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This is to certify that the
dissertation entitled ’

ANNUAL MEDICS AND BERSEEM CLOVER AS EMERGENCY
FORAGES OR GREEN MANURE FOR CANOLA

presented by

Anil Shrestha

has been accepted towards fulfillment
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Ph.D. degree in Crop and Soil Sciences

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ANNUAL MEDICS AND BERSEEM CLOVER AS EMERGENCY FORAGES OR
GREEN MANURE FOR CANOLA

By

Anil Shrestha

A DISSERTATION
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY
Department of Crop and Soil Sciences

1996

ABSTRACT

ANNUAL NIEDICS AND BERSEEM CLOVER AS AN ENIERGENCY FORAGE
OR GREEN MANURE FOR CANOLA

By

Anil Shrestha

Development of cropping systems which provide quality emergency forages and
reduce the need for chemical fertilizer nitrogen (N) in a subsequent non-legume crop
may benefit farmers. This study evaluated the forage dry matter (DM) yield and
quality of three annual medic species [barrel medic (Medicago truncatula Gaertn.
‘Mogul’), burr medic (M polymorpha L. ‘Santiago’), and snail medic (M scutellata L.
‘Sava’)], and berseem clover (T rifolium alexandrinum L.); quantified N accumulated at
plowdown by these species; evaluated N fertilizer replacement value (F RV) of legumes
on a subsequent canola (Brassica napus L.) crop; and compared the response of canola
to fertilizer N under various cropping systems.

The annual medics, berseem clover, alfalfa (M sativa L.), and spring canola
were seeded in early May. All the alfalfa, spring canola, and some annual medic and
berseem clover plots were harvested at 60 days after planting (DAP), while some of
the annual medic and berseem clover plots were grown as green manure for 90 days.
All plots were moldboard plowed 90 DAP and winter canola ‘Ceres’ was planted in
mid—August. Plots were split into 4 sub-plots and fertilizer N was applied in March at
rates of 0, 50, 100, and 150 kg N ha".

Annual medics and berseem clover produced similar or higher yields than did

alfalfa when harvested at 60 DAP. Annual medic regrowth (except Mogul) was less

than regrowth of alfalfa or berseem clover and contained mostly residue and seed
pods. The medics generally had similar crude protein but higher acid detergent and
neutral detergent fiber concentrations than did alfalfa at 60 DAP. Berseem clover
produced DM yield and forage quality comparable to alfalfa at 60 DAP and 90 DAP.
Legumes had little effect on yield of the subsequent canola. Canola responded
to added levels of fertilizer N and no interactions were observed between the cropping
system and N treatments. Harvesting the legume at 60 DAP and plowing down the
regrowth at 90 DAP or plowing down the unharvested legume at 90 DAP produced
similar canola grain yields. The amount of above-ground biomass or N content at
plowdown was not significantly correlated with canola yield. Fertilizer replacement
value of legumes were non-estimable due to lack of significant differences in the yield
of canola following a non-legume or a legume at the 0 N level. Among the annual

legumes tested, berseem clover has the most potential as an emergency forage.

ACKNOWLEDGMENTS

I want to express my appreciation to my guidance committee chairpersons
Dr. 0. B. Hesterman and Dr. L. O. Copeland for allowing me to undertake this
research project and for their continuing advice and support. I also thank Dr. G. H.
Axinn and Dr. R R Harwood for their valuable help and advice during my program
and for serving as members of my guidance committee. My special thanks and
appreciation for all the help rendered to me by Joseph Paling and fellow graduate
student John Squire. I thank my fellow graduate students John Fisk and Peter
Jeranyama for lending me support in my work. I also thank Larry Fitzpatrick for all
his help. Thanks also to Greg Parker and the staff of the Farming Systems Research
Center, Kellogg Biological Station and the staff of Crop and Soil Sciences Farm, East
Lansing. My sincere gratitude to the C. S. Mott Foundation Chair of Sustainable
Agriculture for the fellowship provided for my graduate work at Michigan State
University. Thanks also to Dr. R. R. Harwood and Dr. P. B. Chhetri whose advice
helped me make a decision to come to Michigan State University for my graduate
studies. I thank my wife Reeta, and my son Arwin, for their love, faith, and support.
Finally, I thank my parents for all their guidance and support without which I would

have been unable to reach this stage of my career.

iv

PREFACE

This dissertation is written as a manuscript in the style required for publication in
Agronomy Journal.

TABLE OF CONTENTS

LIST OF TABLES ..................................................................................................
LIST OF FIGURES ................................................................................................

CHAPTER ONE: YIELD AND QUALITY OF ANNUAL IVIEDICS AND
BERSEEM CLOVER AS ENIERGENCY FORAGES .......................................

ABSTRACT ............................................................................................................
INTRODUCTION ...................................................................................................
MATERIALS AND METHODS .............................................................................
RESULTS AND DISCUSSION ..............................................................................
Forage DM yields ........................................................................................
Forage quality ..............................................................................................
SUMMARY .............................................................................................................
REFERENCES ........................................................................................................
CHAPTER TWO: YIELD POTENTIAL OF ANNUAL MEDIC AND
BERSEEM CLOVER UNDER DIFFERENT SYSTEMS OF HARVEST
MANAGEMENT ...................................................................................................
ABSTRACT ............................................................................................................
INTRODUCTION ...................................................................................................
MATERIALS AND METHODS ............................................................................
RESULTS AND DISCUSSION .............................................................................
SUMMARY ...........................................................................................................

REFERENCES .......................................................................................................

vi

Page
viii

xi

1]
11
13
15

16

24
24
26
28
30
32

33

CHAPTER THREE: USE OF ANNUAL MEDICS AND BERSEEM CLOVER
AS A GREEN MAN URE OR AS A ROTATION CROP FOR CANOLA .....

ABSTRACT ...........................................................................................................
INTRODUCTION ..................................................................................................
MATERIALS AND METHODS ...........................................................................
RESULTS AND DISCUSSION ............................................................................
Biomass and nitrogen content of the legumes at plowdown .....................
Canola grain yield ......................................................................................
Canola plant population .............................................................................
Canola response to nitrogen under different cropping systems ..................
Nitrogen fertilizer replacement values (F RV) ............................................
Soil nitrate and ammonium levels .............................................................
SUMMARY ..........................................................................................................
REFERENCES .....................................................................................................

APPENDIX ..........................................................................................................

vii

37
37
39
44
50
50
51
53
54
54
55
57
59

78

LIST OF TABLES

Page

CHAPTER ONE: YIELD AND QUALITY OF ANNUAL MEDICS
AND BERSEEM CLOVER AS EMERGENCY F ORAGES

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

Climatalogical data from May 1994 to August 1994 and May 1995
to August 1995 at East Lansing and Kellogg Biological Station
(KBS), Michigan ..................................................................................... 19

Initial soil test values at East Lansing and KBS in 1994 and 1995 ......... 20

Seeding rates of the various legumes at East Lansing and KBS
in 1994 and 1995 .................................................................................... 21

Legume planting, irrigation, and harvest dates at East Lansing
and KBS in 1994 and 1995 .................................................................... 22

Average dry matter (DM) yield, crude protein (CP), acid-

detergent fiber (ADF), and neutral-detergent fiber (NDF) of the

legume species at harvest 1 (60 days after planting) and harvest 2

(90 days after planting) at East Lansing and KBS in 1994 and

1995 ....................................................................................................... 23

CHAPTER TWO: YIELD POTENTIAL OF ANNUAL MEDIC AND
BERSEEM CLOVER UNDER DIFFERENT SYSTEMS OF HARVEST
MANAGEIVIENT

Table 1.

Table 2.

Table 3.

Seeding dates, seeding rates, and harvest schedules of alfalfa, berseem
clover, barrel medic, and red clover in 1995 ......................................... 34

Dry matter (DM) yields of alfalfa, berseem clover, barrel medic, and red
clover at different dates under the 60-day and 7 5-day systems of cutting
management ........................................................................................... 35

Average dry matter (DM) yields of alfalfa, berseem clover, barrel medic,
and red clover in the following spring .................................................. 36

viii

CHAPTER THREE: USE OF ANNUAL MEDICS AND BERSEEM
CLOVER AS A GREEN MANURE OR AS A ROTATION CROP
FOR CANOLA

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

Table 6.

Table 7.

Table 8.

Table 9.

Table 10.

Table 11.

Table 12.

Climatalogical data from May 1994 to July 1996 at East Lansing

and Kellogg Biological Station (KBS), Michigan ....................................

Initial soil test values at East Lansing and KBS in 1994 and 1995 .........

List of main treatments at East Lansing and KBS in 1994 and

1995 .........................................................................................................

Seeding rate of the species at East Lansing and KBS in 1994 and

1995 ........................................................................................................

Planting, irrigation, harvest, and plowdown dates of the treatments

in 1994 and 1995 at East Lansing and KBS ..........................................

Summary of soil sampling dates at East Lansing and KBS in

1994 and 1995 .......................................................................................

Biomass, nitrogen concentration, and nitrogen content of the
various treatments at plowdown at East Lansing and KBS in
1994 and 1995 .....................................................................................

Average canola yields under different cropping systems and
nitrogen rates at East Lansing and KBS in 1995 and 1996 ..................

Average canola plant population under different cropping systems
at East Lansing and KBS in 1995 and 1996 ........................................

Regression equations on response of canola to fertilizer nitrogen
under different cropping systems at East Lansing and KBS in
1995 and 1996 ......................................................................................

Soil inorganic nitrogen levels under selected treatments at various
dates at a depth of 0-15 cm at East Lansing and KBS in 1994/95 and
1995/96 ................................................................................................

Soil inorganic nitrogen levels under selected treatments at various
dates at a depth of 15-30 cm at East Lansing and KBS in 1994/95
and 1995/96 .........................................................................................

ix

64

65

66

67

68

69

70

71

72

73

74

75

Table A1 Canola yield under different cropping systems and fertilizer nitrogen
levels at East Lansing in 1995 .......................................................

Table A2. Canola yield under different cropping systems and fertilizer nitrogen
levels at Kellogg Biological Station (KBS) in 1995 ......................

Table A3. Canola yield under different cropping systems and fertilizer nitrogen
levels at East Lansing in 1996 .......................................................

Table A4 Canola yield under different cropping systems and fertilizer nitrogen
levels at Kellogg Biological Station (KBS) in 1996 ......................

78

79

80

81

LIST OF FIGURES

CHAPTER THREE: USE OF ANNUAL MEDICS AND BERSEEM
CLOVER AS A GREEN MANURE OR AS A ROTATION CROP
FOR CANOLA

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Response of canola to fertilizer N under different cropping systems
at East Lansing in 1995 ................................................................

Response of canola to fertilizer N under different cropping systems
at KBS in 1995 .............................................................................

Response of canola to fertilizer N under different cropping systems
at East Lansing in 1996 ................................................................

Response of canola to fertilizer N under different cropping systems
at KBS in 1996 ............................................................................

xi

Page

79

79

80

80

Chapter 1
YIELD AND QUALITY OF ANNUAL MEDICS AND BERSEEM CLOVER AS

EMERGENCY FORAGES.

ABSTRACT

Severe winter-kill of alfalfa (Medicago sativa L.) in some years prompts the
need for emergency forages in northern locations. Our primary objective was to
evaluate the forage dry matter (DM) yield and quality of three annual medic species,
[barrel medic (M truncatula Gaertn. cv. Mogul), burr medic (M polymorpha L. cv.
Santiago), and snail medic (M scutellata L. cv. Sava)], and berseem clover (T rifolium
alexandrinum L.) as emergency forages compared to alfalfa. Field experiments were
conducted in 1994 at two locations on a Capac loam (fine-loamy, mixed, mesic Aerie
Ochraqualfs) and Kalamazoo loam (fme-loamy, mixed, mesic Typic Hapludalf). The
experiments were repeated in 1995. Plots were seeded in early May and harvested 60
days after planting (DAP). Dry matter (DM) yields, crude protein (CP), acid detergent
fiber (ADF), and neutral detergent fiber (NDF) were determined. Dry matter yield and
forage quality of the regrowth 30 days after the first harvest were also determined.
Annual medics and berseem clover produced similar or higher yields than alfalfa in the
seeding year in 1995 at one location and in 1996 at another location at first harvest.
Annual medic regrowth (except Mogul) was less than either alfalfa or berseem clover

regrowth and medic biomass contained mostly residue and seed pods. The highest

2

total seasonal average DM yield was obtained from Mogul (4.6 Mg ha"). Berseem
clover produced an average DM yield of 2.2 Mg ha" at first harvest and 1.8 Mg ha" at
second harvest across the 2 locations with average CP, ADF, and NDF concentrations
of 200, 279, and 395 g kg", respectively, at first harvest and 191, 217, and 333 g kg",
respectively, at second harvest. Annual medics had variable forage quality across
locations and years. Crude protein concentration of annual medics ranged from 144 to
187 g kg" and the ADF and NDF concentrations ranged from 276 to 355 g kg" and
361 to 470 g kg" respectively, at first harvest. The average CP, ADF, and NDF
concentration of Mogul at second harvest was 174, 239, and 342 g kg", respectively.
Annual medics can be used as emergency forage if only one harvest is desired.
Berseem clover has potential as an emergency forage. It can produce DM yield and
forage quality comparable to alfalfa in the seeding year and can be harvested twice

during the season.

INTRODUCTION

Severe winter-kill of alfalfa (Medicago sativa L.) in some years prompts the
need for emergency forages in northern locations. Sorghum-sudan grass is commonly
used as an emergency forage in Michigan but its success is limited due to soil moisture
conditions at the time of seeding (Leep, 1996). Sorghum-sudan grass is also generally
lower in crude protein concentration than forage legumes (Hesterman, et al., 1991).
Small grain or small grain/pea mixture has been recommended as an emergency forage
because it allows summer seeding of alfalfa in the same field after the small grain or
small grain/pea mixture is harvested in late June or July (Leep, 1996). Annual
legumes may benefit farmers because they can provide high protein animal feed as
well as fix atmospheric nitrogen in the soil for the next crop.

Potentials for using annual medics (Medicago sp.) and berseem clover
(Trifolium alexandrinum L.) as forages have not been explored in Michigan. Annual
medics are legumes closely related to alfalfa. They are self-pollinating true annuals
which flower, set seed and die within one growing season (Bauchan and Sheaffer,
1994). They are native to the Mediterranean region but now occur in the major
continents of the world and the most widespread species is M polymorpha and M
minima (Crawford, 1985). Lesins and Lesins (1979) recognized only 35 species,
whereas Crawford et al.(1989) recognized 82 species of annual medics. Annual
medics are used as winter annuals in Australia. If planted in spring in a northern

temperate climate they can be grown as summer annuals. They are not known to be

4

cold hardy and are generally susceptible to frost. Most of the medics complete their
life cycle in 65 to 100 days after planting (Bauchan and Sheaffer, 1994).

There is an increasing interest in the use of annual medics in sustainable
agriculture systems. However, the U. S. collection of annual medic germplasm is
underutilized because of lack of agronomic information (Diwan et al., 1994). The use
of annual medics as cover crops is being explored in several states in the US. Studies
are being conducted on their ability to fix biological nitrogen, increase organic matter,
reduce soil erosion, and in pest and weed management. Medics have been found to be
best adapted to soils with a pH of 6 or above. They have been used as a hay crop, but
are difficult to cut and bale, so grazing is a more suitable alternative. When grazed
high, they have been found to regrow. Annual medics have forage quality potential
similar to alfalfa and can cause bloat (Bauchan et al., 1994). Some species of annual
medics have been reported to produce average dry matter (DM) yields of 4.1 to 5.7
Mg ha" when seeded in early May and harvested 70 days later (Sheaffer and Barnes,
1994). Dry matter yields, percent ground cover, senescence characteristics, seeding
characteristics, and forage quality of fourteen cultivars representing five annual
Medicago species have been studied in Indiana. Dry matter yields ranged from 1 to
almost 9 Mg ha" in a single cutting, with crude protein values of 14.9 to 17.6 % of
dry weight (Johnson et al., 1993). Annual medics have also been used as reseeding
pasture legumes in northern Utah. Among the species tested, black medic (Medicago
lupulina L.) was shown to be better adapted to the local environment (Rumbaugh and

Johnson, 1986). Similarly, some species of annual medics were also seeded as pasture

5
legumes in Arizona. Rapidly maturing medics could be established under conditions
of less than 100 mm precipitation (Brahirn and Smith, 1993).

Medics are generally not native to areas that receive significant summer
precipitation. They provide high quality forage in many regions with Mediterranean
climate and they are used on approximately 50 million hectares in Australia in pastures
as a rotation crop (Crawford et al., 1989). Most medic species are winter annuals
adapted to Mediterranean climates. In colder temperate climates they are best used as
summer annuals (Rumbaugh and Johnson, 1986). Medics have been found to establish
best in paddocks in which previous weed control has been excellent. This may require
seeding after one or more cereal crops (Ewing, 1984). Clarkson et al., (1987) reported
8 to 10 Mg ha" DM yields for medics in pastures in Queensland, Australia.

Berseem clover is an erect, cool-season annual legume which is believed to
have originated in the region of Egypt and Syria (Baldridge et al., 1992). It is
commonly called Egyptian clover because it is an important crop in Egypt (Knight,
1985a). Berseem was introduced in the United States in 1896 and was first grown
successfully in California in 1918 (Kretschmer, 1964). Since then, it has been grown
successfully in Washington, Oregon, California, Arizona, and some parts of Florida
(Knight, 1985b). The regions in which the minimum temperatures are greater than
-6° C have been reported suitable for growing berseem clover as a winter annual in the
USA. Its greatest potential is as a green-chopped forage or pasture and it is known to
be non-bloating (Dennis and Massengale, 1962). Dry matter yields ranging from 7.4

to 10 Mg ha" from two to three harvests have been reported from Montana (Baldridge

6

et al., 1992). Similarly, DM yield of 4.5 Mg ha’1 of berseem with 19.5% crude
protein (CP), 27% acid detergent fiber (ADF), and 67.4% total digestible nutrients
(TDN) was reported from Oregon (Saunders et al., 1990). Experiments in California
found DM yields of 16 Mg ha" in six harvests with CP averages of 22% over all
harvests (Williams et al., 1990). It has been recommended in Iowa that the first
cutting from spring planted berseem clover be taken in early June and the next cutting
45 to 50 days later (Hofstetter, 1994). Dry matter yields of 10.7 Mg ha" were found
under different management systems in Montana in which berseem clover responded
better to systems with longer harvest intervals (W estcott et al., 1995).

Berseem is a popular forage crop in other parts of the world such as the
Mediterranean region, Near East, and India (Kretschmer, 1964). It is known to be one
of the most productive and nutritive winter forage crops in sub-tropical regions (Singh,
1993). It is also known to grow in regions such as the semiarid regions of Israel,
where a DM yield of 10 Mg ha" was reported (Kishinevsky et al., 1992).

Forage quality is an important factor in the evaluation of forages as an
emergency feed. Nutritive concentration, digestibility, intake and efficiency of
utilization are often considered essential components of high quality forage. Fiber
analysis is commonly performed on forage samples to estimate nutritive value (Van
Soest and Mertens, 1984). Neutral detergent fiber (NDF) is negatively associated with
forage quality, while crude protein (CP) represents one of the primary nutrients in

most balanced livestock rations (F ick and Mueller, 1989).

7

The objectives of this study were: (i) to determine the forage DM yields of 3
species of annual medic and berseem clover; (ii) to determine the forage quality of

these species; and (iii) to evaluate their use as emergency forages in comparison with

‘Nitro’ alfalfa in the establishment year.

MATERIALS AND METHODS

Experiments were conducted in 1994 and 1995 at two sites in Michigan:
Michigan State University Agronomy Farm, East Lansing on a Capac loam (fme-
loamy, mixed, mesic Aerie Ochraqualfs) and on a Kalamazoo loam (fine-loamy,
mixed, mesic Typic Hapludalf) at the Kellogg Biological Station (KBS), Hickory
Comets. Climatological data for 1994 and 1995 are shown in Table 1. In both years,
P and K were applied to maintain soil test levels at or above those recommended for
alfalfa production. The soil test data for the two years and two locations are
summarized in Table 2. Seed bed preparation included conventional tillage and
cultipacking.

First year: 1994

Main plots of 24.3 by 1.8 m at KBS and 24.3 by 2 m plots at East Lansing
were arranged in a randomized complete block design with four replications. Barrel
medic ‘Mogul’, burr medic ‘Santiago’, Snail medic ‘Sava’, and ‘Nitro’ alfalfa seeds
were inoculated with Rhizobium meliloti while berseem clover seeds were inoculated
with R trifolii and seeded with a small grain drill and cultipacked. The three annual
medic species were chosen to represent three different growth habits, Mogul a semi-
erect, Santiago a prostrate, and Sava an erect growing medic. Seeding rates of the
legumes are listed in Table 3. Determination of seeding rates were based on
approximately 270 pure live seeds (PLS) m". Planting, irrigation, and harvest dates

are summarized in Table 4.

9

A preplant application of Eptam (s-ethyl dipropylthiocarbarnate) at 3.3 kg ha"
a.i. was incorporated at each location. Total water applied to all plots was 5 cm.
Legume yields were measured by cutting 0.9 X 6.1 m strips within each plot to a
stubble height of 5 cm by a flail mower. The first cut was taken approximately 60
days after planting (DAP). Wet forage yield for each plot was adjusted to dry weight
by taking subsamples and drying them in a forced-air oven at 60°C for 72 hours.
Subsamples of approximately 800 g were hand clipped and oven-dried at the same
temperature and for the same duration, ground to pass a 2-mm screen and then through
a 1-mm screen in a cyclone mill (Wiley Corporation) and saved for forage quality
analysis. All plant samples were subjected to the Hach procedure for total N
determination (Hach et al., 1985). The forage CP concentration was estimated by
multiplying total N by 6.25. ADF and NDF concentrations in the samples were
determined by the procedure of Goering and Van Soest (1970). One ml alpha-amylase
was added to each sample in order to digest starch before extracting NDF.

Estimates of forage yield for a second cut were made approximately 30 days
after the first cut by taking 0.25 m2 quadrat measurements. The samples included
stems, leaves, residue, and seed pods of the medics. Wet forage yield adjustments
were made by the same procedure as described earlier.

Second year: 1995

The experiments were repeated in 1995 in different plots at the same locations.

Details of the plots are summarized in Table 2. Similar planting practices were used

as in 1994. The same Rhizobium inoculation was used for alfalfa and berseem as in

10

1994 but the annual medics were inoculated with a 1:1 mixture of R meliloti and
Rhizobium special number 1 (Nitragin, Liphatech Inc). Planting, irrigation, and
harvest dates are summarized in Table 3. Harvesting, yield estimation, subsampling,
grinding, and forage quality determination methods were similar to those described for
1994.
Statistics

Analysis of variance was performed on the data for DM yield, CP, ADF, and
NDF concentration within each location and significant species X location interactions
were identified. Significant differences among species were determined with an F -test
and mean separation was done by using Fisher’s LSD values where the F -test denoted
significance (P 5 0.05). All analyses were performed utilizing GLM of SAS

Statistical Package version 6.0.3 (SAS Institute, 1988).

RESULTS AND DISCUSSION

Forage DM yields

Year effects were detected for first harvest DM yield in one out of the two
years in both locations (Table 5). This suggests that annual medics and berseem
clover can produce as much or more biomass than alfalfa in the seeding year at 60
DAP under favorable conditions. Among the differences observed, Mogul performed
significantly better than the other species in terms of forage biomass production at
KBS in 1994. Sava and berseem clover were similar in DM yields to alfalfa, while
Santiago yielded significantly lower than the other species. Sava yielded significantly
higher than the other medics and alfalfa at East Lansing in 1995. Dry matter yields of
all species at 60 DAP was greater in 1994 than 1995 in East Lansing. This could be
due to lower precipitation in 1995 than in 1994 (Table 1). In contrast, DM yields
across species were generally greater in 1995 than in 1994 at KBS. Some of the
difference in DM yield at KBS can be attributed to seasonal variation between the two
years (irrigation was required at KBS only in 1994).

Even though all species appeared similar in forage DM yields, Santiago grew
very close to the ground and did not appear suitable for harvesting as hay. Mogul,
Sava, and berseem grew more erect and appeared suitable to mechanical harvest.

Sava senesced and contained many seed pods at 60 DAP while Mogul and berseem
remained vegetative with few seed pods. This indicates that Sava should be harvested

a few days earlier if vegetative forage is desired.

11

12

Estimates of forage biomass 30 days after first harvest showed that significant
differences were present in the regrowth of the species in both years (Table 5).
Regrowth of Sava was lowest of all species in both years. Santiago was intermediate
and regrowth of both Mogul and berseem was greater than the other species. The DM
yield of theregrowth of Mogul and berseem was similar to alfalfa and significantly
higher than that of the other medic species at KBS in 1995. At East Lansing, DM
yield of Mogul, berseem, and alfalfa was similar at second harvest in both 1994 and
1995. However, the regrowth of Mogul at both locations and both years was
decumbent and not suited to mechanical harvesting. Whereas, the regrowth of berseem
was more erect and suited to mechanical harvesting. The biomass of Sava at second
harvest consisted mostly of residue and seed pods in both years. The regrowth of
Santiago also contained a lot of seed pods and had very little green, vegetative
structures.

Total seasonal DM yields among species were not significantly different at East
Lansing in 1994. Whereas, in 1995, total seasonal yield of Mogul, berseem, and
alfalfa were similar and significantly higher than the total seasonal yield of Santiago
and Sava at East Lansing. Likewise, total seasonal DM yield of Mogul, berseem, and
alfalfa was similar and significantly higher than that of Santiago and Sava at KBS in
1994 and 1995. Among the annual medics tested, only Mogul appeared suitable for
two harvests. However, the second harvest was not suitable for mechanical harvest
due to the decumbent regrowth. Berseem clover may have good potential as either

hay or fresh green chop in both harvests.

13
Forage quality

A significant species X location interaction occurred in both years for forage
quality parameters. Hence, these parameters were analyzed separately for each
location. Crude protein concentration of berseem was highest among all the species at
first harvest in both years at East Lansing. Whereas, crude protein concentration of
berseem was similar to alfalfa and significantly higher than the other species in 1994
and significantly higher than all other species except Mogul in 1995 (Table 5).
Santiago and Sava had the lowest CP concentrations at East Lansing in 1994, Santiago
was similar in CP concentration to the other species in 1995. Alfalfa had significantly
lower ADF and NDF concentrations in both years at East Lansing. Berseem had
similar ADF and NDF concentrations as Mogul and Santiago in 1994 but significantly
lower than these species in 1995.

At KBS, berseem had the highest CP concentration at 60 DAP in 1994 but was
lower than Mogul, Santiago, and alfalfa in 1995. Santiago and Sava had the lowest
CP concentrations in 1994. As in East Lansing, the ADF and NDF concentration of
alfalfa was lowest at KBS in both years. In both years Sava had the highest ADF and
NDF values. Berseem and Mogul were intermediate between alfalfa and Sava in ADF
and NDF concentrations in both years at KBS. Santiago was similar to Sava in ADF
and NDF concentration in 1994, but had lower concentrations of these quality
parameters than Sava in 1995.

Crude protein concentrations at second harvest showed that alfalfa and berseem

clover had significantly higher CP concentrations than the other species at second

14

harvest at East Lansing in 1994 (Table 5). However, in 1995 the CP concentrations of
all the species were similar at second harvest at East Lansing. Berseem clover
generally had a significantly lower ADF and NDF concentrations than the annual
medics. Santiago and Sava generally had similar ADF and NDF concentrations at
second harvest. Among the annual medics, Mogul had the lowest concentration of
ADF and NDF at second harvest. Differences in forage quality were also observed at
KBS at second harvest. Berseem, alfalfa, and Mogul generally had significantly higher
CP concentrations than Santiago and Sava. The ADF and NDF concentrations of all
species at second harvest varied a great deal from one year to the other. Alfalfa and
berseem clover generally had lower ADF and NDF concentrations than the annual
medics in 1994. However, the ADF and NDF concentrations of alfalfa and berseem
were generally higher than the annual medics in 1995. But, compared to annual
medics, alfalfa and berseem clover may be more palatable forages as they were more
vegetative and contained very little desiccated structures and seed pods at second

harvest.

SUMMARY

In one year out of the two, annual medics and berseem clover produced DM
yields similar to alfalfa in the seeding year when harvested 60 DAP. In the other year,
Mogul produced significantly higher DM yield than alfalfa at East Lansing and Sava
produced significantly higher DM yield than alfalfa at KBS. Among the annual
medics, the highest total season DM yield was produced by Mogul. Regrowth of
annual medics Sava and Santiago was poor in comparison to alfalfa, berseem, and
Mogul and the biomass contained mostly residue and seed pods. Although regrowth of
Mogul was greater, it appeared more suited to grazing than mechanical harvesting due
to its lower grth habit. Berseem clover grew more erect and appeared more suited
to mechanical harvesting in comparison to the annual medics. In addition, berseem
clover had forage quality comparable to alfalfa. Annual medics were variable in CP,
ADF, and NDF concentrations across locations and years. They were comparable to
alfalfa in CP but were generally higher in ADF and NDF concentrations. Mogul was
generally higher in CF and lower in ADF and NDF concentrations than the other
annual medics. Annual medics, specially Mogul, can be used as an emergency forage
legume in Michigan if only one harvest is desired. Berseem clover has good potential
as an emergency forage legume as it can produce good yields and high quality forage

and can be harvested at least twice during the growing season.

15

REFERENCES

Baldridge, D., R Dunn, R Ditterline, J. Sims, L. Welty, D. Wichman, M. Westcott,
and G. Stallknecht. 1992. Berseem clover: A potential hay and green manure crop
for Montana. Montguide January 1992. Montana State Univ. Coop. Ext. Serv.,
Bozeman, MT.

Baucham, G. R and C. C. Sheaffer. 1994. Annual medics and their use in sustainable
agriculture systems. Annual medics. Pre-conference workshop of the 34th North
American Alfalfa Improvement Conference, July 10, 1994. University of Guelph,
Guelph, Ontario, Canada.

Baucham, G. R, N. Diwan, and M. McIntosh. 1994. What are annual medics? Annual
medics. Pre-conference workshop of the 34th North American Alfalfa Improvement
Conference, July 10, 1994. University of Guelph, Guelph, Ontario, Canada.

Brahim, K. and S. E. Smith. 1993. Annual medic establishment and the potential for
stand persistence in southern Arizona. J. Range Manage. 46:21-25.

Clarkson, N. M., N. P. Chaplain, and M. L. Fairbairn. 1987. Comparative effects of
annual medics (Medicago spp.) and nitrogen fertiliser on the herbage yield and quality
of subtropical grass pastures in southern Queensland. Aust. J. Exp. Agric. 27 2257-265.

Crawford, E. J. 1985. Flowering response and centres of origin of annual Medicago
species. In Z. Hochman (ed.) The Ecology and agronomy of annual medics.
Proceedings of a workshop at the agricultural research and advisory station,
Condobolin, Australia, 1981 .

Crawford, E. J., A. W. H. Lake, and K. G. Boyce. 1989. Breeding annual Medicago
species for semiarid conditions in southern Australia. Adv. in Agron. 42:399-437.

Dennis, R, and M. Massengale. 1962. Berseem clover. pp. 1349-1350. In Univ.
Arizona field crop production handbook. Univ. Arizona Exp. Stn., Tucson, AZ.

Diwan, N., G. R. Bauchan, and M. S. McIntosh. 1994. A core collection for the
United States annual Medicago germplasm collection. Crop Science 34:279-285.

Fick, G. W. and S. C. Mueller. 1989. Alfalfa quality, maturity, and mean stage of

development. Cornell University, Cornell Cooperative Extension Information Bulletin
No. 217.

16

17

Hach, C. C., S. V. Brayton, and A. B. Kopelove. 1985. A powerful Kjeldahl
nitrogen method using peroxymonosulfuric acid. J. Agric. Food Chem. 33:1117-
] 123.

Hesterman, O. B., H. F. Bucholtz, and M. S. Allen. 1991. Forage quality: what is
it? Extension Bulletin April 1991. Cooperative Extension Service, Michigan State
University, East Lansing, MI.

Hofstetter, B. 1994. The up-and-coming cover. The New Farm, February 1994, pp.
27-28.

Johnson, K. D., D. K. Greene, M. E. Kuhn, and J. J. Volenec. 1993. Productivity
of annual medics in Indiana. Report of 1993 research sponsored by Purdue University
New Crops and Plant Products Center.

Kishinevsky, B. D., Y. Leshem, Y. Friedman, and G. Krivatz. 1992. Yield and
nitrogen fixation of berseem clover as a potential winter forage crop under semiarid
conditions. Arid Soil Research and Rehabilitation 6:261-270.

Knight, W. E. 1985a. Registration of ’Bigbee’ berseem clover. Crop Sci. 25:571-
572.

Knight, W. E. 1985b. Miscellaneous annual clovers. pp. 547- 562. In N. L. Taylor
(ed) Clover Science and technology. Agron. Mono. 25. ASA, CSSA, and SSSA,
Madison, WI.

Kretschmer A. E. 1964. Berseem clover: a new winter annual for Florida.
Agricultural Experiment Station, University of Florida, Gainesville, FL.

Leep, R H. 1996. Some options for dealing with alfalfa winterkill and injury. Crops
and Soils Newsletter Vol. 22 No. 226 May 20, 1996. Michigan State University
Extension, Department of Crop and Soil Sciences, Michigan State University, East
Lansing, MI.

Lesins, K. A. and I. Lesins. 1979. Genus Medicago (Leguminosae). A taxogenic
study. Junk, The Hague, Netherlands.

Rumbaugh, M. D. and D. A. Johnson. 1986. Annual medics and related species as
reseeding legumes for northern Utah pastures. J. Range Manage. 39:52-58.

SAS Institute. 1988. SAS User’s Guide: Statistics (Version 6.03 ed.). SAS Inst. Inc.,
Cary, NC.

18

Saunders, L., C. Shock, and T. Stieber. 1990. Multicut berseem clover as a double
crop for Eastern Oregon. The Department v. 23. Progress report, clovers and special
purpose legumes research. University of Wisconsin, Dept. of Agronomy, Madison,
Wisconsin.

Sheaffer, C. C. and D. K. Barnes. 1994. Annual medics in Minnesota Agriculture.
Annual medics. Pre-conference workshop of the 34th North American Alfalfa
Improvement Conference, July 10, 1994. University of Guelph, Guelph, Ontario,
Canada.

Singh, V. 1993. Berseem (Trifolium alexandrinum L.)- a potential forage crop.
Outlook on Agriculture 22:49-51.

Van Soest, P. J. and D. R Mertens. 1984. The use of neutral detergent fiber versus
acid detergent fiber in balancing dairy rations. Monsanto Tech. Symp., Fresno, CA.
Nutr. Chem. Div. Monsanto, CO, St. Louis.

Westcott, M. P., L. E. Welty, M. L. Knox, and L. S. Prestbye. 1995. Managing
alfalfa and berseem clover for forage and plowdown nitrogen in barley rotations.
Agron. J. 87:1176-1181.

Williams, W. A., W. L. Graves, C. D. Thomsen, and P. R Miller. 1990. Berseem
and Persian clover production and nitrogen fixation. The Department v. 23. Progress
report, clovers and special purpose legumes research. University of Wisconsin, Dept.
of Agronomy, Madison, Wisconsin.

Table 1. Climatalogical data from May 1994 to August 1994 and May 1995 to August

19

1995 at East Lansing and Kellogg Biological Station (KBS), Michigan.

 

 

Year and Location Month Total Precipitation Mean Temperature
mm °C
1994
East Lansing May 46.2 12.7
June 185.9 19.8
July 121.2 20.9
August 143.3 18.6
KBS May 4.0 15.8
June 174.4 21.5
July 160.2 22.4
August 119.5 21.9
1995
East Lansing May 63.5 12.6
June 42.2 19.8
July 100.6 21.4
August 116.1 23.2
KBS May 72.7 14.8
June 92.2 21.6
July 82.9 24.4
August 110.4 24.8

 

20

Table 2. Initial soil test values at East Lansing and KBS in 1994 and 1995.

 

 

Year and Location Soil pH Avail. P Exch. K
1994 ........ kg ha" ........
East Lansing 7.6 82 228
KBS 7.3 80 130
1995

East Lansing 7.3 82 159

KBS 7.6 74 226

 

21

Table 3. Seeding rate of legumes at East Lansing and KBS in 1994 and 1995.

 

 

Species Seeding rate
kg ha'1
‘Nitro’ Alfalfa 25
‘Mogul’ Barrel medic 15
‘Santiago’ Burr medic 15
‘Sava’ Snail medic 32

Berseem clover 12

 

22

Table 4. Legume planting, irrigation, and harvest dates at East Lansing and KBS in
1994 and 1995.

 

 

Year &

Location Planting Irrigation Harvest 1 Harvest 2
1994

East Lansing 13 May 25 May 18 July 8 August
KBS 6 May 30 May 11 July 9 August
1995

East Lansing 12 May 21 May 17 July 14 August

KBS 8 May - 13 July 10 August

 

23

Table 5. Average dry matter (DM) yield, crude protein (CP), acid-detergent fiber (ADF), and neutral-
detergent fiber (NDF) of legume species at harvest 1 (60 days after planting) and harvest 2 (90 days after
planting) in 1994 and 1995 at East Lansing and Kellogg Biological Station (KBS), Michigan.

 

 

 

 

 

Year, Location, DM Yield Harvest 1 Harvest 2
and Species Harv.1 Harv.2 Total CP ADF NDF CP ADF NDF
------- Mg ha" g kg“'
1994
East Lansing
‘Nitro’ alfalfa 2.1 1.6 3.7 218 255 326 187 183 299
‘Mogul’ medic 3.6 1.4 5.0 170 304 374 142 246 347
‘Santiago’ medic 3.1 1.1 4.2 111 307 382 139 275 350
‘Sava’ medic 3.2 0.6 3.8 151 360 449 131 279 367
Berseem clover 2.7 1.6 4.3 233 280 371 217 180 292
LSD (0.05) NS NS NS 32 37 42 34 47 48
KBS
‘Nitro’ alfalfa 1.8 1.3 3.1 174 211 380 205 200 293
‘Mogul’ medic 2.8 2.6 5.4 186 259 366 174 227 294
‘Santiago’ medic 0.8 1.1 1.9 152 334 461 130 220 300
‘Sava’ medic 1.4 1.1 2.5 168 328 481 146 274 378
Berseem clover 1.2 2.1 3.3 212 257 417 196 197 289
LSD (0.05) 0.7 0.7 0.8 36 28 36 34 27 28
1995
East Lansing
‘Nitro’ alfalfa 1.2 1.9 3.1 170 217 359 186 191 299
‘Mogul’ medic 1.3 2.0 3.3 185 223 321 175 220 339
‘Santiago’ medic 1.2 1.1 2.3 180 319 419 177 241 395
‘Sava’ medic 2.2 0.0= 2.2 158 351 452 145 325 435
Berseem clover 1.7 2.1 3.8 178 263 369 178 245 403
LSD (0.05) 0.5 0.7 0.7 19 17 16 NS 10 14
KBS
‘Nitro’ alfalfa 3.1 1.6 4.7 195 259 383 164 232 372
‘Mogul’ medic 2.9 1.8 4.7 210 318 385 204 264 391
‘Santiago’ medic 2.9 0.7 3.6 205 335 431 110 226 300
‘Sava’ medic 2.2 0.0: 2.3 158 375 498 141 196 302
Berseem clover 3.2 1.6 4.8 178 316 423 175 247 351
LSD (0.05) NS 0.8 1.1 14 19 27 25 23 79

 

= DM yield present only in traces.

Chapter 2
YIELD POTENTIAL OF ANNUAL MEDIC AND BERSEEM CLOVER UNDER
DIFFERENT SYSTEMS OF HARVEST MANAGEMENT

ABSTRACT

Annual medics and berseem clover have been suggested as emergency forages
in northern locations. However, yield potential of these legumes under different
systems of harvest management has not been evaluated. Our objective was to
determine forage dry matter (DM) yields of barrel medic (Medicago truncatula Gaertn.
cv. Mogul) and berseem clover (T rifolium alexandrinum L.) under different harvest
management systems, compare the DM yields with alfalfa (M sativa L.) and red
clover (T rifolium pratense L.), and evaluate their over-wintering capability. A field
experiment was conducted in 1995 on a Capac loam (fme-loamy, mixed, mesic Aeric
Ochraqualfs). The species were seeded in early May and harvested under two systems
of management. In the first system, the first harvest was taken 60 days after planting
(DAP) followed by a second harvest 45 days later. In the second system, the first
harvest was taken 75 DAP followed by a second harvest 45 days later. Berseem
clover produced the highest total seasonal DM yield under both systems of
management (4.5 Mg ha"). The DM yields of all species were similar at first harvest
in the 60-day system, but barrel medic yield was lower than that of the other species at
first harvest in the 75-day system. Barrel medic regrowth was very low in comparison

to the other species and less suited to mechanical harvesting under both harvest

24

25

management systems. Berseem clover regrowth was more erect than regrowth of
barrel medic and was suitable for mechanical harvest. Barrel medic and berseem
clover winter-killed and did not re-seed, whereas good stands of alfalfa and red clover
were obtained in the following season with a DM yield of 5.1 and 11.5 Mg ha"
respectively. Berseem clover may be better than barrel medic in terms of biomass
production as an emergency forage legume and can be grown successfully if the
objective of the producer is not to replant alfalfa in the same field as winter-killed
alfalfa. However, very little or no regrth of berseem clover can be expected the

following spring.

INTRODUCTION

Annual medics (Medicago sp.) and berseem clover (T rifolium alaxandrinum
L.) have been suggested as emergency forages in northern locations (Shrestha et al.,
1995). However, yield potential of these legumes under different systems of harvest
management must be determined for maximizing forage production. Among the
various annual legume species studied, barrel medic (Medicago truncatula Gaertn. cv.
Mogul) and berseem clover appeared most promising in terms of dry matter (DM)
production and forage quality in Michigan (Shrestha and Hesterman, 1995). The
annual legumes in these studies were planted in early May and harvested 60 days after
planting (DAP) followed by a second harvest 30 days later. Substantial regrowth of
Mogul and berseem occurred after the first cut. Shrestha and Hesterman (1995)
reported crude protein (CP) concentrations of Mogul and berseem in the range of 170-
210 g kg" and 178-233 g kg", respectively, at 60 DAP in studies conducted at East
Lansing and Kellogg Biological (KBS), Michigan. The acid detergent fiber (ADF)
and neutral detergent fiber (NDF) concentration of Mogul ranged from 223-318 g kg"
and 321-385 g kg", respectively. Similarly, the ADF and NDF content of berseem
ranged from 257-316 g kg" and 369-423 g kg", respectively.

For barrel medic and berseem clover to be a viable emergency forage legume,
its performance and production must be evaluated under different systems of cutting
management. The affect of cutting time on their productivity must be estimated.

Their performance must also be compared with the dominant forage legumes of the

26

27

region, viz. alfalfa (Medicago sativa L.) and red clover (T nfolium pratense L.) in
order to justify it as an alternative to replanting alfalfa or red clover.

Mogul medic has a semi-erect growth habit, and is difficult to cut and bale as
a hay crop (Baucham et al., 1994). In contrast, berseem clover is an erect, cool-
season annual legume (Kretschmer, 1984). Berseem has been grown successfully in
California, Washington, Oregon, Arizona, and some parts of Florida (Knight, 1985).
It is known to be non-bloating and has been used as a green-chopped forage or
pasture legume (Dennis and Massangale, 1962). Baldridge et a1. (1992) reported DM
yields of 7.4 to 10 Mg ha" from two to three cuts in Montana. Saunders et a1. (1990)
reported DM yield of 4.5 10 Mg ha" in Oregon. Berseem clover is not a new crop in
the United States, whereas, barrel medic is relatively new and its use as a forage is
still under investigation.

The objectives of this study were: (i) to determine forage DM yields of barrel
medic and berseem clover under different harvest management systems, (ii) to
compare the DM yields of barrel medic and berseem clover with alfalfa and red
clover, and (iii) to evaluate the over-wintering capacity of barrel medic and berseem

clover.

MATERIALS AND METHODS

An experiment was conducted in 1995 at the Michigan State University
Agronomy Farm, East Lansing on a Capac loam (fine-loamy, mixed, mesic Aeric
Ochraqualf). Soil samples were taken and phosphorus and potash were applied to
maintain soil test levels at or above that recommended for alfalfa production. Main
plots of 12.2 X 2.1 m were arranged in a randomized complete block design with
four replications. Barrel medic (Mogul), berseem clover, alfalfa cv. Pioneer 5262,
and medium red clover were inoculated with a host specific Rhizobium sp. and seeded
on May 12, 1995 with a row planter. Seeding rates are shown in Table 1. A
preplant incorporation of Eptam (S-ethyl dipropylcarbamothiate) @ 3.3 kg ha" a.i.
was done. Plots were irrigated on June 21 with a total water application of 5 cm and
sprayed on June 23 with 2,4 D-B [4-(2,4-Dicholorophenoxy) butyric acid,
dimethylamine salt] @ 1 kg ha" a.i. for weed control.

The plots were split for harvest dates. Two harvest systems were imposed: (i)
a 60-day system; the first cut was taken 60 DAP followed by a second cut
approximately 45 days later and (ii) a 75-day system; the first out was taken 75 DAP
followed by a second cut 45 days later. Planting and cutting schedules are shown in
Table 1. Legume yields were measured by cutting 6 X 0.9 m" strips within each
plot to a stubble height of 5 cm with a flail mower. Plots were left over winter and
estimates of DM yields the following spring were taken on June 27 by hand clipping

0.25 m2 areas. Wet forage yield for each plot was adjusted to dry weight by taking

28

29

about 500 g subsamples and drying them in a forced-air oven at 60° C for 72 hours.
Analysis of variance was performed on the data and significant differences between
species were determined with an F-test. Mean separation was done by using Fisher’s
LSD where the F-test denoted significance (P g 0.05). All analyses were performed

utilizing GLM of SAS Statistical Package version 6.0.3 (SAS Institute, 1988).

RESULTS AND DISCUSSION

There was little difference among species in total seasonal yields under either a
60-day or a 75—day system (Table 2). Barrel medic was outyielded significantly by
the other species at all cuts except the first out under the 60-day system. Alfalfa,
berseem clover, and red clover had greater biomass at first harvest under the 75-day
system than under the 60-day system. However, barrel medic had similar biomass at
first harvest under the 75-day and 60-day system. This suggests that it is better to
harvest barrel medic at 60 DAP than 75 DAP as more DM yield was obtained at
second out under the 60-day system (Table 2). Barrel medic grew very close to the
ground and was unsuited to mechanical harvesting and appeared more suited to
grazing.

Berseem clover produced as much total biomass as did red clover under both
the 60-day and 75-day system. Regrowth of berseem was more than that of alfalfa
under the 60-day system. Total seasonal yield of berseem clover was significantly
higher than that of alfalfa under a 60—day system. Visual observations showed that it
may be possible to take a third cut of berseem, which was not done in this study.
Total seasonal yield of berseem was identical under a 60-day and 75-day cut system.
However, it may be beneficial to take the first cut at 60 DAP if a third cut is desired.

Red clover and alfalfa are popular forage legumes in Michigan and red clover
outyielded alfalfa in terms of total seasonal yield under the 60-day system.

Observations in Spring of 1996 showed that there was no regrowth of barrel medic or

30

31

berseem clover in any of the plots (Table 3). Alfalfa and red clover did regrow and
yield estimates taken on July 27, 1996 showed that the average DM yield of alfalfa
and red clover was 5.1 and 11.5 Mg ha" respectively under both systems of harvest

management.

SUNIMARY

Barrel medic and berseem clover can be used as an emergency forage in
Michigan if the objective of the producer is not to replant alfalfa in the same field as
the winter-killed alfalfa. In terms of the growth habit, barrel medic appeared more
suited to grazing than mechanical harvesting. It may be better to harvest barrel medic
60 DAP after planting or earlier if substantial regrowth is desired; however, its DM
yields are very low. Berseem clover may be a promising annual forage legume as it
produced DM yields comparable to red clover and greater than alfalfa in the year of
seeding. However, it did not over-winter or re-seed itself the next spring. It may be
beneficial to grow berseem clover if an annual emergency forage legume is desired.
Earlier studies have reported berseem clover to be comparable in forage quality to

alfalfa in the seeding year.

32

REFERENCES

Baldridge, D., R. Dunn, R. Ditterline, J. Sims, L. Welty, D. Wichman, M. Westcott,
and G. Stallknecht. 1992. Berseem clover: A potential hay and green manure crop
for Montana. Montguide, January 1992, Montana State Univ. Coop. Ext. Serv.,
Bozeman, MT.

Baucham, G. R, N. Diwan, and M. McIntosh. 1994. What are annual medics?
Annual medics. Pro-conference workshop of the 34th. North American Alfalfa
Improvement Conference, July 10, 1994. University of Guelph, Guelph, Ontario,
Canada.

Dennis, R, and M. Massengale. 1962. Berseem clover. pp. 1349-1350. In Univ. of
Arizona field crop production handbook. Univ. Arizona Exp. Stn., Tucson, AZ.

Knight, W. E. 1985. Miscellaneous annual clovers. pp. 547-562. In N. L. Taylor
(ed) Clover science and technology. Agron. Mono. 25. ASA, CSSA, and SSA,
Madison, WI.

Kretschmer, A. E. 1964. Berseem clover: a new winter annual for Florida.
Agricultural Experiment Station, University of Florida, Gainesville, FL.

Saunders, L., C. Shock, and T. Stieber. 1990. Multicut berseem clover as a double
crop for Eastern Oregon. The Department v. 23. Progress report, clovers and special
purpose legumes research. University of Wisconsin, Dept. of Agronomy, Madison,
Wisconsin.

Shrestha, A. and O. B. Hesterman. 1995. Annual medics as an emergency forage
crop. Crop and Soils Newsletter, Vol. 21, No. 217, April 14, 1995. Michigan State
University, East Lansing, MI.

Shrestha, A., P. Jeranyama, O. B. Hesterman, and C. C. Sheaffer. 1995. Dry matter
yields, nitrogen production, and forage quality of annual medics and berseem clover.
pp. 99 In Forages: A New Beginning. Proceedings of the 1995 American Forage and
Grassland Council, March 12-14, 1995, Lexington, KY.

33

34

Table 1. Seeding dates, seeding rates, and harvest schedules of alfalfa, berseem
clover, barrel medic, and red clover in 1995.

 

 

Seeding Seeding 60-day system 75-day system
Species date rate lst. cut 2nd. cut 1st. cut 2nd. cut
kg ha"
Alafalfa May 12 25 July 18 Aug.31 Aug.1 Sept.15
Berseem May 12 13 July 18 Aug.31 Aug.1 Sept.15
Barrel medic May 12 16 July 18 Aug.31 Aug.1 Sept.15
Red clover May 12 12 July 18 Aug.31 Aug.1 Sept.15

 

35

Table 2. Dry matter (DM) yields of alfalfa, berseem clover, barrel medic, and red
clover at different dates under the 60-day and 75—day systems of cutting management.

 

 

 

 

60—day system 75-day system
Species 1st. cut 2nd. cut Total lst. cut 2nd. cut Total
Mg ha"
Alfalfa 1.0 2.5 3.5 1.6 1.9 3.5
Berseem 1.4 3.0 4.4 2.3 2.2 4.5
Barrel medic 1.0 0.8 1.8 1.0 0.4 1.4
Red clover 0.9 3.6 4.5 2.1 2.1 4.2

LSD (0.05) NS 0.7 0.8 0.8 0.6 1.0

 

36

Table 3. Average dry matter (DM) yields of alfalfa, berseem clover, barrel medic, and
red clover in the following spring.

 

 

Species DM Yield
Mg ha"
Alfalfa 5.1
Berseem 0.0
Barrel medic 0.0

Red clover 1 1.5

 

Chapter 3
ANNUAL MEDICS AND BERSEEM CLOVER AS GREEN MANURE OR

ROTATION CROPS FOR CANOLA

ABSTRACT

Cropping systems that reduce the need for chemical fertilizer in canola
(Brassica napus L.) have been suggested in the Great Lakes region. The objectives of
this research were to quantify N accumulated at plowdown by annual medics
(Medicago sp.) and berseem clover (T rifolium alexandrinum L.) managed as a forage
or green manure, compare the response of canola to fertilizer N under various cropping
systems, and to estimate the N fertilizer replacement values (FRV) of the annual
legumes. Field experiments were conducted in 1994/95 and 1995/96 at 2 locations in
Michigan on a Capac loam (fine-loamy, mixed, mesic Aerie Ochraqualfs) and
Kalamazoo loam (fme-loamy, mixed mesic Typic Hapludalf). Three species of annual
medics, [barrel medic (M truncatula Gaertn. cv. Mogul), burr medic (M polymorpha
L. cv. Santiago), snail medic (M scutellata L. cv. Sava)], berseem clover, alfalfa (M
sativa L. cv. Nitro), and spring canola were seeded in early May. Gamma medic (M
rugoso L. cv. Paraponto) was also seeded as an ineffective, non-nodulating control.
Some of the barrel medic, burr medic, snail medic, and berseem clover plots were
harvested as a forage 60 days after planting (DAP) while some of the plots were

allowed to grow as a green manure. Alfalfa, gamma medic, and spring canola plots

37

38

were also harvested at 60 DAP. All plots were moldboard plowed 90 DAP and winter
canola cv. Ceres was planted in mid-August. Plots were split into 4 sub-plots and
fertilizer N applied in March at rates of 0, 50, 100, and 150 kg ha". Canola plants
winter-killed in 1996 at East Lansing and spring canola was re-planted in mid-May.
Winter canola was harvested in July, whereas spring canola was harvested in late
August. The effect of annual legume species on yield of the following canola crop
was significant at only one location in 1995. Fertilizer N had a significant linear
effect on the yield of canola in one year and a quadratic effect in the other year at
both locations. There was no interaction between the main treatments and N sub-
treatrnents. Except at one location in 1995, canola grain yield was not significantly
different when the preceding legume was harvested at 60 DAP and the regrowth
plowed down at 90 DAP or when the entire above-ground biomass was plowed down
as green manure at 90 DAP. The amount of above-ground biomass or N at plowdown
were not significantly correlated with subsequent canola yield. The soil N03 and NH4
levels measured at 3 different times were similar for all treatments. The FRV of
legumes were non-estimable as there was no significant difference between canola
following a non-legume or a legume at the 0 N level. Among the annual legumes
tested, berseem clover was the most promising species in terms of biomass and N

production, and in contribution to the yield of the subsequent canola crop.

INTRODUCTION

Development of cropping systems which reduce chemical fertilizer nitrogen (N)
requirements for canola (Brassica napus L.) has been suggested in the Great Lakes
region. By definition, canola is the seed of B. napus L. or B. rapa L., the oil
component of which contains 20 g kg" or less of erucic acid (22:1) and the meal
component of which contains 30 pmol g" or less of oil-extracted, air-dried meal of any
one or any mixture of the aliphatic glucosinolates, 3-butenyl, 4-pentenyl, 2-hydroxy-3-
butenyl and 2-hydroxy-4-pentenyl glucosinolate (Canola Council of Canada, 1990). In
other words, canola is a type of rapeseed with low glucosinolates and low erucic acid
(Grant and Bailey, 1993). Rape has been grown as a forage crop in the USA since the
early 1900’s (Karow, 1986). But, the oil of rapeseed was not much used as edible oil
due to health concerns over its high levels of erucic acid (Downey, 1976). As an
animal feed, the oil-free meal of rapeseed is an excellent source of protein but it
contains high levels of glucosinolates which can cause nutritional disorders in animals
(Thomas, 1986). Rapeseed oil is also used in producing a variety of polymer and
lubricant products and the USA alone uses more than 4.5 million kg of the oil, a large
part of which is imported (Auld and Mahler, 1987; Francois, 1994). The health
concerns of rapeseed oil led to the development of "double-low" (low erucic acid and
low glucosinolate) cultivars of rapeseed known as canola. The term ‘canola’ is a
trademark registered by the Canola Council of Canada and used to differentiate

between non-canola rapeseed cultivars and the double-low cultivars (Thomas, 1986;

39

4O

Francois, 1994). Canola was developed through intensive breeding programs by
Canadian scientists. In 1985, the US Food and Drug Administration (FDA) recognized
that canola was different from rapeseed and granted canola generally recognized as
safe (GRAS) status (Shahidi, 1990). Canola oil is now the world’s third largest source
of edible oil after soybean (Glycine max [L.] Merr.) and palm (Elaeis oleifero [HBK]
Cortes) oil Nowlin (1991). Estimates from USDA in 1991 show consumption of
canola oil in the USA at 0.36 million Mg and canola acreage between 42525 and
56700 hectares (Thompson et al., 1993). Canola has been considered a promising
winter cash-crop in the southeast and as a production alternative to winter wheat in the
midwestem USA (Porter, 1993; Thompson et al., 1993). Canola was introduced in
Michigan in the mid-1980’s and since then, there has been an increase the area of
canola under cultivation in the upper Great Lakes region of the USA. Canola is
known to have relatively high nutrient requirements compared with cereal crops (Grant
and Bailey, 1993). Holmes (1980) suggested that oilseed rape has a high requirement
for N and needs considerably more than that provided by most soils. Bullock and
Sawyer (1991) calculated an optimum economic N fertilizer rate of up to 264 kg ha"
for canola. Porter (1993) reported that total N application of 135 kg ha" gave
maximum canola grain yield in a study in South Carolina. Nuttall et a1. (1992) also
found good response of canola yield to applied N. An experiment in England showed
winter oilseed rape to require 200 kg N ha" for optimum yield (Scott et al., 1973).
Increasing prices of N fertilizer, desire to promote agricultural sustainability, pollution

concern, and efforts to conserve natural resources have prompted researchers to

41

develop cropping systems that reduce N fertilizer applications and make more efficient
use of organic N sources (Heichel and Barnes, 1984; Hargove et al., 1988; Fauci and
Dick, 1994; Sweeney and Moyer, 1994).

Farmers have used forage legumes in cropping systems for many years to take
advantage of the N contribution of the legume and to enhance the productivity of a
succeeding nonlegume crop (Hesterman, 1988). Many researchers have accepted that
at least a portion of the major effect of legumes in crop rotations is their contribution
of mineral N (Stickler et al., 1958; Bolton et al., 1976; Baldock et al., 1981; Martin
and Touchton, 1983; Hesterman et al., 1987; Bruulsema and Christie, 1987; Scott et
al., 1987; Badaruddin and Meyer, 1989). Green manuring was first utilized in ancient
China and the practice has been defined as an enrichment of the soil by incorporating
fresh plant material other than just plant residues (Pieters, 1927). Both legumes and
non-legume crops are used as green manures, but from a N standpoint legumes are
more beneficial as green manures because they fix atmospheric dinitrogen (Giddens et
al., 1965). The use of green manures with various crops such as corn, wheat, rice,
oats, cotton, and sugarbeets have been reported by various authors (Mahler and Auld,
1989), but very little literature exists on the use of green manures for canola.
Numerous reports indicate that availability of green manure N depends mainly on type
and quantity applied, time of incorporation, and the following crop (Mahler and
Hemamda, 1993). Studies have also demonstrated that harvest management of
legumes affects the quantity of N-rich herbage returned which consequently influences

subsequent crop yields. Contribution of N at plowdown is greater was more from

42

legumes that are not harvested (Robinson, 1968; Groya and Sheaffer, 1985; Hesterman
et al., 1986; Sparrow et al., 1995). However, Sheaffer et al. (1991) concluded that the
greatest positive effect on yield of a subsequent corn crop from non-harvested legume
plowdown is from legume stands older than 2 years. It is still unclear from previous
research if harvesting an annual forage legume has any significant impact on the
subsequent non-legume crop. Several researchers have attributed the effect of legumes
on subsequent crop yields to both the effect of N and the net effect of all other
contributions termed as "rotation effects" (Baldock et al., 1981; Hesterman, 1988;
Russelle et al., 1987; Pierce and Rice, 1988).

Most legumes used as forage, green manure, or cover crops in the North
Central USA are perennial species. However, perennial legumes may deplete soil
moisture sufficiently to reduce the yield of the succeeding crop (Army and Hide, 1959;
Hesterman et al., 1992). In many situations, such as winter canola or winter wheat,
annual legumes may be beneficial. They may be planted in early spring so that they
can mature before the optimum seeding time of the main crop, put on high quantity of
biomass before plowdown, and decompose quickly to make nutrients available to the
subsequent crop. Annual legumes can also be used as quality emergency forages
(Shrestha et al., 1995). Annual medics (Medicago sp.) are self-pollinating true
annuals. They flower, set seed, and die within one growing season (Bauchan and
Sheaffer, 1994). Annual medics provide high quality forage (Bauchan et al., 1994;
Shrestha et al., 1995) and are used on approximately 50 million hectares in Australia

in pastures as a rotation crop (Crawford et al., 1989). Lake (1994) reported that

43

annual medics are known to improve soil structure, increase soil nitrogen, and reduce
soil erosion. Berseem clover is an erect, cool-season annual legume believed to have
originated in the region of Egypt and Syria (Baldridge et al., 1992). Berseem was
introduced in the USA in 1896 and it has been grown successfully in Washington,
Oregon, California, Arizona, and some parts of Florida (Kretschmer, 1964; Knight,
1985). It’s greatest potential is as a green-chopped forage or pasture and it is known
to be non-bloating (Dennis and Massengale, 1962). Berseem has been successfully
used as a green manure and rotation crop (Baldridge et al., 1992; Westcott et al.,
1995)

The N benefit to a subsequent crop is often reported as the N-fertilizer
replacement value (FRV) and yield responses to previous legumes can be expressed on
the basis of N-FRV. Fertilizer replacement value has been defined as the amount of N
fertilizer required by a non-legume crop in monoculture to produce yields equivalent to
those produced after incorporation of a legume (Hesterman, 1988). Various authors
have used this method to report the N benefit of a legume to a subsequent crop
(Clegg, 1982; Wright, 1990; Griffin and Harris, 1991; Hesterman et al., 1992; Pare et
al., 1993; Jeranyama, 1995; Torbert et al., 1996). Fertilizer replacement values have
been estimated for legumes like faba bean (Vicia faba L.), field pea (Pisum sativum
L.), and lentil (Lens culinaris Moench) in barley (Hordeum vulgare L.) production
(Wright, 1990). Similarly, Clegg (1982) estimated FRV of soybean (Glycine max [L.]
Merr) to subsequent grain sorghum (Sorghum bicolor [L.] Moench). Hesterman et al.

(1992) estimated the FRV of alfalfa and red clover (T rifolium praiense L.) to the

44

subsequent corn (Zea mays L.). Jeranyama (1995) estimated the FRV of annual
medics to be 40 kg N ha" on the succeeding corn. However, literature does not exist
on estimation of FRV of annual medics and berseem clover on a subsequent canola
crop. The objectives of this research were to: (i) quantify N accumulation at
plowdown by annual medics and berseem clover managed as a forage or green
manure; (ii) compare the response of canola to fertilizer N after a legume managed as
a forage or green manure and after a nonlegume; and (iv) estimate the FRV of the

previous crop management system on the subsequent canola.

MATERIALS AND METHODS

Field experiments were initiated in 1994 at two locations in Michigan:
Michigan State University, Crop and Soils Farm, East Lansing on a Capac loam (fine-
loamy, mixed, mesic Aerie Ochraqualfs) and on a Kalamazoo loam (fme-loamy,
mixed, mesic Typic Hapludalf) at the Kellogg Biological Station (KBS), Hickory
Corners. The experiments were repeated in 1995 at the same locations.
Climatological data for 1994, 1995, and 1996 are shown in Table 1. In both years, P
and K were applied to maintain soil test levels at or above those recommended for an
alfalfa-canola rotation. Soil test data for the two years and two locations are
summarized in Table 2. Seedbed preparation included conventional tillage and

cultipacking.

First cycle: 1994/1995

Main plots of 24.3 by 2 m at East Lansing and 24.3 by 1.8 m at KBS were
arranged in a randomized complete block design with four replications. The main
plots included twelve treatments (Table 3). Barrel medic ‘Mogul’, burr medic
‘Santiago’, snail medic ‘ Sava’, berseem clover, alfalfa ‘Nitro’, gamma medic
‘Paraponto’, and spring canola ‘A114’ were seeded with a small grain drill and
cultipacked. Mogul, Santiago, Sava, and alfalfa seeds were inoculated with Rhizobium
meliloti and berseem clover seeds were inoculated with R trifoli prior to seeding.

Paraponto seeds were not inoculated because it was chosen as an ineffective, non-

45

46

nodulating control treatment. Spring canola was seeded to create a continuous canola
situation. The three nodulating annual medic species were chosen to represent three
different growth habits, Mogul a semi-erect, Santiago a prostrate, and Sava an erect
growing medic. The seeding rates of the legume species were determined at 270 pure
live seeds (PLS) m'2 (Table 4). A preplant application of Eptam (S-ethyl
dipropylthiocarbamate) at a rate of 3.3 kg ha" was incorporated in all the plots except
those containing spring canola. Treflan (a,a,a,-trifluora-2,6-dinitro-N,N-dipropyl-p-
toluidine) was preplant incorporated in the plots containing spring canola at a rate of
2 l a.i. ha" . Fertilizer N was applied at a rate of 20 kg N ha" in the plots containing
spring canola. Both locations were irrigated with a total water application of 5 cm.
All treatments designated as FOR, Paraponto, alfalfa, and canola were harvested
approximately 60 days after planting (DAP) with a flail mower to a stubble height of 5
cm. Spring canola and fallow plots were roto-tilled after the harvest at 60 DAP. The
FOR, Paraponto, and alfalfa treatments were allowed to regrow. Spring canola had
not reached harvest maturity at this time and seed yields were not recorded. Green
manure treatments were allowed to grow until approximately 90 DAP. All plots were
plowed under by a mold board plow. Estimates of above-ground biomass were made
prior to plowdown by taking 0.25 m2 quadrat measurements. Biomass within the
quadrat was hand clipped and adjusted to dry weight by drying in a forced-air oven at
60°C for 72 hours. Samples were ground to pass through a 1-mm screen in a cyclone
mill (Wiley Corporation). Ground samples were subjected to the Hach procedure for

total N determination (Hach et al., 1985) to obtain an estimate of N contained in the

47

biomass at plowdown. Roundup (Isopropylamine salt of glyophosate) was sprayed on
the plots at East Lansing three days prior to plowdown. Planting, irrigation, harvest,
and plowdown dates are summarized in Table 5.

Winter canola ‘Ceres’ was planted at a rate of 5 kg ha" in all plots on 24
August 1994 at East Lansing with a small grain drill and on 26 August 1994 at KBS
with a power drill and cultipacked. Plots at both locations were disked twice and
Treflan was sprayed at a rate of 2 l a.i. ha" and incorporated a week prior to planting
winter canola. Main plots were split into 4 subplots and fertilizer N in the form of
urea was applied as surface topdress at 4 rates (0, 50, 100, and 150 kg N ha") on 22
March 1995 at East Lansing and 17 March 1995 at KBS. Each subplot was 6 by 2 m
at East Lansing and 6 by 1.8 m at KBS and arranged in a split block design. A 90 cm
alleyway was cut between the subplots by a flail mower on 22 May 1995 at East
Lansing and 23 May 1995 at KBS. Bird netting was applied on the entire plot on 16
June 1995 at East Lansing and 27 June 1995 at KBS. Plots were harvested on 8 July
1995 at East Lansing and 12 July 1995 at KBS. Plant population of each treatment
was estimated by counting number of stems within a 0.25 m2 area immediately after
harvest. Seeds were air dried and weighed. Seed moisture content was determined
using seed moisture meter and seed yields were adjusted to a moisture content of 100
g kg".

Soil Sampling and Analysis Soil samples were taken 3 times during the course of the
experiment by a manual soil probe at two depths; 0-15 cm and 15-30 cm. The

samples were immediately air-dried and ground to pass a 2 mm sieve. Total inorganic

48

N, nitrate-N, and ammonium-N were determined on each sample using KCl extraction
procedure for inorganic N. The procedure consisted of shaking 10 g dry soil in 50 ml
of 1 M KCl for 30 minutes. Inorganic N in filtered KCl extracts was assayed
colorimetrically on a Lachat flow injector analyzer using Lachat Quickchem Method

12-107-04-1-A. The soil sampling dates are summarized in Table 6.

Second cycle: 1995/1996

The experiment was repeated in 1995 in different plots at the same two
locations. Details of the plots are summarized in Table 2. Similar planting and
cultural practices were used as in 1994. The same Rhizobium inoculation culture was
used for alfalfa and berseem as in 1994 but the annual medics were inoculated with a
1:1 mixture of R meliloti and Rhizobium special number 1 (Nitragin, Liphatech Inc).
Only East Lansing was irrigated with a total water application of 5 cm. Planting,
irrigation, harvest, and plowdown dates are summarized in Table 5. Winter canola cv.
Ceres was planted at a rate of 5 kg ha" on 23 August 1995 at East Lansing and 24
August 1995 at KBS. Canola at East Lansing failed to germinate due to dry
conditions and was replanted on 12 September 1995. Fertilizer N in the form of urea
was applied at four rates (0, 50, 100, and 150 kg N ha") on 18 March 1996 at KBS
and 21 March 1996 at East Lansing. The severe winter in 1995/96 resulted in almost
100 per cent winter-kill of the canola at East Lansing. Roundup was sprayed on the
plots at East Lansing on 17 May 1996 to kill weeds and the few surviving canola

plants. Spring canola ‘Cyclone’ was planted on 20 May 1996 at East Lansing, but it

49

failed to germinate because of soil crusting. Re-planting was done by no-till drill on
28 May 1996. Only 3 replications were planted as the area containing the fourth
replication was too wet for field activities and use of machinery. Alleyways were out
between subplots as in 1995. Bird netting was put on at KBS on 1 July 1996 and 9
August 1996 at East Lansing. The plots were harvested on 16 July 1996 at KBS and
on 28 August 1996 at East Lansing. Seed yield of each treatment and plant population
was determined similarly as in 1995. Similar soil sampling and analysis procedures
were followed as in the previous year. Soil sampling dates are summarized in Table

6.

Statistics

Analysis of variance was performed on the data for N in biomass at plowdown,
canola seed yield, canopy height, plant population, and soil inorganic-N values within
each location because significant treatment X location interactions were detected.
Significant differences among treatments were determined with an F -test and mean
separation was done using Fisher’s Least Significant Difference (LSD) where the F -
test denoted significance (P5005). Single degree of freedom orthogonal contrasts
were used to compare canola yield under green manure and forage treatments, berseem

and medics, and continuous and rotation treatments.

RESULTS AND DISCUSSION

Biomass and nitrogen content of the legumes at plowdown

Estimates of the amount of N in above ground biomass being plowed under
showed that there were significant differences among treatments and species (Table 7).
Berseem as a green manure had a significantly higher N content at plowdown than the
other species at East Lansing and KBS in 1994. In 1995, Mogul and berseem as green
manure had significantly higher N content at plowdown than the other species at both
locations. Contrasts showed that the legume species when managed as a green manure
had a significantly higher amount of N being plowed down than when managed as a
forage. This was due to the fact that there was significantly higher amount of above
ground biomass at the time of plowdown in the GM treatments than the FOR
treatments at both locations in both years. However, the N concentration in the
biomass was generally significantly higher in the FOR treatments than the GM
treatments showing that N concentration in the regrowth of the biomass was higher
when the plants are harvested at 60 DAP than the unharvested plants. The contrasts
also showed that there was no significant difference between Paraponto (ineffective
control) and the N—fixing legume treatments in terms of amount of N at plowdown in
East Lansing in 1995. This was primarily due to the high biomass of Paraponto at
plowdown rather than differences in N concentration. The amount of N in above
ground biomass at plow down was not correlated with the average grain yield of

succeeding canola.

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51

Canola grain yield
Severe winter-kill caused almost 100 % loss of canola plants at East Lansing

in 1996, while at KBS, the loss was about 33 % compared to the plant population in
1995. Spring canola was re-planted at East Lansing. Therefore, interactions for
location X year, and year X main treatment were not analyzed. The main treatment X
N level interactions were not significant at the 0.05 level; therefore data for canola
grain yield were pooled and are presented for each main treatment averaged over N
application rates. Canola yields under different cropping systems and N levels are
summarized in Appendix Tables A1 to A4.

Neither preceding crop nor management practice had significant effect on
canola grain yield in either year at East Lansing or in 1996 at KBS (Table 8).
However, in 1995, species and management practices were associated with significant
differences in the subsequent canola yield at KBS. Highest canola yields were
obtained from the plots in which berseem had been managed as a green manure. The
lowest yields were obtained from plots in which Santiago had been managed as a
forage. The canola yield following the legumes managed as green manure was
significantly higher than when the legumes were managed as forage. In 1995, at East
Lansing, canola grain yield following berseem FOR was the highest, but was not
significantly different from canola yield following other cropping systems. Orthogonal
contrasts indicated no significant difference in canola grain yield under a continuous
canola cropping system versus a crop rotation system (Table 7). Yields were higher

when a crop rotation was followed but differences were not significant at a 0.05 level.

52

Contrasts also indicated that harvesting the preceding annual legume as a forage at 60
DAP and plowing down the regrowth and residue at 90 DAP or plowing down the
entire biomass as green manure at 90 DAP had no differential effect on canola grain
yield except at KBS in 1995 (Table 8). Canola following berseem clover managed
either as a forage or green manure was similar to canola following all the other annual
medics managed as a forage or green manure in East Lansing and KBS in 1996.
However, in 1995, canola yield following berseem clover was significantly higher than
canola yield following annual medics in both locations.

As expected, canola yield at East Lansing in 1996 was very low due to delayed
planting. The average yield under all treatments was less than 1 Mg ha". There were
no significant differences among the main treatments in terms of effect on the
following canola yield. Contrasts also showed that canola yield under a crop rotation
system and under a continuous canola system was not significantly different.

Similarly, canola yield following the GM or FOR, and berseem or medic treatments
were not significantly different.

It is apparent from Table 8 that canola grain yields at KBS in 1996 were
affected by winter-kill. Canola response to the treatments was influenced by the
severe weather conditions in 1996 as it did not simulate the responses in 1995. Yields
were generally lower in 1996 than 1995 under all treatments. Canola plant population
and yield was respectively 33 % and 9 % lower in 1996 compared to that in 1995.
The highest yield of canola grain was obtained when canola followed Mogul FOR but

it was not significantly different from the other cropping systems at the 0.05 level.

53

It can be inferred that the canola yield following berseem clover managed
either as a forage or green manure was generally higher than the other treatments even
though statistical significance at 0.05 level was obtained only at KBS in 1995. In
general, harvesting the preceding annual legume as a forage at 60 DAP and plowing
down the regrowth and residue at 90 DAP or plowing down the entire biomass as

green manure at 90 DAP had no significant effect on canola grain yield.

Canola plant population

Differences in cropping system had no effect on plant population of the
subsequent canola at both locations in 1995 (Table 9). Canola plant population was
generally higher at KBS than at East Lansing. Canola experienced severe winter-kill
in 1996. Winter-kill may have been due to colder temperatures and lack of snow
cover in 1996 compared to 1995 (Table l), and heaving of canola plants. As a result,
spring canola was planted at East Lansing to measure FRV’s of the legumes. As in
1995, the preceding cropping system had no effect on canola population at KBS in
1996. Although, the loss in plant population was 33 %, the loss in canola grain yield
was only about 9 %. This indicates that the loss in plant population may have been
compensated by more branching and subsequently more pods per plant due to less

inter-plant competition for resources.

54

Canola response to nitrogen under different cropping systems

The effect of nitrogen fertilizer on canola grain yield was highly significant at
both locations in 1995 and 1996. Trend analysis showed that N had significant (P:
0.05) linear and quadratic effects on canola grain yield at East Lansing in 1995 and at
KBS in 1996 (Table 8). The quadratic effect of N at KBS in 1995 can be explained
by the fact that the plants had lodged in several plots which had the highest N level.
Whereas, at East Lansing it was observed that the spring canola plots with the highest
N level were generally greener and less mature than the plots with a lower N level
thus affecting the yield at 150 kg N ha" level. Figures 1 to 4 show the degree of
response of canola to fertilizer N under various cropping systems in 1995 and 1996 at
East Lansing and KBS. Regression equations describing response curves of canola

yield to fertilizer N in Figures 1 to 4 are listed in Table 10.

Nitrogen fertilizer replacement values (FRV)

It has been suggested that, for a FRV to be valid and useful there must be a
significantly higher yield of a crop following a legume than following a nonlegume
control when no N fertilizer is used in either system (Hesterman et al., 1992). Based
on this suggestion FRV’s of the legumes were non-estimable in this study as canola
yield following a legume and the nonlegume control at 0 N level was not significantly
different in either year at both locations. Several researchers have attributed increased
yields in a crop following legumes to effects termed as "rotation effects" which

includes improved soil physical, chemical, and biological properties (Ries et al., 1977;

55

Russelle et al., 1987; Torbert et al., 1996). However, rotation effects were not visible
in this experiment as no significant differences between treatments were found in
canola yield. Paraponto was used in this experiment in order to differentiate non-N
effects from N-effects of the nodulating legumes. However, the results obtained in

this experiment did not help in differentiating these effects.

Soil nitrate and ammonium levels

The soil tests for N03 and NH, at three different periods during the course of
the experiment showed that there were no significant differences between treatments at
both East Lansing and KBS in 1995 (Table 11 and 12). The N03 levels under each
treatment were generally higher at East Lansing than at KBS. However, time trends of
NO3 and NH, levels were evident. The NH, levels were higher than the N03 levels at
the second sampling in October 1994 at both locations. The NH, levels at this
sampling date were almost twice as high in KBS than at East Lansing. However, in
1995 the peaks of NH, at the October sampling date was not so evident as in 1994.
Significant differences were found in the N03 levels both at East Lansing and KBS
only in the August sampling date in 1995. The N03 levels in the fallow and
continuous canola plots were higher than in the other treatments at East Lansing.
However, the fallow plot was not significantly different from the plot with alfalfa.
This indicates that nitrogen from the legumes had not yet mineralized at this sampling
date. Similarly, the highest NO, levels were in the fallow plots at KBS. No

significant differences were found in NH, levels. At East Lansing, the March 1996

56
samples showed higher levels of NO3 than the samples of March 1995. It may be
recalled that the canola plants had winter-killed in 1996 and there was no uptake of
nitrogen. This suggests that N03 is generally taken up by the plants at or before this

sampling date.

SUMMARY

The presence of an annual legume as a preceding crop did not result in
significantly higher yields of the subsequent canola crop. Fertilizer N had a significant
linear and quadratic effect on the canola yield and the trend of the effect was similar
for canola grown under different cropping systems. The practice of harvesting the
annual legume as a forage 60 DAP and plowing down the regrowth at 90 DAP versus
the practice of plowing down the entire above ground biomass at 90 DAP without
harvesting it as a forage showed no differences in terms of the yield of the subsequent
canola crop. However, significant differences between these practices were obtained at
KBS in 1995, where the harvested treatments were associated with significantly lower
canola yields than the unharvested treatments. This suggests that it is possible to take
one harvest of annual legumes as a forage and still get benefits equivalent to the
unharvested legumes in terms of contribution to the yield of the following crop. The
yield of canola following berseem clover was generally higher than when following an
annual medic. The amount of above ground biomass and N content at plowdown had
no significant effect in the yield of the following canola crop. There were generally
no significant differences in the soil NO3 and NH, levels between treatments at various
sampling dates. This could be due to the leaching of nitrates or lack of synchrony
between the release of N from the legume residues and uptake of N by the canola
plants. The legumes did not produce any significant FRV thus questioning their use in

reducing fertilizer N need in canola under such cropping systems. The annual medic

57

58
species used in this experiment are not quite adapted to this region (Michigan) in terms
of use as a green manure or as a rotation crop. However, berseem clover generally
produced higher biomass, higher forage quality (Shrestha et al., 1995), and had a

significant effect on the yield of the following canola crop in one year.

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59

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61

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62

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63

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64

Table l. Climatalogical data from May 1994 to July 1996 at East Lansing and
Kellogg Biological Station (KBS), Michigan.

 

 

Year Month East Lansing KBS
Tot. Precip. Mean Temp. Tot. Precip. Mean Temp.
mm °C mm °C
1994 May 46.2 12.7 3.96 15.8
Jun. 185.9 19.8 174.4 21.5
Jul. 121.2 20.9 160.2 22.4
Aug. 143.3 18.6 119.5 21.9
Sept. 118.9 16.7 29.6 17.9
Oct. 80.8 10.7 73.4 12.0
Nov. 120.7 5.7 106.7 6.9
Dec. 39.9 -0.2 40.5 1.2
1995 Jan. 15.0 -3.8 31.2 -2.6
Feb. 27.2 -6.0 13.1 -4.2
Mar. 35.6 2.0 35.6 3.7
Apr. 69.3 5.2 76.8 6.7
May 63.5 12.6 72.7 14.8
Jun. 42.2 19.8 92.2 21.6
Jul. 100.6 21.4 82.9 24.4
Aug. 116.1 23.2 110.4 24.8
Sept. 32.3 14.6 48.4 16.1
Oct. 69.1 11.2 58.9 12.0
Nov. 78.5 -0.7 90.8 0.8
Dec. 22.6 -5.1 14.7 -3.5
1996 Jan. 32.0 -6.5 20.3 -5.1
Feb. 19.1 -5.2 32.1 -3.4
Mar. 12.7 -2.1 11.4 -O.8
Apr. 98.0 6.1 81.9 7.1
May 71.9 12.6 70.3 14.5
Jun. 140.5 19.6 130.4 21.6
Jul. 29.5 19.7 2.56 21.3

 

65

Table 2. Initial soil test values at East Lansing and KBS in 1994 and 1995.

 

Year and Location Soil pH Avail. P Exch. K

 

1994 ........ kg 1134------"
East Lansing 7.6 82 228
KBS 7.3 80 130
1995

East Lansing 7.3 82 159

KBS 7.6 74 226

 

66

Table 3. List of main treatments at East Lansing and KBS in 1994 and 1995.

 

Treatment No.

Treatment description

 

\OOOQQUIAUJNt—i

Fallow

Spring canola cv. A114

‘Paraponto’ gamma medic (Ineffective)

‘Nitro’ alfalfa

‘Mogul’ barrel medic managed as forage (FOR)
‘Mogul’ barrel medic managed as green manure (GM)
‘Santiago’ burr medic managed as forage (FOR)
‘Santiago’ burr medic managed as green manure (GM)
‘Sava’ snail medic managed as forage (FOR)
‘Sava’ snail medic managed as green manure (GM)
Berseem clover managed as forage (FOR)

Berseem clover managed as green manure (GM)

 

67

Table 4. Seeding rate of the species in the main treatments at East Lansing and KBS
in 1994 and 1995.

 

 

Species Seeding rate
kg ha"
‘Nitro’ Alfalfa 20
‘Mogul’ Barrel medic 15
‘Santiago’ Burr medic 15
‘Sava’ Snail medic 32
‘Paraponto’ Gamma medic 25
Berseem clover 12

Spring canola 5

 

68

Table 5. Planting, irrigation, harvest, and plowdown dates in 1994 and 1995 at East
Lansing and Kellogg Biological Station (KBS), Michigan.

 

 

Location Planting Irrigation Harvest] Harvest2 Plowdown
1994

East Lansing 13 May 25 May 18 July 8 August 8 August
KBS 6 May 3 May 11 July 9 August 9 August
1995

East Lansing 12 May 21 May 17 July 14 August 21 August

KBS 8 May - 13 July 10 August 21 August

 

69

Table 6. Summary of soil sampling dates at East Lansing and KBS in 1994, 1995 and
1996.

 

 

Year Location Soil sampling dates

1994/95 East Lansing 23 Aug. ’94, 17 Oct. ’94, 22 Mar. ’95
1994/95 KBS 18 Aug. ’94, 12 Oct. ’94, 17 Mar. ’95
1995/96 East Lansing 23 Aug. ’95, 30 Oct. ’95, 11 Apr. ’96

1995/96 KBS 16 Aug. ’95, 23 Oct. ’95, 18 Mar. ’96

 

70

Table 7. Biomass, nitrogen concentration, and nitrogen content of the various treatments at plowdown at
East Lansing and KBS in 1994 and 1995.

 

 

 

Location 1994 1995
& Treatment DM N cone. N cont. DM N cone. N cont.
Mg ha" g kg" kg ha" Mg ha" g kg" kg ha"
East Lansing
Paraponto 1.15 17.1 19.6 2.25 22.5 50.2
Alfalfa 1.55 30.0 47.1 1.94 29.8 58.0
Mogul (GM) 3.31 21.9 78.6 2.61 26.8 70.2
Mogul (FOR) 1.41 22.6 35.4 1.99 28.0 55.4
Santiago (GM) 1.98 15.7 30.2 1.49 25.1 37.2
Santiago (FOR) 1.09 22.3 24.5 1.14 28.4 32.0
Sava (GM) 1.57 20.0 31.7 Traces - -
Sava (FOR) 0.65 21.0 13.8 Traces - -
Berseem (GM) 4.98 24.8 122.9 3.25 25.3 82.3
Berseem (FOR) 1.62 34.6 56.1 2.08 28.4 58.7
LSD (0.05) 1.23 4.8 31.1 0.8 3.0 21.9
CV(%) 43.5 13.9 45.9 25.7 6.4 26.8
Contrasts
GM VS FOR I”? ** ** ** *1: *
Ben VS med *4! *4! *4! ** NS *4!
Para. vs leg. NS NS ** NS ** NS
KBS
Paraponto 1.88 18.9 36.7 0.98 28.8 29.6
Alfalfa 1.33 32.7 42.8 1.65 33.7 55.3
Mogul (GM) 3.53 29.1 104.3 3.30 26.2 87.2
Mogul (FOR) 2.56 27.8 70.5 1.80 26.9 47.5
Santiago (GM) 1.12 22.1 24.9 1.94 32.6 62.3
Santiago (FOR) 1.09 20.8 22.3 0.98 36.2 35.2
Sava (GM) 1.36 20.5 27.9 Traces - -
Sava (FOR) 1.05 23.4 26.4 Traces - -
Berseem (GM) 3.55 30.7 110.0 4.43 22.6 100.4
Berseem (FOR) 2.09 31.3 65.4 1.64 29.3 48.1
LSD (0.05) 0.7 5.1 27.8 0.7 4.2 18.7
CV(%) 26.4 13.7 36.0 22.5 9.8 22.1
Contrasts
GM VS FOR *4! NS ** ** *4: II!
Ber. vs med. ** ** ** NS ** NS
Para. vs leg. NS ** ** ** NS **
GM = Green manure FOR = Forage
Ber. = Berseem Med. = Medics

Para. = Paraponto (ineffective) Leg. = Legumes (effective)
*, *"‘ Significant at the 0.05 and 0.01 levels respectively. NS = Not significant at the 0.05 level.

71

Table 8. Average canola yields under different cropping systems and nitrogen rates at
East Lansing and KBS in 1995 and 1996.

 

 

 

 

East Lansing KBS
Cropping System 1995 1996 1995 1996
Mg ha"
Fallow-canola (F -C) 2.31 0.72 3.18 2.80
Canola-canola (C-C) 2.33 0.71 3.15 2.92
Paraponto-canola (P-C) 2.38 0.58 3.17 2.89
Alfalfa-canola (A-C) 2.54 0.63 3.29 2.89
Mogul GM-canola (MG-C) 2.48 0.67 3.16 2.86
Mogul FOR-canola (MF-C) 2.45 0.64 3.16 3.04
Santiago GM-canola (SaG-C) 2.32 0.66 3.24 2.91
Santiago FOR-canola (SaF-C) 2.29 0.68 2.95 2.81
Sava GM-canola (SvG-C) 2.31 0.78 3.31 2.96
Sava F OR-canola (SvF-C) 2.47 0.53 3.04 3.03
Berseem GM-canola (BG-C) 2.53 0.70 3.43 2.93
Berseem FOR-canola (BF-C) 2.61 0.72 3.27 2.87
LSD (0.05) NS NS 0.26 NS
Contrasts
N linear ** *4! ** *IIK
N quadratic NS ** ** NS
N cubic NS NS NS NS
Rotation vs contcanola NS NS NS NS
GM vs FOR NS NS ** NS
Medics vs Berseem ** NS ** NS
CV% 8.1 16.2 7.6 7.6

 

** Significant at the 0.01 level; NS = nonsignificant at 0.05 level.
GM = Green manure
FOR = Forage

72

Table 9. Average canola plant population under different cropping systems at East
Lansing and KBS in 1995 and 1996.

 

East Lansing KBS
Cropping System 1995 1996 1995 1996

 

Plants ha’1 (in thousands) ..............

 

F-C 1350 1640 1610 1100
C-C 1210 1350 1360 1100
P-C 1290 1560 1710 1030
A-C 1080 1310 1520 980
MG—C 1090 1360 1610 1040
MF-C 1300 1430 1200 1070
SaG-C 1380 1470 1550 980
SaF-C 1290 1560 1830 1090
SvG-C 1040 1550 1890 1030
SvF-C 1180 1650 1450 1020
BG-C 1270 1560 1620 1000
BF-C 1200 1320 1540 1070

NS NS NS NS

CV% 15.5 10.9 23.0 9.5

 

 

73

Table 10. Regression equations on response of canola to fertilizer nitrogen under different cropping
systems at East Lansing and KBS in 1995 and 1996.

 

 

Cropping 1995 1996

System Equation 1'2 Equation r2
East Lansing

F-C Y= 1.81 + 0.007N 0.95 Y= 0.62 + 0.003N - 0.00002N2 0.96
C-C Y= 1.72 + 0.008N 0.97 Y: 0.53 + 0.005N - 0.00002N’2 0.99
P-C Y= 1.76 + 0.008N 0.98 Y= 0.41 + 0.005N - 0.00002N2 0.96
A-C Y= 2.10 + 0.006N 0.87 Y= 0.53 + 0.006N - 0.00004N2 0.90
MG-C Y= 2.06 + 0.006N 0.95 Y= 0.60 + 0.002N - 0.000011? 0.67
MF-C Y= 1.93 + 0.007N 0.98 Y= 0.52 + 0.004N - 0.00002N2 0.92
SaG-C Y= 1.81 + 0.007N 0.93 Y= 0.53 + 0.003N - 0.00001N2 0.99
SaF-C Y= 1.77 + 0.007N 0.94 Y= 0.56 + 0.004N - 0.00002NQ 0.89
SVG-C Y= 1.80 + 0.007N 0.97 Y= 0.65 + 0.002N - 0.00001N’z 0.96
SVF-C Y= 1.99 + 0.006N 0.91 Y= 0.44 + 0.003N - 0.00001NQ 0.89
BG-C Y= 2.06 + 0.006N 0.78 Y= 0.55 + 0.006N — 0.00003N2 0.87
BF-C Y= 2.15 + 0.006N 0.94 Y= 0.64 + 0.003N - 0.00001N’2 0.99
KBS

F-C Y= 2.76 + 0.02N - 0.00009N’ 0.99 Y= 2.65 + 0.002N 0.72
C-C Y= 2.78 + 0.01N - 0.00004N2 0.97 Y= 2.52 + 0.005N 0.90
P-C Y= 2.89 + 0.01N - 0.00004N‘2 0.94 Y= 2.63 + 0.003N 0.91
A-C Y= 2.91 + 0.01N - 0.00005N2 0.91 Y= 2.66 + 0.003N 0.85
MG—C Y= 3.05 + 0.01N - 0.00009N2 0.99 Y= 2.59 + 0.003N 0.92
MF-C Y= 2.85 + 0.01N - 0.00007N2 0.93 Y= 2.79 + 0.003N 0.93
SaG-C Y= 2.93 + 0.01N - 0.00004N’2 0.92 Y= 2.75 - 0.001N 0.21
SaF-C Y= 2.61 + 0.01N - 0.00002N2 0.99 Y= 2.55 + 0.003N 0.94
SvG-C Y= 3.00 + 0.01N - 0.00004N2 0.99 Y= 2.66 + 0.004N 0.93
SvF-C Y= 2.68 + 0.01N - 0.00005N2 0.83 Y= 2.66 + 0.005N 0.99
BG-C Y= 3.14 + 0.01N - 0.0000219" 0.98 Y= 2.74 + 0.003N 0.96
BF—C Y= 3.07 + 0.002N - 0.00001N2 0.86 Y= 2.51 + 0.005N 0.99

 

N = Nitrogen (kg ha")

 

 

74

 

 

 

 

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4 Cropping System

 

——-C-C
F-C
P-C
A-C
MG-C
MF-C
SeG-C
SaF-C
SvG-C
SvF-C
BG-C
BF-C

-l

Canola grain yield (Mg ha )
N

 

 

 

 

0 rrr T

0 50 100 150
Fertilizer N application rate (kg lni1 )

fl
l
.OIDOODDXIU

 

 

 

Figure 1. Response of canola to fertilizer N under different cropping systems at East
Lansing in 1995.

 

Cropflng System
C-C
F-C
P-C
A-C
MG-C
MF-C
SaG-C
SaF-C
SvG-C
SVF-C
BG-C
BF-C

 

 

 

Canola grain yield (Mg ha‘)

 

 

 

0 I T
0 S0 100 150

Fertilizer N application rate (kg ha!)

.OIDOODDXID

 

 

 

Figure 2. Response of canola to fertilizer N under different cropping systems at East
Lansing in 1996.

77

 

 

 

 

 

 

 

4 Cropping System
A —C-C
'3 3 I n F-C
Bl)
é ° 4 - P-C
g x A-C
.2
hz- A MG-C
a) A MF-C
2 0 SaG-C
gl‘ 0 SaF-C
U D SvG-C
I SvF-C
0 l T
o BG—C
0 50 100 150
.. . . -1 O BF-C
Fertilizer N application rate (kg ha )

 

Figure 3. Response of canola to fertilizer N under difi‘erent cropping systems at Kellogg
Biological Station (KBS) in 1995.

 

4 Cropflng System
C-C
F-C
3 P-C
A-C
MG-C
MF-C
SaG-C
SeF-C
SvG-C
&/F-C
BG-C
BF-C

 

 

D

Canola grain yield (Mg hi‘ )
l-I N

 

 

.OIUOODDXI

 

0 u u
0 ' . 50 100 150
Fertilizer N application rate (kg luil )

 

 

 

Figure 4. Response of canola to fertilizer N under different cropping systems at Kellogg
Biological Station (KBS) in 1996.

APPENDIX

78

Table A.1. Canola yield under different cropping systems and fertilizer nitrogen levels
at East Lansing in 1995.

 

Fertilizer N (kg N ha")
Cropping System 0 50 100 150

 

 

Canola yield (Mg ha" ) ..............

Fallow-canola (F-C) 1.73 2.28 2.45 2.76
Canola-canola (C-C) 1.66 2.25 2.46 2.94
Paraponto-canola (P-C) 1.68 2.30 2.57 2.99
Alfalfa-canola (A-C) 1.98 2.51 2.80 2.84
Mogul GM—canola (MG-C) 2.02 2.44 2.54 2.94
Mogul F OR-canola (MP-C) 1.90 2.24 2.22 2.98
Santiago GM-canola (SaG-C) 1.69 2.28 2.56 2.73
Santiago FOR-canola (SaF-C) 1.69 2.28 2.38 2.81
Sava GM-canola (SvG—C) 1.72 2.25 2.50 2.79
Sava FOR-canola (SvF-C) 1.87 2.45 2.69 2.85
Berseem GM-canola (BG-C) 1.85 2.64 2.79 2.86
Berseem FOR-canola (BF-C) 2.05 2.59 2.77 3.01

LSD(0.05) NS 0.24 NS NS

 

79

Table A2. Canola yield under different cropping systems and fertilizer nitrogen levels
at Kellogg Biological Station (KBS) in 1995.

 

Fertilizer N (kg N ha")
Cropping System 0 50 100 150

 

Canola yield (Mg ha“1 ) ..............

 

 

Fallow-canola (F-C) 2.76 3.33 3.46 3.18 "
Canola-canola (C-C) 2.76 3.21 3.29 3.32 n
Paraponto-canola (P-C) 2.87 3.27 3.28 3.27

Alfalfa-canola (A-C) 2.88 3.42 3.40 3.46 7
Mogul GM-canola (MG-C) 3.06 3.37 3.38 2.83 i
Mogul FOR-canola (MP-C) 2.87 3.20 3.44 3.11 L
Santiago GM-canola (SaG-C) 2.95 3.20 3.49 3.32 '
Santiago FOR-canola (SaF-C) 2.62 2.86 3.12 3.19

Sava GM-canola (SvG-C) 3.00 3.34 3.49 3.42

Sava FOR-canola (SvF-C) 2.64 3.21 3.11 3.19

Berseem GM-canola (BG-C) 3.15 3.37 3.61 3.61

Berseem FOR-canola (BF-C) 3.10 3.08 3.42 3.50

LSD(0.05) NS NS NS 0.40

 

80

Table A3. Canola yield under different cropping systems and fertilizer nitrogen levels
at East Lansing in 1996.

 

Fertilizer N (kg N ha")
Cropping System 0 50 100 150

 

-------------- (Canola yield Mg ha-l) --------------

Fallow-canola (F -C) 0.63 0.73 0.80 0.73
Canola-canola (C-C) 0.52 0.75 0.80 0.79
Paraponto-canola (P-C) 0.42 0.56 0.70 0.65
Alfalfa-canola (A-C) 0.54 0.68 0.77 0.53
Mogul GM-canola (MG-C) 0.61 0.63 0.75 0.69
Mogul FOR-canola (MP-C) 0.53 0.63 0.73 0.65
Santiago GM-canola (SaG—C) 0.53 0.63 0.72 0.75
Santiago FOR-canola (SaF-C) 0.57 0.68 0.80 0.69
Sava GM-canola (SvG-C) 0.64 0.78 0.81 0.89
Sava FOR-canola (SvF-C) 0.43 0.57 0.56 0.57
Berseem GM-canola (BG-C) 0.57 0.71 0.85 0.66
Berseem FOR-canola (BF-C) 0.64 0.74 0.77 0.74

LSD(0.05) NS NS NS NS

 

 

81

Table A4 Canola yield under different cropping systems and fertilizer nitrogen levels
at Kellogg Biological Station (KBS) in 1996.

 

Fertilizer N (kg N ha")

 

 

Cropping System 0 50 100 150
Canola yield (Mg ha‘1 ) --------------

Fallow-canola (F -C) 2.68 2.65 2.94 2.92
Canola-canola (C-C) 2.50 2.83 3.22 3.17
Paraponto-canola (P-C) 2.70 2.71 2.96 3.19
Alfalfa-canola (A-C) 2.67 2.75 3.09 3.07
Mogul GM-canola (MG-C) 2.65 2.71 2.94 3.12
Mogul FOR-canola (NtF-C) 2.81 2.99 3.05 3.37
Santiago GM-canola (SaG-C) 2.79 2.87 2.97 2.37
Santiago FOR-canola (SaF-C) 2.53 2.77 2.81 3.24
Sava GM-canola (SvG—C) 2.71 2.76 3.10 3.26
Sava FOR-canola (SvF-C) 2.63 2.95 3.15 3.38
Berseem GM-canola (BG-C) 2.71 2.91 2.97 3.21
Berseem FOR-canola (BF -C) 2.54 2.70 3.02 3.23

LSD(0.05) NS NS NS NS

 

 

HICHIGRN STQTE UNIV. LIBRRRIES
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