrid
types responded differently to row spacing, population, and planting date. Between 1997
and 1999, narrow row trials covering 15 site-years were conducted across Michigan. The
largest yield increase came fiom an increase in plant population. Corn was planted at
population levels of 26K, 30K, 34K, 38K, and 42K plants per acre. On average, grain
yield increased one bushel per acre for every additional 918 plants. Planting dates early in
May out-yielded later planting dates. In the Central maturity zone in Michigan, 15-inch
row spacing out-yielded 30-inch rows by 8.5 bushels per acre when averaged across
years. There were significant yield differences between hybrids correlated with maturity.
However, there was no interaction of hybrids by row spacing. Grain moisture declined as
row width was narrowed. Total plant dry matter production increased as plant population
increased. There were inherent differences between hybrids, which affected silage
quality. Digestibility of corn silage decreased as population increased. Silage quality
was not affected by row spacing. Total plant dry matter increased as row width

decreased.

ACKNOWLEDGMENTS

I would like to sincerely thank the members of my graduate committee, Dr. Darryl
Warncke, Dr. Chris DiFonzo, Dr. James Kells, and Dr. Kurt Thelen. Special thanks to

Dr. Darryl Warncke for serving as my academic advisor.

I would like to thank Dr. Kurt Thelen for serving as my mentor and for his assistance
with this thesis. My thanks also go to Keith Dysinger and Sue Canty for their hard work
and help in the field. Thanks to The Corn Marketing Program of Michigan whose

commitment to research has fimded this project.

I would like to extend my heartfelt gratitude to my parents, George and Evelyn, whose
faith in God has encouraged and guided me throughout my life. Finally, my profound
appreciation and love goes to my wife Melinda for her constant support, patience, and

faith in my abilities, which enabled me to complete this project.

iii

TABLE OF CONTENTS

LIST OF TABLES ....................................................................................................... vi

LIST OF FIGURES .................................................................................................... viii
CHAPTER 1

NARROW ROW CORN PERFORMANCE ................................................................... 1

Abstract .............................................................................................................. 1

Introduction ........................................................................................................ 2

Materials and Methods ........................................................................................ 4

Results and Discussion ........................................................................................ 8

Grain Yield .......................................................................................... 15

Grain Moisture ..................................................................................... 18

Test Weight ..................................... - ..................................................... 21

Stalk Lodging ....................................................................................... 24

Conclusion ....................................................................................................... 26

References ....................................................................................................... 29
CHAPTER 2

NARROW ROW DATE OF PLANTING ................................................................... 31

Abstract ........................................................................................................... 31

Introduction ..................................................................................................... 32

Materials and Methods ..................................................................................... 34

Results and Discussion ..................................................................................... 37

Soil Temperatures ................................................................................ 38

Light Measurements ............................................................................. 40

Grain Yield .......................................................................................... 45

Grain Moisture ..................................................................................... 50

Test Weight .......................................................................................... 51

Stalk Lodging ....................................................................................... 54

Plant Height ......................................................................................... 58

Ear Height ............................................................................................ 60

Conclusion ....................................................................................................... 63

Reference ...................................................................................... - ................... 65
CHAPTER 3

NARROW ROW CORN SILAGE PERFORMANCE ................................................. 67

Abstract ........................................................................................................... 67

Introduction ...................................................................................................... 68

Materials and Methods ..................................................................................... 70

Results and Discussion ..................................................................................... 72

Percent Dry Matter ................................................................................ 75

Green Weight (Tons/Acre) ................................................................... 78

Dry Weight (Tons/Acre) ....................................................................... 80

iv

Harvest Index ....................................................................................... 85

Dry Matter Digestibility ....................................................................... 87

Acid Detergent Fiber ............................................................................ 90

Neutral Detergent Fiber ........................................................................ 92

Crude Protein ....................................................................................... 94

Conclusion ....................................................................................................... 96

References ....................................................................................................... 99
CHAPTER 4

NARROW ROW TRANSGENIC Bt CORN PERFORMANCE ................................ 100

Abstract ......................................................................................................... 100

Introduction ................................................................................................... 101

Methods and Materials ................................................................................... 103

Results and Discussion ................................................................................... 105

Grain Yield ........................................................................................ 108

Grain Moisture ................................................................................... 1 11

Test Weight ........................................................................................ 112

Stalk Lodging ..................................................................................... 1 13

Conclusion ..................................................................................................... 1 1 5

References ..................................................................................................... 116

LIST OF TABLES

CHAPTER 1
Table 1.1: Test locations by year and region. ................................................................... 5
Table 1.2: Hybrid maturity and agronomic characteristics. .............................................. 7
Table 1.3: Monthly growing degree day (GDD)l accumulations for the 1997- 1999
growing seasons by regions. ........................................................................... 9
Table 1.4: Monthly accumulated precipitation (inches) for the 1997- 1999 growing
season. ......................................................................................................... 10
Table 1.5: Planting and harvesting dates. ....................................................................... 11
Table 1.6: 1997 summary of combined analysis of variance for grain yield (GY), percent
grain moisture (%H20), test weight (TSTW), and stalk lodging (SL). .......... 12

Table 1.7: 1998 and 1999 summary of combined analysis of variance for grain yield
(GY), percent grain moisture (%H20), test weight (TSTW), and stalk lodging

(SL). ............................................................................................................ 13
Table 1.8: Summary of combined analysis of variance for grain yield, comparing
significance between Central and Southern Zones in 1998 and 1999 -. ........... 14
Table 1.9: Grain yield (bushels per acre) by row spacing with advantage over 30-inch
rows for comparison ..................................................................................... 16
Table 1.10: Grain yield (bushels per acre) by hybrid, year, and zone .............................. 18
Table 1.11: Grain moisture (percent) by hybrid, year, and zone. .................................... 19
Table 1.12: Grain moisture (percent) by row spacing. .................................................... 19
Table 1.13: Test weights (pounds per bushel) by hybrid, year, and zone. ....................... 21
Table 1.14: Test weights (pounds per bushel) by zone, year, and row spacings. ............. 22
Table 1.15: Percent stalk lodging by hybrid, year, and zone. .......................................... 24
Table 1.16: Percent stalk lodging by zone, hybrid, year, and row spacing. ..................... 25
CHAPTER 2
Table 2.1: Hybrid maturity and agronomic characteristics. Hybrids are listed in order of
maturity ....................................................................................................... 35
Table 2.2: Monthly precipitation (inches) and growing-degrec-day (GDD) accumulation
for the 1998 and 1999 growing seasons. ....................................................... 37
Table 2.3: Planting and harvesting dates for the date of planting study for 1998 and 1999
.................................................................................................................... 38

Table 2.4: Planting date summary of combined analysis of variance for grain yield (GY),
percent grain moisture (%H20), grain test weight (TSTW), stalk lodging

(SL), plant height (PLH), and ear height (ERH) for 1998 and 1999. ............. 44
Table 2.5: Grain yield (bushels per acre) by hybrid, planting date, and year. Hybrids are
listed in order of maturity. ............................................................................ 47
Table 2.6: Grain yield (bushels per acre) by row spacing, planting date, and year. ......... 48
CHAPTER 3
Table 3.1: Monthly precipitation (inches) and growing-degrce-day (GDD) accumulation
for the 1998 and 1999 growing seasons. ....................................................... 73

vi

Table 3.2: Summary of combined analysis of variance for dry matter (%DM), green
weight per acre (th/A), dry weight per acre (Dwt/A), and harvest index (HI)
for 1998 and 1999. ....................................................................................... 74

Table 3.3: Summary of combined analysis of variance for dry matter digestibility
(%DMD), acid detergent fiber (%ADF), neutral detergent fiber (%NDF), and

crude protein (% CP) for 1998 and 1999. ..................................................... 75
CHAPTER 4
Table 4.1: Monthly growing degree day (GDD) ' accumulation for the 1998- 1999
growing seasons by regions. ....................................................................... 106
Table 4.2: Monthly accumulated precipitation (inches) for the 1998- 1999 growing
season ........................................................................................................ 107

Table 4.3: Narrow Bt summary of combined analysis of variance for grain yield (GY),
percent grain moisture (%H20), test weight (TSTW), and stalk lodging (SL)

for 1998 and 1999. ..................................................................................... 108
Table 4.4: Grain yields (Bu/Acre) by row spacing with advantage over 30-inch rows for
comparison. ................................................................................................ 109

vii

LIST OF FIGURES

CHAPTER 1
Figure 1.1: Grain yield response across row spacing to population by years; 1997, 1998
and 1999 ..................................................................................................... 15
Figure 1.2: Grain moistures by year and populations. .................................................... 20
Figure 1.3: Test weight by year and population .............................................................. 23
Figure 1.4: Percent stalk lodging by year and population. .............................................. 26
CHAPTER 2
Figure 2.1: Soil growing degree accumulations by row spacing and month. ................... 39
Figure 2.2: Percent intercepted PAR by planting date and day of year. .......................... 40
Figure 2.3: Percent intercepted PAR by planting date and hybrid. .................................. 41
Figure 2.4: Percent intercepted PAR by planting date and row spacing. ......................... 42
Figure 2.5: Percent intercepted PAR by planting date and population. ........................... 43
Figure 2.6: Grain yield by planting date and year ........................................................... 46
Figure 2.7: Grain yield by population and year. ............................................................. 49
Figure 2.8: Grain moisture by planting date. .................................................................. 50
Figure 2.9: Grain moisture by hybrid. ............................................................................ 51
Figure 2.10: Grain moisture by population ..................................................................... 52
Figure 2.11: Test weight by planting date and year. ....................................................... 53
Figure 2.12: Test weight by hybrid. ............................................................................... 54
Figure 2.13: Stalk lodging by planting date and year ...................................................... 55
Figure 2.14: Stalk lodging by hybrid .............................................................................. 56
Figure 2.15: Stalk lodging by planting date and hybrid. ................................................. 57
Figure 2.16: Stalk lodging by population. ...................................................................... 58
Figure 2.17: Plant height by planting date averaged over 1998 and1999. ....................... 59
Figure 2.18: Plant height by population averaged over 1998 and 1999 ........................... 60
Figure 2.19: Ear height by planting date averaged over 1998 and 1999. ......................... 61
Figure 2.20: Ear height by hybrid averaged over 1998 and 1999. ................................... 62
Figure 2.21: Ear height by population averaged over 1998 and 1999 ............................. 62
CHAPTER 3
Figure 3.1: Dry matter by hybrid and year. .................................................................... 76
Figure 3.2: Dry matter by row spacing and year ............................................................. 77
Figure 3.3: Dry matter by population and year. .............................................................. 78
Figure 3.4: Green weight by hybrid and row spacing. .................................................... 79
Figure 3.5: Green weight by population and year ........................................................... 80
Figure 3.6: Dry weight by hybrid and year ..................................................................... 81
Figure 3.7: Dry weight by row spacing and year. ........................................................... 82
Figure 3.8: Dry weight by hybrids and row spacing. ...................................................... 83
Figure 3.9: Dry weight by population and year. ............................................................. 84
Figure 3.10: Harvest index by hybrid and years. ............................................................ 85
Figure 3.11: Harvest index by hybrid and population. .................................................... 86
Figure 3.12: Dry matter digestibility by hybrids and years. ............................................ 87

viii

Figure 3.13: Dry matter digestibility by population and years. ....................................... 88

Figure 3.14: Dry matter digestibility by population and row spacing .............................. 89
Figure 3.15: Acid detergent fiber by hybrid and year. .................................................... 91
Figure 3.16: Acid detergent fiber by population and years. ............................................ 92
Figure 3.17: Neutral detergent fibers by hybrids and years ............................................. 93
Figure 3.18: Neutral detergent fiber by population and years. ........................................ 94
Figure 3.19: Crude protein by hybrid and year. .............................................................. 95
Figure 3.20: Crude protein by population and year. ....................................................... 96
CHAPTER 4

Figure 4.1: Grain yields by population. ........................................................................ 110
Figure 4.2: Grain moisture by population and hybrid ................................................... 111
Figure 4.3: Test weight by hybrid and year. ................................................................. 112
Figure 4.4: Test weight by row spacing and hybrid. ..................................................... 113
Figure 4.5: Stalk lodging by row spacing and year. ...................................................... 114

ix

CHAPTER 1

EFFECT OF ROW SPACIN G AND PLANT POPULATION ON
HYBRID CORN PERFORMANCE IN MICHIGAN

Abstract

In recent years, Michigan corn growers have been interested in growing corn (Zea mays
L.) in row widths narrower than 30-inches. Planting corn in narrower rows would allow
Michigan farmers who grow soybeans [Glycine max (L.) Merr.] in 15-inch rows and
sugar beets (Beta vulgaris) in 22-inch row spacings to better utilize equipment resources.
Narrow row research has yielded inconsistent results ranging fiom 0 % to 7 % yield
increase. Researchers have questioned whether the selection of hybrid by plant type was
important to increasing yield in narrow row systems. Michigan Sate University
conducted a three-year study covering 15 site-years. The objectives of this study were to
a) determine the effects of narrow rows on corn production, b) determine the influence of
hybrid type on narrow row systems, and c) study the response of narrow row systems to
changes in plant populations. Four hybrids with differing plant characteristics were
planted at three row spacings of 30-, 22-, and 15-inches. The three row spacings in turn
were planted at five plant population levels of 26K, 30K, 34K, 39K, and 42K. Plots were
arranged randomly in a split-split plot configuration. Results of this study indicate that as
plant population levels increased, yield consistently increased. Narrow rows appear to
have a yield advantage over wider rows at the northern locations. Results also showed
that well adapted hybrids that yield well in 30-inch row systems also yield well in narrow

row systems.

Introduction

In recent years, producers have been interested in producing corn (Zea mays L.) in row
spacings narrower than 30-inches. Producers, who wish to maximize equipment use
between different crops, have driven this trend. Sugar beet growers using 22-inch row
spacing for both sugar beets (Beta vulgaris) and soybeans [Glycine max (L.) Merr.]
began to ask questions whether corn could also be produced in 22-inch rows. Corn and
soybean growers, who plant soybeans with row splitters, also began to question whether
corn could be efficiently produced in 15-inch rows. The question of growing corn in
narrow rows historically generated much debate about optimal row spacing and
population Researchers looked at these questions over the years and are reassessing the
possibilities as corn genetics continue to evolve. In 1908, Hume et al. reported a slight
advantage of 33 x 33-inch over 44 x 44-inch spacing of hill plots in northern Illinois at
both the two- and three-kernel planting rate. These debates of row spacing and corn

population will continue as producers look for ways to optimize their corn production.

Development of more effective herbicides with longer residual activity reduced reliance
on cultivation for weed control and eliminated the need for check-row planting which
facilitated cross row cultivation. This allowed for the introduction of drilled corn, which
changed planting patterns within the row. In Michigan, Rounds et al. (1951) found that
in ten plots, drilled corn yielded 7% better than did corn planted in hills. Drilling corn
allowed higher plant densities than utilized under previous hill planting systems. Higher
plant densities had a greater effect on yield than row width or planting patterns (Rossman

et al., 1966). Growing corn in an equidistant planting pattern reduces inter-plant

competition, allowing better utilization of nutrients, moisture, and solar radiation.
Uniformity between plants within rows also affects yields by increasing bushels per acre

(Krall et al., 1997; Nafziger, 1996).

Further advancement in engineering produced harvesting equipment that allows
harvesting of ultra narrow rows (1 5-inch). These new technologies spurred the debate
on the interaction of row spacing and plant density. Extensive research in Minnesota
(Porter et al., 1997; Westgate et al., 1997), Indiana (Bullock et al., 1988; Nielson , 1988),
New York (Cox et al., 1998), Ontario (Scheifele et al., 1996; Murphy et al., 1996),
Kansas (Krall et al., 1977), Illinois (Ottrnan and Welch, 1989), and Ohio (Thomison and
Jordan 1995) added to our understanding of the interaction of narrow row spacing and

plant population.

Corn grain yield results from narrower row studies are not consistent. Results vary fiom
zero yield advantage of planting corn in narrow rows (Johnson et al., 1998), to a 7%
increase in yield over wider rows as reported by Porter et al. (1997). Nielson (1988)
reported a 2.7% increase in yield of narrow rows over wider rows across nine Indiana
locations. The advantage of narrower rows seems to be in the northern locations where
the growing season is short. Paszkiewicz (1997) summarized eighty-four university and
industry studies and reported corn grown north of the I-90 corridor responded on average
with an 8 % increase in yield than did wider 30-inch rows. Cox et al. (1998)
summarizing Paszkiewicz, suggested that com grown in narrow rows north of the 44°N

latitude had a yield advantage over wider rows.

Hybrids developed in the last few years are able to withstand higher plant populations
better than older hybrids as reported by Tollenaar (1989). The newer hybrids could
withstand populations better because of a decrease in stalk lodging. Also newer hybrids
were able to withstand stress better resulting in production of fewer barren plants
(Tollenaar, 1991). When selecting hybrids for higher plant densities, Thomison and
Jordan (1995) reported that hybrid car type was of limited importance in determining
optimum plant densities. Nafziger (1994) evaluated two hybrids with reportedly different

responses to plant density and found no significant hybrid x plant population interaction.

The objectives of this study were to a) determine the effects of row spacing on corn yield,
maturity, and lodging in Michigan; b) determine the influence of hybrid type and row
spacing on yield response; and c) study the influence of plant population and row spacing

on on yield response.

Materials and Methods

Field research was conducted in 1997, 1998, and 1999 throughout Michigan (Table 1.1),
resulting in 15 site-years. Trial locations were chosen that best represented the diverse
soil types and cultural practices utilized in the state of Michigan. The trials were
separated into Southern and Central Zones. Three locations were planted in the Central

Zone, in 1997.

 

Table 1.1: Test locations by year and region.

 

Region 1 997 1 998 1999 Zone
Central * * * Central
Saginaw Valley * * * Central
Thumb * * * Central
South East * * Southern
South West1 * * Southern

 

 

1 Location had both irrigated and non-irrigated trials.

 

The experiment was designed as a randomized complete block with a split-split plot
arrangement with four replications. The hybrid represented the whole plot (110 by 30
feet), row spacing represented the split-plot (110 by 10 feet), and plant population
represented the split-split plot (22 by 10 feet). This design was chosen so the interaction

between hybrid, row spacing, and plant population could be observed.

To more efficiently plant and harvest these trials, a seven-row, 15-inch corn planter was
built in 1997. This planter also adjusted to plant 30- and 22-inch rows. To configure the
planter for four 30-inch rows, units 2, 4, and 6 were locked up with their seed drives
turned off. The planter toolbar extended to plant five 22-inch rows. Row units 1 and 7
were locked up and turned off, so they would not interfere with adjacent plots. An Accu-
plantTM programmable rate control processor was installed on the planter so quick
population changes could be made. Tractor wheel spacing was adjusted so wheel tracks
did not interfere with planted rows. Two mechanical corn heads were also built to harvest

the 15- and 22-inch rows. One conventional three-row, 30-inch corn head was fitted with

five 15-inch row units utilizing one gathering chain per unit. The original row units were

then mounted on a narrower frame and adjusted to 22 inches.

Four hybrids were selected and planted at three different row spacings of 30-, 22-, and
15-inch rows. Within each row spacing, hybrids were planted at five target populations
of 26K, 30K, 34K, 38K, and 42K plants per acre. The middle rows of each plot were
harvested for yield to allow one border row on each side of the plot. In the 30-inch rows,
only two rows were harvested, while in the 22- and 15-inch plots, three and five rows

were harvested, respectively.

To better match the hybrid to each location and zone, hybrids with different maturity
dates and agronomic characteristics were chosen. The same hybrids were planted at all
locations in 1997. In 1998 and 1999, six different hybrids were selected and matched to
the maturity zones. Of these six hybrids, four were selected for each maturity zone. The
two earliest hybrids were used in the Central Zone along with the two medium-maturing
hybrids. The same medium-maturing hybrids were then used in the Southern Zone along

with the two later-maturing hybrids (Table 1.2).

 

 

 

 

Table 1.2: Hybrid maturity and agronomic characteristics. Hybrids are listed by year
utilized and in order of maturity.
1997
Company Hybrid Maturity Ear Type He'ght Leaf typ_e
Pioneer P10 375] 97 day Flex Med-tall Wide
Great Lakes GL 4929 99 day Determinate Short Semi-upright
Garst GRST 8735 102 day Determinate Med-short Thin-upright
Garst GRST 8640 104 day Flex Tall Wide-upright
1998 — 1999
Company Hybrid Maturity Ear Type He'ght Leaf typ_e
Novartis Max 86 93 day Determinate Tall Erect
Renk RK 552 95 day Indeterminate Medium Erect
Great Lakes GL 4758 100 day Flex Med-tall Semi-upright
Pioneer PIO 3573 103 day Flex Med-short Semi-upright
Great Lakes GL 5715 105 day Determinate Medium Wide
Renk RK 775 108 day Indeterminate Medium Semi-upright

 

 

Plant population was determined at all locations after corn emergence. Plots were thinned
by hand if plant population exceeded target levels for the plot. Lodging observations
were recorded prior to harvest. Plants were considered lodged if corn stalks were broken
below the ear. The percent of lodging was calculated based upon the total number of

plants per plot.

Plots were harvested mechanically for corn grain. Moisture content and field weights
were automatically measured by the GrainGageTM, a HarvestData SystemTM mounted on
a plot combine. Grain yields are reported at a standard 15.5 % moisture. Test weights

were also recorded and reported at harvest moisture.

All data was analyzed with the analysis of variance (AN OVA) and the Mixed Linear
Model in SAS Statistical Software Package version 6.12 (1989-1996 SAS Institute Inc.,

Cary, NC.,). The Mixed Linear Model is able to calculate the appropriate error terms for

tests associated with the split-split plot design. Mean separations between all variables
were obtained by Tukey's Least Significant Difference Test. To control experimental
error, data was blocked by location (Kuehl, 1994). All other variables (hybrid, row
spacing, and population) were considered fixed. Regression analysis was used where
appropriate. Analyses for 1997 were kept separate from 1998-99 due to a difierent set of
hybrids used that year. Effects were considered significant in all statistical calculations if

P-values < 0.05.

Results and Discussion

Weather over the three years of the study played an important part in the variability
between years and between trial locations within years. In 1997, accumulated growing-
degree-days (GDD) (Table 1.3) were on average 403 GDD below the 30-year average,
ranging from 165 to 491 GDD below normal. Precipitation (Table 1.4) in 1997, on
average, remained near normal and ranged from 1.5 inches below average to 5.3 inches
above the 30-year average. This cooler than normal season delayed crop physiological
maturity until mid-November. The 1998 and 1999 growing seasons exceeded the 30-year
average for GDD accumulation. The range of accumulated GDD over locations for 1998
was 206 below normal and 491 above normal. The 1999 season ranged from 12 GDD
below to 412 GDD above the 30-year average. The largest accumulation of GDD
occurred in the southeastern portion of the state where hot and dry conditions prevailed
throughout the season. In 1999, there was a condition called "Growing-Degree-Day
Compression" (Andresen, 1999) early in the growing season. Growing-Degree-Day

Compression happens when there are small differences in GDD accumulations between

central and southern growing areas within the state. These small differences in GDD are
reflected in small differences in crop pheno logy between central and southern areas.

Precipitation levels for the 1998 and 1999 growing season were 2.8 and 2.4 inches,

 

 

 

 

 

 

 

 

 

Table 1.3: Monthly growing degree day (GDD)l accumulations for the 1997-

1999 growing seasons by regions. Thirty-year means have been included for

comparison (1951-1980).

Month

Region Year May June July Aug. Sept. Total DEV

Central 1997 185 533 589 468 380 2155 -369
1998 456 529 630 627 488 2730 206
1999 399 595 740 555 415 2704 180
30 yr. 338 530 640 598 418 2524

Saginaw Valley 1997 170 550 601 469 372 2162 -491
1998 465 586 701 695 512 2959 306
1999 378 600 700 540 423 2641 -12
30 yr. 367 555 670 623 438 2653

Thumb 1997 109 518 577 432 349 1985 -350
1998 391 500 609 622 498 2620 285
1999 343 590 697 520 426 2576 241
30 yr. 298 479 602 569 387 2335

South East 1998 509 622 719 697 545 3092 491
1999 437 645 811 617 503 3013 412
30 yr. 353 542 658 616 432 2601

South West 1998 473 557 681 681 512 2904 197
1999 419 616 762 554 436 2786 79
30 yr. 373 562 681 641 450 2707

' GDD calculated at base 50°F, with 50°F and 86°F cutoffs.

Data courtesy of the MSU Agricultural Weather Office.

 

 

 

Table 1.4: Monthly accumulated precipitation (inches) for the 1997- 1999
growing season. Thirty-year means have been included for comparison

(1951-1980).

 

 

 

 

 

 

 

 

 

Month
Region Year May June July Aug. Sept. Total DEV
Central 1997 2.7 2.3 2.5 3.3 5.2 15.9 1.0
1998 1.5 2.7 2.7 3.9 1.5 12.2 -2.8
1999 2.1 2.0 4.1 2.1 2.0 12.3 -2.6
30yr. 3.0 2.7 3.5 3.1 2.5 14.9
Saginaw Valley 1997 3.1 1.0 2.8 3.5 3.3 13.7 -0.8
1998 1.2 1.8 1.3 1.5 1.9 7.6 -6.8
1999 2.3 1.9 4.5 1.8 3.2 13.7 -0.7
30yr. 2.8 2.5 3.1 3.3 2.8 14.5
Thumb 1997 4.8 1.3 3.3 5.5 4.4 19.4 5.3
1998 1.4 1.9 1.8 3.2 4.2 12.4 -1.7
1999 2.4 2.7 6.5 1.7 3.5 16.8 2.7
30yr. 2.9 2.6 2.9 3.0 2.7 14.1
South East 1998 0.8 1.8 3.4 5.1 0.6 11.8 -4.1
1999 3.5 2.0 2.0 1.3 1.0 9.8 -6.1
30yr. 3.7 3.0 3.3 3.2 2.6 15.9
South West 1998 1.8 4.4 2.9 8.4 2.0 19.4 2.7
1999 1.7 2.8 3.5 2.8 1.9 12.6 -4.1
30yr. 3.2 3.9 3.5 3.3 2.9 16.7

Data courtesy of the MSU Agricultural Weather Office.

 

 

10

 

respectively, below the 30-year average. Precipitation ranged from 6.8 inches below in

the central areas to 2.7 inches above in some southern areas in 1998. In 1999,

precipitation ranged fiom 6.1 inches below in the southeast to 2.7 inches above in the

central regions.

Over the course of the three years, all plots were harvested and planted in a timely
manner (Table 1.5). However, in 1997, due to some last minute equipment changes plots
were planted later than intended. A drier than normal spring in 1998 allowed for an early
planting season in the Central Zones. More normal planting conditions returned in 1999,
and planting was finished by May 11. Harvesting was delayed until mid-November in
1997 due to the higher levels of precipitation and cooler temperatures throughout the
growing season. The 1998 and 1999 seasons had a warm, dry fall, allowing corn grain to

reach harvest moisture early and harvest to be completed earlier than normal.

 

 

 

 

Table 1.5: Planting and harvesting dates.

Planting Date Harvest Date
Region 1997 1998 1999 1997 1998 1999
Central May 20 April 30 May 6 Nov. 8 Oct. 3 Oct. 2
Saginaw Valley May 24 April 29 May 10 Nov. 11 Sept. 29 Oct. 5
Thumb“ May 24 May 14 May 10 Nov. 11 Oct. 5
South East May 13 May 5 Oct. 13 Oct. 11
South West May 11 May 11 Oct. 26 Oct. 12
* Location not harvested in 1998 due to poor emergence.

 

 

 

11

Statistical analyses were conducted separately for 1997. The summary of the 1997
ANOVA table (Table 1.6) shows the significance of the main effects of hybrids, row
spacing, population, and their interactions. Locations were significant for all traits
measured due to the variability in yield from north to south. When residuals were
analyzed for each location, the graphs were similar in shape but shifted up or down

depending on yield levels. Differences between hybrids were not significant for grain

 

Table 1.6: 1997 summary of combined analysis of variance for
grain yield (GY), percent grain moisture (%H20), test weight
(TSTW), and stalk lodging (SL).

 

 

‘ Probability P=0.05

 

Source of variation GY %H2O TSTW SL
P-values from ANOVAT

Location 0.0001 0.0001 0.0001 0.0001
Hybrid 0.0542 0.0001 0.0001 0.0002
Row Spacing 0.0126 0.4819 0.6867 0.0001
Hyb*Row 0.3951 0.3019 0.4546 0.9822
Population 0.0001 0.0860 0.3879 0.0001
Hyb*Pop 0.9327 0.31 12 0.0024 0.0056
Row *Pop 0.0607 0.7986 0.9709 0.4631
Hyb*Row*Pop 0.5871 0.0601 0.6314 0.9845

 

 

yield but were significant for moisture, test weight, and lodging. Differences between
row spacing was significant for grain yield and lodging (Table 1.8). The absence of a
hybrid x row spacing interaction would indicate that, of the hybrids investigated, hybrid
selection was not critical for determining yield advantage in narrow row production.
Plant population was found to influence grain yield and grain moisture at harvest. Corn
grain moisture at harvest was influenced by a hybrid x row spacing x population

interaction, which may be indicative of an individual hybrid's ability to tolerate stress.

12

Grain test weight was influenced by a hybrid x population interaction, which may

indicate how kernel size might be affected by plant population pressures.

The AN OVA table (Table 1.7) is summarized for the 1998-99 growing seasons for the
main effects of hybrid, row spacing, and plant population, along with the respective
interactions. Location had the greatest affect on stalk lodging. Hybrid effect on grain
yield was statistically significant in 1997 but not in 1998 or 1999. When yield was
summarized by com maturity zones, differences between hybrids evaluated in the Central
Zone were not significant (Table 1.8). However, yields among hybrids in the Southern
Zone were significantly different. This difference in significance may be due to the
varying types of hybrids used in the Southern Zone. Row spacing affected grain yield,
grain moisture, and stalk lodging but not test weight. In 1998-99, there was no hybrid x

row spacing interaction. Plant population affected all variables. The hybrid x population

 

Table 1.7: 1998 and 1999 summary of combined analysis of
variance for grain yield (GY), percent grain moisture (%H20),
test weight (TSTW), and stalk lodging (SL).

 

 

 

Source of variation GY %HZO TSTW SL
P-values from ANOVA1

Location 0.0001 0. 1934 0.4022 0.9702
Hybrid 0.0001 0.0001 0.0001 0.0001
Row Spacing 0.0001 0.0001 0.7751 0.0077
Hyb*Row 0.2862 0.1649 0.8450 0.1408
Population 0.0001 0.0001 0.0001 0.0004
Hyb*Pop 0.0050 0.0001 0.0104 0.1317
Row*Pop 0.1579 0.0272 0.3910 0.8963
Hyb*Row*Pop 0.0077 0.7436 0.8578 0.0227
' Probability P=0.05

 

13

 

interaction had an effect on all variables except lodging. Row spacing x population
interaction affected only grain moisture content. The hybrid x row spacing x population

interaction affected both grain yield and lodging.

 

Table 1.8: Summary of combined analysis of variance for grain
yield, comparing significance between central and southern
zones in 1998 and 1999.

 

 

‘Probability P=0.05

 

Source of variation Central Zone Southern Zone
P-values fi'om AN OVAI
Location 0.0001 0.0001
Hybrid 0.0542 0.0001
Row Spacing 0.0126 0.4819
Hyb*Row 0.3951 0.3019
Population 0.0001 0.0860
Hyb*Pop 0.9327 0.3112
Row *Pop 0.0607 0.7986
Hyb*Row*Pop 0.5871 0.0601

 

14

 

Grain Yield

The factor with the most influence on yield was plant population. As plant population

increased so did grain yield (Figure 1.1

). However, yields were not always significantly

different at the higher population levels. Row spacing affected grain yield. In 1998 and

1999, the 15-inch rows resulted in greater yields in the Central Zone than did the 22- and

30-inch row widths. The Central Zone

in 1997 had a lower than normal GDD

accumulation and higher than normal precipitation for the season, resulting in relative

 

 

 

 

 

 

 

 
 

 

 

 

 

 

 

 

 

 

200
195 1
190 1999
R2 = 0.9444
185 _ W
A ......-----""' 1997
g ' R2 = 0.9597
9. 180
2
.2
>
5 175 «——-—— -
E
0 /
170
01997
165 4 l
, I 1998
160
155 r f . T

 

 

years are:

1997 - y = 16.252Ln(x) + 14.179
1998 - y = 52.092Ln(x) - 357.66
1999 - y= 29.416Ln(x) - 120.11

 

20.000 21,500 23,000 24,500 26,000 27,500 29,000 30,500 32,000 33,500 35.000 36.500 38.000 39,500

Population (plantain)

Figure 1.1: Grain yield response across row spacing to population by years; 1997,
1998 and 1999. Regression equations for predicting grain yield from population by

 

15

 

yields with 15-inch rows that were not consistent with those obtained in 1998 and 1999
(Table 1.9). In 1997, the 22-inch row spacing had a 3.6 bushels per acre yield advantage
over the 30-inch rows, but there was a 0.6 -bushe1 yield reduction when row width was
reduced to 15-inches as compared to 30-inches. In the 1998 growing season, the Southern

Zone had a 7.4 bushel yield advantage of 22-inch and 15-inch rows over the 30-inch

 

Table 1.9: Grain yield (bushels per acre) by row spacing with advantage over 30-
inch rows for comparison.

 

 

 

 

 

Row Spacing 19971 1998 1999 Avg. '98-'99.
Central Zone
30—inch 181.6b 162.7b 189.8b 176.6b
22-inch 185.1a 163.9b 193.4b 178.6b
15-inch 181.0b 168.9a 200.6a 184.7a
Central Zone Advantage of Narrow Rows over 30-inch
22-inch 3.6 ----2 ---- ----
lS-inch ---- 6.1 10.8 8.5
Southern Zone
30-inch 180.0b 171.3a 175.6b
22-inch 187.3a 171 .5a 179.4ab
15-inch 187.3a 173.4a 180.3a
Southern Zone Advantage of Narrow Rows over 30-inch
22-inch 7.4 ---- ----
15-inch 7.4 ---- 4.9

' Grain yields within year and zones followed by the same letter are not
significantly different.
2 Comparison is not significantly different.

 

 

 

rows. The Central Zone, in 1998, had only a 1.2 and 6.1 bushel yield advantage for the
22-inch and the lS-inch row spacings, respectively, over the 30-inch rows. These
differences may be due to the inadequate rainfall that occurred in the Central Zone in
1998. The weather conditions were reversed for the 1999 growing season, resulting in a

10.8 bushels per acre yield advantage of the 15-inch rows over the 30-inch rows in the

16

central zone. This deviation from the 30-year norm would indicate that narrow rows tend
to have a greater yield advantage over wide rows when water is not a limiting factor
(Stickler, 1964; Fulton, 1970) and when planted at higher populations (Hoff and

Mederski, 1969; Fulton, 1970).

Hybrid selection was crucial to grain yield. The later maturing hybrids generally had the
yield advantage with a few exceptions. In 1999, yields in the Central Zone were above.
In 1998, the central zone did not yield as well due to drought conditions. Yields in the
southern zone were hindered in 1998 and 1999 due to higher accumulation of heat units
and lower precipitation. Hybrid yield was also dependent upon the interaction of the
hybrid with plant population level and how well each hybrid could withstand stress.
Yield averages of individual hybrids ranged from 169.8 - 195.6 bushels per acre (Table

1.10).

17

 

 

 

 

Table 1.10: Grain yield (bushels per acre) by hybrid, year, and zone. Hybrids are
listed in order of maturity within year and zone.
Hybrid 19971 1998 1999 Avg.
Central Zone
PIO 3751 185.5a 185.5a
GL 4929 180.8a 180.8a
GRST 8735 178.0a 178.0a
GRST 8640 185.7a 185.7a
Max 86 157.0b 196.13 176.53
RK 552 167.7a 194.6a 181 .la
GL 4758 163.83 195.8a 179.8a
PIO 3573 172.0a 192.0a 182.0a
Southern Zone
GL 4758 177.8b 173.6b 175.7b
PIO 3573 182.5b 167.6b 175.1b
GL 5715 173.0b 166.5b 169.8b
RK 775 206.2a 181.0a 193.6a
1 Grain yields within year and zones followed by the same letter are not
significantly different.

 

 

 

Grain Moisture

Grain moistures were strongly correlated with hybrid maturity. The later maturing
hybrids usually had the highest grain moisture content at harvest (Table 1.11). There
were differences in grain moisture across years, corresponding with the different growing
conditions within each year. Grain moisture content was higher for the 1997 season,
ranging from 25.7 - 28.5 % due to the cool, wet growing conditions. Grain moisture in

1998 and 1999 was much drier due to the higher accumulated GDD.

18

 

 

 

 

Table 1.11: Grain moisture (percent) by hybrid, year, and zone. Hybrids are listed
in order of maturity within year and zone.
Hybrid 19971 1998 1999 AggL
Central Zone
P10 3751 25.7c 25.7c
GL 4929 27.8ab 27.83b
GRST 8735 27.6b 27.6b
GRST 8640 28.53 28.53
Max 86 20.00 19.0b 19.5b
RK 552 18.9d 17.4c 18.1c
GL 4758 21 .5b 19.2b 20.4b
PIO 3573 22.93 20.53 21.73
Southern Zone
GL 4758 18.4b 18.3b 18.4b
PIO 3573 18.9b 18.0b 18.4b
GL 5715 21.03 19.73 20.33
RK 775 20.73 18.6b 19.63
1 Grain moisture levels within year and zones followed by the same letter are not
significantly different.

 

 

 

The 22-inch row spacing in 1997 had a higher grain moisture content than did the 30-inch
rows. In all other incidences, the narrow rows were drier than the 30-inch rows. The

difference in grain moisture ranged from 0.01 to 0.70 % (Table 1.12).

 

 

 

 

Table 1.12: Grain moisture (percent) by row spacing.

Row Spacing 1997l 1998 1999 Avg. '98-'99
Central Zone ‘
30-inch 27.43 21.13 19.13 20.13
22-inch 27.53 21.03 19.03 20.03
15-inch 27.4a 20.4b 19.03 19.7b
Southern Zone

30-inch 20.03 18.83 19.43
22-inch 19.6b 18.6b 19.1b
15-inch 19.7b 18.6b 19.1b

' Grain moisture levels within year and zones followed by the same letter are not

significantly different.

 

 

 

l9

In 1998 and 1999, as population increased fi'om lowest to highest, the grain moisture

dropped 0.4 and 0.7 %, respectively. In 1997, grain moisture increased slightly (0.3 %)

as plant population increased (Figure 1.2).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

29.0
4——v————v———-‘
27.0 —+
R2 = 0.6619
25.0 _ __
O 1997
g I 1998
g 23° A1999
3 ,
£
*5 2‘ '0 R‘ = 0.9393
5 I—.——I—__.u_F
19.0 '+ W15—
R2 = 0.9928
17.0
15.0 . . . . . . . . .
20,000 22,000 24.000 35.000 20.000 30.000 32.000 34.000 36.000 30.000 40.000
Population (puma)
Figure 1.2: Grain moistures by year and populations. Regression equations for
predicting grain moisture by years are:
1997 - y = 2E-05x + 26.91
1998 - y = -2E-05x + 20.896
1999 - y = -5E-05x + 20.37

 

 

 

20

Test Weight

The inherent differences in the hybrids evaluated had the greatest impact on grain test
weight at harvest. There was a strong negative correlation between test weights and grain
moisture. As grain moisture increased, test weight decreased. This correlation was most

evident when the test weight for 1997, where gain moistures were high (see Table 1.11),

 

 

 

 

Table 1.13: Test weights (pounds per bushel) by hybrid, year, and zone. Hybrids
are listed in order of maturity within year and zone.
Hybrid 1997‘ 1998 1999 Avg.
Central Zone
PIO 3751 52.83 52.83
GL 4929 50.1b 50.1b
GRST 8735 52.53 52.53
GRST 8640 49.50 49.50
Max 86 61.63 59.43 60.53
RK 552 56.2b 55.0b 55.61)
GL 4758 57.0b 55.7b 56.4b
PIO 3573 55.00 53.80 54.5c
Southern Zone
GL 4758 59.23 61.13 60.23
PIO 3573 58.1b 59.5b 58.8b
GL 5715 59.33 61.13 60.23
RK 775 55.40 59.7b 57.50
1 Test weights within year and zones followed by the same letters are not
significantly different.

 

 

 

is compared with the test weight results from 1998 and 1999 (Table 1.13). Grain test
weight on average was 51.2, 57.7, and 58.2 pounds per for 1997, 1998, and 1999,
respectively. Row spacing did not affect grain test weight when test weight was averaged
by row with (Table 1.14). Again, there were differences between years, due to higher

grain moisture in 1997. The differences were consistent across 311 row spacings.

21

 

Table 1.14: Test weights (pounds per bushel) by zone, year, and row spacings.

 

 

 

Row Spacing 1997‘ 1998 1999 Avg.'98-'99
Central Zone
30-inch 51.33 57.73 55.93 56.83
22-inch 51.23 57.4b 56.13 56.83
lS-inch 51.23 57.26 56.03 56.63
Southern Zone
30-inch 58.03 60.33 59.23
22-inch 57.73 60.33 59.13
lS-inch 58.03 60.43 59.23

1 Test weights within year and zones followed by the same letter are not
significantly different.

 

 

 

Plant population also affected grain test weight. As plant population increased, grain test
weight tended to increase (Figure 1.3). The exception to this was, once again in 1997,
when the test weight dropped 0.01 pounds as plant population increased from lowest to
highest. In 1998 and 1999, the test weight increased 0.04 and 0.50 pounds, respectively,
as population increased. The large difference in grain test weight between the 1997 and

1998-1999 growing season is again due to the higher grain moisture at harvest.

22

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R’ - 0.9325
53 ‘ _' ‘
R’ - 0.1299
57
. 56
i ..
I 01997
i 54 I 1999
3 A1999
*-
53
52
a“ - 0.1073
51 —.'___I . ' o
w I I V 1
20.000 25.000 30.000 35.000 40.000 45.000

Population (piantala)

Figure 1.3: Test weight by year and population. Regression equations for
prediction test weight fiom population by years are:

1997 - y = 3E-06x + 51.126

1998 - y = 5E-06x + 57.604

1999 - y = 3E-05x + 57.234

 

23

 

Stalk Lodging

Stalk lodging was most affected by the inherent characteristics of the hybrids selected for
this test. Each individual hybrid could withstand stress to some degree (Table 1.15). The
amount of stalk lodging also appeared to be dependent on the different environmental
conditions within each year. The 1997 growing season had the highest level of stalk

lodging.

 

 

 

 

Table 1.15: Percent stalk lodging by hybrid, year, and zone. Listed in order of
hybrid maturity within year and zone.
Hybrid 1997‘ 1998 1999 Avg.
Central Zone
PIO 3751 7.63 7.63
GL 4929 3.9b 3.9b
GRST 8735 2.8b 2.8b
GRST 8640 3.5b 3.5b
Max 86 0.3b 1.4b 0.8b
RK 552 0.4b 5.03 2.73
GL 4758 0.36 4.43 2.43
PIO 3573 0.93 4.83 2.83
Southern Zone
GL 4758 0.4b 0.9b 0.6b
PIO 3573 1.63 1.63b 1.63
GL 5715 0.4b 1.0b 0.7b
RK 775 1.336 2.43 g 1.93
' Stalk lodging within year and zones followed by the same letter are not
significantly different.

 

 

 

When row spacing narrowed, the percentage of stalk lodging increased (Table 1.16). The
largest increase in stalk lodging was found in 1997 when the 22-inch rows showed a
1.3% increase in stalk lodging and the 15—inch rows exhibited a 1.5% increase in stalk

lodging over the 30-inch rows. The average of the 1998-1999 growing seasons showed

24

the 22-inch rows had a 0.1 % reduction in stalk lodging in the Central Zone and a 0.6%
increase in stalk lodging in the Southern Zone compared to corn grown in 30-inch rows.
The 15-inch rows had a 0.2% reduction of stalk lodging in the Central Zone. In the

Southern Zone, the lS-inch rows had a 0.1 % increase in stalk lodging.

 

Table 1.16: Percent stalk lodging by zone, hybrid, year, and row spacing.

 

 

 

Row Spacing 1997‘ 1993 1999 Avg. '98-'99
Central Zone
30-inch 3.5b 0.4a 4.13 2.243
22-inch 4.83 0.53 3.93 2.183
15-inch 5.03 0.53 3.73 2.073
Southern Zone

30-inch 0.823 ' 1.1b 1.0b
22-inch 1 .143 2.03 1 .63
15-inch 0.783 1.4b 1.1b

' Stalk lodging within year and zones followed by the same letter are not
significantly different.

 

 

 

25

 

 

l07997
‘i‘—‘A199797J

U!

 

 

 

 

R2 = 0.6159
— ——I—-————

 

 

 

 

0 . . f M . . . .
20.000 22,000 24.000 26.000 28.000 30.000 32.000 34,000 36,000 38.000 40,000
Population (plantala)

Figure 1.4: Percent stalk lodging by year and population. Regression equations
for predicting stalk lodging from population by years are:

1997 - y = 0.0001x + 0.7871

1998 - y = 1E-05x + 0.3674

1999 - y = 7E-05x + 0.5109

 

 

 

Stalk lodging increased as plant population increased (Figure 1.4). Stalk lodging in 1998
was much less than in the other two years of the study, resulting in only a 0.2 % increase
in stalk lodging as plant population increased fiom lowest to highest. In 1997, stalk
lodging increased 1.5 % as plant population increased. Stalk lodging increased 1.1 % in

1999.

Conclusion

This data indicates that of the parameters measured, plant population had the greatest

influence on yield. As plant population increased, so did grain yield. Differences in

26

yield, however, were not always significant at the higher plant populations. This increase
in yield indicates that by increasing plant population, yield may be increased without
changing row width. Care should be taken when choosing hybrids. Corn hybrids with
good stress tolerance, that can withstand high populations without producing barren
plants, should be chosen. When planting 30-inch rows, plant population should start at
about 32,000 plants per acre and then be adjusted up or down, depending upon the soil
type, fertility level, and the water-holding capacity of the soil. As row spacing narrows,
the inter-row competition is reduced, allowing plant population to be increased. When
considering planting corn in 15-inch rows, plant population may be set at about 36,000
plant per acre and adjusted up or down, depending upon the soil conditions stated above.
For 22- inch rows, plant populations should begin at about 34,000 plants per acre and

adjusted according to the soil conditions.

Data over the three-year duration of this study indicates that there is a yield advantage in
planting corn in row spacings narrower then 30-inch rows. The data indicated that 15-
inch rows have a yield advantage over 30-inch rows in the central growing zone by at
least 8.5 bushels per acre. This data showed, in the southern growing zones, the yield
advantage was 4.9 bushels per acre. Twenty-two inch row spacings had a 2.4-bushel
yield advantage in the Central Zone over the 30-inch rows. The yield advantage of the
22-inch row spacings over the 30-inch row spacings was 3.8 bushels per acre when the
22-inch rows were planted in the southern growing zone. Corn producers in the central
growing zone had a greater yield advantage when corn was planted in the 15-inch rows.

This supports the findings of Steve Paszkiewicz (1997) who, summarizing data from 84

27

locations across the Corn Belt, concluded that areas north of I-90 had the greatest
advantage for narrow rows. Cox et al. (1998) summarizing Paskiewiez’s work suggested
the greatest yield response to narrow rows was above the 44°N Latitude. The data from
the 1997 to 1999 growing seasons indicated that narrow rows in Michigan have a greater

yield advantage in the Michigan maturity zones two or greater.

Grain moisture, test weight, and stalk lodging are all strongly influenced by the inherent
characteristics of the corn hybrid selected. The selection of a later-maturing hybrid tends
to increase the grain moisture at harvest and this, in turn, reduces test weight. Later-
maturing hybrids, when harvested with higher grain moisture content, tend to not have
problems with stalk lodging because the plant has not started to deteriorate as rapidly.
Higher population is an important element in improving yield, coupled with hybrid
selection. The next logical step to increase yield is to reduce plant competition within the
row by reducing row width. The reduction in row width allows the plant to better utilize
soil nutrients and moisture. Narrow rows also increase the canopy density, allowing the

corn to more efficiently harvest sunlight, resulting in increased yields.

28

References

Andresen, J. 1999. 1999 Growing season weather summary. In Corn hybrids compared in
the 1999 season. Michigan State University Extension Bulletin E-431.

Bullock, D. G., R. L. Nielsen, and W. E. Nyquist. 1988. A growth analysis comparison of
corn grown in conventional and equidistant plant spacing. Crop Sci. 28:254-258.

Cox, W. J ., D. R Chemey, and J. J. Hanchar. 1998. Row Spacing, hybrid, and plant
density effects on corn silage yield and quality. J. Prod. Agric., 11:128-134.

Hume, A. N., O. D. Center, and A. Hegnauer. 1908. Distance between hills of corn in the
Illinois Corn Belt. Illinois Experiment Station Bulletin 126.

Fulton, J. M. 1970. Relationships among soil moisture stress, plant populations, row
spacing and yield of corn. Can. J. Plant Sci. 50:31-38.

Johnson, G. A., T. R. Hoverstad, and R. E. Greenwald. 1998. Integrated weed
management using narrow corn row spacing, herbicides, and cultivation. Agron. J.
90:40-46.

Krall, J. M., H. A. Esechie, R. J. Raney, S. Clark, G. TenEyck, M. Lundquit, N. E.
Humburg, L. S. Axthelm, A. D. Dayton, and R. L. Vanderlip. 1997. Influence of
within-row variability in plant spacing on corn grain yield. Agron. J. 69:797-799.

Kuehl, R O. 1994. Complete Block Designs. In Statistical Principles of Research Design
and Analysis. Duxbury Press.

Murphy, S., Y. Yakubu, S. F. Weise, and C. J. Swanton. 1996. Effect of planting patterns
and inter-row cultivation on competition between corn (Zea mays) and late emerging
weeds. Weed Science 44:856-870.

Nafziger, E. D. 1996. Effects of missing and two-plant hills on corn grain yield. J. Prod.
Agri. 9:238-240.

Nafzinger, E. D. 1994. Corn planting date and plant population. J. Prod. Agric. 7:59-62.

Nielson, R. L. 1988. Influence of hybrids and plant density on grain yield and stalk
breakage in corn grown in 15-inch row spacing. J. Prod. Agric. 1:190-195.

Ottman, M. J. and L. F. Welch. 1989. Planting patterns and radiation interception, plant
nutrient concentration, and yield in corn. Agron. J. 81:167-174

29

Paszkiewicz, S. 1997. Narrow row width influence on corn yield. In Proc. 5]“ Annu.

Corn and Sorghum Res. Conf., Chicago, IL. Am. Seed Trade Assoc., Washington
DC.

Porter, P. M., D. R. Hicks, W. E. Lueschen, J. H. Ford, D. D. Warnes, and T. R.
Hoverstad. 1997. Corn response to row width and plant population in the northern
corn belt. J. Prod. Agric. 10:293-300.

Rossman, E. C., and R. L. Cook. 1966. Soil preparation and date, rate, and pattern of
planting. In W. H. Pierrce, S. A. Aldrich, and W. P. Maring (eds). Advances in corn
production: Principles and practices. Iowa State Univ. Prss.

Rounds, W. T., E. C. Rossman, W. Zurakowski, and E. E. Down. 1951. Method, and date
of planting corn. Michigan Agr. Exp. Sta. Quart. Bull. 33:372-87.

SAS Institute. 1985. SAS user's guide: Statistics. 5“ ed. SAS Inst., Cary, NC.

Scheifele, G., S. Jay, and J. Horn. 1996. 1991-1996 Research report for narrow row corn
production in southwestern Ontario. Agronomy Department, Ridgetown College of
Agricultural Technology, Ridgetown, Ontario, NOP 2C0.

Stickler, F. C. 1964. Row width and plant population studies with corn. Agron. J. 56:438-
441.

Thomison, P. R and D. M. Jordan. 1995. Plant population effects on corn hybrids
differing in ear growth habit and prolificacy. J. Prod. Agric. 8:394-400.

Tollenaar, M. 1989. Genetic improvement in grain yield of commercial maize hybrids
grow in Ontario from 1959 to 1988. Crop Sci. 29:1365-1371.

Tollenaar, M. 1991. Physiological basis of genetic improvement of maize hybrid in
Ontairo from 1959 to 1988. Crop Sci. 31:119-124.

Westgate, M. E., F. F orcella, D. C. Reicosky, and J. Somsen. 1997. Rapid canopy closure
for maize production in the northern US corn belt: Radiation-use efficiency and grain
yield. Field Crops Research 49:249-258.

30

CHAPTER 2

EFFECT OF ROW SPACING, PLANT POPULATION AND
PLANTING DATE ON HYBRID CORN PRODUCTION IN
MICHIGAN

Abstract

New corn hybrids (Zea mays L.) have improved genetics allowing them to better
withstand stress better. With the improved genetics comes the ability for the hybrid
seedlings to withstand cooler growing conditions. Producers can take advantage of
higher yielding, longer maturing hybrids by planting them earlier in cooler soils. An
earlier planting date in effect increases the length of the growing season. It has been
proven that earlier planted corn will out yield corn been planted later in the season.
When producers are considering utilizing a narrow row system they need to consider
wither the architecture of a narrow row canopy will affect the optimum planting date. A
two year study was conducted at Michigan State University to determine the effect of
planting date, row spacing, and plant population on corn grain production in Michigan.
Three planting dates of April 27‘", May 12‘“, and May 25th were selected. These planting
dates with the two-week intervals span typical planting date range in Michigan. Three
hybrids were selected so that one of the hybrid's maturity best matched one planting date.
The three hybrids were planted at 30-, 22-, and 15-inch row spacings. Each combination
of planting date, hybrid, and row spacing were planted at 26K, 32K, and 38K plant per
acre. The plots were planted in a split-split-split plot arrangement. In 1998, the

advantage of earlier planted corn was negated by weather patterns favoring later

31

plantings. This abnormal weather pattern produced inconclusive results on how planting
date effects corn yield. There was, with each increase in plant population, an increase in
grain yield. In 1998, the 15-inch row out yielded the 30-inch row at the later planting
dates by 7.9 bushels/acre. In 1999, the 15-inch row had a 15.2-bushel yield increase over
the 30-inch row. Grain moisture content increased as planting dates were delayed.
Moisture content was also highest in the later maturing hybrids. Test weight was closely
correlated to the moisture content of the grain. As moisture content of the grain increased
test weight declined. Seasonal differences and hybrid characteristics affected stalk
lodging more than any other variable. Plant and ear height increased as planting date was

delayed and when plant population increased.

Introduction

New corn hybrids (Zea mays L.) are being introduced to the rmrket each year with better
and improved genetics. Contemporary hybrids have greater cold tolerance and seedling
vigor, which have allowed for earlier planting dates. Earlier planting dates, in turn, enable
producers to take advantage of fuller season hybrids. Full season hybrids, which take
longer to mature, generally have a yield advantage over shorter season hybrids
(Harpstead and Dysinger, 1998). Early planting dates lengthen the effective- growing
season for corn, thereby increasing the chance for corn to reach physiological maturity .
before a killing frost. This facilitates faster dry down of grain, which can reduce

production cost.

32

There are trade offs between planting date and corn maturity. Planting full season hybrids
will generally provide larger yields. But, if physiological maturity is not reached, gains
in yields will be offset by higher drying cost. Regardless of the maturity of the hybrid,
yield declines as the date of planting is earlier or delayed from the optimum planting date.
(Imholte and Carter, 1987; Swanson and Wilhehn, 1996; Nafziger, 1994; Staggenborg et
31., 1999). Yields of full season hybrids decline at a greater rate than do short season
hybrids as the planting date is delayed (Lauer et al., 1999). Rossman and Cook (1966)
summarized 14 years of data in Michigan, between 1949 and 1963, and concluded corn
grain yields for early May plantings were 9% higher than mid-May plantings, 16% higher

than late May plantings, and 27% higher than June plantings.

Late planting dates and low plant populations can reduce corn grain yield (N afziger,
1994; Benson, 1990). Hybrids developed in the last few years are able to withstand
higher populations better than older hybrids. Optimum planting densities were lower for
hybrids released in the 1960's than for hybrids released in the 1980's, due to better stress
tolerance (Tollenaar, 1989). Tollenaar reported that contemporary hybrids could
withstand high populations better because of a decrease in stalk lodging. Tollenaar (1991)
also reported that modem-day hybrids withstand stress better and do not produce as many
barren plants when subject to high plant populations. Thomison and Jordan (1995)
reported hybrid ear type was of limited importance in determining optimum plant
densities. Nafziger (1994) evaluated two hybrids with reportedly different responses to

plant density and found no significant hybrid x plant population interaction.

33

The yield advantage of early planted corn is due to increased radiation interception
(Pendleton and Egli, 1969). Other ways to increase radiation interception is to
manipulate the canopy architecture by changing plant population and row spacing. The
redistribution of radiation to lower leaves of the plant is beneficial because lower leaves
are more efficient at low levels of radiation (Loomis and Williams, 1969). Narrow row
production systems reduce interplant competition, thus allowing more radiation to reach
the lower leaves of the corn plant. The lower leaves of the plant are primary sources of
carbohydrates for the roots (Palmer et al., 1973; F airey and Daynards, 1978). Wide rows
(30-inches) consistantly intercepted less photosynthetically active radiation (PAR) than
did narrow rows (10- and 15- inches) (Forcella et al., 1992). The plant population level
within narrow rows also changed the PAR interception. Narrow rows (20-inches)
intercepted up to 7 and 11% more radiation than wider rows (40-inches), at a planting

population of 28- and 32-thousand (Yao and Shaw, 1964).

The objective of this study was to determine the effect of planting date, row spacing, and

plant population on corn grain yield, maturity, and lodging in Michigan.

Materials and Methods

Field studies were implemented in 1998 and 1999 at Michigan State University in East
Lansing, M] on a Capac Loam soil that had been in a soybean [Glycine max. (L.) Merr] -
corn rotation. Three planting dates were selected, which would cover the range of
planting dates common for planting corn in Michigan. Planting dates selected were April

27'”, May 12th, and May 25"". This allowed for two-week planting intervals. Corn was

34

planted in 30-, 22-, and 15-inch row spacings. Each of the row spacings were planted at
three population levels (low, medium, and high) with a target population of

26-, 32-, and 38-thousand plants per acre, respectively. The experiments were arranged
as a split-split-split plot with a randomized complete block design. The date of planting
represented the main plots (198 by 30 feet), hybrid represented the first split (66 by 30
feet), row spacing represented the second split (66 by 10 feet), and plant population was
the final split (22 by 10 feet). This experimental design allowed the effects of planting

date, hybrid, row spacing, population, and their interactions to be observed.

Three corn hybrids were selected from hybrids well adapted for the growing conditions in
mid-Michigan (Dysinger et at., 1997). Relative hybrid maturities were selected so one
hybrid would best fit the maturity for each planting date. Hybrids were also selected

based upon differing ear and plant physical characteristics (Table 2.1).

 

Table 2.1: Hybrid maturity and agronomic characteristics. Hybrids are listed in
order of maturity.

 

Company Hybrid Maturity Ear Type Height
Novartis Max 86 93 day Deterrrrinate Tall
DeKalb DK 493 99 day Indeterminate Medium
Pioneer PIO 3491 107 day Flex Short

 

 

 

Temperature probes were inserted 2-inches into the soil at the root zone of the medium
population plots representing each planting date and row spacing. Plant populations were
determined in all plots after corn emerged. Plots were hand thinned if populations
exceeded target levels for that plot. For 1999, light interception measurements were

taken for each plot, as close to solar noon as possible and then averaged by treatment.

35

Light interception readings were taken beginning at 8, 7, and 6 weeks after planting for
the planting dates of April 23”, May 14th, and May 25'”, respectively. Plant and ear
height measurements were taken for each plot after pollination. Ear height was
measured fiom the ground to the node of attachment. Plant height measurements were
taken fiom the tip of the tassel to the ground. Stalk lodging observations were recorded

at harvest.

Plots were harvested mechanically for corn grain. Moisture content and field weights
were automatically measured by the GrainGageTM, a HarvestData SystemTM mounted on
3 plot combine. Grain yields were reported at a standard 15.5% moisture. Test weights

were recorded and reported at harvest moisture.

All data was analyzed using analysis of variance (AN OVA) and the Mixed Linear Model
in SAS Statistical Software Package version 6.12 (1989-1996 SAS Institute Inc., Cary,
NC). The Mixed Linear Model is able to calculate the appropriate error terms for tests
associated with the split-split-split plot design. Mean separations between all variables
were obtained by Tukey's Least Significant Difference Test. All variables were
considered fixed (planting date, hybrid, row spacing, and population). Regression
analysis was used where appropriate. Effects were considered significant in all statistical

calculations if P-values < 0.05.

36

Results and Discussion

Similar weather patterns occurred in 1998 and 1999. The 1998 growing season had near
norrml precipitation between May and August (Table 2.2). Precipitation for September
was markedly lower than the 30—year average. Over all, the 1998 season ended with a
precipitation deficit of 1.6 inches as compared to the 30-year average. In 1998, growing-
degree-day (GDD) accumulation was 144 GDD below norml. Most of the accumulated
GDD for the season occurred in the later part of May, and August through September.
Precipitation was 3.4 inches below the 30-year average for the 1999-growing season.
However, timely precipitation (6.8 inches) in July and August increased kernel set at
pollination and facilitated kernel fill. This precipitation helped boost yields for the
season. Grong degree-day accumulation for the 1999 growing season was near

normal.

 

Table 2.2: Monthly precipitation (inches) and growing-degree-day (GDD)
accumulation for the 1998 and 1999 growing seasons. Thirty-year means have
been included for comparison (1951-1980).

 

 

Precipitation Growing Degree Days1
Month 1998 1999 30 yr. 1998 1999 30 yr.
May 2.73 1 .78 2.73 442 385 338
Jun 2.51 1.07 3.54 522 474 530
July 2.83 4.75 3.02 618 729 640
August 3.94 2.09 3.12 617 551 598
September 1.29 1.84 2.50 471 424 418
Seasonal Total 1 3.30 1 1 .53 14.91 2668 2562 2524
DEV2 -1.61 -3.33 144 38

 

lGDD calculated for corn at a base 50°F, with 3 50°F and 86°F cutoffs.
2 The deviation from the 30-year mean.
Data recorded at the Horticultural Research Station, East Lansing, MI.

 

 

 

37

Dry field conditions in both 1998 and 1999 allowed plots to be planted in a timely
manner (Table 2.3). Lower precipitation in 1999 allowed harvesting of plots earlier than

in 1998. Both years had drier and warmer than average conditions at harvest.

 

Table 2.3: Planting and harvesting dates for the date of planting study for 1998
and 1999.

 

Planting Date Harvesting Date
Trial 1998 1999 1998 1999
Date 1 April 25 April 29 October 4 September 25
Date 2 May 9 May 14 October 11 September 25
Date 3 May 23 May 27 October 19 and October 3
October 23

 

 

 

 

Soil Temperatures

Soil growing degree accumulations recorded within rows and averaged over two years
indicated that a 15-inch row canopy kept soil temperatures cooler (Figure 2.1). Soil
growing degree monthly accumulations under corn canopies peaked in June, after which
time they decreased due to shading within the row. The accumulation of growing
degrees was slower in bare soils due to radiation loss early in the season. This loss was
caused by cool nights with no canopy cover to trap heat reflectance fiom the soil. Bare
soils, once warmed, tended to hold heat longer because of increased direct radiation later
in the season. Soil under a corn canopy tended to accumulate less growing degrees than

bare soil.

38

 

 

 

800

 

 

 

700 R A \
600

 

 

a
/
/

 

 

5

Growing Dagrooa ('F)
vb
8

 

 

 

 

 

 

 

 

 

 

 

 

200 J Th—o— 8;;
—I— 30
+ 22
100 f— :9- 15__.
0 *r l T I
May June July Amust Sept.
Month

Figure 2.1: Soil growing degree accumulations by row spacing and month.

 

 

Light Measurements

The percent of PAR intercepted by the corn canopy varied by planting date. The percent
of PAR intercepted by the corn canopy is dependent on the height of the canopy, which is
in direct relationship to the growth stage of the plant. Corn planted at the later planting
dates intercepted greater percent of PAR than did the earlier planted corn after the 195th
day of the year (Figure 2.2). The percent of PAR intercepted by hybrids also increased as
planting date was delayed from April 29°I (Figure 2.3). Row spacing also affected the
percent of intercepted PAR. Corn grown in 15-inch rows always intercepted the highest
percentage of PAR (Figure 2.4). As planting date was delayed, all treatments, regardless

of row spacing, had an increase in intercepted PAR. The lowest plant populations

 

100

 

Pylon / Pollen
95 P lie

‘0/ n \
90 \-

 

 

 

 

 

 

 

 

g. [/L/ A
70 fig”, ,
,. / :22;

 

 

 

 

 

Z +27-May
60

 

 

 

 

 

 

170 177 184 191 198 205 212 219 226 233 240
Day of Year

Figure 2.2: Percent intercepted PAR by planting date and day of year.

 

 

 

40

intercepted the least percent of PAR. Higher plant populations also intercepted more PAR

as planting dates were delayed (Figure 2.5).

 

 

 

 

 

 

 

 

94
. PIO 3491
92 OMax86 R2 3
IDK 496
APio 3491 R2 4938
= 0.
L L

 

 

 

 

 

 

 

 

 

 

 

w I I I I I
24-Apr 29-Apr 04—May 09-May 14-May 19-May 24—May 29-Ma
Planting Data

fir

Figure 2.3: Percent intercepted PAR by planting date and hybrid. Regression
equations for predicting percent PAR from planting date by hybrids are:

Max 86 - y = 9433.2Ln(x) - 99051

DK 496 - y = 11762Ln(x) - 123523

PIO 3491 - y = 10914Ln(x) - 114608

 

 

 

41

 

 

 

R2193-01011
0.9959
92

%
90 R2 09703
.. y A.
R’= 09414
// . /
‘7/ /
94 r
I /
82 030-11131
/ I22-inch
4415:1291
so a ..
o

78 T I I I I I
24-Apr 29—Apr 04-May 09-May 14-May 1 9—May 24-May 29—May
Planting on.

 

 

 

 

mu m
8

 

 

 

 

 

 

 

 

 

 

 

Figure 2.4: Percent intercepted PAR by planting date and row spacing. Regression
equations for predicting percent PAR fiom planting date by row spacing are:
30-inch - y = 12683Ln(x) - 133202

22-inch - y = 10708Ln(x) - 112444

15-inch - y = 88408me) - 92823

 

 

 

 

 

95 ~————~

93

 

 

91

 

 

 

'\
\\
\l

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I
83 /
81 924,917
./ new
79 » - £939:
77 .-. .. _—_ _._ -__ ..___ __ _
75 I T T I I I
24-Apr 29-Apr 04-May 09-May 14-May 19-May 24-May 29-May

Planting Data

Figure 2.5: Percent intercepted PAR by planting date and population. Regression
equations for predicting percent PAR from planting date by population levels are:
24,917 - y = 12354Ln(x) - 129751
29,990 - y = 8909.4Ln(x) - 93545
35,461 - y = 10988Ln(x) - 115388

 

43

 

Statistical analyses were combined over the two years of the study. The summary of the
ANOVA table (Table 2.4) shows the significance of the main effects of planting date,
hybrid, row spacing, population, and their interactions. Years were significant for test
weight and stalk lodging only. Planting date was significant for percent grain moisture,

test weight, and plant and ear height, but not grain yield. The lack of a response of grain

yield to planting date could be due to environmental conditions, which favored later

planted corn. Hybrids were significant for all traits: grain yield, grain moisture, test

weight, stalk lodging, and plant and ear height. The nurin effect of row spacing was only

significant for grain yield. Plant population was significant for grain yield, grain

 

Table 2.4: Planting date summary of combined analysis of variance for grain yield
(GY), percent grain moisture (%H20), grain test weight (TSTW), stalk lodging (SL),
plant height (PLH), and ear height (ERH) for 1998 and 1999.

 

 

 

Source of Variation GY %H20 TSTW SL PLH ERH

P-values from ANOVA1
Year 0.2178 0.5504 0.0001 0.0009 0.7475 0.9892
Planting Date 0.261 1 0.0001 0.0001 0.6405 0.0090 0.0034
Hybrid 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001
Date*Hyb 0.5979 0.5368 0.0307 0.0087 0.5581 0.7503
Row Spacing 0.0004 0.3297 0.2444 0.4718 0.7563 0.3663
Date*Row 0.1465 0.0045 0.3052 0.2971 0.0978 0.5821
Hyb*Row 0.2276 0.8983 0.3064 0.5234 0.1222 0.2623
Date*Hyb*Row 0.0988 0.5231 0.0854 0.2686 0.9828 0.9307
Population 0.0001 0.0443 0.5978 0.0010 0.0338 0.0001
Date*Pop 0.0036 0.1811 0.4719 0.7614 0.0102 0.2627
Hyb*P0p 0.7496 0.0169 0.0005 0.5228 0.5696 0.9706
Date*Hyb*Pop 0.1227 0.2990 0.0353 0.0822 0.7295 0.6352
Row*Pop 0.0241 0.5548 0.4536 0.9679 0.8562 0.7541
Date*Row*Pop 0.3883 0.0287 0.0121 0.1690 0.0156 0.6764
Hyb*Row*Pop 0.6617 0.0397 0.0038 0.7316 0.8334 0.0552
Date*Hyb*R0w*Pop 0.8576 0.4251 0.0232 0.5839 0.9517 0.5773
'Probability P=0.05

 

44

 

moisture, stalk lodging, and plant and ear height. Two traits, test weight and stalk
lodging, were affected by the planting date x hybrid interaction. The absence of a hybrid
x row spacing interaction indicates that of the hybrids used, all responded similarly to
differences in row spacing. Grain yield and plant height was affected by the planting date
x population interaction. The hybrid x population interaction affected only grain
moisture. The interaction of row spacing x population affected only the corn grain yield.
The three-way interaction of planting date x hybrid x row spacing did not affect any of
the traits observed. The planting date x hybrid x population interaction affected only test
weight, while the planting date x row spacing x population interaction and the hybrid x
row spacing x population interaction affected grain moisture and test weight. Grain test
weight was the only trait affected by the four-way interaction of planting date x hybrid x

row spacing x population.

Grain Yield

Typically corn grain yield is reduced as planting date is delayed, but in 1998 corn grain
yield increased by 3.3 bushels per acre with delayed planting due to weather conditions in
the spring which favored later planted corn (Figure 2.6). The grain yield in 1999 was
reversed from that of 1998. When planting date was delayed in 1999, fiom April 27th to
May 25‘", yield decreased, on average, 15.4 bushels per acre.

Yield performance of the hybrids was positively correlated with the maturity of the
hybrids. The later maturing hybrids out-yielded the shorter season hybrids. There were
difierences between hybrids on how they responded to the delay in planting dates (Table

2.5).

45

 

 

188

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

\ O
186 ‘4 4’
\
\
182 ~1- . A7 . 4b
\
\ \

“ 180 v
3 \
g \

178 \
4.. \
I \ \
z 176 -< \
E \ \
o 174 1 —-— - - \

01998; \ \
_ L
‘72 ' 19931 \
\
170 19$ \ .
R2 = 0.7324
168
I
166 I I I I I I r
1 9-Apr 24-Apr 29-Apr 04-May 09-May 14-May 1 9-May 24—May 29-May
Planting Data

Figure 2.6: Grain yield by planting date and year. Regression equations for
predicting grain yields fiom planting date by year are:

1998 - y = 0.1188x - 4171

1999 - y = -0.5355x + 19808

 

46

 

 

 

Table 2.5: Grain yield (bushels per acre) by hybrid, planting date, and year.

Hybrids are listed in order of maturity.

 

 

 

 

 

Planting
Hybrid Date 1 9981 1 999 Average
Max 86 April 27 175.9b 172.8ab 174.40
May 12 177.3b 183.03b 180.23bc
May 25 181.3ab 164.03b 172.7c
Averagez 178.2b 173.3b 175.7b
DK 493 April 27 170% 169.23b 170.10
May 12 175.7b 165.4ab 170.5c
May 25 173.8b 148.7cb 161.2c
Average 173.5b 161.0b 167.3b
PIO 3491 April 27 203.33 205.93 204.63
May 12 194.53b 197.7ab 196. lab
May 25 205.03 188.53b 196.73
Average 200.93 197.33 199.13

 

' Grain yields for planting dates within year followed by the same letter are not
significantly different.
2 Average yield within year followed by the same letter are not significantly

different

 

Row spacing was also a determining factor in grain yield. Corn planted in narrow rows

consistently out-yielded the wider 30-inch rows except in 1999, when the 30-inch rows

out-yielded the 22-inch rows for the May 12th planting date by 4.6 bushels per acre

(Table 2.6). In 1998, the narrow rows had a yield advantage over the 30-inch rows in the
later planting dates. The 22-inch rows had a 7.0 bushels per acre advantage on the May

12th planting date, while the 15-inch rows out-yielded the 30-inch rows by 7.9 bushels per

acre on the later May 25th planting date. This trend was reversed in 1999, with the

narrow 22- and 15-inch rows out-yielding the 30-inch rows by 10.38 and 15.2 bushels per
acre, respectively, for the earliest planting date. When grain yield was averaged across

years, corn grown in 15-inch rows had a yield advantage of 8.5 bushels per acre. Corn

47

 

grown in the 22-inch row spacing out-yielded the corn grown in 30-inch rows by 7.9
bushels per acre. This increase in yield was observed at the earliest planting date. Corn

grown in narrow rows out-yielded the 30-inch row corn when yield was averaged across

 

 

 

 

 

 

 

 

 

 

Table 2.6: Grain yield (bushels per acre) by row spacing, planting date, and year.
Planting
Row Spacing Date 19981 1999 Average
30-inch April 27 181.03b 173.9b 177.4b
May 12 179.03b 182.9ab 181.03b
May 25 183.7b 166.53b 175.23b
Average2 181.3b 174.4b 177.93
22-inch April 27 186.33b 184.23b 185.33
May 12 185.9ab 178.3ab 182.13b
May 25 184.53b 168.2ab 176.3ab
Average 185.63 176.93b 181.23
15-inch April 27 182.83b 189.13 186.03
May 12 182.53b 184.9ab 183.7ab
May 25 191.83 166.53b 179.13b
Average 185.73 180.23 I . 182.93
Advantage of Narrow Row Over 30-Inch by Planting Date
22-inch 27-Apr ---3 --- 7.9
12-May --- --- ---
25-May --- --- ---
lS-inch 27-Apr --- 15.2 8.5
12-May --- --- ---
25-May 7.9 --- ---
Advantage of Narrow Row Over 30-Inch Averaged across Planting Date
22-inch Average 4.3 --- ---
lS-inch Average 4.4 5.8 ---
1 Grain yields for planting dates within year followed by the same letter are not
significantly different.
2 Average yield within year followed by the same letter are not significantly
different.
3 Comparison is not significantly different.

 

 

 

48

years for the two later dates. These differences in grain yield, however, were not as

significant as the differences observed at the early planting date.

Grain yield increased as plant population increased. In 1998, as plant population

increased from lowest to highest, yields increased 15.5 bushels per acre, or 10.3% (Figure

2.7). There was also a substantial increase in yield as the plant population increased for

each planting date. As plant population increased, so did yield for each row spacing.

 

 

190

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Population (plantala)

grain yield from plant population by year are:
1998 - y = 37.395Ln(x) - 203.25
1999 - y = 29.609Ln(x) - 127.91

 

1996
2:
188 R 0.93331
166 .1998L /.
- .1999] /
‘34 ’ 1999—
R’=0.7234
162 r‘
I
g 180 / //f
)-
176
C
0 176 / /
172 4 — —
170 4 / I.—
168 T I I I I I I I
20.000 22,000 24,000 26,000 26.000 30.000 32.000 34.000 36,000 36,000

Figure 2.7: Grain yield by population and year. Regression equations for predicting

 

49

 

Grain Moisture

Late planted corn had the highest grain moisture at harvest. When averaged over 1998
and 1999, grain moisture increased as planting date was delayed. Grain moisture
increased 4.7 % when planted on April 24Ill as compared to May 25‘h (Figure 2.8). Grain
moisture followed hybrid maturity. Late maturing hybrids always had higher grain
moisture (Figure 2.9). Grain moisture, when averaged over row spacing, increased 4.7%
as planting date was delayed. When plant population was increased, grain moisture
dropped 0.3% (Figure 2.10). This was also evident, but not as pronounced, when hybrids

were averaged over populations.

 

27

 

R2 = 0.9755
25 -_ #7 ,9

.. /

 

 

Grain Molatura ($9)

 

 

 

1 5 . . . r . .
24-Apr 29-Apr 04-M 3y 09-May 14-May 19-May 24-May 29-Ma)
Planting Data

 

Figure 2.8: Grain moisture by planting date. Regression equations for predicting grain
moisture from planting date is y = 0.1663x - 6074.6

 

 

 

50

 

Grain Moistura (it)

 

ME 11(493 PlO3491
Hybrid

Figure 2.9: Grain moisture by hybrid. Hybrids are listed in order of maturity.
Columns with the same letter are not significantly different.

 

 

 

Test Weight

Grain test weight was negatively correlated with grain moisture. When grain moisture
increased, test weight tended to be reduced. Test weight, when averaged over planting
date, was reduced by 3.3 lbs. in 1998, and 4.4 lbs. in 1999, as planting date was delayed
(Figure 2.11). Hybrid maturity also affected test weight. The later maturing hybrids had
consistantly higher grain moisture and tended to have lower test weights. There was a
6.0 lb difference in test weight with only a 14 day spread in relative hybrid maturity
(Figure 2.12). Test weight for all hybrids declined as planting date was delayed. There
were differences in test weight between hybrids as plant population increased, but not

significant enough to be an effective management tool.

51

 

 

22. 50

 

22.45 ’\

 

22.40 «H - \

'8
o

 

 

Grain Molatura (16)
E
8

\ #1309038
22.25

 

22.20

 

 

22.15

 

 

22.000 24.000 26.000 28,000 30,000 32,000 34,000
Population (piantala)

Figure 2.10: Grain moisture by population. Regression equations for predicting
grain moisture from population is y = -0.7034Ln(x) + 29.579

36,000

 

52

 

 

 

 

61

 

 

 

 

 

 

 

 

 

 

 

 

 

 

60 h.
l o 1996]
o . 1999 i
59 ~ ‘
\ .
58 \
‘7' 57
g ‘ \
s ‘ I
3 56 ‘ ~ 3 1996
V.‘ 2
'5 ~ g R = 0.8521
I- ‘ -\ ‘
\
w ‘3‘ .
~ \
‘ s
‘ \
54 ‘ ‘~ \ m
I ~ \‘ R’ = 0.8873
‘
\
§
53 ‘ = ‘-
52 . . . . . .
25-Apr 30-Apr 5-M ay 10-May 15-M ay 20-M ay 25-M 3y

Planting Dato

Figure 2.11: Test weight by planting date and year. Regression equations for

predicting test weight from planting date by year are:
1998 - y = -5725.9Ln(x) + 60232
1999 - y = -4354.4Ln(x) + 45817

 

53

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

52 . — .. #flaa -7 . 7 7 . i.
I Max 86 _ __
13 BK 493
61 P10 3491
E;
E b
i
E 0
BK 493 I PlO 3491
Hybrids
Figure 2.12: Test weight by hybrid. Hybrids are listed in order of maturity. Columns
with the same letter are not significantly different.

 

 

 

Stalk Lodging

The different weather patterns between the two years of the study had varying impacts on
stalk lodging. For the 1998 growing season, stalk lodging was reduced by 0.8% when the
planting date was delayed from April 2"d to May 25‘". Stalk lodging in 1999 increased
1.3% when the planting date was delayed for the same period of time (Figure 2.13).
There was a difference in stalk lodging between hybrids as well. On average, the earlier
manning hybrids had fewer stalks lodged than did the later maturing hybrids (Figure
2.14). The latest maturing hybrid, PIO 3491, had a 1.9% increase in stalk lodging when
planting dates were delayed from April 27th to May 25*. The earliest maturing hybrids,

Max 86 and DK 493, had a 0.5% and 0.6% decrease in stalk lodging, respectively, for the

54

same delay in planting date (Figure 2.15). Plant population also affected stalk lodging.

As plant population increased, so did the number of plants lodged. Stalk lodging

increased 0.7% as plant population increased from lowest to highest (Figure 2.16).

 

 

 

 

 

 

 

 

 

 

 

3.0
.1996 TI
1.1999,
2'5 1999 '
2.0
E /
3 .
g 1.5
‘5‘
'0 I
1.0 "‘
\\‘\
0 5 ~\. ‘ 1998
' ‘-. R2 = 0.995
\*\.~
0.0 . . r . . . .
19-Apr 24-Apr 29-Apr 04-May 09-May 14-May 19-May 24-May 29-Ma
Planting Data
Figure 2.13: Stalk lodging by planting date and year. Regression equations for
predicting stalk lodging from planting date by years are:
1998 - y = -997.58Ln(x) + 10485
1999 - y = 1743.4Ln(x) - 18321

 

55

 

 

 

 

—I
O

51.111 Lodging (at)
O
a

.9
a

0.4

0.2

0.0

 

Max 66 OK 493 P10 3491
Hybrid

Figure 2.14: Stalk lodging by hybrid. Hybrids are listed in order of maturity.
Columns with the same letter are not significantly different.

 

56

 

 

 

2.6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.4 714—“ 86 I RP5303491
I 0K 493 I :,.'
2.2 if 3 HQ 3491 l x"
—_ ‘ O
2 0 -hhhh-h i"'
M...“ .M.“ ’l"

1 8 .‘°-——_‘-.~ {'1
A N
I. 1 6 "v A
v "' 2 - .
E 1.4 ”gr R - 0.7618
3'

1 2 79'
5 ,0"
3 1.0 x"

a"
0.8 ’9"
I
0"
0.6 - ,
K
0.4 '13—‘86
. R2 = 0.9602
0.2 W“
0.0 I I I I I
27-Apr 02-May 07-May 12-May 17-May 22-May
Planting Date

Figure 2.15: Stalk lodging by planting date and hybrid. Regression equations for

predicting stalk lodging by hybrids are:
Max 86 - y = -595.96Ln(x) + 6263.6
DK 493 - y = -746.4Ln(x) + 7846

PIO 3491 - y = 2467.8Ln(x) - 25934

 

57

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.5
R2 = 0.9422
2.0 4.4
o
E 15
E /
3’
i 1.0
w
0.5 t, g
0.0 f .
24,225 29,663 35,065
Population (plantain)
Figure 2.16: Stalk lodging by population. Regression equation for predicting stalk
lodging fi'om population is y = 0.6698Ln(x) + 1.324.

 

 

 

Plant Height

Plant height changed with planting date. Corn hybrids planted early in the season were
usually shorter in stature than later planted corn. When plant height was averaged over
the two years of the study, and by planting date, the earliest planted corn was the shortest
at 109.1 inches (Figure 2.17). As planting date was delayed until May 121', com height
was 113.5 inches, which was an increase of 4.3 inches. When planting date was delayed
to May 25'“, there was a 3.4 inch increase in height compared to the earliest planted corn.
Hybrid characteristics also influence the height of the corn. The hybrids PIO 3491, Max
86, and DK493 were 118.2, 110.1, 106.4 inches tall, respectively (Figure 2.18). Plant

population also influenced plant height. Plant height increased as plant population

58

increased. When plant height was averaged over plant population, there was a 1.2 inch
increase in plant height. As plant population was averaged over planting date, the last
planting date of May 24th had a reduction in plant height at the highest population. All

other planting dates had an increase in plant height as population increased.

 

 

114

R’=0.5016
113 /
112 / o

 

 

 

 

d
d
d

 

 

Plant Holght (In)
5

76
o

 

 

 

108

 

107

 

 

 

1 06 I I I I I I I
27-Apr 1—May 5-May 9-May 113-May 17-May 21-May 25-May
Planting Dab

Figure 2.17: Plant height by planting date averaged over 1998 and 1999. Regression
equations for predicting plant height from planting is y = 4116.5Ln(x) - 43150.

 

 

 

59

 

 

 

 

 

 

 

 

 

 

 

112.5
0
R2=0.8024
112.0
2 111.5
g o
‘c‘ o
a 111.0 ,
110.5
110.0 . .
24.225 29.663 35,065
Population (plantain)

Figure 2.18: Plant height by population averaged over 1998 and 1999. Regression
equations for predicting plant height from population is y = 1.0494Ln(x) + 110.95.

 

 

 

Ear Height

The height at which a corn plant sets an ear is correlated with the height of the plant. Like
plant height, ear height is also affected by planting date. As the planting date was
delayed from April 27th to May 12‘”, ear height increased from 40.9 inches to 44.9 inches,
a difference of 4.0 inches. The rate of increase in height leveled off, and by the May 25"I
planting, there was only a 0.1 inch increase in ear height over the May 1211. planting date
(Figure 2.19). Ear height was strongly correlated to the height of the hybrid. The hybrids,
listed in order of total plant height, are PIO 3491, Max 8, and DK 493. They had ear

heights of 46.1, 43.1, and 41.6 inches, respectively (Figure 2.20). An increase of within

60

row competition, due to an increase in plant population, also caused ear height to
increase. When ear height was averaged by plant population there was an increase of 2.2

inches in ear placement as population increased (Figure 2.21).

 

 

 

 

 

 

 

 

 

 

 

 

 

46
45 . / ¢
44 /
A 43
S /
E
i 42
.- /
13
41 «T _
40
39
38 I I I I T
27-Apr 2-May 7-May 12-May 17-May 22-May
Planting Date

Figure 2.19: Ear height by planting date averaged over 1998 and 1999. Regression
equations for predicting ear height from planting date is y = 0.1495x - 5436.7.

 

 

61

 

 

Ear Hum (ln.)

 

Max 66 OK 493 FIG 3491
Hybrid

Figure 2.20: Ear height by hybrid averaged over 1998 and 1999. Hybrids are listed
in order of maturity. Columns with the same letter are not significantly different.

 

 

 

 

R2 = 0,9969/ {

44.5

 

44.0

 

 

 

Ear mm (In.)
t»
O

 

420 ,fi,fi,“in_‘_¥_i #7-.“ .“

 

 

24.225 29.663 35.065
Populaflon (pl-null)

Figure 2.21: Ear height by population averaged over 1998 and 1999. R2 value
included for reference. Regression equation is y = 1.1009x + 41.396.

 

62

 

Conclusion

The importance of planting date has always been a major consideration when planting
corn. Rossman and Cook (1966) summarized 14 years of data in Michigan and
concluded corn grain yield for early May plantings out-yielded corn planted at later dates.
The results of this study are not always consistent with the work of Rossman and Cook.
Weather patterns in 1998 favored later planting dates. In 1999 this study concurred with
Rossman and Cook that earlier planted corn out-yields later planted corn. Planting date
has a large impact on grain moisture. Based on this study, grain moisture content
significantly increased as the planting date was delayed. These differences in grain
moistures also affected grain test weight, which is an indication of grain quality. Yearly
environmental factors affected stalk lodging as planting date was delayed. Plant and ear

heights dramatically increased as the planting date was delayed.

The selection of hybrids is crucial for maximum corn grain yields. Hybrids should be
selected which will reach physiological maturity for the planting date utilized to reduce
drying costs in the fall (Harpstead and Dysinger, 1998). Inherent characteristics of the
hybrid should play a major role in hybrid selection. Hybrids that yield well under stress
and high plant populations should be selected. Well-adapted hybrids yield equally well
under varying row widths and population conditions. Hybrid selection also influences

test weight, stalk lodging, as well as plant and ear height.

Row spacing impacted grain yields to a lesser degree than did population and hybrid

selection. As row spacing narrowed fi‘om 30-inches to 22-, and then to 15-inches, yields

63

increased. Corn grown in narrow row spacing tended to have a yield advantage over corn
grown in 30-inch row spacing at earlier planting dates. On average, corn grown in 22-
inch rows had a 7.9 bushel per acre increase and corn grown in lS-inch row spacing had
an 8.5 bushel per acre increase over the 30-inch rows. Smaller yield advantages were
observed in corn grown in narrow rows as planting date was delayed. Row spacing did

not affect other traits in the study.

Plant population had the greatest impact on grain yield. As plant population increased, so
did grain yield. In 1998, there was a 15.5 bushel per acre increase in yield as plant
population increased from 24,000 to 35,000 plants per acre. Yields in 1999 were slightly
lower due to environmental conditions resulting in a 10.3 bushel per acre increase from
low to high plant populations. As plant population increased, grain moisture decreased
by only 0.3%. Never-the-less, this small decrease was statistically significant at the 0.05
level. As plant population increased, stalk lodging also increased by 0.7%. Plant and ear

height also increased as plant population increased.

Reference

Benson, G. O. 1990. Corn replant decisions: a review. J. Prod. Agric. 3:180-184.

Dysinger, K, S. M. Canty, J. J. Kells, M. Allen, and D. E. Main. 1997. Corn hybrids
compared in the 1997 season. Michigan State University Extension Bulletin E-431.

Fairey, N. A., and T. B. Daynard. 1978. Assimilated distribution and utilization in maize.
Can. J. Plant Sci. 58:719-730.

F orcella, F anck, and Mark E. Westgate, and Dennis D. Warnes. 1992. Effect of row
width on herbicide and cultivation requirements in row crops. American J. Altern.
Agric. 7:161-167.

Harpstead, D. D., and K. Dysinger. 1998. Relative economic consequences of grong
early or late maturing corn hybrids. In Proc. 53rd Annu. Corn and Sorghum Res.
Conf., Chicago, IL. Am. Seed Trade Assoc., Washington, DC.

Imholte, A. A. and P. R. Carter. 1987. Planting date and tillage effects on corn following
corn. Agron. J. 79:-746—751.

Lauer, J. G., P. R. Carter, T. M. Wood, G. Diezel, D. W. Wiersma, R. E. Rand, and M. J.
Mlynarek. 1999. Corn hybrid response to planting date in the northern corn belt.
Agron. J. 91:834-839.

Loomis, R. S., and W. A. Williams. 1963. Maximum crop productivity: An estimate.
Crop Sci. 3:67-72.

Nafziger, E. D. 1994. Corn planting date and plant populations. J. Prod. Agric. 7:59-62.
Palmer, A. F. E., G. H. Heichel, and R B. Musgrave. 1973. Patterns of translocation,
respiratory loss, and redistribution of 14C in maize labeled afier flowering. Crop Sci.

13:371-376.

Pendelton, J. W., and D. B. Egli, 1969. Potential yield of com as influenced by planting
date. Agron. J. 61:70-71.

Rossman, E. C., and R. L. Cook. 1966. Soil preparation and date, rate, and pattern of
planting. In W. H. Pierrce, S. A. Aldrich, and W. P. Maring (eds). Advances in corn

production: Principles and practices. Iowa State Univ. Prss.

SAS Institute. 1985. SAS user's guide: Statistics. 5th ed. SAS Inst., Cary, NC.

65

Staggenborg, S. A., D. L. Fjell, D. L. Devlin, W. B. Gordon, L. D. Maddux, and B. H.
Marsh. 1999. Selecting optimum planting dates and plant populations for dryland
corn in Kansas. J. Prod. Agric. 12:85-90.

Swanson, Stephan P. and Wallace W. Wilhelm. 1996. Planting date residue rate effects
on growth, partitioning, and yield of corn. Agron. J. 88:208-210.

Thomison, P. R and D. M. Jordan. 1995. Plant population effects on corn hybrids
differing in ear growth habit and prolificacy. J. Prod. Agric. 8:394-400.

Tollenaar, M. 1989. Genetic improvements in grain yield of commercial maize hybrids
grown in Ontario fiom 1959 to 1988. Crop Sci. 29:1365-1371.

Tollenaar, M. 1991. Physiological basis of genetic improvement of maize hybrid in
Ontairo from 1959 to 1988. Crop Sci. 31:119-124.

Yao, A. Y. M., and R. H. Shaw. 1964. Effect of planting population and planting pattern
of corn on the distribution of net radiation. Agron. J. 56:165-169.

66

CHAPTER 3

EFFECT OF ROW SPACING AND PLANT POPULATION ON CORN
SILAGE PRODUCTION IN MICHIGAN

Abstract

Historically, the evaluation of corn hybrids (Zea mays L.) for silage production has been
performed with dual-purpose hybrids. Dual-purpose hybrids can be used either for corn
grain production or for forage production There have been in recent years, corn hybrids
that have been developed with favorable forage production characteristics. Narrow row
studies utilizing dual-purpose hybrids have shown that dry matter increases as row
spacing narrows (Cox et al., 1998). A two-year narrow row study was initiated at
Michigan State University in 1998 utilizing corn hybrids developed specifically for
forage production. The object of this study was to determine the effect of row spacing,
hybrid type, and plant population on silage quality and yield in Michigan. Four corn
hybrids developed specifically for silage production were selected. Each of the four
hybrids were planted in 30-, 22-, and 15-inch row spacings. The combination of each
hybrid and row spacing was also planted at three plant population levels of 26-, 32-, and
36-thousand plants per acre. The plots were arranged as a split-split-plot design with four
replications. There were differences in the quality of the forage harvested between years
due to the condition of the plant when the kernel milk line reached the two thirds level.
Hybrid, row spacing, and plant population effected dry matter content. Hybrid selection
and plant population affected the unadjusted green weight yield in the field. Dry weight

yield was affected by the selection of hybrid, row spacing, and plant population. Hybrid

67

selection and plant population affected harvest index. Hybrid selection, plant population,
and the interaction of row spacing and plant population affected dry matter digestibility.
Acid detergent fiber and neutral detergent fiber were not affected by row spacing.

Hybrid and plant population affected crude protein content. When considering specialty
forage hybrids in narrow row systems, hybrid selection, specifically the ability to

withstand higher plant populations, is important.

Introduction

Narrow row corn has been gaining interest in recent years. Most of the research on
narrow row corn has been to determine the effects on grain yield. A study utilizing dual-
purpose hybrids by Cox et a1. (1998) in New York found that corn silage yield increased
as row spacing narrowed. Row width did not affect silage quafity analyses for the three

years of his study.

In the past, the evaluation of corn hybrids (Zea mays L.) for silage use was conducted on
hybrids that were dual-purpose hybrids. Farmers who planted these dual-purpose hybrids
could use them for either silage or grain production depending upon the need. In recent
years, seed companies have developed hybrids with more favorable silage qualities.
These newer hybrids have higher digestibility traits and higher protein content than do

the older dual-purpose hybrids.

New hybrids can withstand higher plant population densities than older hybrids

(Tollenaar, 1989). Corn silage dry matter increases as plant population levels increase

68

(Cox, 1996). It is recommended that silage corn be planted at plant population levels
7.5% higher, on average, than corn grain (Cox, 1997). Acid detergent fiber and neutral
detergent fiber were not affected by increases in plant population levels (Graybill et al.,

1991).

Harvest index is defined as the weight of the grain fraction of the silage divided by the
weight of the fodder. A high harvest index indicates a higher grain content in the forage.
High grain content makes better ensiling characteristics and increases dry matter and
palatability. The harvest index of older hybrids is generally reduced with increases in
plant population because of interplant competition reducing the grain portion of the
forage (Duncan, 1984). The harvest index of newer released hybrids generally does not
decrease as plant population increases (Tollenaar, 1989). The grain content, energy

density, and digestibility of maize forage is influenced by the harvest index.

Hybrid selection is key to improving silage quality for optimum animal output. There is
significant genetic variability for silage quality between hybrids (Roth et. al., 1970).
Acid detergent fiber, neutral detergent fiber, crude protein, and cell wall digestibility are

all dependant on the plant genotype (Deinum, 1984).

The objectives of this study were 1) to determine the effects of row spacing on silage
yield and silage quality, 2) to evaluate the influence of hybrid type on silage yield
response to row spacing, and 3) to document the influence of plant population on silage

yield response within row spacings.

69

Materials and Methods

Field trials were conducted in 1998 and 1999 on a Capac loam soil at the Michigan State
University Research Farm in East Lansing, MI. The soil is well drained with a pH of
6.75. Three hundred pounds of urea (0-0-60) per acre and 200 pounds of 6-24-24 per

acre were broadcast prior to planting. In both years of the study, soybean preceded corn.

Four maize hybrids BR X6690, PIO 36H36, TMF 106, and TMF 108 with relative
maturity ratings of 108, 100, 106, and 108 days, respectively, were used in this study. All
hybrids were planted in 30-, 22-, or lS-inch rows. Each row spacing was planted at
population levels of 26-, 32-, and 36-thousand plants per acre. Plots were arranged in a
randomized complete block design as a split-split plot with four replications. The main
plots were represented by hybrids (66 by 30 feet), row spacing was the first split (66 by

10 feet), and plant population represented the split-split plot (22 by 10 feet).

Plant population was determined in all plots after corn emerged. Plots were thinned by
hand if the plant population exceeded the established population level for the plot. Plots
were harvested with a mechanical, single row, side-mount forage harvester. The middle
two rows for the 30-inch plots, the middle three rows for the 22-inch plots, and the
middle five rows for the 15-inch plots were harvested as close to the 2/3 milk line stage
as possible. Ears from one row of each plot were harvested by hand and weighed to
determine the harvest index. (For the purpose of this study the harvest index is defined as
the ratio between ear dry matter and fodder dry matter). Sub samples were collected after

plot weight was recorded for quality analyses and to determine silage dry matter content.

70

Silage samples fi'om each plot, containing both fodder and grain, were weighed and oven
dried to determine silage dry matter. Separate ear samples and fodder samples were also

weighed and oven dried to obtain the harvest index.

Silage samples for quality analyses were ground sequentially through a Wiley mill and
Cyclone mill. Dry matter digestibility was obtained by wet chemical analysis from a 0.02
oz. forage sample. In 1998, a wet chemical analysis procedure, using an enzymatic
technique outlined by DeBoever (1986), was used to obtain dry matter digestibility. A
cellulase solution technique was used to obtain dry matter digestibility in 1-999 (Bqu
et al., 1992). Other silage quality components including acid detergent fiber, neutral

detergent fiber, and crude protein were determined using near-infra-red spectrometry.

All data was analyzed with the analysis of variance (AN OVA) and the Mixed Linear
Model in SAS Statistical Software Package version 6.12 (1989-1996 SAS Institute Inc.,
Cary, NC,). The Mixed Linear Model is able to calculate the appropriate error terms for
statistical tests associated with the split-split plot design. Mean separations were
obtained using Tukey's Least Significant Difference Test. To control experimental error,
data was blocked by years (Kuehl, 1994). All other variables (hybrid, row spacing, and
population) were considered fixed. Regression analysis was used where appropriate.

Effects were considered significant in all statistical calculations if P-values <0.05.

71

Results and Discussion

Remarkably different weather patterns in 1998 and 1999 affected the plots differently.
The 1998 growing season had near normal precipitation May through August (Table 3.1).
Precipitation for September was markedly lower than the 30-year average. Over all, the
1998 season ended with a precipitation deficit of 1.6 inches compared to the 30-year
average. In 1998, growing-degree-day (GDD) accumulation was 144 GDD below
normal. Weekly data indicated most of the accumulated GDD for the season occurred
during the later part of May, and August through the first part of September.
Precipitation fell 3.4 inches below the 30-year average for the 1999-growing season.
Timely precipitation (6.8 inches) in July and August increased kernel set at pollination
and facilitated kernel fill. This precipitation helped boost yields for the season.

Growing degree-day accumulation for the 1999 growing season was near normal.

72

 

Table 3.1: Monthly precipitation (inches) and growing-degree-day (GDD)
accumulation for the 1998 and 1999 growing seasons. Thirty-year means have
been included for comparison (1951-1980).

 

 

Precipitation Growing Degree Days1
Month 1998 1999 30 yr. 1998 1 999 30 yr.
May 2.73 1.78 2.73 442 385 338
Jun 2.51 1.07 3.54 522 474 530
July 2.83 4.75 3.02 618 729 640
August 3.94 2.09 3.12 617 551 598
September 1 .29 1 .84 2.50 471 424 418

SeasonalTotal 13.30 11.53 14.91
DEV2 -1.61 -3.38

2 The deviation from the 30-year mean.

 

 

2668 2562 2524
144 38

' GDD calculated for corn at a base 50°F, with a 50°F and 86°F cutoffs.

Data recorded at the Horticultural Research Station, East Lansing, MI.

 

Favorable field conditions, in both 1998 and 1999, allowed plots to be planted in a timely
manner. Plots were planted May 8th and May 4th in 1998 and 1999, respectively. Silage
was harvested when the milk line in the kernel was near 65%. In 1998, there was a larger

differentiation between hybrid maturities resulting in the longer season hybrids needing

more time for the milk line in the kernel to reach 65%. Consequently, harvest was

prolonged over a longer period. Harvesting occurred between August 24til and August

31st in 1998. In 1999, harvest occurred on September 3rd due to the degree day

compression of the hybrids.

73

 

Statistical analyses were combined for the 1998 and 1999 growing seasons. The
summary of the AN OVA table for silage yield shows the significance of the main effects
of hybrids, row spacing, population, and their interactions for dry matter, green weight
per acre, dry weight per acre, and harvest index (Table 3.2). The summary of the
ANOVA table for the silage quality components shows the significance of the main

effects and the respective interactions for dry matter digestibility, acid detergent fiber,

 

Table 3.2: Summary of combined analysis of variance for dry matter

(%DM), green weight per acre (th/A), dry weight per acre (Dwt/A),
and harvest index (PH) for 1998 and 1999.

Source of variation %DM th/A Dwt/A HI

 

 

P-values from ANOVA1
Year 0.0001 0.0002 0.0001 0.0001
Hybrid 0.0001 0.0733 0.0001 0.0038
Row Spacing 0.0322 0.1887 0.0005 0.3903
Hyb*Row 0.3963 0.0072 0.0006 0.4254
Population 0.0121 0.0001 0.0001 0.6355
Hyb*Pop 0.9850 0.0639 0.1322 0.0010
Row *Pop 0.5896 0.2592 0.0703 0.8472
Hyb*Row*Pop 0.2750 0.9764 0.6739 0.2239

' Probability P=0.05

 

 

 

neutral detergent fiber, and crude protein (Table 3.3). Years were significant for all traits
measured due to physiological maturity differences between corn harvest at two-thirds
milk line. The hybrid main effect showed significant differences for all traits measured
in this experiment, except for green weight per acre. Row width was found to affect dry
matter and dry weight per acre. The two-way interaction between hybrid and row
spacing was significant for green weight per acre and dry weight per acre. Plant
population was significant for all traits, except for harvest index. Harvest index was

significantly affected by the two-way interaction of the main effects of hybrid and plant

74

population. Dry matter digestibility was also affected by a two-way interaction of row

spacing and plant population.

 

 

 

 

 

 

Table 3.3: Summary of combined analysis of variance for dry
matter digestibility (%DMD), acid detergent fiber (%ADF),
neutral detergent fiber (%NDF), and crude protein (% CP) for
1998 and 1999.
Source of variation %DMD %ADF %NDF %CP
P-values from ANOVA1

Year 0.0001 0.0001 0.0024 0.0007
Hybrid 0.0001 0.0001 0.0004 0.0043
Row Spacing 0.8001 0.2547 0.6904 0.7804
Hyb*Row 0.9841 0.6395 0.6318 0.5582
Population 0.0298 0.0021 0.0068 0.0001
Hyb*Pop 0.6963 0.5901 0.3769 0.7492
Row *Pop 0.0111 0.4945 0.2127 0.5539
Hyb’Row*Pop 0.841 5 0.8576 0.5903 0.1 889
' Probability P=0.05

Percent Dry Matter

The differences in silage dry matter (%DM) between years were significant (Figure 3.1).
These differences were caused by variations in physiological maturity of the corn fiom
1998 and 1999. Silage harvested in 1998 averaged 32.6% DM, while the average for
1999 was 40.3% DM. This difference in DM was caused by the variation in plant health
when the milk line in the kernel reached two-thirds. Because of these differences in DM,

all other variables in this study were affected.

75

 

 

 

There were also difi‘erences between hybrids and the percent dry matter. There was a
strong correlation between hybrid maturity and dry matter content (Figure 3.1). The later

maturing hybrids had the highest percent dry matter, while the shorter season hybrids had

the lowest.

 

 

 

 

 

 

8

Dry Matter (96)
'6’

3

 

 

 

P10 36H36 TM: 106 BR X6690 TM: 108
Hybrid

Figure 3.1: Dry matter by hybrid and year. Hybrids are listed in order of maturity.
Columns within a year followed by the same letter are not significantly different.

 

 

 

 

As row spacing narrowed, the percent dry matter increased (Figure 3.2). Dry matter
increased by 1.1 and 0.9% in 1998 and 1999, respectively, as row spacing was narrowed

fi'om 30-inches to lS-inches.

76

As plant population increased, dry matter content dropped 0.6% in 1998 due to stress
associated with lack of moisture (Figure 3.3). This trend was reversed in 1999 when dry
matter content increased by 2.9% as plant population increased. There was also a
difference in dry matter between row spacing by years. In 1998, the dry matter content

averaged 32.6%, and in 1999, the average dry matter content was 39.7%.

 

42

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1999
.4 R’ = 0.999
M?—
40 W
36
6
E 36 _
5 01996
E .1999
34
J 1998
R2 = 0.6413
W
32 °
30 a .
30-inch 22-inch 15-inch
Row Spaclng (in.)

Figure 3. 2: Dry matter by row spacing and year. Regression equations for predicting
dry matter fiom row spacings by years are:

1998- y= 0. 8738Ln(x) + 32.074

1999 - y = 0.8323Ln(x) + 39.763

 

 

77

 

 

 

 

 

42 7-777!

€38-E__'_i__7V_ 7
*3
2
gss;-—— 7,,_ iii _ a
u__*_ a A- v,__ _ in

32 , ,, -A 77-

 

 

 

 

20,000 22,000 24.000 26.000 28.000 30.000 32.000 34.000 36.000 38.000
Population (plantsla)

Figure 3.3: Dry matter by population and year. Regression equations for predicting
dry matter from population by year are:

1998 - y = 7.7114Ln(x) - 39.254

1999 - y = -1.8455Ln(x) + 51.58

 

 

 

Green Weight (T ons/Acre)

Silage green weight was affected by a two-way interaction of hybrid by row spacing
(Figure 3.4). As row spacing was narrowed to less than 30—inches, green weight
increased for all hybrids. All hybrids, except for TMF 106, had an increase in green
weight for 22-inch rows. The lS-inch rows had higher green weight yield across hybrids,
except BR X6690, where the green weight yield was lower than for the 30-inch row

spacing.

78

 

 

28.00

27.00 a J= 33 inch l

 

8
8

 

 

Oran Weight (tannin)

22.00 -

 

 

 

Figure 3.4: Green weight by hybrid and row spacing. Hybrids are listed in order of
maturity. Columns followed by the same letter are not significantly different.

 

 

 

Green weight response to plant population was markedly different between years. In
1998, green weight yield increased 2.9 ton per acre from the lowest to highest plant
population (Figure 3.5). In 1999, there was a drop in green weight of 0.2 ton per acre as
plant population increased. In 1998, the average green weight was 26.7 ton per acre. The
average for 1999 was 23.4 ton per acre when averaged across plant population. This
difference in green weight may be due to the lower precipitation totals for 1999 prior to
silage harvest.

79

 

 

 

 

 

Green Weight (tons/a)

 

 

 

 

24 1999
‘1 7 n 4 v _ 7 T’
R - 0.5284
I -
23 1* . ¥—¥ * 7%
22 4r .2
21 1 4—1

 

 

20 l I I l l I I I
20.000 22.000 24.000 26.000 28.000 30.000 32.000 34.000 36.000 38.000
Population (phntala)

 

Figure 3.5: Green weight by population and year. Regression equations for predicting
green weight from population by year are:

1998 - y = 8.1308Ln(x) - 56.94

1999 - y = -0.5664Ln(x) + 29.268

 

 

 

Dry Weight (T ons/Acre)

Silage dry weight yield differences between years were significant (Figure 3.6). The dry
weight yield averages for 1998 and 1999 were 8.6 ton per acre and 9.3 ton per acre,
respectively. The dry weight yield was different among hybrids. The shorter season
hybrids yielded less dry matter per acre than did the later maturing hybrids. This trend

between hybrids was evident both years of the study.

80

 

 

 

 

 

Dry Weight (ionsIA)

  

 

 

 

PIO 38H38 TMF 106 BR X6890 TMF 108
Hybrid

Figure 3.6: Dry weight by hybrid and year. Hybrids are listed in order of maturity.
Columns with the same year followed by the same letter are not significantly different.

 

 

 

Silage dry weight yield increased as row spacing was narrowed from 30-inches to 15-
inches. Differences in dry weight yield by row spacing was also observed between years
(Figure 3.7). The silage dry weight yield averaged over row spacing was 8.6 ton per acre
and 9.4 ton per acre for 1998 and 1999, respectively. In 1998, silage dry weight
increased 0.2 ton per acre from 30-inch rows to 15-inch rows. There was a 0.1 ton per
acre drop in silage dry weight for the same year when row spacing was narrowed from
30-inches to 22-inches. There was a 0.6 ton per acre increase in 1999 as row spacing was

narrowed fi'om 30-inch to 15-inch row spacing.

81

 

 

9.80

9.60 1

so so so
8 8 8

Dry Weight (tons/a)
on on
8 8

8.40 a

8.20

8.00

7.80

r r ** * /.
[-1999 R’ = 0.8877
,x"
.9"
I
o
——_ 1998
W R2 = 0.2838
L
ISO-inch 22-inch I 15-inch
Row Spacing
Figure 3.7: Dry weight by row spacing and year. Regression equations for
predicting dry weight from row spacing by year are:
1998 - y = 0.2019Ln(x) + 8.4873
1999 - y = 0.6092Ln(x) + 8.9861

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

There was a hybrid by row spacing interaction that affected silage dry weight yield. Most
of the hybrids had an increase in dry weight yield as row spacing was narrowed from 30-
inches (Figure 3.8). Two of the hybrids showed inconsistencies in yields for the 22-inch
row spacing. The 22-inch row spacing yielded 0.2 ton per acre less than the 30-inch rows
for TMF106 when averaged over the two years of the study. There was a 0.5 ton per acre
increase of the 22-inch row spacing over the 15-inch row spacing for BR X6690. The
largest increase in dry weight for narrow rows occurred with the TMF 108 hybrid. There
was a 1.2 and a 0.6 ton per acre dry weight yield increase for 22- and 15-inch row

spacings, respectively, over the 30-inch row spacing.

82

 

 

 

 

10.5 lfi-trtcb a 1
D22-inch "— .
E115-inch ‘

7 , ab

10.0% v- .7 7 77-

 

 

 

Dry Weight (tonala)

 

 

 

 

 

 

 

PIO 36H36 TMF 106 BR xseQO TMF 108
Hybrids

Figure 3.8: Dry weight by hybrids and row spacing. Hybrids are listed in order of
maturity. Columns followed by the same letter are not significantly different.

 

83

 

 

 

Silage dry weight yield differed over years when averaged across plant population. In
1998, the average silage dry weight yield was 8.6 ton per acre when yield was averaged
across plant population (Figure 3.9), and there was a 0.8 ton per acre increase in silage
dry weight as plant population was increased from lowest to highest. As plant population
increased from lowest to highest in 1999, there was a 0.6 ton per acre increase in dry

weight and the average silage dry weight yield was 9.4 ton per acre.

 

 

 

 

 

 

 

 

 

 

9.8 ~——--- ,,7,7,..,__ , —— -~ « - - i—w-r—w-h—
1999
- e R2 = 0.905
9 6 01998 ,4
I 1999 /
‘ I
94 - — _-
/ 1998 I
9'2 R: = 0.9978 l
3 » ‘
O
a... . a; 74%.
:7 3
g l
.9 r
O a.
3 8.8
3‘ i
n l
8.6 - , .
6.4 - ——«7 — i i,
I
l
6.2 if, r 7 ‘
8.0 f

 

20.000 22.000 24.000 26,000 28.000 30.000 32.000 34 .000 36.000 38.000
Population (plantala)

Figure 3.9: Dry weight by population and year. Regression equations for predicting
dry weight from population by year are:

1998 - y = 2.2009Ln(x) - 14.032

1999 - y = 1.5852Ln(x) - 6.9954

 

 

84

 

Harvest Index

Harvest index, the percentage of corn grain in the forage mix, is a good indicator of the
energy available in silage. There were differences between years when harvest index was
averaged over hybrids (Figure 3.10). The harvest index in 1998 was the lowest,
averaging 50.6%. In 1999, the harvest index was 55.8% of corn grain in the total silage
mix. Hybrids exhibited different harvest indices. Hybrid TMF 106 produced the lowest
harvest index (46%) by any hybrid in 1998. The highest harvest index, 57.4%, was
produced by PIO 36H36 in 1999. The most consistent harvest index was produced by

TMF 108. It had a harvest index of 50.6% and 53.4% for 1998 and 1999, respectively.

 

 

.1996
E1999

 

Harvest index (it)

 

 

 

PIO 36H36 TMF 106 BR X6690 TMF 106
Hybrid

Figure 3.10: Harvest index by hybrid and years. Hybrids are listed in order maturity.
Columns within a year followed by the same letter are not significantly different.

 

 

 

85

 

 

 

 

 

56 TMF108 7 BR X6690
\ R2 = 0.0472 0 A 1?: o 4148
. 1
54 7 77 7 7 7 7 7 7.
PHI 36H36

.122: 03%;.

 

 

Harvest Index (56)
8 is

 

‘r—r'imaanaa
‘ITMF 106
l
44 . A BR X6690

L0 M Lou

 

l

42 . . , . 7 . . . . . . 1

23.499 24.303 24.770 25.269 29.383 29.762 30.144 30.911 34.868 35.585 35.915 36.268
Population (plantain)

 

 

Figure 3.11: Harvest index by hybrid and population. Regression equations for
predicting the harvest index from population by hybrid are:

PIO 36H36 - y = 0.8721Ln(x) + 52.098

TMF 106 — y = -3.4347Ln(x) + 55.695

BR X6690 - y = 0.3548Ln(x) + 54.383

TMF 108 - y = 0.1269Ln(x) + 54.953

 

 

 

The harvest index was affected by the two-way interaction of hybrid and plant population
(see Figure 3.11). The two hybrids, TMF 108 and BR X6690, held a consistent harvest
index as population increased. The harvest index increased for PIO 36H36 as plant
population increased from lowest to highest. There was a significant drop in harvest
index for TMF 106 as plant population increased. The harvest index dropped from 58%
to 48% as plant population was increased from lowest to highest. The interaction
between plant population and harvest index may be correlated with a hybrid's ability to

withstand high plant population stress.

86

Dry Matter Digestibility

There were differences in hybrid dry matter digestibility between years. The average
digestibility of the hybrids, when averaged over years, was 67.6% and 62% for 1998 and
1999, respectively (Figure 3.12). Dry matter digestibility of the hybrids was lower in
1999 than in 1998. This difference in digestibility was due to differences in hybrid
physiological maturity at which hybrids were harvested each year. The same hybrid,
TMF 106, had the lowest digestibility both years of the study. The hybrid with the

highest digestibility for both years of the study was BR X6690.

 

 

70 , ,_ -7 , , I1999

 

 

8

 

3

 

Q
N
l

8

Dry Matter Digestibility (is)

 

 

 

PIO 36H36 TMF 106 BR X5690 TMF 108

Figure 3.12: Dry matter digestibility by hybrids and years. Hybrids listed in order
of. Columns within a year followed by the same letter are not significantly different.

 

 

 

87

Plant population affected silage dry matter digestibility. As plant population increased,
silage dry matter digestibility decreased (Figure 3.13). In 1998, when silage dry matter
digestibility was averaged over plant population, it averaged 67.6%. The dry matter
digestibility dropped only 0.4% in 1998 as plant population increased fiom lowest to
highest. In 1999, dry matter digestibility decreased 1.7% as plant population was
increased from lowest to the highest. The average silage dry matter digestibility, for the

1999-growing season, was 62%.

 

Silage dry matter digestibility was affected by the interaction of hybrid and row spacing.

Silage fiom corn grown in narrow row widths had higher dry matter digestibility than did

 

69 7--

 

 

 

 

 

 

 

 

 

 

 

63 ,__ W Z 1998
R = 0.9198 .
67 777 7 7 - 7 7
7
T 66 7 ~ 7 - 7.
g .1998 l
g .1999
2 I
H 65
0
2’
O
‘5 64
’6'
E
E 63
\-
62 319%,, I,
\~__~“ ‘
81 I l
80

 

 

20.000 22.000 24.000 26.000 28.000 30,000 32.000 34.000 36.000 38,000
Population (plants/a)

Figure 3.13: Dry matter digestibility by population and years. Regression
equations for predicting dry matter from population by year are:

1998 - y = -1.1386Ln(x) + 79.287

1999 - y = -4.235Ln(x) + 105.66

 

 

 

88

the 30-inch row. The 22-inch row spacing had higher DNfl) the lS-inch row spacing at
the lower two population levels of 24,460 and 30,050 plants per acre. The 22-inch row
spacing had a 3% decrease in dry matter digestibility fiom the 30-inch row spacing, while

the 15-inch row spacing had a 0.3% increase over the 30-inch rows (Figure 3.14).

 

    

a 'I 304691
66.0 UZ2-inch

El 15-ind't

 

65,5 4 430—“
i 65.0 7
E

g 64.5 7
i

g 64.0 ._2
g 63.5 __

63.0 -

62.5 «

 

 

 

 

 

 

 

62.0 -

 

 

 

24.460 30.050 35.659
Popouiation (plantIIa)

Figure 3.14: Dry matter digestibility by population and row spacing. Columns
followed by the same letter are not significantly different.

 

 

 

89

 

Acid Detergent Fiber

Acid detergent fiber contains cellulose, lignin, and heat-damaged protein. It is the
fraction insoluble in an acid detergent solution. Acid detergent fiber is closely related to
the digestibility of the forage. The relationship between acid detergent fiber and
digestibility is an inverse relationship in that, as acid detergent fiber decreases, the

potential digestibility of the forage increases (Cullison, 1982).

. -r-...~ 'J—Nawa.’

Hybrid selection affected silage acid detergent fiber. There was a significant difference 1'.

 

”fur

between the hybrids selected for this trial. There was also a difference between the years
of the study. In 1998, the acid detergent fiber was 24.1% when averaged over hybrids
(Figure 3.15). The acid detergent fiber levels were, on average, 28.8% for the 1999
season. In 1998, TMF 106 had the highest level of acid detergent fiber, while

BR X6690 had the lowest level of acid detergent fiber. Again, in 1999, TMF 106 had the
highest level of acid detergent fiber but PIO 35H36 had the lowest level.

As plant population increased fi'om lowest to highest, the percentage of acid detergent E.
fiber increased. In 1998, acid detergent fiber increased 0.4% when plant populations

increased (Figure 3.16). There was a 1.7% increase in acid detergent fiber level as plant

 

population increased in 1999. On average, acid detergent fiber levels were 24.0% and "r

28.3% for 1998 and 1999, respectively.

90

 

 

 

 

25—

Acid Datarpent Fiber (55)

 

 

 

Hybrida

Figure 3.15: Acid detergent fiber by hybrid and year. Hybrids are listed in order of
maturity. Columns followed by the same letter are not significantly different.

 

91

 

 

31

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

30 _ 1999
l .1998 i R‘ = 0.6964.
.1999‘
29 '“
/
.. 26 5.7"”
1'.
‘3’ 27
ii:
$26
3 1996
3 25 Rf: 0.9216
3 24 ‘4’ I E
i—— r
'1
23 3.
3.
22 I:
21 r I I I I I I 1 d
20.000 22.000 24,000 26.000 28.000 30.000 32.000 34.000 36.000 38.000

Popllation (plan!!!)

Figure 3.16: Acid detergent fiber by population and years. Regression equations
for predicting acid detergent fiber from population by year are:

1998 - y =1.1852Ln(x)+ 11.9

1999 - y = 4.3765Ln(x) - 16.369

 

 

 

Neutral Detergent Fiber

Neutral detergent fiber is the percentage of cell wall material or plant structural

components in forage. The total fiber content of forages is contained in the neutral

 

detergent fiber fiaction. The neutral detergent fiber contains cellulose, hemicellulose,
lignin, and heat -damaged protein. Neutral detergent fiber is inversely related to the

intake potential of the forage (Cullison, 1982).

Corn silage neutral detergent fiber was afiected by hybrid selection There were also

differences between years for each hybrid selected for this study. The average neutral

92

detergent fiber across all hybrids for 1998 and 1999 was 43.5% and 46.3%, respectively
(Figure 3.17). The neutral detergent fiber levels for TMF 106 were the highest for both
years of the study. The lowest percent of silage neutral detergent fiber were for BR

X6690, in 1998 and P10 36H36 in 1999.

 

 

 

60

 

50

:5
O
7

Nautrai Detergent Fiber (5%)
N (a)
O O
‘ i

 

 

 

PiO 36H36 TMF 106 BR X8690 TMF 108
Hybrid

Figure 3.17: Neutral detergent fibers by hybrids and years. Hybrids are listed in order
of maturity. Columns followed by the same letter are not significantly different.

 

 

 

Silage neutral detergent fiber increased as plant population increased. In 1998, neutral
detergent fiber averaged across plant population was 43.5% and increased 0.3% as plant
population increased (Figure 3.18). There was a 2.7% increase in neutral detergent fiber
in 1999, as plant population increased. The average neutral detergent fiber level, when

averaged across all populations for 1999, was 45.5%.

93

 

 

49

 

 

48 01998
11999 1999 I

 

 

 

 

”3°
Y

 

\

Neutral Detergent Fiber (16)
a

 

1996
R2 = 0.2394

:

 

 

 

 

 

If

 

42 I I I T I I V
20.000 22.000 24.000 26.000 28.000 30.000 32.000 34.000 36.000 38.00
Popdation (plantela)

Figure 3.18: Neutral detergent fiber by population and years. Regression equations
for predicting neutral detergent fiber from population by year are:

1998 - y = 0.9732Ln(x) + 33.528

1999 - y = 6.8533Ln(x) - 24.396

 

 

 

Crude Protein

Silage crude protein was affected by the inherent characteristics of the hybrids. There

were significant differences in silage crude protein levels fiom year to year. In 1998, the

 

average protein level was 7.1%, and in 1999 it was 7.7% (Figure 3.19). PIO 36H36 had
the most consistent levels of crude protein between the two years of the study. In 1998,
PIO 36H36 had the highest level of crude protein at 7.8% and the second highest level of

crude protein in 1999 at 7.9%. The highest level of crude protein in 1999 was BR X6690

at 8.1%.

94

Plant population affected silage crude protein. As plant population increased, silage
crude protein decreased. In 1998, crude protein levels decreased 0.2% as plant
population increased from lowest to highest (Figure 3.20). There was a 0.5% drop in
silage crude protein in 1999, as plant population increased. The average crude protein for

1998 and 1999 was 7.1% and 7.9%, respectively.

 

 

 

 

Crude Protein (96)

 

 

 

PlO 36H36 TMF 106 BR X6690 TMF 108
Hybrid

Figure 3.19: Crude protein by hybrid and year. Hybrids are listed in order of
maturity. Columns followed by the same letter are not significantly different.

 

 

 

95

 

 

 

8.20 1 -~ ~ - 7 77 . , . .7 -.- ., If.

 

 

 

 

 

 

71996

8.00 __

‘I\ I 1999
7.60 ‘xx‘

5“!
‘~~-‘ R2 = 0.993
7.60 “~V,__
“i

crude Puebla (11.)

N
fit
0
|
l

 

7.20 ,\

7.00 7 i

6.80 r t r . t r r
22,000 24,000 26,000 28.000 30.000 32.000 34,000 36.000 38.000

Populdion (phnbll)

O
O
"1.
ll
9
to
I:
"a"

 

 

21

Figure 3.20: Crude protein by population and year. Regression equations for
predicting crude protein from population by year are:

1998 - y = -0.6474Ln(x) + 13.79

1999 - y = -1.2137Ln(x) + 20.251

 

 

 

Conclusion

The physiological maturity of corn hybrids is critical when harvesting corn for silage.

The quality of corn silage is dependent upon the stage at which the corn is harvested.

 

This can be observed in the difference between the silage quality traits over the two years
of this study. In 1998, silage was harvested at earlier physiological maturity than in
1999. As corn advances in maturity, dry matter increases within the plant. Subsequently,
tissues within the plant contain less water and more components that are harder to digest.
This increase in lignin, cellulose, and hemicellulose decreases the dry matter digestibility

of the silage. This, in turn, affects the acid detergent fiber and the neutral detergent fiber.

96

The only silage component that increases as corn matures is crude protein. Crude protein
increases as the grain in the silage matures and ripens. As harvest is delayed, the increase

in dry matter affects the green weight yield, resulting in less total tonnage per acre.

The inherent characteristic of hybrids selected for corn silage appears to have a
significant impact on many aspects of corn silage, with the exception of green weight per
acre. Plant architecture will affect the yield. Plants that are taller tend to produce more
tonnage per acre than do shorter plants at the same population. The genetic
characteristics of the plant tend to affect the digestibility of the silage as well as the
potential intake. The harvest index on a hybrid is a good indication of how a hybrid
responds to stress. If the harvest index does not decrease as plant population increases
the hybrid is able to withstand stress well. The harvest index is also closely related to the

crude protein in the silage.

Row spacing affected the dry matter content of the corn silage. Corn grown in narrow
rows tended to be drier than corn grown in wide rows. Narrow rows will also promote
more plant growth than wider rows. Corn grown in narrow rows tended to be taller, thus
producing more tonnage per acre. Row spacing affected green weight yield and the dry

weight yield (tons per acre).

Plant population affected all aspects of silage production and quality, except for the

harvest index. As one would expect, as the number of plants per acre increase, so does

the tonnage produced per acre. The amount of silage dry matter also increases. Stresses

97

 

r. I‘lf.”

 

associated with the higher plant population may reduce the digestibility of the silage.
The interaction between hybrids and plant population also affects the harvest index that is
produced. Dry matter digestibility is affected by the interaction of row spacing and

population.

98

 

 

References

Bughrara, S. S. and D. A. Sleper, 1986. Digestion of several tempaerate forage species by
a prepared cellulase solution. Agron. J. 84:94—98.

Bughrara, S. S., D. A. Sleper, and P. R. Beuselinck, 1992. Comparison of cellulase
solutions for use in digesting forage samples. Aron. J. 14:203-214.

Cox, William J ., 1996. Whole-plant physiological and yield response of maize to plant
density. Agron. J. 88:489-496.

Cox, William J. 1997. Corn silage and grain yield response to plant densities. J. Prod.
Agric. 10:405-410.

Cox, William J ., Debbie R. Cherney, and John J. Hanchar. 1998. Row Spacing, hybrid,
and plant density effects on corn silage yield and quality. J. Prod. Agric., 11:128-134.

 

Cullison, Arthur, 1982. Feeds and Feeding third edition. Reston Publishing Co. Inc.,
Reston VI.

De Boever, J. L., B. G. Cottyn, F. X. Buysse, F. W. Wainman, and J. M. Vanacker, 1986.
The use of an enzymatic technique to predict digestibility, metabolism and net energy
of compound feed stuffs for ruminants. Anirn. Feed Sci. Technol., 14:203-214.

Deinum, W. G. 1984. A theory to explain the relationship between corn population and
grain yield. Agron. J. 24:1141-1145.

Duncan, W. G., 1984. A theory to explain the relationship between corn population and
grain yield. Agron. J. 24:1141-1145 Ir-

Graybill, J. S., W. J. Cox, and D. J. Otis. 1991. Yield and quality of forage maize as
influenced by hybrid, planting date and plant population. Agron. J. 83:559-564.

Kuehl, Robert O. 1994. Complete Block Designs. In Statistical Principles of Research
Design and Analysis. Duxbury Press.

 

Roth, L. S., G. C. Marten, W. A. Compton, and D. D. Stuthman, 1970. Genetic variation
of quality traits in maize (zea mays L.) forage. Crop Science 10:365-367.

SAS Institute. 1985. SAS user's guide: Statistics. 5th ed. SAS Inst., Cary, NC.

Tollenaar, M. 1989. Genetic improvement in grain yield of commercial maize hybrids
grow in Ontario from 1959 to 1988. Crop Sci. 29:1365-1371.

99

CHAPTER 4

EFFECT OF ROW SPACING AND PLANT POPULATION ON
TRANSGENIC Bt CORN PERFORMANCE IN MICHIGAN

Abstract

European Corn Borer (Ostrinia nubilalis) is a significant pest in the corn growing area of
North America. In the predominant corn growing areas European Corn Borers (ECB)

will produce two generations of offspring per season. The feeding damage of ECB can

 

result, on average, in a 16 bushel per acre yield loss (Rice, 1997). Seed corn companies
have developed ECB resistant hybrids that produce a toxin that kills ECB upon ingestion
of plant material. This toxin is produced fiom a Bacilllus thuringensis (Bt) gene that is
inserted into the corn genome. A two year study was conducted at Michigan State
University in 1998 and 1999 to determine whether corn hybrids containing the B! gene

are better suited for narrow row corn production systems than conventional hybrids.

 

Three near-isogenic hybrids were selected for this study. One of the three hybrids was a '6;
conventional hybrid without any transgenic genes. The other two hybrids contained one '
additional gene of CrylAb or Cryl Ac each. Each of the three hybrids were planted at

it

three row spacings of 30-, 22-, and 15-inch rows. Each row spacing and hybrid
combination was planted at three plant populations. The plots were arranged in a split-
split-plot design. The effect of ECB pressure could not be assessed due to weather
conditions that did not favor ECB infestation. As expected, hybrid type did not have an
affect on grain yield due to the fact that the hybrids were near-isogenic. There was an

increase in grain yield as plant population increased. The 15-inch row spacing had an

100

average of 8.7 bushel per acre yield advantage over the 30-inch row spacing. Only plant
population affected grain moisture. Large differences in test weight were affected by the
growing condition from year to year and by row spacing. Differences in stalk lodging
were observed between years and row spacings. These results indicate that genetically
engineered hybrids yield equally well in narrow row systems which utilize higher

populations.

Introduction

The European Corn Borer (ECB), Ostrinia nubilalis, is a devastating insect pest in the
corn growing regions of North America and Europe (Beck, 1987; Hudon et al., 1987).
Throughout the North American Corn Belt, two generations of ECB are typical. The first
generation ECB causes damage by feeding on the whorl leaf and tasseL as well as stalk
tunneling. The second generation attacks the tassel, silks, and ear shanks. Yield losses are
caused by reduced plant growth, stalk lodging, dropped ears, and poor grain quality. In
Iowa, during the five years between 1991 and 1996, yield losses, on an average, were 16

bushels per acre due to ECB (Rice, 1997).

In recent years, much publicity has been generated about ECB-resistant com. This
resistance is achieved by inserting a gene from the soil bacterium Bacillus thuringiensis
(Bt) into the corn plant. The Bt gene produces a crystal protein that is toxic to insects.
There are over 3,000 strains of the B! organism that have been identified and each
produces a different protein that is toxic to certain target insects (Feitelson et al., 1996).

The crystal protein, which is produced to provide resistance from ECB, is from the strain

101

 

 

B. t. kustaki. This protein is deadly only to Lepidoptera larvae when ingested. Once the
protein is ingested, the crystal protein binds to the midgut of the ECB. The binding of the
crystal protein causes the gut to rupture or leak. This process stops the ECB from feeding

and it may or may not cause it to die.

The genes that produce this crystal protein are either the CrylAb or CrylAc gene. The
CrylAb gene has been inserted into plants three different times and each insertion is
known as an event. These different events, utilizing the CrylAb, have become known as

176, Bt-l 1, and MON-810. The CrylAc event is known as the DBT 418. Each event

 

expresses the crystal protein in the plant differently and for a different duration. Events
MON-810 and Bt-ll provide 99% control of first and second generation ECB. Events
176 and DBT 481 provide 99% control of first generation ECB, but only control 50-75%

of second generation ECB.

Differences in the expression of the CrylAb gene are due to the location of gene insertion
into the corn chromosome. This point of insertion could potentially interfere with the
yield of the hybrid. Some have suggested there might be a “yield drag” associated with

ECB-resistant corn, similar to that seen in Imidazolinone-resistant corn hybrids (Kells

i"
‘3

and Dysinger, 1996).

ECB-resistant corn hybrids grown in the absence of ECB pressure, may yield less than
other new corn hybrids. (Hayenga et al., 1992). This difference in yield may be due to

the time lag it takes to backcross transgenic traits into the inbred parents of the existing

102

hybrid (Greaves et al., 1993). The backcrossing technique requires four to seven
generations to transform the trait into the recurrent inbred and recovers 99% of the
recurrent inbred’s genetic background (Greaves et al., 1993; Newhouse et al., 1991a). In
addition, the transgenic inbreds might take up to three years of testing to ensure that near-
isogenic inbreds have been recovered (N ewhouse et al., 1991a). The time required to
backcross the transgenic trait into an inbred will cause a transgenic hybrid to lag behind
the yield advantage of new hybrids, which have expected yield increases of 1-2% per

year (Hallauer et al., 1988).

Hybrids transformed with the Bt genes are available and are being highly marketed by
seed companies. Michigan growers need to know how these hybrids compare to non-
transgenic hybrids under environmental conditions within the state. Growers should be
informed about their options and how these corn hybrids perform for them. In the past,
transgenic hybrids yielded less than their non-transgenic, near-isogenic counterparts
when compared under low ECB pressure. Recent data, however, shows the transgenic,
near-isogenic hybrids are improving and may yield more than non-transgenic, near-
isogenic hybrids. Nevertheless, the question remains whether transgenic hybrids respond

similarly to row spacing and population across different 8! events.

Methods and Materials

Field studies were conducted in southern Michigan in 1998 and 1999. Trial locations in
Calhoun and Monroe counties were chosen to ensure sufficient levels of ECB infestation.

Three near-isogenic hybrids were selected for this study. Two of the three hybrids, DK

103

 

 

580BtX and DK 580BtY, were genetically modified for resistance to corn borer using
CrylAb or Cry] Ac gene, respectively. The hybrid DK 580 was selected as the non-
transgenic hybrid for comparison. The three hybrids were planted in 30-, 22- and 15-inch
row spacings. Each of the row spacings were planted at population levels of 26-, 32-, and

38-thousand plants per acre.

The trials were arranged as a split-split-plot design with a complete block randomization !
and four replications. The whole plot was represented by the hybrids (66 by 30 feet), row

spacing represented the split-plot (66 by 10 feet), and the population (22 by 10 feet)

 

represented the split-split plot. This design was chosen so main effects and their

interactions could be better observed.

Plots were planted with a mechanical planter capable of planting in 30, 22, and 15 inch
row widths. After plants emerged, stand counts were taken on all plots to determine the
population. Plots were thinned by hand if population levels exceeded levels assigned to

the particular plot.

At planting time, an additional lO-foot plot was planted at the end of each plot to assess

 

ECB population levels. Five consecutive corn plants were selected, prior to harvest, from
each plot to determine the amount of plant injury from natural infestation of corn borer.
These five corn plants were dissected to assess the number of ECB larvae per plant, and

the length of tunneling.

104

Lodging notes were taken prior to corn grain harvest. Only plants with stalks broken
below the ear were counted as lodged. The percent of lodging was calculated based upon

the total number of plants in the plot.

Plots were harvested mechanically for corn grain. Moisture content and field weights
were automatically measured by the GrainGageTM, a HarvestData SystemTM mounted on
the plot combine. This system used the grain samples from each plot and sped up the
harvesting and data collection procedure. Grain yields were reported at a standard 15.5%

moisture. Test weights were recorded and reported at harvest moisture.

All data was analyzed with the analysis of variance (ANOVA) and the Mixed Linear
Model in SAS Statistical Software Package version 6.12 (1989-1996 SAS Institute Inc.,
Cary, NC,). The Mixed Linear Model is able to calculate the appropriate error terms for
tests associated with the split-split-split plot design. Mean separations between all
variables were obtained by Tukey's Least Significant Difference Test. All variables were
considered fixed (planting date, hybrid, row spacing, and population). Regression
analysis was used where appropriate. Effects were considered significant in all statistical

calculations if P-values < 0.05.

Results and Discussion

Weather patterns for the 1998 and 1999 growing seasons were similar. The growing
degree-day (GDD) accumulations for 1998 were 491 GDD in the South East and 197

GDD in the South West above the 30-year means (Table 4.1). In 1999, the South East

105

 

III—II

portion of Michigan had 412 GDD and the South West had 79 GDD accumulations above
the 30-year means. Precipitation was 4.1 and 6.1 inches below the 30-year norm for the
South East portion Michigan in 1998 and 1999, respectively (Table 4.2). The South West
portion of Michigan was 2.7 inches above the 30-year norm in 1998. In 1999,
precipitation was 4.1 inches less than the 30-year norm. Timely rainfall during
pollination and kernel fill helped to increase yields that would have otherwise been

reduced. This drier than normal weather also attributed to a reduction in ECB pressure. ’

 

Table 4.1: Monthly growing degree day (GDD)l accumulation for the 1998- . ..
1999 growing seasons by regions. Thirty-year means have been included for {-

 

 

 

comparison (1951-1980). - 4.,
Month

Region Year May June July Aug. Sept. Total DEV

South East 1998 509 622 719 697 545 3092 491

1999 437 645 811 617 503 3013 412
30 yr. 353 542 658 616 432 2601

 

 

South West 1998 473 557 681 681 512 2904 197
1999 419 616 762 554 436 2786 79
30 yr. 373 562 681 641 450 2707

 

' GDD calculated at base 50°F, with 50°F and 86°F cutoffs.
Data courtesy of MSU Agricultural Weather Office.

 

 

 

 

106

 

Table 4.2: Monthly accumulated precipitation (inches) for the 1998- 1999

growing season. Thirty-year means have been included for comparison (1951-
1980).

 

Month
Mon Year May June Jty Au; Sept. Total DEV
South East 1998 0.8 1.8 3.4 5.1 0.6 11.8 -4.1
1999 3.5 2.0 2.0 1.3 1.0 9.8 -6.1
30yr. 3.7 3.0 3.3 3.2 2.6 15.9

 

 

SouthWest 1998 1.8 4.4 2.9 8.4 2.0 19.4 2.7
1999 1.7 2.8 3.5 2.8 1.9 12.6 -4.1
30yr. 3.2 3.9 3.5 3.3 2.9 16.7

 

Data courtesy of MSU Agricultural Weather Office.

 

 

 

 

The summary of the combined ANOVA table for 1998 and 1999 shows the significance
of the main effects of location, hybrid, row spacing, population, and their interactions
(Table 4.3). There were no traits that were statistically different between years. The only
significant difference between hybrids was grain test weight. The lack of observed
differences between hybrids could be due to the fact that all hybrids are near-isogenic.
Row width was found to influence grain yield and stalk lodging. Plant population also
influenced grain yield. There was only one trait that was significant for the two-way

interaction of hybrid x row spacing, and that was test weight. The two-way interaction of

 

row spacing x population showed a significant effect for percent grain moisture only.
The two-way interaction of row spacing x population and the three-way interaction of

hybrid x row spacing x population did not affect any of the traits observed.

107

 

Table 4.3: Narrow Bt summary of combined analysis of
variance for grain yield (GY), percent grain moisture (%H20),
test weight (TSTW), and stalk lodging (SL) for 1998 and 1999.

Source of variation GY %H20 TSTW SL

 

 

P-values from ANOVA1
Year 0.1709 0.9454 0.1672 0.2065
Hybrid 0.3250 0.3182 0.0243 0.2358
Row Spacing 0.0011 0.0995 0.6336 0.0048
Hyb*Row 0.5730 0.7814 0.0024 0.2621
Population 0.0001 0.1835 0.0677 0.2500
Hyb*Pop 0.4362 0.0255 0.4877 0.7667
Row*Pop 0.6777 0.7535 0.3105 0.5375
Hyb*Row*Pop 0.7018 0.1416 0.0632 0.5624

 

 

'Probability P = 0.05

 

Grain Yield

There were only two main effects that had an impact on grain yield. They were row
spacing and plant population. The selection of hybrids that were near-isogenic
eliminated any interaction of hybrids with grain yield. Grain yield increased as row
spacing narrowed. The 15-inch row spacing had the largest, consistent increase in yield
over the two years of the study. In 1998, lS-inch rows had a 6.6 bushels per acre yield
advantage over the 30-inch rows (Table 4.4). There was also a 10.9 yield advantage of
the 15-inch rows over the 30-inch rows in 1999. These large yield advantages resulted in
an average of 8.7 bushels per acre increase for the 15-inch rows over the course of the
two years. The 22-inch row spacing also had a yield advantage over the 30-inch rows but
this was much smaller. The 22-inch row only had a 1.8 bushels per acre advantage, on

average, over IWO years.

108

 

 

 

Yield perfomrances of the three hybrids were closely related to plant population. As
plant population increased from 25,850 to 31,004 plants per acre, there was a 6.5 bushels
per acre increase in grain yield (Figure 4.1). When plant population increased fiom

31,004 to 35,728 plants per acre, there was only a 0.5 bushel per acre increase.

 

Table 4.4: Grain yields (Bu/Acre) by row spacing with
advantage over 30-inch rows for comparison.

 

 

 

Row Spacing 19981 1999 Average
30-inch 181.5b 155.5b 168.5b '
22-inch 182.4ab 1 58.23b 170.3b km
lS-inch 188.13 166.3a 177.2a _ I. "

Advantage of Narrow Rows over

30-inch l

22-inch -—2 -- ---
15-inch 6.6 10.95 8.7

' Grain yields within year and zone followed by the same
letter are not significantly different.
2 Comparison is not significantly different.

 

 

 

 

109

 

 

 

176

 

174 7
172 w—W /
170

 

 

 

Grain Yield (hula)
a

 

 

 

 

 

 

O
166
164
162 T I A
25,850 31 ,004 36,728
Population (pl-Mala)

Figure 4.1: Grain yields by population. Regression equation for predicting grain
yields fiom plant population is y = 6.656Ln(pop) + 168.03.

 

110

 

 

Grain Moisture

Grain moisture at harvest was affected by a hybrid and plant population interaction.
There was a reduction in grain moisture for each hybrid as plant population increased.
The hybrid DK 593BtX had the highest grain moisture content of all and decreased 0.1%
in moisture as plant population increased (Figure 4.2). The largest drop in grain moisture
was for DK 593BtY. It dropped 0.5% over the same span of population increase. The
hybrid without any genetic modifications, DK 593, had a 0.1% drop in grain moisture as

plant population increased fi'om 25,850 to 36,728 plants per acre.

 

19.1

 

19.0

18.9 fl:
A 2
\ R =0.919

' OK 593
R2 = 0.9901
19.5

\. OK 593 an! I

 

 

 

.a
m
N

 

 

 

Gnln Moltturo (96)
a;
O)

 

 

 

 

 

 

 

 

2 =

19.4 J, R 0.9995
19 3 ODK 593 l

' IDK 593911! '

ADK 5939a
19.2 r—"
19.1 . .
25,950 31 .004 36,728

Population (plantsla)

Figure 4.2: Grain moisture by population and hybrid. Regression equations for
predicting grain moisture from population for each hybrid are:

DK 593 - y = -0.1281Ln(x) + 18.702

DK 593 BtY - y = -0.4091Ln(x) + 18.889

DK 593BtX - y = -0.1271Ln(x) + 18.96

 

 

 

111

 

 

Test Weight

There were differences in test weight between hybrids even though the hybrids were
near-isogenic. As one would expect, there were differences in test weight between years.
Test weights were lower for the 1998-growing season (Figure 4.3). DK 583BtY had the
lowest test weight in 1998 at 56.3 lbs., while DK 583BtX had the lowest test weight of
59.1 lbs. in 1999. DK 583 consistently had the highest test weight for both years. It

weighed in at 57.1 and 60 lbs. for 1998 and 1999, respectively.

 

 

 

 

 

Test Weight (lbs.)

 

 

 

OK 583 OK 58381Y DK 5933a
Hybrid

Figure 4.3: Test weight by hybrid and year. Columns within years followed by the
same letter are not significantly different.

 

 

 

The interaction of hybrid and row spacing had an inconsistent affect on test weight. The
transgenic hybrids were inconsistent in test weight as row spacing narrowed. The hybrid

l
DK 593 consistantly had a reduction in test weight as row spacing narrowed. As row 1
l

112

spacing narrowed to 22-inches from 30—inchs, DK 593 lost 0.2 lbs. in test weight (F igurc
4.4). When row spacing was further narrowed to lS-inches, test weight continued to drop
for DK 593 to 0.3 lbs. The total reduction in test weigh for DK 593 was 0.3 lbs. as the
row spacing narrowed. There was a drop of 0.7 lbs. in test weight as row spacing for DK
593BtX narrowed from 30- to 22-inches. However, DK 593BtY had an increase of 0.3

lbs. as row spacing narrowed from 22- to 15-inches, resulting in a net gain in test weight.

 

Test Weight (lbs.)

 

 

 

 

 

 

 

 

30—inch 224mb 15-ineh
Row Spacing (In)

Figure 4.4: Test weight by row spacing and hybrid. Columns followed by the same
letter are not significantly different.

 

 

 

Stalk Lodging

Row width was the only main effect that influenced stalk lodging. In 1998, the stalk
lodging did not have as much variation as in 1999. In 1999, there was an unexplained

exaggerated increase in stalk lodging in the 22-inch rows. Stalk lodging decreased as

113

 

rows narrowed to the lS-inch row width (Figure 4.5). In 1998, stalk lodging did not drop
below or increase above the level of the 30-inch rows. However, stalk lodging for 1999

dropped below the levels of the 30-inch rows when row width was narrowed to 15-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

inches.
3.0
I
2.5
1999
—— R2 = 0.0041
2.0 —
a: I
g 1.5 l
i
1.0
1999
0.5 R2 = 04322
e
e
rm
0.0 1 r
30-inch 22-inch 1 5-inch
Row Spacing (In.)
Figure 4.5: Stalk lodging by row spacing and year. Regression equations for -
predicting stalk lodging from row spacing within years are: "
1998 - y = 0.1193Ln(x) + 0.2417
1999 - y = -0.0742Ln(x) + 2.0742
1!
"a;

 

 

114

Conclusion

The selections of near-isogenic hybrids, as expected, eliminated any affect hybrids had on
grain yield, grain moisture, and stalk lodging. Grain test weight was affected by the

different hybrids. The test weights varied from hybrid to hybrid and from year to year.

Grain yield was affected by row width The narrow rows out-yielded the wider 30-inch

rows. The yield differences, on average, were as much as 8.2 and 1.8 bushels per acre for 5
15-inch and 22-inch row spacings, respectively. The 22-inch row spacing had the highest . = ' '
stalk lodging of any row spacing, while the 30- and 15-inch row spacings had less stalk -

lodging. There were different responses from year to year between row widths. The
interaction of row spacing and hybrid also had a significant impact on test weight. The
differences in test weight had more to do with hybrid reaction to row width than to row

width alone.

Once again it was clear that plant population was of more importance to grain yield than
were other factors. Grain yield increased as plant population increased. There was a 6.5
bushels per acre yield increase when plant population increased fi'om low to high.

Population did not effect grain moisture, test weight, or stalk lodging. The interaction

 

between populations and hybrids had a significant affect on grain moistures. The effect
of this interaction on grain moistures caused a reduction in moisture in each hybrid as

population was increased from 25,859 to 36,728 plants per acre.

115

References

Beck, S. D. 1987. Development and seasonal biology of Ostrinia nubilalis. Agric. Zool.
Rev. 2:59-96.

Feitelson, J. S., J. Payne, and L. Kim. Bacillus thuringiensis: Insects and Beyond.

Greaves, J. A., G. K. Rufener, M. T. Chang, and P. H. Koehler. 1993. Development of
resistance to Pursuit herbicide in corn —the IT gene. Report of the 48th Annual Corn
and Sorghum Research Conference. 48:104-118.

Hallauer, A. R., W. A. Russel, and K. R. Lamkey. 1991. Corn breeding. In G.F. Spargus
and J. W. Dudleys, eds. Corn and Corn Improvement Volume 18. Agronomy,
Madison, WI: American Society of Agronomy. pp 463-564.

Hayenga, M., L. C. Tompson, C. Chase, and S. Kaaria. 1992. Economic and
enviromental implications of herbicide-tolerant corn and processing tomatoes. J. Soil
Water Conserv. 47:41 1-417.

Hudon, M., E. J. LeRoux, and D. G. Harcourt. 1987. Seventy years of European corn
borer (Ostrinia nubilalis) research in North America. Agri. Zool. Rev. 2:1-44.

Kells, J. J ., K. Dysinger. 1996. Yield potential of selected IMI corn hybrids, In K.
Dysinger, D. D. Harpsted, R. H. Leep, J. Lempke, M. Allen, and D. Mains, eds. Corn
Hybrids Compared in the 1995 Season. Michigan State University Extension Bulletins
E-431. p5.

Newhouse, K., B. Singh, D. Shaner, and M. Stidharn. 1991a. Mutations in corn (Zea
mays L.) conferring resistance to irnidazoline herbicides. Theror. Appl. Genet. 83:65-
70.

Newhouse, K., T. Wing, and P. Anderson, 1991b. Imidazolinone-tolerant crops. In D. L.
Shaner, and S. L. O’Connor, eds. The Imidazolinone Herbicides. Boca Raton, Fl:
CRC. pp. 139-150.

Rice, M. E. 1997. Bt corn: Its strengths and limitations. In Integrated Crop Management.
Iowa State University Extension Bulletins. IC-478(2).

SAS Institute. 1985. SAS user's guide: Statistics. 5th ed. SAS Inst., Cary, NC.

116

 

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