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This is to certify that the
thesis entitled

OVERCOMING THE ROTATIONAL ANTAGONISM OF CORN
FOLLOWING WHEAT IN HIGH RESIDUE CROPPING
SYSTEMS

presented by

ANATOLIY G. KRAVCHENKO

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OVERCOMING THE ROTATIONAL ANT AGONISM OF CORN FOLLOWING
WHEAT IN HIGH RESIDUE CROPPING SYSTEMS

By

Anatoliy G Kravchenko

A THESIS

Submitted to

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

MASTER OF SCIENCE

Department of Crop and Soil Sciences

2006

ABSTRACT

OVERCOMING THE ROTATIONAL ANT AGONISM OF CORN
FOLLOWING WHEAT IN HIGH RESIDUE CROPPING SYSTEMS
By
Anatoliy G Kravchenko
Two established methods for increasing the sustainability of production

agricultural cropping systems are (i) increasing crop residue levels by reducing tillage
and (ii) including a winter annual crop in the rotation. However, many crops following
wheat in tillage and reduced tillage systems have reduced grain yields. The objective of
this study was to develop management practices to overcome the observed negative yield
response in corn (Zea mays L.) grain grown following winter wheat (Triticum aestivum
L.) in no-till, high residue cropping systems. We hypothesized that management practices
including using a presidedress nitrogen test (PSNT) and using a PSNT in combination
with manure and clover cover crops, or a combination of the two could be used to
overcome the rotational wheat antagonism in such cropping systems. The experimental
design was a randomized complete block design. Experimental factors were: presence of
wheat residue from the previous crop with three levels (no residue, root residue, or root
and shoot residue); (2) manure application with two levels (with or without); and, (3) red

clover (Trifolium pretense L.) with two levels (with or without).

TABLE OF CONTENTS

LIST OF TABLES ................................................................................... v
LIST OF FIGURES ................................................................................. vi
ABSTRACT .......................................................................................... 1

CHAPTER 1: EFFECT OF WINTER WHEAT CROP RESIDUE ON NO-TILL CORN
GROWTH AND DEVELOPMENT

Abstract ....................................................................................... 3
Introduction ................................................................................... 5
Material and Methods ...................................................................... 11
Results ....................................................................................... 15
Weather conditions of 2003-2005 growing seasons .......................... 15
Effect of wheat residue on soil temperature ................................... 15
Effect of wheat residue on soil moisture ....................................... 18
Effect of wheat residue on date of corn emergence ........................... 27
Effect of wheat residue on stand population of com ......................... 29
Effect of wheat residue on corn date of tasselling ............................ 31
Effect of wheat residue on corn height ......................................... 32
Effect of wheat residue on corn leaf chlorophyll content .................... 37
Effect of wheat residue on PSNT results. . ..................................... 39
Effect of wheat residue on com grain moisture, test weight and
yield......... ............................................................................................... 39
Summary ..................................................................................... 41
References ........................................................................................ 42

CHAPTER 2: NITROGEN MANAGEMENT STRATEGIES FOR OVERCOMING
THE WHEAT RESIDUE ANTAGONISM OF NO-TILL CORN

Abstract ...................................................................................... 46
Introduction .................................................................................. 48
Material and Methods ..................................................................... 56
Results ....................................................................................... 61
Effect of clover on soil temperature ............................................. 61
Effect of manure on soil temperature ........................................... 66
Effect of treatments on PSNT results ........................................... 69
Effect of clover and manure on chlorophyll content in corn
leaves ................................................................................ 73
Effect of treatments on corn grain moisture and test weigh ................. 77
Effect oftreatments on corn yields... .............80

N management practices effect corn growth and development

iii

Effect of clover and manure on corn date of
emergence..............

Effect of clover and manure on corn plant stand and date of

tasselling ................................................................... 88

Effect of clover and manure on height of com ....................... 89

Conclusion ............................................................................... 93
References ........................................................................................ 94
APPENDIX ......................................................................................... 100

iv

LIST OF TABLES
Table 1.1. Monthly precipitation, temperature, and growing degree days at East Lansing,
MI during the 2003- 2005 seasons ................................................................ 16

Table 1.2. Treatment effects on corn emergence, population, and time of tasseling ....... 28

Table 1.3. Effect of treatments on the soil pre-sidedress nitrogen test (PSNT) (kg ha")
results and on the total amounts of nitrogen added to the soil as a fertilizer (kg ha"). . ...31

Table 1.4. Effect of treatments on height of corn (m) during the 2003-2005 growing
seasons ................................................................................................ 32

Table 1.5. Effect of treatments on the amount of chlorophyll in corn leaves observed

during the 2004 and 2005 growing seasons ...................................................... 37
Table 1.6. Treatment effects on corrn grain moisture at harvest, test weight, and

yield ................................................................................................... 40
Table 2.1. Average percent of soil surface cover by manure, residue, and clover in 2005
studied treatments ................................................................................... 64
Table 2.2. Summary of clever and manure effects on soil temperature ..................... 65

Table 2.3. Effect of studied treatments on the soil pre-sidedress nitrogen test (PSNT) (kg
ha") results and on the total amounts of nitrogen added to the soil as a fertilizer (kg ha"

') ....................................................................................................... 70
Table 2.4. Manure analysis during three years of application ................................. 73
Table 2.5. Grain moisture at harvest, test weight, and yields of corn ........................ 78
Table 2.6. Decrease in corn population (%) compared to NWR (control) .................. 81

Table 2.7. Emergence, population, and time of tasseling of corn in 2003- 2005 growing
seasons ................................................................................................ 87

Table 2.8. Summary of nitrogen management strategies effectiveness in overcoming
wheat residue antagonism on corn grain yield ................................................. 93

LIST OF FIGURES

Figure 1.1. Treatment effects on soil temperature and average air temperatures in

2003 ................................................................................................... 17
Figure 1.2. Treatment effects on soil temperature and average air temperatures in

2004 ................................................................................................... 19
Figure 1.3. Treatment effects on soil temperature and average air temperatures in

2005 ................................................................................................... 20
Figure 1.4. Treatment effects on soil moisture and precipitation in 2003 ................... 21
Figure 1.5. Treatment effects on soil moisture and precipitation in 2004 ................... 22
Figure 1.6. Treatment effects on soil moisture and precipitation in 2005 ................... 24
Figure 1.7. Relationship between A soil temperatures and A soil moistures in 2003 ...... 25

Figure 1.8. Relationship between A soil temperature and A soil moisture in 2004. . . . .....25
Figure 1.9. Relationship between A soil temperature and A soil moisture in 2005. ....... 26

Figure 1.10. Relationship between percents of soil surface covered by wheat residues and
A soil temperatures in 2005 ........................................................................ 26

Figure 1.11. Relationship between soil surfaces covered by wheat residues and A soil
moistures in 2005 .................................................................................... 27

Figure. 1.12. Relationship between date of corn emerged and A soil temperature in
2003 ................................................................................................... 28

Figure 1.13. Relationship between date of corn emerged and A soil temperature in
2005 ................................................................................................... 29

Figure 1.14. Relationship between A temperatures and stand population of corn in
2003 ................................................................................................... 30

Figure 1.15. Relationship between A temperatures and corn stand populations in
2005 ................................................................................................... 30

vi

Figure 1.16. Relationship between corn heights and leaf chlorophyll contents on 28 July

2004 ................................................................................................... 33
Figure 1.17. Relationship between corn heights and leaf chlorophyll contents on 2

August 2004 .......................................................................................... 34
Figure 1.18. Relationship between corn height and PSNT result in 2004 ................... 34
Figure 1.19. Relationship between corn heights and leaf chlorophyll contents on 21 June
2005 ................................................................................................... 35
Figure 1.20. Relationship between corn heights and chlorophyll contents on 28 June

2005 ................................................................................................... 36
Figure 1.21. Relationship between corn height and PSNT result in 2005 ................... 36
Figure 1.22. Relationship between soil nitrate levels and leaf chlorophyll content on 8
July 2004 ............................................................................................. 38
Figure 1.23. Relationship between soil nitrate levels and leaf chlorophyll content on 21
June 2005 .............................................................................. . .............. 38
Figure 2.1. 2003 means of soil temperature ( oC) ............................................... 62
Figure 2.2. 2004 means of soil temperature ( °C) ............................................... 62
Figure 2.3. 2005 means of soil temperature ( °C) .............................................. 64.

Figure 2.4. Relationship between percent of soil covered by clover and soil
temperatures .......................................................................................... 65

Figure 2.5. Relationship between percent of soil cover by manure and soil temperature in

2005 ................................................................................................... 68
Figure 2.6. Effect of treatments on leaf chlorophyll content in 2004 ........................ 74
Figure 2.7. Effect of treatments on leaf chlorophyll content in 2005 ........................ 74
Figure 2.8. 2004 SPAD readings plotted versus soil nitrate levels in 2004 .................. 75
Figure 2.9. Management practice: PSNT ......................................................... 82
Figure 2.10. Management practice: PSNT and clover cover crop ........................... 83
Figure 2.11. Management practice: PSNT and manure ........................................ 84
Figure 2.12. Management practice: PSNT, clover, and manure ............................. 85

vii

Figure 2.13. Height of com in 2003 treatments ................................................. 90
Figure 2.14. Height of corn in 2004 treatments ................................................. 90

Figure 2.15. Height of corn in 2005 treatments ................................................. 92

viii

ABSTRACT

Two established methods for increasing the sustainability of production
agricultural cropping systems are (i) increasing crop residue levels by reducing tillage
and (ii) including a winter annual crop in the rotation. However, many crops following
wheat in tillage and reduced tillage systems have reduced grain yields. The objective of
this study was to develop management practices to overcome the observed negative yield
response in corn (Zea mays L.) grain grown following winter wheat (Triticum aestivum
L.) in no-till, high residue cropping systems. We hypothesized that management practices
including using a presidedress nitrogen test (PSNT) and using a PSNT in combination
with manure and clover cover crops, or a combination of the two could be used to
overcome the rotational wheat antagonism in such cropping systems. The experimental
design was a randomized complete block design. Experimental factors were: presence of
wheat residue from the previous crop with three levels (no residue, root residue, or root
and shoot residue); (2) manure application with two levels (with or without); and, (3) red
clover (Trifolium pretense L.) with two levels (with or without). Data were collected in
2003, 2004, and 2005. In all years the presence of winter wheat residue decreased soil
temperature, increased soil moisture, and decreased chlorophyll content in corn leaves
and plant height in the early stages of corn development. Winter wheat residue decreased
the amount of plant available N, and increased grain moisture and test weight of corn
grain at harvest. Emergence and population of corn in 2003 and 2005 were reduced. A
PSNT nitrogen strategy was effective in maintaining corn grain yields in wheat residue
systems equivalent to no-wheat residue systems in 4 of 6 site years. Similar results were

obtained for PSNT plus clover cover crop and PSNT plus manure plus clover cover crop

N management systems. Using PSNT and manure system equalized high wheat residue

yields to no-wheat residue in 6 of 6 site years.

CHAPTER 1

EFFECT OF WINTER WHEAT CROP RESIDUE ON NO-TILL CORN GROWTH

AND DEVELOPMENT

ABSTRACT

Two established methods for increasing the sustainability of production
agricultural cropping systems are (i) increasing crop residue levels by reducing tillage
and (ii) including a winter annual crop in the rotation. However, many crops following
wheat in tillage and reduced tillage systems have reduced grain yields. The objective of
this study was to evaluate the effect of winter wheat (T riticum aestivum L.) crop residue
on the growth and development of no-till corn (Zea mays L.).

The experimental design was a randomized complete block design. Treatments
consisted of no-till systems with three levels of winter wheat residue (no wheat residue,
wheat root residue only, and wheat root and shoot residue). Data were collected in 2003,
2004, and 2005. Measurements included corn grain yield, grain moisture and test weight
of com at harvest, plant growth characteristics (emergence, plant height, time of tasseling
(VT stage), chlorophyll content), presidedress nitrogen test (PSNT), and soil moisture
and temperature taken weekly during the spring and early summer. In all years, the
presence of winter wheat residue above and below ground decreased soil temperature,
increased soil moisture, and decreased chlorophyll content in corn leaves and plant height
in the early stages of corn development. VT stage of corn was delayed for about 1 week

in residue systems. Winter wheat residue decreased the amount of plant available N and

increased grain moisture and test weight of corn grain at harvest. Emergence and

population of corn in 2003 and 2005 were reduced.

INTRODUCTION

High residue cropping systems such as no-till and reduced-till systems contribute
signiﬁcantly to the sustainability of production agriculture. No-till and reduced-till
farmers in the United States occupy 21 million ha of land, about 38% of the United States
cropland (Conserv. Techno]. Inf. Cent, 2000). These systems reduce soil erosion and run-
off and increase the percolation of rainfall (Cavigelli, 1998). Additionally, soil organic C
levels are increased, leading to improved soil nutrient holding capacity and structure
(Tisdall and Oades, 1982). Maintenance of soil organic matter has long been recognized
as a strategy to reduce soil degradation in agricultural systems.

Soil structure is an important property that mediates many soil physical and
biological processes and controls soil organic matter decomposition (van Veen and
Kuikman, 1990). Soil aggregates are the basic units of soil structure and are composed of
primary particles and binding agents (Edwards and Bremner, 1967; Tisdall and Oades,
1982; Haynes et al., 1991). Soil organic matter is a major binding agent that stabilizes
soil aggregates (Haynes et al., 1991).

The amount and turnover of soil organic matter can be altered by different
management practices. Cultivation affects soil structure by destroying soil aggregates,
resulting in loss of soil organic matter (Tisdall and Oades, 1982; Elliott, 1986; Angers et
al., 1992). Incorporation of plant residues in soil affects the soil microclimate and
increases plant residue contact with soil, increasing the rate of residue decomposition and
organic matter transformation (Beare et al., 1992; Cambardella and Elliott, 1993;

Paustian et al., 1997). Tillage enhances decomposition of organic matter by mixing plant

residues into the soil, increasing aeration, and enhancing dry-wet and freeze-thaw cycles
(Paustian et al., 1997). Also, tillage disrupts soil aggregation and exposes physically
protected organic material (Blevins and Frye, 1993; Beare et al., 1994b). In contrast, no-
till systems reduce soil mixing and soil disturbance, allowing soil organic matter
accumulation (Blevins and Frye, 1993). Many studies have shown that no-till farming
improves soil aggregation and aggregate stability (Beare et al., 1994b; Six et al., 1999).
Mycorrhizal fungi, which are promoted by no-till systems, contribute to formation and
stabilization of macroaggregates (Tisdall and Oades, 1982; O’Halloran et al., 1986; Beare
and Bruce, 1993). Also, no-till signiﬁcantly increases soil total C and N levels, water-
stable aggregates, and labile C and N associated with macroaggregates, compared with
conventional tillage (Mikha and Rice, 2004).

Michigan growers increased winter wheat production from 214,650 ha in 2002 to
255,150 ha in 2004, a 20% increase (Michigan Agricultural Statistics Service, 2004).
Winter wheat is generally grown in rotation with corn and soybean. The growth cycle of
soybeans makes winter wheat a logical fallow crop in the rotation, which is usually
planted right aﬁer soybean harvest. Growers typically follow wheat with corn. There are
many advantages of including a winter annual crop such as winter wheat in a cropping
system. Sanchez et al. (2001a) reported that N mineralization was increased in a diverse
cropping system including wheat in the rotation. In addition, pest cycles can be disrupted
with the inclusion of a winter annual crop (Cavigelli, 2000). Wicks et al. (1995) reported
reduced weed emergence when no-till corn was planted into winter wheat residue.
Copeland et al. (1997) estimated a 10% com grain yield increase when com was rotated

with wheat.

The agronomic and environmental advantages of reduced-tillage, high residue
cropping systems have been well documented (Cavigelli et al., 1998, Sanchez, 2001b).
Despite many advantages, there are also negative impacts associated with high residue
systems. One such negative impact is a com-wheat antagonism that results in lower corn
grain yield following wheat (Beuerlein and Houdashelt, 1997). Similar reports that com
following wheat in the crop rotation seems to have reduced grain yields came from no-till
and reduced-till growers in the Great Lakes Region (K.Thelen, personal communication).

Cox et al. (1990) noted that cool conditions in May in years with less than normal
growing degree days may result in poorer emergence under reduced tillage because high
residue inhibits soil warming and delays corn emergence in northern latitudes. Also,
Drury et al. (2003), in a four-year study in a winter wheat- corn-soybean rotation with
and without red clover, reported different emergence rates of corn in different tillage
systems. In no-till systems corn emergence rates were slower compared with
conventional tillage over 3 years. However, despite low emergence rates, ﬁnal plant
stands were not signiﬁcantly different between treatments in some years. Also,
emergence of corn depended on time of planting (early or late) and spring weather
conditions (wet or dry, cool or warm).

Beuerlein and Houdashelt’s (1997) results contradict the notion that cooler soil
temperature in the spring, because of the presence of wheat residue, is the only cause of
corn-wheat antagonism. In a study, they grew wheat adjacent to bare soil plots. After
harvesting the wheat, they removed the above ground wheat residue and transferred it to

the bare soil plots without disturbing the soil. The following spring, corn was planted into

the crops. Interestingly, the removal of the above ground wheat residue did not overcome
the corn yield antagonism.

One other possible cause of com/winter wheat antagonism is allelopathy.
Allelopathy results from plant-plant and plant- microorganism interactions mediated by
several secondary metabolites released to the environment from the donor plant. These
secondary metabolites or allelochemicals stimulate or inhibit the growth of plants and
microorganisms by acting directly on some essential biological processes (respiration,
photosynthesis, membrane permeability, cellular division, and protein synthesis) or
indirectly on soil microorganisms, interfering with the establishment of some bacterial-
plant or fungi-plant symbiosis (Golovko, 1999).

Winter wheat is an active allelopathic plant. The allelopathic nature of wheat
residue has been demonstrated in fields where residues are mulched on the soil surface
(Krupa, 1982). Winter wheat straw signiﬁcantly inhibits emergence, seedling growth, and
dry matter accumulation of various weeds (Wu et al., 2000). The release of
allelochemicals of different chemical classes from wheat has been well documented.
These include tannins, cyanogenic glycosides, several ﬂavonoids, and phenolic acids
such as ferulic, p-coumaric, syringic, vanilic, and p-hydroxybenzoic acids (Einhellig,
1995).

The main sources of phenolic compounds in soil are root exudates of
allelopathically active plants, products of decomposition of root residues, and
intermediate products of humus transformations (guayacol, quayacol-hydroxyphenol, and
others) (Golovko, 1999). Soil toxicity depends not only on root excretions, but also on

decomposition of residue. Krupa (1982) reported that residue from winter wheat

signiﬁcantly decreased productivity of corn in an Alﬁsol soil under moldboard tillage
systems. In winter wheat residue, he found ﬁve phenolcarboxilic acids: phenolic, ferulic,
coumaric, vanilic, and caffeic. The same acids were also found in the soil in high
concentrations. Lower yields resulted from accumulation of soil nitrophenols, which,
after addition of fertilizers, turned into aminophenols and stimulated plant growth
(Golovko, 1984).

During cool, wet springs in Ohio, farmers and researchers often noticed that no
till corn planted into wheat residue does not grow as rapidly as corn planted with
conventional tillage. Thomison (1995) explained that under cool soil conditions and no-
till farming practices winter wheat residues concentrated near the soil surface break down
more slowly and tie up N longer than when residue is incorporated, making N less
available for crop growth. This slow decomposition can be attributed to the high C-N
ratio of wheat residue and environmental conditions. Another biological process that may
also contribute to the slow growth of corn following wheat involves the production and
release of phytotoxins from decomposing wheat residues. The allelopathic effects of
wheat straw on corn growth may be related to either anaerobic production of microbial
byproducts using wheat residue as a C source and/or direct release of organic compounds
from the decomposing residue. Cool temperature, anaerobic conditions, and low pH
increase leaching of amino acids and carbohydrates from the plant roots. Anaerobic
conditions contribute to exudation of alcoholic substances that are toxic to plants
(Christiansen et al., 1970).

Phytotoxic strains of microorganisms produce more than 45% of the common

pool of soil phenolic compounds. Among the microorganisms that most actively produce

polyphenols are: Pseudomonas rubigenosa, Bacillus rusticus, and F usarium solani
(Golovko, 1999). Other researchers (Dill-Macky and Jones, 2000) cited increased
substrate for disease, such as F usarium graminearum, as a potential concern to long term
rotations including winter wheat.

Rice (1984) most vividly showed the relationship between the allelopathy and
microbial activities that determine plant available N in soils. He found that active
allelopathic compounds inhibit N fixation by free-living and symbiotic microorganisms.
These compounds inﬂuence nitriﬁcation, but do not inﬂuence denitriﬁcation processes.

Allelopathy is also of agricultural importance because of the phenomenon of
autotoxicity. The negative impact of wheat autotoxicity on agricultural production
systems has been reported when wheat straws are retained on the soil surface for
conservation fanning purposes (Wu et al., 2001).

Greenhouse studies have shown that toxins and bacteria from decaying residue
affect growth of new plants (Krupa, 1982). In the ﬁeld, it is difﬁcult to separate
allelopathic effects from soil temperature effects. Further, many researchers believe that
the toxic effect is most likely to occur when com follows corn, rye, or winter wheat and
when residue is on or near the soil surface in the row area.

Our objective was to verify the reported antagonism of winter wheat residue on

no-till corn growth and development.

10

MATERIAL AND METHODS

Experimental site and data collection

We conducted the research at the Michigan State University Agronomy Farm, in
East Lansing, MI. The experiment was established on soybean-winter wheat-com
cropping systems from 2001 through 2005 with three cycles. The ﬁrst cycle included
plots planted to soybeans in 2001, winter wheat in fall 2001, and corn in 2003. The
second cycle included plots planted to soybeans in 2002, winter wheat in 2002, and corn
in 2004. A similar third cycle was implemented with soybeans and wheat planted in 2003
and with corn planted in 2005. Treatments with no wheat residue had a second year of
soybean substituted for wheat in the second year of each cycle.

The ﬁrst cycle was established on a Capac loam soil (Fine loamy, mixed, mesic
Typic Hapladulfs). The second and third cycles were established on Colwood (Fine
loamy, mixed, mesic Typic Haplaquolls) - Brookston (Fine loamy, mixed, mesic Typic
Argiaquolls) loam soils.

The experiment was a randomized complete block design with treatments
consisting of three levels of winter wheat residue (no wheat residue, wheat residue above
and below ground, and wheat residue below ground only). In the ﬁrst cycle, the
experiment had four replications. Plots were 14.0 m long and 6.1 m wide. In the second
and third cycles the treatments were replicated eight times. Plots were 9.1 m long and 6.1
m wide. Distance between rows of planted corn was 76 cm.

In the second year of the experimental cycle, soybean (Dekalb 23-51) was planted

on 5 May 2002, 19 April 2003, and 29 May 2004 (rate of planting was 444,600 seeds ha'

11

l) for treatments having neither above or below ground wheat residue. ”Soybean was
harvested on 28 September 2002, 13 October 2003, and 20 December 2004. At planting
time, liquid starter fertilizer 6-24-6 (28 kg ha") was added, providing 1.7 kg N ha'I
similar to local common production practices. Yields of soybean were not signiﬁcantly
different between plots (p>0.05). In 2002 soybean yielded 3.59 Mg ha", in 2003 2.25 Mg
ha", and in 2004 3.26 Mg ha".

Winter wheat (Harus) was planted in the fall of 2001, 2002, and 2003. In the
following spring, at green up, wheat plots received 246 kg ha'lof granular urea (46-0-0).

Winter wheat yielded an average of 5.65 Mg ha'1 in 2002, 7.65 Mg ha'1 in 2003, and 4.95
Mg ha'l in 2004 with no yield signiﬁcant differences between plots. Aﬁer harvest the

remaining wheat straw was about 30 cm tall. The remaining residue was returned to the
plots with below and above ground wheat residue and removed from treatments having
below ground wheat residue only. The amount of straw left in the treatments with wheat
root and shoot residue (WRSR) was 10.73, 7.39, and 9.63 Mg ha" in 2003, 2004, and
2005, respectively, with no signiﬁcant differences between plots. The highest amount of
wheat residue left in the plots was from the ﬁrst cycle (2001-2003).

An early maturity corn variety DKC44-46 (YieldGard Corn Borer/Roundup
Ready, Residue Proven, 94-day relative maturity) was planted into plots by a customized
John Deere no-till planter. Com was planted at a target population of 69,000 plants ha"I
on 30 April 2003, 29 May 2004, and 19 April 2005 and harvested on 16 October 2003, 22
October 2004, and 27 September 2005. In 2003 and 2005, starter fertilizer 6-24-24 was

placed in furrow and in row (269 kg ha"), providing 16 kg N ha". In 2004 starter

fertilizer 19-19-19 was added (140 kg ha 'l), providing 26.6 kg N ha '1.

l2

Based on PSNT results, on 25 June 2003, 15 July 2004, and 20 June 2005, we
applied N to every plot (based on yield goal of 8.8 Mg ha"). The soil samples for the
PSNT test were taken from a depth of 0-30 cm on 17 June 2003, 7 July 2004, and 7 June
2005. Soil pH, nitrate, and phosphorus levels were determined from separate soil samples
obtained each spring. The average pH values based on all the plots were 6.1 and 5.6 (1:1
soil/water), in 2003 and 2004, respectively. The average phosphorus values were 97.5
and 107 kg ha'1 (Bray P1), respectively. Treatments had no signiﬁcant effect on either pH
or phosphorus. Potassium content was not measured but assumed sufﬁcient based on soil
test data obtained prior to the experiments.

In the early spring and early summer of 2004 and 2005, soil temperature
measurements were taken weekly at a depth of 10 cm. In the early spring of 2003, soil
temperature was measured at a depth of 20 cm at the early sampling dates and then from
a depth 10 cm for the later sampling dates. Soil moisture was measured using a Trime—
FM3 moisture meter with a P3 probe (Mesa Systems Co. Framingham, MA) at a depth of
0-15 cm.

Changes in soil temperature or moisture values of wheat root residue (WRR)
treatments and WRSR as compared to the control no wheat residue (N WR) treatments
were expressed as a ratio between soil temperature or moisture values measured in WRR
and WRSR plots and the average soil temperature or moisture value from the NWR plots,
and are called A temperature or A moisture.

To monitor corn development, we recorded emergence, postemergence stand
count, time of tasseling (VT stage), and stalk lodging. Corn height was measured at the

V9 stage until VT stage every week. Chlorophyll content of the uppermost corn leaf that

13

had formed a collar was measured weekly using a SPAD-502 meter (Specialty Products
Agricultural Division, Minolta Co. LTD, Japan) in 2004 and 2005, when com was at the
V6 stage until VT stage.

Growing degree days (GDD) were calculated as GDD = [(Tmu+Tmm)/2]-10,

where Tm, and Tm," are the daily maximum and minimum temperatures (0 C),

respectively. If Tmax was greater than 30 ° C, then we set Tmax to be equal to 30 ° C. If
Tmin was less than 10 ° C, then we set Tmin to be equal to 10 ° C.

Two center rows of corn from each plot were machine harvested. Moisture
content, test weight, and ﬁeld weight of corn were measured by a Grain Gagetm and
HarvestMasterSystemtm (Juniper Systems, Inc., Logan, UT) mounted on a plot combine.
Grain yield was reported at 15.0 % moisture content. Grain test weight is reported at
harvest moisture.

Percent of soil surface cover by wheat residue was determined using digital
images. In WRSR treatments the soil was covered by winter wheat residue at a level of

72.6 % and in WRR treatments at a level of 57.5 % with no differences between plots.

Data analysis

Analysis of variance was performed to test signiﬁcance of the factors and their
interactions. Statistical analyses were conducted using the PROC MIXED procedure in
SAS (SAS Inc., 2002). Normality of the residuals and homogeneity of variances were
evaluated. When the variances were not homogeneous, the REPEATED /GROUP option
of PROC MIXED was used. When the F-test showed a signiﬁcant treatment effect we

conducted mean separations using Fisher protected t-tests (P=0.05).

14

RESULTS

Weather conditions of 2003-2005 growing seasons

The 2003 growing season had persistently cool temperatures, delayed crop
growth, and abnormal dryness during the later half of the season (Table 1.1). The spring
of 2003 was cooler than normal and cooler than the 2004 spring season. Although, the
amount of precipitation was above normal in May 2003, the overall 2003 growing season
had below normal precipitation. In contrast, the 2004 growing season had above normal
precipitation. Because of the very wet and cool spring of 2004, corn was planted one
month later than in 2003. In both 2003 and 2004, during the 5-month May-September
period, growing degree day accumulations were below normal. The 2003 growing season
accumulated fewer growing degree day units than 2004. In 2005 both growing degree
days and precipitation were close to the 30-years norms. Temperatures in May 2005 were
below average. However, the temperatures during the rest of the 2005 growing season

were above the 30 — year average for the East Lansing area.

Effect of wheat residue on soil temperature
Wheat residue affected soil temperature. In 2003, WRSR treatments had
signiﬁcantly lower soil temperatures compared to NWR and WRR treatments in all
studied dates (Figurel .1). The exception was 8 May when soil temperatures in WRSR
treatments were not different from soil temperatures in NWR treatments. Soil
temperatures in NWR and WRR treatments were not signiﬁcantly different in all studied

dates.

15

Table 1.1. Monthly precipitation, temperature, and growing degree days at East Lansing,

MI during the 2003- 2005 seasons (Data courtesy of MSU Agricultural Weather Ofﬁce).

 

 

 

 

 

 

 

Precipitation (mm) 2003 2004 2005 Norma
OBS DEV OBS DEV OBS DEV
May 100.8 31.5 265.2 195.9 33.2 -36.1 69.3
June 47.8 -42.2 78.2 -11.7 108.7 18.8 89.9
July 45.9 -30.7 96.5 19.8 116.3 39.6 76.7
August 32.3 -46.9 81.0 1.8 16.3 -62.9 79.2
September 45.7 -17.8 25.9 -37.6 76.7 13.2 63.5
Total 272.5 -106.1 546.8 168.2 351.2 -27.4 378.6
Growing Degree Days (°C)
May 140 -48 193 5 96.5 -91 .5 188
June 247 -47 264 -30 349.9 55.9 294
July 334 -22 330 -26 354.3 -1.7 356
August 340 8 274 -58 348.3 16.3 332
September 217 -15 264 32 241.7 9.7 232
Total 1278 -124 1325 -77 1390.7 -11.3
Mean Temperature (”C)
May 12.2 -2.2 14.8 0.6 11.9 -2.3 14.2
June 17.5 -2.0 18.4 -1 .1 22.1 2.6 19.5
July 20.5 -1.3 20.7 -1.1 22.1 0.3 21.8
August 20.9 0.1 18.6 -2.0 21.9 1.1 20.8
September 15.9 -0.7 18.6 2.0 18.5 1.9 16.6

OBS-Total observed

*- 1951—1980 means for East Lansing area

16

DEV- Deviation of observed from normal

Figure 1.1. Treatment effects on soil temperature, and average air temperatures in 2003.

 

 

. ‘b

l e“

l B

. s

l a.

l E

l 2

l 3

.- 0 * ' g * s .. j
0 30¢ - f - ~--- - - --+-- m;
j o a l
I 2,. 25

g 201 ,
l 0 . I
1 g r l
. 3 151 1
i f 10 i‘ e
l 5’ l l
l g 5 l y
[ > .

l < 1

4/15 4/25 5/5 5/15 5/25 6/4 6/14 6/24

Date

17

In 2004, WRSR treatments had signiﬁcantly lower soil temperatures than NWR
and WRR treatments in all studied dates. Soil temperatures in NWR and WRR treatments
were not different on 5 of 8 studied dates (Figure 1.2). The 23 and 29 April dates
represent the beginning of the sampling period and 21 June the last sampling date. This
suggests that soils were uniformly cool and warm at the beginning and at the end of the
sampling period respectively and that treatments had more of an effect on soil
temperature during the transitional soil warm-up phase.

In 2005, soil temperatures in WRSR treatments were signiﬁcantly lower than soil
temperatures in NWR and WRR treatments on all dates (Figure 1.3). Also, NWR
treatments had signiﬁcantly higher soil temperatures than WRR treatments on 5 of 6

dates. On 10 May there were no differences between NWR and WRR treatments.

Effect of wheat residue on soil moisture

Wheat residue affected soil moisture. In 2003, WRSR treatments had signiﬁcantly
higher soil moisture levels on all sampling dates compared to NWR and WRR treatments
(Figure 1.4). The exception is 28 May 2003 when treatments were not different. Also,
soil moistures in WRSR and NWR treatments were not different on 14 May, 16 June, and
18 June. Soil moistures in NWR and WRR treatments were not signiﬁcantly different on
most dates.

In 2004, WRSR treatments had signiﬁcantly higher soil moistures compared to
NWR and WRR treatments (Figure 1.5). Soil moistures in NWR and WRR treatments

were not different on all dates.

18

Figure 1.2. Treatment effects on soil temperature, and average air temperatures in 2004.

25-——-—--— — _.,_.. AW-“

 

 

 

; i: .
‘ 2' 1
l a 1
l E 5 ,
a. j .
‘ E i
[a - , . l
I 10 l 0"-WRR l l ‘
—-El-—NWR ! l
‘ --a—WRSR{ l
l "T —_’ "“T‘ l ‘
5 ..‘ , _ , A L 7 .'= I
j‘°30 a
i U ; i l
l 2 25 I l l
‘ 8 20 t l j
g 3- l l
e 15 «, ‘
| 3 7 l ‘
' h - 1
1| .5 10 all i i
i a i ‘ 1‘
I g 5 ‘
'. g ‘
1 < 0 . .. _z.. _.___...w- _.__ . ..... _. __-
4/1 5 4/25 5/5 5/1 5 5/25 6/4 6/14 6/24

Date

19

Figure 1.3. Treatment effects on soil temperature, and average air temperatures in 2005.

25 ‘ 7 7 7 7 77 7 7 77 77 7 77 7 77 7 ‘ 7 7 77

15-

Soil temperature, C °

10:

 

Average air temperature,
c 0

4/15 4/25 5/5 5/15 5/25
Date ‘

20

Figure 1.4. Treatment effects on soil moisture, and precipitation in 2003.

Soil moisture, %

10?

Precipitation, mm

35 »
30
25 F
20
15 ‘
45
40 +;
35 ﬁ

4
304
i
251
i

_a_\.
01001

0 L JJ:
4/15

-T_,_. ,

4/25

5/5

0 ”V'VRWR ’
1" ‘B‘ - NWR :

‘.—*—_ __ “__.WR_SB..'

ILJ H] Wilr rt...‘
5/15 5/25 6/4
Date

21

_-J._ I”;

 

l
i
1
|

6/14

Soil moisture, %

10~

Precipitation, mm

357

 

35

302
251

20

15:
10.,
5.

O :

 

 

 

 

 

 

it I -5 II _I .J, I ILA

 

4/15 4/25 5/5 5/15 5/25 6/4

22

 

Figure 1.5. Treatment effects on soil moisture, and precipitation in 2004.

In 2005, WRSR treatments had signiﬁcantly higher soil moistures compared to
NWR and WRR treatments on all dates (Figure 1.6). Soil moisture in NWR and WRR
treatments were not different on all dates. The exception was 18 May when WRSR and
WRR treatments were not different. NWR and WRR treatments were also not different
on this date.

In all three years, the values of A temperature and A moisture from WRR and
WRSR treatments were signiﬁcantly negatively correlated (p<0.05). Lower A
temperature values corresponded to higher A moisture, and higher A temperature values
were observed in drier soil (Figures 1.7, 1.8, and 1.9).

Both A temperature and A moisture were strongly related to percent of residue
cover (Figures 1.10 and 1.11). Higher residue cover corresponded to lower soil
temperature and higher soil moisture.

The observed cooler temperatures and higher moistures at higher residue cover
are consistent with other observations. Researchers (TeKrony et al., 1989) and growers
have speculated that com grain yield antagonism may be attributable to cooler soil
temperature in the spring from the wheat residue. Lund et al. (1993) associated the
reduced yield of no-till, continuous corn with the greater crop residue and cooler soil
temperature in the spring (2.7 °C lower). Wilhelm and Wortmann (2004) concluded that
the advantage of moldboard tillage over no-till for corn yield was greatest in years with
low spring temperatures. Tillage may be preferred for soils that are slow to warm or when

early planting is preferred.

23

Figure 1.6. Treatment effects on soil moisture, and precipitation in 2005.

, 25 ; » ee

15

Soil moisture, %

 

 

_L
O _s
O
|
I
|

Precipitation, mm
—3 N 00 b 01 O) \l (I) to

 

 

_ _T' A

5/15 5/25

,1 ll .1. 551 I. .

4/15 4/25
I Date

24

 

 

 

Figure 1.7. Relationship between A soil temperature and A soil moisture in 2003.

 

1.4,- -, _._., -

_.x
00
U!

—L
0‘wa

—L '
A

   

A soil moisture

1.05 -
1 4 y = -1.9341x + 2.9603 0
0,95 1 R2 = 0.8355 1

091 e . .. . . . .
0.7 0.75 0.8 0.85 0.9 0.95 1 1.05 1.1

A soil temperature

 

 

 

Figure 1.8. Relationship between A soil temperature and A soil moisture in 2004.

 

1.25 .
1.2 -

_s
o
(11

1 ;

0.95 ,

09 , y = -0.5815x + 1.5874
R2 = 0.5083

 

A moisture

0.85
0.6 0.7 0.8 0.9 1 1.1
Atemperature

 

 

 

Figure 1.9. Relationship between A soil temperature and A soil moisture in 2005.

 

1.3
1.25
1.2
1.15 1
1.1 1

1.05
1 - y = 08693x + 1.8801 °
W=0mm

 

A moisture

0.95 .

0.9: .- w .
0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1

A temperature

 

 

 

Figure 1.10. Relationship between percents of soil surface covered by wheat residues and

A soil temperatures in 2005.

 

0.95 - 0

.0
co

0.85 ~<

.0
on

0.75 I

A temperature

y = -0.011x + 1.5544

R2 = 0.8759
0.65 I I

0.6 -. .-. .- ~. —
50 55 60 65 70 75

Residue cover, %

_o
w
1..
0.. O”

 

 

 

26

Figure 1.11. Relationship between soil surfaces covered by wheat residues and A soil

moistures in 2005.

 

1.3—e — . _. ._ - ... _._ A
1.25 '1 O
1.2 - o .
1.15
1.1 .
1.05 .

A moisture

O-

y = 0.0108x + 0.4447
1 “ R2 = 0.7553
095 -

0.9 . _ A _ ,.___.__ 1.
55 5° 65 70 75

Residue cover, %

 

 

 

Effect of wheat residue on date of corn emergence

In 2003 and 2005, in WRSR treatments corn emerged signiﬁcantly later than in
NWR and WRR treatments (Table 1.2). There was a difference between NWR and WRR
treatments. The negative effect of wheat residue on corn emergence can be related to the
relatively early planting of com (17 April and 30 April). Soil temperatures in WRSR
treatments were lower compared to NWR and WRR treatments, explaining the delayed
corn emergence. Also, the early cool spring of 2005 delayed corn emergence. In both
2003 and 2005, corn emergence was signiﬁcantly negatively correlated with A soil
temperature (p<0.05) (Figures 1.12 and 1.13). These results are consistent with many
reports of reduced emergence and yields under no-till compared with conventional till

farming, especially in humid and cool temperate climates (Fortin and Pierce. 1991).

27

Table 1.2. Treatment effects on corn emergence, population, and time of tasseling.

 

Treatment 2003 2004 2005 2003 2004 2005 2003 2004 2005
Emergence (date) Population (plants ha'1) VT stage (date)
WRR 5/25 b'I’ 6/10 a 5/20 b 66297 b 62827 a 62505 b 7/27 a 8/4 a 7/15 b
NWR 5/19 a 6/10 a 5/15 a 67863 b 59705 a 64962 b 7/24 a 8/4 a 7/12 a
WRSR 5/29 c 6/10 a 5/25 c 62674 a 65455 a 57383 a 7/30 b 8/10 b 7/18 0

 

 

 

T-Means within each column followed by the same letter are not signiﬁcantly different (Fisher protected

LSD, P<0.05).

In 2004, because of the very wet and cool spring, com was planted relatively late
(29 May). Higher soil temperatures observed in late May and early June promoted
germination of corn, thus potentially being the reason for the same corn emergence time
in all treatments in that year. There was no signiﬁcant relationship between the date of

corn emerged in 2004 and A soil temperature.

Figure. 1.12. Relationship between date of corn emerged and A soil temperature in 2003.

 

30
28 -

92.
86

 

24
y = ~23.297x + 49.159

22 a R2 = 0.4848 ;

20 W _ .--- e A -----. 1
0.7 0.8 0.9 1 1.1 1.2

A temperature

 

 

 

28

Figure 1.4. Treatment effects on soil moisture, and precipitation in 2003.

Soil moisture, °/o

Precipitation, mm

35

207

15‘

10'

451- »

404
351
301
25 1
20 i
15 .
10 -

51
01—.Lh

4

4/15

4/25

 

J

 

5/

...II
5

L1.

5/1 5
Date

21

 

. .I.,.; I- ..lu I-J_-

5/25

6/4

6/14

Figure 1.5. Treatment effects on soil moisture, and precipitation in 2004.

35 - e e

Soil moisture, °/o

 

104

30 1
25'-
20%

I
101 1

I CALL- II] .1. 1 _ I .IIA - LLI
1 5/5

4/15 4/25 5/ 15 5/25 6/4 6/ 14
Date

Precipitation, mm

 

 

 

 

 

 

 

 

 

22

In 2005, WRSR treatments had signiﬁcantly higher soil moistures compared to
NWR and WRR treatments on all dates (Figure 1.6). Soil moisture in NWR and WRR
treatments were not different on all dates. The exception was 18 May when WRSR and
WRR treatments were not different. NWR and WRR treatments were also not different
on this date.

In all three years, the values ofA temperature and A moisture from WRR and
WRSR treatments were signiﬁcantly negatively correlated (p<0.05). Lower A
temperature values corresponded to higher A moisture, and higher A temperature values
were observed in drier soil (Figures 1.7, 1.8, and 1.9).

Both A temperature and A moisture were strongly related to percent of residue
cover (Figures 1.10 and 1.1 1). Higher residue cover corresponded to lower soil
temperature and higher soil moisture.

The observed cooler temperatures and higher moistures at higher residue cover
are consistent with other observations. Researchers (TeKrony et al., 1989) and growers
have speculated that com grain yield antagonism may be attributable to cooler soil
temperature in the spring from the wheat residue. Lund et al. (1993) associated the
reduced yield of no-till, continuous com with the greater crop residue and cooler soil
temperature in the spring (2.7 °C lower). Wilhelm and Wortmann (2004) concluded that
the advantage of moldboard tillage over no-till for com yield was greatest in years with
low spring temperatures. Tillage may be preferred for soils that are slow to warm or when

early planting is preferred.

23

Figure 1.6. Treatment effects on soil moisture, and precipitation in 2005.

Soil moisture, %

Precipitation, mm

 

25

20 ~

15-

_s
o —L
'O

O—‘NQAU‘ICDNOJCO

4/15

 

.|.

4/25

5/5
Date

 

5/15

 

 

 

5/25

Figure 1.7. Relationship between A soil temperature and A soil moisture in 2003.

 

1.41e - e e -, e. .. -, 4..
1.35 ‘
1.31
1.25
1.21
1.151
1.1.

1.05 I
1 1 y = -1.9341x + 2.9603

(195 g R2 = 0.8355

09 1- 1A. . --- .---
0.7 0.75 0.8

   

A soil moisture

0.85 0.9 0.95 1 1.05 1.1

A soil temperature

 

 

 

Figure 1.8. Relationship between A soil temperature and A soil moisture in 2004.

 

1.25 1 ~ ~ A
1.2 1 ‘

_s
'_;
(J1

 

A moisture
o _.l
01 _s

1 1‘
0.95 1 1
09 1 y = -0.5815x+1.5874 1
. 2:
0.85 1 R 0.5083
0.6 0.7 0.8 0.9 1 1.1

A temperature

 

 

 

25

Figure 1.9. Relationship between A soil temperature and A soil moisture in 2005.

 

1.3 e ,

_L
L.
0"

A moisture

 

1.05 i
1, y=-0.8693x+1.8801 ° ‘
R2=0.8586 1
0.95 - I
0.9 - I

0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1
Atemperature

 

 

 

Figure 1.10. Relationship between percents of soil surface covered by wheat residues and

A soil temperatures in 2005.

 

0.95 1 9

.0
(0

0.85

.0
on

0.75 ‘

A temperature

y = —0.011x +1.5544
R2 = 0.8759

9
\r
0.. O”

0.65 i

50 55 60 65 70 75

Residue cover, %

 

 

 

26

Figure 1.11. Relationship between soil surfaces covered by wheat residues and A soil

moistures in 2005.

 

1.25 I ’
1.2 1 e .
1.15 -

1.1 1 1
1.05 1 I

A moisture
O 00

y = 0.0108x + 0.4447
1 " R2 = 0.7553
0.95 ,.

0.9 e-______-_____.__,, ,, _1 1 _ _1 11ﬂ_‘__1
55 60 65 70 75

Residue cover, °/o

 

 

 

Effect of wheat residue on date of corn emergence

In 2003 and 2005, in WRSR treatments corn emerged signiﬁcantly later than in
NWR and WRR treatments (Table 1.2). There was a difference between NWR and WRR
treatments. The negative effect of wheat residue on corn emergence can be related to the
relatively early planting of com (17 April and 30 April). Soil temperatures in WRSR
treatments were lower compared to NWR and WRR treatments, explaining the delayed
corn emergence. Also, the early cool spring of 2005 delayed corn emergence. In both
2003 and 2005, corn emergence was signiﬁcantly negatively correlated with A soil
temperature (p<0.05) (Figures 1.12 and 1.13). These results are consistent with many
reports of reduced emergence and yields under no-till compared with conventional till

farming, especially in humid and cool temperate climates (Fortin and Pierce, 1991).

27

Table 1.2. Treatment effects on corn emergence, population, and time of tasseling.

 

Treatment 2003 2004 2005 2003 2004 2005 2003 2004 2005
Emergence (date) Population (plants ha") VT stage (date)
WRR 5/25 b1 6/ 10 a 5/20 b 66297 b 62827 a 62505 b 7/27 a 8/4 a 7/15 b
NWR 5/19 a 6/10 a 5/15 a 67863 b 59705 a 64962 b 7/24 a 8/4 a 7/12 a
WRSR 5/29 c 6/10 a 5/25 0 62674 a 65455 a 57383 a 7/30 b 8/10 b 7/18 c

 

 

T-Means within each column followed by the same letter are not signiﬁcantly different (Fisher protected

LSD, P<0.05).

In 2004, because of the very wet and cool spring, corn was planted relatively late
(29 May). Higher soil temperatures observed in late May and early June promoted
germination of corn, thus potentially being the reason for the same corn emergence time
in all treatments in that year. There was no signiﬁcant relationship between the date of

corn emerged in 2004 and A soil temperature.

Figure. 1.12. Relationship between date of corn emerged and A soil temperature in 2003.

 

32
30 .
28 .

325
86

 

24
y = -23.297x + 49.159

22 1 R2 = 0.4848

20 : __- . . A--. . .- . .-- -
0.7 0.8 0.9 1 1.1 1.2

A temperature

 

 

 

28

Figure 1.13. Relationship between date of corn emerged and A soil temperature in 2005.

 

27 : - ﬂ ,, v 7 — 7 - - A
26 1
25 - e
24
23 1'
g 22 i
21
20 . y = —25.776x+44.069
19 . R2=0.8941
18 Q -
0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1

A temperature

   

 

 

 

Effect of wheat residue on stand population of corn

In 2003 and 2005, WRSR treatments had lower corn plant stands than NWR and
WRR treatments, likely due to the delayed corn emergence and cooler soil temperatures
(Table 1.2). The corn population trends resemble those observed with date of emergence.
NWR and WRR treatments were not different. In both 2003 and 2005, soil temperature
affected corn stand population with higher values observed in plots with larger A
temperature values (temperature relative to NWR plots) (Figures 1.14 and 1.15). This is
consistent with ﬁndings of Katsvairo and Cox (2000) who recorded that com densities
were less under reduced tillage compared to moldboard plow systems when com
followed corn or wheat/red clover.

In 2004 there were no differences in corn plant stands between WRSR, WRR, and
NWR treatments. The lack of a treatment effect on 2004 corn plant stands is likely due to

the relatively late planting date of corn and higher soil temperatures.

29

Figure 1.14. Relationship between A temperatures and stand population of corn in 2003
(data for individual plots are shown).

 

28000 1 e , .- W

27500 i y=10813x+15723 . ... .
R2=0.4447

  

NNN
(DON
0010
GOO
000

25000 1 0

population, plantslha

0.6 0.7 0.8 0.9 1 1.1 1.2

 

 

 

Figure 1.15. Relationship between A temperatures and corn stand populations in 2005.

 

63000 .

62000 1 y = 26300x + 36994
61000 e‘ R2 = 0.694
60000 7

59000 J

58000 1 . O . 0
57000 ;

§56000«
55000-1
54000:--- . _. ,-
0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1

A temperature

ulation, plants/ha

 

 

 

30

Effect of wheat residue on corn date of tasseling
In all years, corn tasselling was delayed in WRSR treatments as compared with
NWR and WRR treatments (Table 1.2) likely due to lower soil temperatures, delayed

emergence, and lower amounts of plant available N (Table 1.3).

Table 1.3. Effect of treatments on the soil pre-sidedr6ess nitrogen test (PSNT) (kg ha")

results and on the total amounts of nitrogen added to the soil as a fertilizer (kg ha"').

 

 

 

Treatment PSNT Added N
2003 2004 2005 2003 2004 2005
WRR 69.5 b1 108.5 a 29.2 a 101 58 145
NWR 92.5 b 161.5 b 83.2 b 101 31 90
WRSR 43.7 a 87.8 a 29.6 a 134 105 145

 

T-Means within each column followed by the same letter are not signiﬁcantly different (Fisher protected

LSD, P<0.05)

In 2004, despite a lack of differences in corn emergence and relatively high soil
temperatures, com tasselling was signiﬁcantly delayed in WRSR treatments as compared
with NWR and WRR treatments. The delay in corn reaching the VT stage may be
attributable to the lower soil nitrate levels measured in WRSR treatments (Table 1.3).
The wheat residue results in microbial immobilization of N because of the very high C:N
ratio of the wheat residue (80:1) and also possible allelopathy effects. Rice (1984)
reported that high soil temperature promoted ﬁxing of soil residual N by soil
microorganisms increasing their populations. Rice also found that active allelopathic
compounds from wheat residue inhibit N ﬁxation by free-living and symbiotic
microorganisms. These compounds inﬂuence nitriﬁcation, but do not inﬂuence

denitriﬁcation processes.

31

In 2003 and 2004, in WRR treatments tasselling of corn was not delayed and
WRR treatments were not different from NWR treatments. In 2005, a delay in reaching
VT stage was observed for WRR treatments. This delay in reaching VT stage can be
related to microbial immobilization of N, because of high C: N ratio of wheat root

residue, and/or allelopathy effect (Krupa, 1982, Rice, 1984).

Effect of wheat residue on corn height
The presence of wheat residues affected corn height. In 2003, corn plants in
WRSR and WRR treatments were shorter compared with NWR treatments in all dates

(Table 1.4). Corn heights in WRSR and WRR treatments were not signiﬁcantly different.

Table 1.4. Effect of treatments on height of corn (m) during the 2003-2005 growing

seasons.

 

TreatmenL 2003 | 2004 1 2005

 

9-July 15-July 22-July 20-July 28-July 4-Aug. 20-June 27-June 5-July

 

WRR 1.14 at 1.50 ab 1.86 a 0.91 b 1.43 b 2.00 a 0.72 b 0.90 b 1.29 b
NWR 1.36b 1.75b 2.17b 0.95b 1.43b 1.96a 0.85c 1.17c 1.55c
WRSR 1.03 a 1.40 a 1.85 a 0.67 a 0.98 a 1.84 a 0.55 a 0.76 a 1.11 a

 

T-Means within each column followed by the same letter are not signiﬁcantly different (Fisher protected

LSD, P<0.05)

In 2004, corn plants in WRSR treatments were shorter compared with heights in
NWR and WRR treatments in the early stages of corn development. Corn heights in
NWR and WWR treatments were not signiﬁcantly different. Around VT stage (4 August)

heights in all three treatments equalized. During the earlier stages of corn development

32

plant height was found to be positively related (p<0.05) to chlorophyll leaf content with
taller plants having higher chlorophyll contents (Figures 1.16 and 1.17). Higher plant

heights (p<0.05) were also correlated with soil nitrate levels (Figure 1.18).

Figure 1.16. Relationship between corn heights and leaf chlorophyll contents on 28 July

 

2004.
60 1 e _ -
50 9
I e W
. ’5 40 0
I ‘2 9". .' O ’
7 § 30 ‘ °
I 2" 1
1 3'20- 1
1 E 10 . y=8.9124x+30.735 .
I 0 R2=o.3079 I
0; - -- - e ,. - -___-— ——————— . a
0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 1
Height,m

33

Figure 1.17. Relationship between corn heights and leaf chlorophyll contents on 2 August

 

 

2004.

50 - 9
E .
o .
0
2» 45 l
O.
2
O 1
E 1
0 . 0 y = 9.7702x + 27.089

. ’ R2 = 0.3995
40 . 9 , 9 . «— — 1
1.4 1.6 1.8 2 2.2 2.4
Height, m

 

 

 

Figure 1.18. Relationship between corn height and PSNT result on 20 July 2004.

 

1.20 — , ;
1.10 .
1.00 -
e
J 0.90 +
u:
.9 0.30 1
:3
0.70 -
0.60 1 3 y= 0.0035x+0.494
0.50 1 ° R2= 0.5131 '
0.40 .- - -, 2 , .
0 50 100 150 200
Nitrate, kglha

 

 

 

 

34

In 2005, WRSR treatments had shorter plants than NWR and WRR treatments at
all sampling dates. F urtherrnore, the heights of plants in NWR and WWR treatments
were signiﬁcantly different, with NWR treatments having taller plants than WRR
treatments. In two earlier sampling dates (21 and 28 June), the heights of corn were
positively correlated to chlorophyll content (Figures 1.19 and 1.20). However, the
correlation between plant height and chlorophyll content did not continue beyond the 28
June sampling date. As in 2004, higher plant height (p<0.05) was observed in plots with

higher nitrate levels (Figure 1.21).

Figure 1.19. Relationship between corn heights and leaf chlorophyll contents on 21 June

 

 

2005.
50 1 2- v — -
45
‘5
12
3 40
i»
g 35 -
O
- = 30.601 + 15.922
5 30 " y 2_ x
R - 0.8338
25 . . , , ,. .
0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
Height, m

 

 

 

35

Figure 1.20. Relationship between corn heights and chlorophyll contents on 28 June

2005.

 

55 7
50
45 '

40

   

35 3
y = 30.738x + 9.9069

30 . o R2= 0.7706

Chlorophyll content

25.

Height, m

 

 

 

Figure 1.21. Relationship between corn height and PSNT result on 20 July 2005.

 

1
0.9
0.8 1
3:, 0.7 l
.9 0.6 1
f 0-5 — y = 0.0038x + 0.5421
04. 0 ’ W=0wn
0.3 W 1
0.2 .— v - 22
0 20 40 60 80 100 120
Nitrate, kglha

  

 

 

 

36

Effect of wheat residue on chlorophyll content in corn leaves
In 2004 and 2005, in the early to mid-stages of corn development, WRSR
treatments had signiﬁcantly lower leaf chlorophyll contents compared with NWR and

WRR treatments (Table 1.5).

Table 1.5. Effect of treatments on the amount of chlorophyll in corn leaves observed

during the 2004 and 2005 growing seasons.

 

 

 

Treatment 2004 [ 2005
8-July 15-July 26-July 2-Aug 21-June 28-June 5-July
WRR 40.4 b'l 42.2 b 43.3 b 46.4 a 38.6 b 37.4 ab 45.6 a
NWR 42.0 b 45.2 b 44.9 b 45.3 a 43.6 c 45.5 b 47.2 a
WRSR 33.3 a 36.9 a 37.8 a 46.0 a 32.3 a 32.4 a 46.6 a

f-Means within each column followed by the same letter are not signiﬁcantly different (Fisher protected

LSD, P<0.05).

In 2004, in NWR and WRR treatments chlorophyll contents were similar prior to
the VT stage. But, in 2005, chlorophyll contents in WRR and NWR treatments were
different, especially before added N which was side—dressed according to PSNT results.
However, by August 2 and July 5, just prior to tasseling, the amount of chlorophyll was
found to be similar in all treatments, likely due to different N application rates based on
PSNT results. Variability in soil nitrate levels between treatments is likely a primary
reason for the observed differences in chlorophyll content. Soil nitrate and corn leaf
chlorophyll were found to be positively correlated (p<0.05) at early stages of corn

development (8 July 2004 and 21 June 2005) (Figures 1.22 and 1.23).

37

Figure 1.22. Relationship between soil nitrate levels and leaf chlorophyll content on 8

July 2004.

 

50- 9 - --

#1 «bu
O U!

00
U1

 

y = 0.1396x + 24.213
° R2 = 0.6689

Chlorophyll content
N 00
01 O

N
o
l
1
l

0 50 100 150 200
Nitrate, kglha

 

 

 

Figure 1.23. Relationship between soil nitrate levels and leaf chlorophyll content on 21

June 2005.

 

50 - -- — ————— — _____2__2

Chlorophyll content

= 0.1617X ‘1' 30.957
30 ,. . Q . y 2
R '-'- 0.5435

0 20 40 60 80 100
Nitrate, kglha

 

 

 

38

Effect of wheat residue on PSNT results

In all three years, PSNT levels were the highest in NWR treatments compared to
WRSR and WRR treatments (Table1.3). The soil in NWR treatments warmed faster
compared with the other treatments, thus the rate of N mineralization was probably
higher in the early spring. In addition, the NWR soil had higher amounts of residual N
due to soybean being the previous crop. Also, low plant available N in WRSR and WRR
treatments can be explained by microbial immobilization of N because of the very high
C:N ratio of wheat residue (80: 1). However, in 2003, WR and NWR treatments PSNT
levels were not different.

Generally, relatively lower amounts of plant available nitrate were in the soil in
2003 and 2005 compared to 2004. The higher soil nitrate levels in 2004 are likely due to

a later PSNT sampling date.

Effect of wheat residue on corn grain moisture, test weight and yield

Wheat residue affected corn grain moisture. In all years, WRSR treatments had
signiﬁcantly higher grain moisture at harvest than NWR and WRR treatments (Table
1.6). This is likely due to delayed emergence observed in 2003 and 2005 and delayed
time of tasseling in all three years. NWR and WRR treatments were not different in all
years.

In 2003 and 2005, WRSR treatments had signiﬁcantly lower test weights at
harvest than NWR and WR treatments (Table 1.6). This is likely due to the higher grain
moisture levels, delayed emergence (2003 and 2005), delayed tasseling, and lower

amounts of soil plant available N resulting from microbial N immobilization. In 2004, the

39

test weights in all treatments were lower than usual, possibly due to late planting date and
higher than usual grain moisture at harvest. There were no differences between the test
weights of the three treatments.

Despite late emergence, delayed VT stage, and lower amount of plant available N
in WRSR treatments than in WRR and NWR treatments, in 2003 and 2004, yields of corn
in all treatments were not different (Table 1.6). The lack of a yield effect is likely due to
different rates of added N according to PSNT results. The WRSR treatments had the
highest amounts of added nitrogen in all years. In 2005, corn grain yields in WRSR and
WRR treatments were not different, but both were less than the grain yields from NWR
treatments. Yields in WRSR and WRR treatments were close to the planned yield goal

(8.8 Mg ha").

Table 1.6. Treatment effects on corn grain moisture at harvest, test weight, and yield.

 

 

 

Treatment Grain moisture (%) Test weight (kg m'3) Yield (Mg ha'I)
2003 2004 2005 2003 2004 2005 2003 2004 2005
WRR 19.8
a'l' 28.6a 18.1a 708.5b 608.2a 722.0b 6.90a 8.79a 9.01a

NWR 19.5 a 28.0 a 17.9 a 711.9 b 615.2 a 732.7 c 8.64 a 8.62 a 9.99 b
WRSR 25.4 b 32.4 b 20.2 b 679.1 a 612.9 a 708.1 a 8.71 a 8.57 a 8.27 a

T-Means within each column followed by the same letter are not signiﬁcantly different (Fisher protected

LSD, P<0.05)

40

SUMIVIARY

In all years, WRSR treatments had decreased soil temperatures and increased
soil moisture levels compared to NWR and WRR treatments. In 2003 and 2005, when
com was planted early, WRSR treatments delayed emergence and reduced the corn
populations compared to NWR and WRR treatments. In each year, the time to reach
VT stage was lengthened for the WRSR treatments. In all years, WRSR treatments had
signiﬁcantly lower plant heights, especially in early growth stages. In the early stages
of development (prior to sidedress N application), corn leaves in WRSR treatments had
signiﬁcantly lower chlorophyll content. In WRSR and WRR treatments the amount of
plant available N as determined by the PSNT results was decreased compared to NWR
treatments. In all years, WRSR treatments had higher grain moisture at harvest. In 2003
and 2005, corn in WRSR treatments had lower test weights compared to NWR and
WRR treatments. In 2003 and 2004, yields in WRSR, WRR, and NWR were not
signiﬁcantly different. In 2005, WRR and NWR treatments had higher grain yield than
the targeted N-based yield goal. WRSR treatments were not different from WRR

treatments and yielded similar to the targeted yield goal.

41

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Cambardella, C.A., and ET. Elliott. 1993. Carbon and nitrogen distribution in aggregates
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physical and corn physiological characteristics. Agron. J. 82:806-812.

Dill-Macky, R., and R.K. Jones. 2000. The effect of previous crop residues and tillage
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Drury, C.F., C. S. Tan, W. D. Reynolds, T. W. Welacky, S. E. Weaver, A. S. Hamill, and
T. J. Vyn. 2003. Impacts of Zone Tillage and Red Clover on Corn Performance and Soil
Physical Quality. Soil Sci. Soc. Am. J. 67:867-877.

Edwards, AP. and J .M. Bremner.1967. Microaggregates in soils. J. Soil Sci.18:64-73.

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Elliot, ET. 1986. Aggregate structure and carbon, nitrogen, and phosphorus in native and
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Golovko, EA. 1999. Allelopathy soil sickness: basic and methodological aspects. p. 315-
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Fortin, M.C., and F .J . Pierce. 1991. Timing and nature of mulch retardation of corn
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(pasture-arable) on organic matter content, stable aggregation, and clod porosity in a
group of soil. Soil Tillage Res. 19:77-87.

Katsvairo, T.W., and W.J. Cox. 2000. Tillage x rotation x management interactions in
corn. Agron J. 92: 493-500.

Krupa, LL 1982. Allelopathic features in main farm cultures of cereal-beet crop rotation
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Coll. Kiev. Naukova dumka . Ukraine.

Lund M.G., Carter RR, and ES. Oplinger. 1993. Tillage and crop rotation affect corn,
soybean, and winter wheat yields. J. Prod. Agric. 6:207-213.

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Maysoon M. Mikha and Charles W. Rice. 2004 Tillage and Manure Effects on Soil and
Aggregate-Associated Carbon and Nitrogen. Soil Sci. Soc. Am. J. 68: 809-816.

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O'Halloran, I.P., M.H. Miller, and G. Arnold. 1986. Absorption of P by com (Zea mays
L.) as inﬂuenced by soil disturbance. Can. J. Soil Sci. 66:287—302.

Paustian, K., H.P. Collins, and EA. Paul. 1997. Management controls on soil carbon. p.
15-49. In E.A. Paul et al. (ed.) Soil organic matter in temperate agroecosystems: Long-
term experiments in North America. CRC Press, Boca Raton, FL.

Rice, EL. 1984. Allelopathy. Second edition. Academic press Inc. Orlando.

Sanchez, J .E., T.C. Wilson, K. Kizilkaya, B. Parker, and RR. Harwood. 2001a.
Enhancing the mineralizable nitrogen pool through substrate diversity in long term
cropping systems. Soil Sci. Am. J. 65:1442-1447.

Sanchez, J ., R. Harwood, J. LeCureux, J. Shaw, M. Shaw, S. Smalley, J. Smeenk, and R.
Voelker. 2001b. Integrated Cropping Systems for Com-Sugar Beet-Dry Bean Rotation:

The Experience of the Innovative Farmers of Michigan. Michigan State University
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Six, J ., E.T. Elliott, and K. Paustian. 1999. Aggregate and soil organic matter dynamic
under conventional and no-tillage systems. Soil Sci. Soc. Am. J. 63:1350—1358.

TeKrony, D.M., D.B. Egli, and DA. Wickham. 1989. Corn seed vigor effect on no-
tillage ﬁeld performance. 1. Field emergence. Crop Sci. 29:1523-1528.

Tisdall, J .M. and J .M. Oades. 1982. Organic matter and water-stable aggregates in soils.
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Crop Management). 19 April 1995. Number 5.

van Veen, J .A. and P.J. Kuikman. 1990. Soil structural aspects of decomposition of
organic matter by microorganisms. Biogeochemistry 11:213-223.

Wicks, G.A., G.W. Mahnken, and GE. Hanson. 1995. Inﬂuence of small grain crops on
weeds and corn (Zea mays). Weed Sci. 43:128-133.

Wilhelm, W.W., and Charles S. Wortmann. 2004. Tillage and rotation interactions for

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96:425-432.

44

Wu H, Pratley J ., Lemerle D., Haig T 2000. Evaluation of seedling allelopathy in
453 wheat (Triticum aestivum) accessions against annual ryegrass (Lolium rigidum) by
the equal-compartment-agar method. Austral. J. Agric. Res 51: 937-944.

Wu H, Pratley J ., Lemerle D., Hai g T. 2001. Allelopathy in wheat (T riticum aestivum).
Ann. Appl. Biol. 139: 1-9.

45

CHAPTER 2

NITROGEN MANAGEMENT STRATEGIES FOR OVERCOMING THE

WHEAT RESIDUE ANTAGONISM OF NO-TILL CORN

ABSTRACT

Two established methods for increasing the sustainability of production
agricultural cropping systems are (i) increasing crop residue levels by reducing tillage
and (ii) including a winter annual crop in the rotation. However, many crops following
wheat in tillage and reduced tillage systems have reduced grain yields. The objective of
this study was to develop management practices to overcome the observed negative yield
response in corn (Zea mays L.) grain grown following winter wheat (T riticum aestivum
L.) in no-till, high residue cropping systems. We hypothesized that management practices
including using a presidedress nitrogen test (PSNT) and using a PSNT in combination
with manure and clover cover crops, or combination of the two could be used to
overcome the rotational wheat antagonism in such cropping systems. The experimental
design was a randomized complete block design. Experimental factors were: presence of
wheat residue from the previous crop with three levels (no residue, root residue, or root
and shoot residue); (2) manure application with two levels (with or without); and, (3) red
clover (Trzfolium pretense L.) with two levels (with or without). Data were collected in
2003, 2004, and 2005. Measurements included corn grain yield, grain moisture and test
weight of corn at harvest, plant growth characteristics (emergence, plant height, time of

tasseling (VT stage), chlorophyll content), PSNT, and soil moisture and temperature

46

taken weekly during the spring and early summer. In all years the presence of winter
wheat residue decreased soil temperature, increased soil moisture, and decreased
chlorophyll content in corn leaves and plant height in the early stages of corn
development. VT stage of corn was delayed for about 1 week in residue systems. Winter
wheat residue decreased the amount of plant available N, and increased grain moisture
and test weight of corn grain at harvest. Emergence and population of corn in 2003 and
2005 were reduced. A PSNT nitrogen strategy was effective in maintaining corn grain
yields in wheat residue systems equivalent to no-wheat residue systems in 4 of 6 site
years. Similar results were obtained for PSNT plus clover cover crop and PSNT plus
manure plus clover cover crop N management systems. Using PSNT and manure system

equalized high wheat residue yields to no-wheat residue in 6 of 6site years.

47

INTRODUCTION

High residue cropping systems such as no-till and reduced-till systems contribute
signiﬁcantly to the sustainability of production agriculture. No-till and reduced-till
farmers in the United States occupy 21 million ha of land, about 38% of the United States
cropland (Conserv. Techno]. Inf. Cent, 2000). These systems reduce soil erosion and run-
off and increase the percolation of rainfall (Cavigelli, 1998). Additionally, soil organic C
levels are increased, leading to improved soil nutrient holding capacity and structure
(Tisdall and Oades, 1982). Maintenance of soil organic matter has long been recognized
as a strategy to reduce soil degradation in agricultural systems. No-till, manure additions,
and planting legume cover crops are management practices that can increase soil organic
matter content and improve soil structure.

Soil structure is an important property that mediates many soil physical and
biological processes and controls soil organic matter decomposition (van Veen and
Kuikman, 1990). Soil aggregates are the basic units of soil structure and are composed of
primary particles and binding agents (Edwards and Bremmer, 1967; Tisdall and Oades,
1982; Haynes et al., 1991). Soil organic matter is a major binding agent that stabilizes
soil aggregates (Haynes et al., 1991).

The amount and turnover of soil organic matter can be altered by different
management practices. Cultivation affects soil structure by destroying soil aggregates,
resulting in loss of soil organic matter (Tisdall and Oades, 1982; Elliott, 1986; Angers et
al., 1992). Incorporation of plant residues in soil affects the soil microclimate and

increases plant residue contact with soil, increasing the rate of residue decomposition and

48

organic matter transformation (Beare et al., 1992; Cambardella and Elliott, 1993;
Paustian et al.,l997). Tillage enhances decomposition of organic matter by mixing plant
residues into the soil, increasing aeration, and enhancing dry-wet and freeze-thaw cycles
(Paustian et al., 1997). Also, tillage disrupts soil aggregation and exposes physically
protected organic material (Blevins and Frye, 1993; Beare et al., 1994b). In contrast, no-
till systems reduce soil mixing and soil disturbance, allowing soil organic matter
accumulation (Blevins and Frye, 1993). Many studies have shown that no-till farming
improves soil aggregation and aggregate stability (Beare et al., 1994b; Six et al., 1999).
Mycorrhizal fungi, which are promoted by no-till systems, contribute to formation and
stabilization of macroaggregates (Tisdall and Oades, 1982; O’Halloran et al., 1986; Beare
and Bruce, 1993). Also, no-till signiﬁcantly increases soil total C and N levels, water-
stable aggregates, and labile C and N associated with macroaggregates, compared with
conventional tillage (Mikha and Rice, 2004).

Application of manure is another management practice that can improve the
nutrient status of the soil and increase soil organic matter (Rochette and Gregorich,
1998). Aoyama et al. (1999) observed an increase in soil organic matter with addition of
manure and consequently the formation of shaking-resistant macroaggregates (250-1000
um diam). Mikha and Rice (2004) concluded that manure signiﬁcantly increased total
soil C and N levels through improved formation of water- stable aggregates and increased
aggregate-associated C and N. In general, it has been observed that the combination of a
high residue cropping system, such as no-till, with manure application signiﬁcantly
improves soil aggregation and aggregate-associated C and N compared with conventional

tillage.

49

However, manure application in a no-till system has certain disadvantages.
Surface manure application may not be as efﬁcient as incorporation of manure because of
N loss (volatilization of ammonia and runoff) or nutrient stratiﬁcation. Still, many studies
have reported that net N mineralization from manure is often similar in no-till and
conventional tillage systems. Eghball (2000) reported that 11% of the organic N applied
the previous fall was mineralized from composted beef cattle manure; N mineralization
was similar in no-till and conventional tillage systems even though the compost was
surface-applied in no-till. Eghball and Power (1999a) reported similar corn grain yields in
no-till and conventional tillage systems with beef manure in 3 of 4 years in Nebraska. In
the fourth year, a no-till system yielded less than conventional tillage with compost
application. They concluded that surface application of beef manure did not result in
signiﬁcant N loss. N requirements for no-till versus conventional tillage systems may
differ. Stecker et al. (1995) found that no-till corn following soybeans on poorly drained
soils required 17 kg ha'1 more fertilizer N for maximum corn yield than a chisel-disk
system and 45 kg ha'1 more N for maximum proﬁt.

Michigan growers increased winter wheat production from 214,650 ha in 2002 to
255,150 ha in 2004; a 20% increase (Michigan Agricultural Statistics Service, 2004).
Winter wheat is generally grown in rotation with corn and soybeans. The growth cycle of
soybeans makes winter wheat a logically fallow crop in the rotation, which is usually
planted right after soybean harvest. Growers typically follow the wheat with corn. There
are many advantages of including a winter annual crop such as winter wheat in a
cropping system. Sanchez et al. (2001a) reported that N mineralization was increased in a

diverse cropping system including wheat in the rotation. In addition, pest cycles can be

50

disrupted with the inclusion of a winter annual crop (Cavigelli, 2000). Wicks et al. (1995)
reported reduced weed emergence when no-till corn was planted into winter wheat
residue. Copeland et al. (1997) estimated a 10% com grain yield increase when com was
rotated with wheat.

Including a legume cover crop in a cropping system can reduce soil erosion
(Smith et al., 1987), increase water inﬁltration (McVay et al., 1989), improve soil tilth
(Marten and Touchton, 1983), contribute biologically ﬁxed N (Heichel et al., 1985), and
increase yield of subsequent crops (Baldock et al., 1981). Red clover underseeded in
cereals can provide large amounts of plant biomass and ﬁx N in the nodules, providing
the equivalent of 90-125 kg ha'1 of N to the following crop (Bruulsema and Christie,
1987). Don et al. (1995) reported that mineralized N concentrations from red clover that
had been seeded into wheat peaked about four weeks after planting of the following corn
crop, and that grain yield in corn was similar to those obtained where fertilizer N was
applied without legume N. In Wisconsin, Mallory and Posner (1994) found that
overseeding red clover into wheat increased yields of corn grown the following year. In
Ontario, Raimbault and Vyn (1991) found similar results. Furthermore, red clover may be
effective in cool temperate climates for increasing microbial biomass (Drury et al., 1991),
accelerating the decomposition of surface crop residues (Drury et al., 1999), and tying up
residual soil N after grain harvest (Ditsch et al., 1993). Other advantages attributed to
legume cover crops include improved soil structure and increased soil organic matter
content (Bruce et al., 1990), increased water penetration (Benoit et al., 1962), weed
suppression (Worsham, 1991), and increased beneﬁcial insect populations (Roberts and

Cartwright, 1991).

51

Despite many advantages of planting legume cover crops, non-legume crops
following a legume do not always show yield increases. Under certain conditions, legume
cover crops actually can have a negative effect upon a subsequent crop. Under water-
limiting conditions, corn crops following a legume cover crop exhibited reduced
emergence (Holderbaum et al., 1990) and reduced grain yield (Touchton and Whitwell,
1984; Hesterrnan et al., 1992). The likely cause of this negative effect was depletion of
soil moisture content by the actively growing legume (Ebalhar et al., 1984; Badarrudin
and Meyer, 1990).

Herbicide burn down or plow down of a cover crop two weeks before planting a
subsequent crop (Hargrove and Frye, 1987; Munawar et al., 1990) may minimize the risk
of yield loss from cover crop induced soil water deﬁcit. Munavar et al. (1990) found
timing of killing cover crops had no effect on soil water content at the time of no-tillage
corn planting. Timing of legume cover crop desiccation or incorporation may be an
effective technique for managing green manure water use. When water is plentiful, cover
crops could be allowed to grow until planting of the subsequent crop. Under water
surplus conditions, cover crop spring grth may actually reduce soil water content,
potentially reducing leaching of nitrate and allowing earlier ﬁeld operations (McCracken
et al., 1988).

The agronomic and environmental advantages of reduced-tillage, high residue
cropping systems have been well documented (Cavigelli, 1998, Sanchez, 2001b). Despite
many advantages, there are also negative impacts associated with high residue systems.
One such negative impact is a com-wheat antagonism that results in lower corn grain

yield following wheat (Beuerlein and Houdashelt, 1997). Similar reports that com

52

following wheat in the crop rotation seems to have reduced grain yields came from no-till
and reduced-till growers in the Great Lakes Region (K.Thelen, personal communication).
Researchers (Tekrony, 1989) and growers have speculated that com grain yield
antagonism may be attributable to cooler soil temperature in the spring from the wheat
residue. There are many reports of reduced corn emergence and yields under no-till
compared with conventional till farming, especially in humid and cool temperate climates
(Fortin and Pierce, 1991). Lund et al. (1993) associated the reduced yield of no-till,
continuous corn with the greater crop residue and cooler soil temperature in the spring
(2.7°C lower). Wilhelm and Wortmann (2004) concluded that the advantage of
moldboard tillage over no-till for corn yield was greatest in years with low spring
temperatures. Tillage may be preferred for soils that are slow to warm or when early
planting is preferred. Katsvairo and Cox (2000) recorded that corn densities were less
under reduced tillage compared to moldboard plow systems when com followed corn or
wheat/red clover. Cox et al. (1990) noted that cool conditions in May in years with less
than normal growing degree days may result in poorer emergence under reduced tillage
because high residue inhibits soil warming and delays corn emergence in northern
latitudes. Also, Drury et al. (2003), in a four-year study in a winter wheat- com-soybean
rotation with and without red clover, reported different emergence rates of corn in
different tillage systems. In no-till systems corn emergence rates were slower compared
with conventional tillage over 3 years. However, despite low emergence rates, ﬁnal plant
stands were not signiﬁcantly different between treatments in some years. Also,
emergence of corn depended on time of planting (early or late) and spring weather

conditions (wet or dry, cool or warm).

53

Beuerlein and Houdashelt’s (1997) results contradict the notion that cooler soil
temperature in the spring, because of the presence of wheat residue, is the only cause of
corn-wheat antagonism. In a study, they grew wheat adjacent to bare soil plots. After
harvesting the wheat, they removed the above ground wheat residue and transferred it to
the bare soil plots without disturbing the soil. The following spring, corn was planted into
the crops. Interestingly, the removal of the above ground wheat residue did not overcome
the corn yield antagonism.

During cool, wet springs in Ohio, farmers and researchers often noticed that no
till corn planted into wheat residue does not grow as rapidly as corn planted with
conventional tillage. Thomison (1995) explained that under cool soil conditions and no-
till farming practices winter wheat residues concentrated near the soil surface break down
more slowly and tie up N longer than when residue is incorporated, making N less
available for crop growth. This slow decomposition can be attributed to the high C-N
ratio of wheat residue and environmental conditions. Another biological process that may
also contribute to the slow growth of corn following wheat involves the production and
release of phytotoxins from decomposing wheat residues. The allelopathic effects of
wheat straw on corn growth may be related to either anaerobic production of microbial
byproducts using wheat residue as a C source and/or direct release of organic compounds
from the decomposing residue. Cool temperature, anaerobic conditions, and low pH
increase leaching of amino acids and carbohydrates from the plant roots. Anaerobic

conditions contribute to exudation of alcoholic substances that are toxic to plants

(Christiansen et al., 1970).

54

Nitrogen fertilizers are important for corn production, but there is concern that
large amounts of fertilizers may have adverse effect on ground water quality (Blackmer,
1987). It is very difﬁcult to determine the appropriate rate of N fertilizer application,
especially considering the possibility for N loses by leaching and denitriﬁcation before
the crop can utilize the fertilizer. The pre-sidedress soil nitrate test (PSNT) based on the
quantity of nitrate that is present in the soil at that time, a decision is made on how much
more N fertilizer should be applied. The PSNT has potential for detecting the amounts of
available N released from organic N sources, such as legume crop residues, manure, and
soil organic matter, as well as any residual nitrate in the surface foot of soil (Silva, 1998).
There are situation when PSNT has not been accurate as desired, like leaching of nitrate
from the surface before the PSNT sampling date but large amounts still remained in the
root zone, heavy rainfall which can cause leaching of nitrate out of the root zone, and
cool wet conditions early in the season with low mineralization of organic N followed
after PSNT sampling by conditions that promote N mineralization.

Our objective was to develop management practices to overcome the observed
negative yield response in corn grain grown following winter wheat in no-till, high
residue cropping systems. We hypothesized that a PSNT nitrogen management system
alone or combined with legume cover crops and manure compost soil amendments could
be used to overcome the rotational wheat antagonism in reduced tillage, high residue

cropping systems.

MATERIAL AND METHODS

Experimental site and data collection

We conducted the research at the Michigan State University Agronomy Farm, in
East Lansing, MI. The experiment was established on soybean-winter wheat-com
cropping systems from 2001 through 2005 with three cycles. The ﬁrst cycle included
plots that were planted to soybeans in 2001, winter wheat in fall 2001, and corn in 2003.
The second cycle included plots that were planted to soybeans in 2002, winter wheat in
2002, and corn in 2004. A similar third cycle was implemented with soybeans and wheat
planted in 2003 and with corn planted in 2005. The treatments with no winter wheat
residue had a second year of soybean substituted for wheat in the second year of each
cycle.

The ﬁrst cycle was established on a Capac loam soil (ﬁne loamy, mixed, mesic
Typic Hapladulfs). The second and third cycles were established on Colwood (ﬁne
loamy, mixed, mesic Typic Haplaquolls) - Brookston (ﬁne loamy, mixed, mesic Typic
Argiaquolls) loam soils.

The experiment was a randomized complete block design with treatments
consisting of four nitrogen management practices: 1) PSNT; 2) PSNT with clover; 3)
PSNT with manure; 4) PSNT with clover and manure. Treatments were imposed on three
levels of wheat residue: no wheat residue (NWR), wheat residue from roots and shoots
(WRSR), and wheat residue from roots only (WRR).

In the ﬁrst cycle, the experiment had four replications. Plots were 14 m long and

6.1 m wide. In the second and third cycles the treatments were replicated eight times.

56

Plots were 9.1 m long and 6.1 m wide. Distance between rows of planted corn was 76
cm.

Winter wheat (Harus) was planted in the fall of 2001, 2002, and 2003. In the
following springs, at green up, wheat plots received 246 kg ha'lof granular urea (46-0-0).

Winter wheat yielded an average of 5.65 ton ha‘1 in 2002, 7.65 ton ha‘1 in 2003, and 4.95
ton ha'I in 2004 with no differences between plots. After harvest of winter wheat, the

height of the remaining wheat straw was about 30 cm. The remaining residue was
returned to the plots having below and above ground wheat residue (WRSR) and
removed from treatments having below ground wheat residue only (WRR). The amount
of straw left in the treatments with wheat residue above and below ground was not
signiﬁcantly different between treatments in any year. The highest amount of wheat
residue left in the plots was from the ﬁrst cycle (2001-2003).

In the second year of the experimental cycle, soybean (Dekalb 23-51) was planted
on 5 May 2002, 19 April 2003, and 29 May 2004 (rate of planting was 444,600 seeds ha'
|) for treatments having neither above or below ground wheat residue. Soybean was
harvested on 28 September 2002, 13 October 2003, and 20 December 2004. At planting
time, liquid starter fertilizer 6-24-6 (28 kg ha'l) was added, providing 1.7 kg N ha'l
similar to local common production practices. Yields of soybean were not signiﬁcantly
different between plots (p>0.05). In 2002 soybean yielded 3.59 ton ha", in 2003 2.25 ton
ha", and in 2004 3.26 ton ha".

In the ﬁrst and second cycles, manure was applied by broadcast method in the late
fall following wheat and soybean harvest in 2002 (86.3 Mg ha") and in 2003 (81.5 Mg

ha'l). In the third cycle, manure was applied in the early spring 2005 (105.5 Mg ha") due

57

to inclement fall weather. The manure was obtained from the Michigan State University
Dairy Farm, in East Lansing, MI.

Red clover (22.4 kg ha") was frost seeded by hand into the plots where wheat was
growing on 14 March 2002, 24 March 2003, and 30 March 2004. In 2005, the average
biomass of clover before herbicide bumdown was 2 Mg ha'1 and there was no signiﬁcant
difference in clover biomass between the treatments. In 2003 and 2004, the clover stand
was poor, two to three times less than that in 2005. Glyphosate (2.34 L ha'l with 2.04 kg
100'I L of ammonium sulfate) was used to burn down clover and weeds, 7-10 days before
planting of corn in 2003 and 2004. In 2005, due to spring manure application and having
a goal of early planting of corn, clover was sprayed with glyphosate after planting of corn
on 22 April. Because clover was not killed completely, it was sprayed the second time on
5 May 2005. In all years, glyphosate was applied after corn emergence to control weeds,
prior to applying nitrogen according to PSNT recommendations.

An early maturity corn variety DKC44-46 (YieldGard Corn Borer/Roundup
Ready, Residue Proven, 94-day relative maturity) was planted into plots by a customized
John Deere no-till planter. Corn was planted at a target population of 69,000 plants ha’l
on 30 April 2003, 29 May 2004, and 19 April 2005 and harvested on 16 October 2003, 22
October 2004, and 27 September 2005. In 2003 and 2005, starter fertilizer 6-24-24 was

placed in furrow and in row (269 kg ha'l), providing 16 kg N ha]. In 2004 starter
fertilizer 1919-19 was added (140 kg ha °'), providing 26.6 kg N ha ".

Based on PSNT results, on 25 June 2003, 15 July 2004, and 20 June 2005, we
applied N to every plot (based on yield goal of 8.8 Mg ha"). The soil samples for the

PSNT test were taken from a depth of 0-30 cm on 17 June 2003, 7 July 2004, and 7 June

58

2005. In addition, soil was resampled in the fall and evaluated for residual N. Also, soil
pH, nitrate, and phosphorus levels were determined from separate soil samples obtained
each spring. The average pH values based on all the plots were 6.1 and 5.6 (1:1
soil/water), in 2003 and 2004, respectively. The average phosphorus values were 97.5
and 107 kg ha'1 (Bray Pl), respectively. Treatments did not have a signiﬁcant effect on
either pH or phosphorus. Potassium content was not measured but assumed to be
sufﬁcient based on soil test data obtained prior to experiment establishment.

In the early spring and early summer of 2004 and 2005, soil temperature
measurements were taken weekly at a depth of 10 cm. In the early spring of 2003, soil
temperature was measured at a depth of 20 cm and then from depth 10 cm. Soil moisture
was also measured using a Trime — FM3 moisture meter with a P3 probe (Mesa Systems
Co. Framingham, MA) at a depth of 0-15 cm.

Changes in soil temperature or moisture values of treatments WRR and WRSR as
compared to the control NWR treatments were expressed as a ratio between soil
temperature or moisture values measured at WRR and WRSR plots and the average soil
temperature or moisture value from the NWR plots, and are called A temperature or
A moisture.

To monitor corn development, we recorded emergence, postemergence stand
count, time of tasseling (VT stage), and stalk lodging. Plant height was measured when
com was at the V9 stage until VT stage every week. Chlorophyll content of the
uppermost leaf of corn that had formed a collar was measured weekly using a SPAD-502
meter (Specialty Products Agricultural Division, Minolta Co. LTD, Japan) in 2004 and

2005, when com was at the V6 stage until VT stage.

59

Two center rows of corn from each plot were machine harvested. Moisture
content, test weight, and ﬁeld weight of corn were measured by a Grain Gage‘m and
HarvestMasterSystemtm (Juniper Systems, Inc., Logan, UT) mounted on a plot combine.
Grain yield was reported at 15.0 % moisture content. Grain test weight is reported at
harvest moisture.

Percent of soil surface cover by manure, residue and clover was determined using

digital imagery.

Data analysis
SPAD (leaf chlorophyll) data was ﬁtted with a logistic growth curve model:

It
— 1+ ((k + n0)/n0)e"N

 

where N is the N03 level, k describes the SPAD reading as N approaches inﬁnity,

no is the SPAD reading at zero N, and r is the rate of increase.

Statistical analyses were conducted using the PROC MIXED procedure in SAS
(SAS Inc., 2002). Normality of the residuals and homogeneity of variances were
evaluated. When the variances were not homogeneous, the REPEATED /GROUP option
of PROC MD(ED was used. When the F-test showed a signiﬁcant treatment effect we

conducted mean separations using Fisher protected t-tests (P=0.05).

60

RESULTS

Effect of clover on soil temperature

In 2003, in WRSR treatments without manure, clover did not affect soil
temperature in all studied dates compared to treatments without clover (Figure 2.1). In
treatments with manure, clover did not affect soil temperatures on 6 of 8 dates. On 11 and
30 June, soil temperatures in these treatments were signiﬁcantly higher when clover was
present compared to treatments without clover. The observed increases in soil
temperature on these later sampling dates may be due to the increased soil biological
activity associated with the presence of the decomposing clover roots. In WRR
treatments without manure, clover signiﬁcantly decreased soil temperature on 5 of 8
dates. The cooler soil temperatures with the presence of the clover residue appear to be
associated with the earlier sampling dates, suggesting that the clover residue effectively
insulated the soil delaying warm-up. In treatments with manure, the effect of clover on
soil temperature was not signiﬁcant in all studied dates, suggesting that the soil insulating
effect of the manure masked that effect of the clover residue.

In 2004, in WRSR treatments with and without manure, clover did not affect soil
temperature on 6 of 8 dates (Figure 2.2). But, on 13 May, treatments with and without
manure had signiﬁcantly lower soil temperatures and, on 29 April treatments with

manure had signiﬁcantly higher soil temperatures compared to treatments without clover.

61

Figure 2.1. 2003 means of soil temperature ( 0C).

r__

‘

 

 

Soil temperature, °C

8011 temperature, °C

 

7 Lﬂm- ..

4117 4124 511

 

 

 

 

 

 

 

"T __

518 5115 5122 5129 615

Date

 

 

1'— _ ""‘__T—_

6112 6119 6126

 

 

 

 

516

5116
Date

 

 

 

62

—- +WRR

 

 

+ WRR Clover
and Manure

——er— WRR and
Mantle

-—x-—NWR

—+—-NWRand
Mame

--+-- WRSR and
Clover

— -o-- WRSR
Clover and

Mame
—o— WRSR am

Mame

 

 

 

 

6115

 

ﬁ

“Hr-WRR

 

l

--B— WRR and
Clover

_._ WRR Clover

and Manure
-+— WRR and
Mantle

--l—- NWR

_._ NWR and
Manue

---+-~WRSR

—e— WRSR and
Clover

-----WRSR Clover
and Manure

-—o— WRSR and
Mame

 

In WRR treatments without manure, clover signiﬁcantly reduced soil temperatures on 6
of 8 studied dates compared to treatments without clover. On 6 May and 21 June, there
were not signiﬁcant differences between treatments. In WRR treatments with manure,
clover signiﬁcantly reduced soil temperature on 4 of 8 dates. On 16 April, 6 May, 6 June,
and 21 June, clover did not have an effect on soil temperatures compared to treatments
without clover. The 16 April date represents the beginning of the sampling period and 6
June and 21 June are the last two sampling dates. This suggests that soils were unifome
cool and warm at the beginning and the end of the sampling period, respectively, and that
treatments had more of an effect on soil temperature during the transitional soil warm-up
phase.

In 2005, clover again affected soil temperature (Figure 2.3). Soil temperature was
strongly related to percent of clover cover (F igure.2.4 and Table 2.1). Higher clover
cover corresponded to lower soil temperature. In WRSR treatments with and without
manure, clover signiﬁcantly reduced soil temperature on all but one sampled date
compared to treatments without clover. This is likely due to the heavy 2005 clover stand
and the cooler 2005 air temperatures resulting in an enhanced insulating effect from the
clover residue. In WRR treatments with and without manure, clover signiﬁcantly
decreased soil temperatures in all but one date (1 8 May) compared to treatments without

clover.

63

Figure 2.3. 2005 means of soil temperature (°C).

 

Soil temperature °C

 

 

4118 4128

 

 

  
  
  

: --I-WRR and
Clover

—-e— WRR Clover
and Manue

 

 

 

 

Table 2.1. Average percent of soil surface cover by manure, residue, and clover in 2005

 

 

treatments.

Treatment Manure Residue Clover Total
WRR - 57.5 - 57.5
WRR and Clover - 22.3 70.6 92.9
WRR Clover and Manure 45.6 20.6 27.9 94.1
WRR and Manure 54.0 40.9 - 94.9
NWR - 22.9 - 22.9
NWR and Manure 80.5 15.1 - 95.6
WRSR - 72.6 - 72.6
WRSR and Clover - 26.2 53.4 79.6
WRSR Clover and Manure 64.2 13.4 19.1 96.7
WRSR and Manure 50.5 45.2 - 95.7

 

Figure 2.4. Relationship between percent of soil covered by clover and soil temperatures.

 

 

 
  

 

 

 

 

 

 

 

23 ~ -
21 ?
g; 19 3 ~
3 17
9 15 1 °
3 1
E 13 Q
f 11 4 0
'5 9 g y = -0.0824x + 17.495 ’
”’ R2 = 0.4853 ’ °
7 .
0 20 40 60 80
Clover cove r, %
Table 2.2. Summary of clover and manure effects on soil temperature.
Treatment 2003 2004 2005
Effect of clover
WRSR without manure 8 of 8 no effect 6 of 8 no effect 5 of 6 decreased
WRSR with manure 6 of 8 no effect 6 of 8 no effect 5 of 6 decreased
WRR without manure 5 of 8 decreased 6 of 8 decreased 5 of 6 decreased
WRR with manure 8 of 8 no effect 4 of 8 decreased 5 of 6 decreased
Effect of manure
WRSR without clover 6 of 8 no effect 6 of 8 no effect 6 of 6 decreased
WRSR with clover 6 of 8 no effect 6 of 8 no effect 4 of 6 decreased
NWR 6 of 8 decreased 7 of 8 decreased 6 of 6 decreased
WRR without clover 7 of 8 decreased 7 of 8 decreased 6 of 6 decreased
WRR with clover 8 of 8 no effect 5 of 8 decreased 3 of 6 decreased

 

65

Summarizing the effect of clover on soil temperature (Table 2.2), in 2003 and
2004, in WRSR treatments with and without manure, clover did not affect soil
temperature. But, in 2005, clover signiﬁcantly decreased soil temperature in these
treatments. In 2005, clover stands were two to three times graeter than in 2003 and 2004.
In all years, in WRR treatments with and without manure, clover signiﬁcantly decreased
soil temperatures on most studied dates. The fact that clover residue decreased soil
temperatures in WRR treatments and not in WRSR treatments in 2003 and 2004 is
attributable to the insulating value of the above ground wheat residue. When the above
ground wheat residue was present the addition of clover residue provided only a
negligible additional insulating effect not sufﬁcient to further reduce soil temperature.
Without the masking effect of the above ground wheat residue, the clover residue effect
on soil temperature in WRR treatments was measurable. The exception was 2003 WRR
treatments with manure, where the effect of clover on soil temperature was not
signiﬁcant. However, in 2003, in the early dates, soil temperature was measured at 20 cm
which may have been too deep to be sensitive to the temperature change imposed by the

clover residue.

Effect of manure on soil temperature
In 2003, in WRSR treatments with and without clover, manure had no effect on
soil temperatures on 6 of 8 studied dates (Figure 2.1). On 11 and 30 June, in treatments
without clover, manure signiﬁcantly decreased soil temperatures. In NWR treatments,
manure signiﬁcantly decreased soil temperatures on 6 of 8 dates compared to treatments

without manure. On May 28 and June 23, there was no effect of manure. In WRR

66

treatments without clover, manure signiﬁcantly decreased soil temperatures on 7 of 8
studied dates compared to treatments without manure. On 23 June, manure did not affect
soil temperatures in these treatments. In WRR treatments with clover, manure had no
effect on soil temperatures in all studied dates. Clover had already signiﬁcantly lowered
soil temperature on these treatments. The addition of manure to the clover residue plus
wheat root residue provided insufficient increased insulating value to further signiﬁcantly
decrease soil temperature.

In 2004, in WRSR treatments with and without clover, manure did not affect soil
temperatures on 6 of 8 dates (Figure 2.2). In the early season (16 April and 29 April), in
treatments with clover, manure signiﬁcantly decreased soil temperatures compared to
treatments without manure. In NWR treatments, manure signiﬁcantly decreased soil
temperatures on 7 out of 8 dates. In WRR treatments without clover, manure signiﬁcantly
decreased soil temperatures on 7 of 8 studied dates compared to treatments without
manure. In WRR treatments with clover, especially in the early season, manure
signiﬁcantly decreased soil temperature on 5 of 8 dates compared to treatments without
manure. On 6 May, 27 May, and 21 June, there was no effect of manure on soil
temperature.

In 2005, manure affected soil temperature (Figure 2.3). Soil temperature was

strongly related to percent of manure cover (Figure 2.5).

67

Figure 2.5. Relationship between percent of soil cover by manure and soil temperature in

 

 

 

2005.
25 .2. . 2 2 2 2 2 2 22 2 _ 2 .
20 I I
t :2
g ‘15 1 ‘L g l
a. O
* f 1
g 10 o o
E 5 y = -0.0577x + 17.366 |
‘ R2 = 0.3593 1
0 ... 2 .2 . _2 __ . . 222..- . 2 2.2,
0 20 40 60 80 100
Manure cover, %

 

 

 

Higher manure cover corresponded to lower soil temperature. In WRSR
treatments without clover, manure signiﬁcantly decreased soil temperatures in all dates
compared to treatments without manure. In WRSR treatments with clover, manure
signiﬁcantly decreased soil temperatures on 4 of 6 dates. In NWR treatments, manure
signiﬁcantly reduced soil temperatures in all sampled dates compared to treatments
without manure. In WRR treatments without clover, manure signiﬁcantly decreased soil
temperatures in all dates compared to treatments without manure. In WRR treatments
with clover, manure signiﬁcantly decreased soil temperatures on 3 of 6 studied dates
compared to treatments without manure, especially in the early growing season (1 8 April
and 29 April). On 5 May, 10 May, and 26 May, there was no effect of manure in soil

temperature for WRR treatments.

68

Summarizing manure effects on soil temperature (Table 2.2), in 2003 and 2004, in
WRSR treatments with and without clover, manure did not affect soil temperatures on the
most of the studied dates. In 2005, manure signiﬁcantly decreased soil temperatures in
these treatments. This was likely due to the timing and rate of manure application and
cooler than average May temperature in 2005. Prior to the 2003 and 2004 growing
seasons, manure was applied in the fall in amounts of 20 Mg ha'1 less than the spring
application in 2005. There could be some losses of manure, run off, decomposition,
mineralization, and other processes that affected soil coverage by manure with the winter
applications in 2003 and 2004. In all years, in NWR treatments and WRR treatments
without clover, manure signiﬁcantly decreased soil temperature. In WRR treatments with
clover, manure did not affect soil temperature relative to WRR treatments with clover and

without manure in 2003 and tended to lower soil temperature in 2004 and 2005.

Effect of treatments on PSNT results

In all three studied years, PSNT levels were the highest in NWR treatments
(Table 2.3). The soil in these treatments warmed faster compared with the soil in the
other treatments. Thus, rate of mineralization of N was probably higher and the soil had a
higher amount of residual N. Also, low plant available N in WRSR treatments can be
explained by microbial immobilization of N because of the very high C:N ratio of wheat
residue (80:1) and allelopathy effect (Rice 1984). Rice found that active allelopathic
compounds inhibit N ﬁxation by free-living and symbiotic microorganisms. These

compounds inﬂuence nitriﬁcation, but do not inﬂuence denitriﬁcation processes.

69

Table 2.3. Effect of studied treatments on the soil pre-sidedress nitrogen test (PSNT) (kg
ha'l) results and on the total amounts of nitrogen added to the soil as a fertilizer (kg ha").

 

 

 

Treatment PSNT Added N
2003 2004 2005 2003 2004 2005
WRR 69.5 bcT 108.5 be 29.2 a 101 58 145
WRR and Clover 78.0 cd 134.9 cd 14.3 a 101 31 145
WRR Clover and Manure 54.2 ab 69.9 a 77.2 c 118 112 101
WRRand Manure 57.1 abc 81.9 ab 76.4 be 118 112 101
NWR 92.5 cd 161.5 d 83.2 cd 101 31 90
NWR and Manure 95.8 d 92.1 abc 95.3 d 101 58 90
WRSR 43.7 a 87.8 ab 29.6 a 134 105 145
WRSR and Clover 50.6 ab 98.5 abc 20.5 a 134 112 145
WRSR Clover and Manure 81.1 cd 65.3 a 94.7 d 101 105 90
WRSR and Manure 47.4 ab 69.8 a 58.7 b 134 129 112

 

’r-Means within each column followed by the same letter are not signiﬁcantly different (Fisher

protected LSD, P<0.05

WRR treatments with manure had high rates of N application based on relatively
low PSNT levels. The relatively low PSNT N levels found in the manured plots was
likely due to a slow rate of mineralization of soil N and slow rate of mineralization of
manure N due to lower soil temperatures associated with the manure layer on the soil
surface insulating the soil and delaying spring warm up. The soil temperature in these
treatments was signiﬁcantly lower compared with temperature in the rest of the
treatments. Also, in 2004 and 2005, the very wet and cool springs further retarded N
mineralization and contributed to the low PSNT levels observed in these treatments.

In 2003 and 2004, WRR treatments with and without clover and without manure
had high amounts of plant available nitrate that was likely due to higher soil temperatures

and a higher rate of mineralization of soil N. In contrast, in 2005, WRR treatments with

70

and without clover and without manure had low amounts of plant available nitrate. In
WRR treatments without clover and manure that was likely due to the early 2005
sampling date (7 June), microbial immobilization of N, because of high C:N ratio of
wheat root residue, and/or allelopathy effect (Rice, 1984). In WRR treatments with clover
and without manure, the low amount of plant available nitrate was likely due to the above
factors plus early season N uptake by the clover and low soil temperature (the heavy
residue after herbicide bumdown clover decreased soil temperature in these treatments)
that inhibited rate of mineralization of soil N and nitrogen ﬁxation by clover. Rhizobia
inﬂuences nodule growth, nitrogen ﬁxation, and the time period when nodules remain
active. Rhizobia are mesophiles and most do not grow below 10° C. Azizi et al. (2004)
found that the best temperature for nitrogen ﬁxation and nodule formation for annual
medics (Medicago polymorpha cv. Santiago) at root zone was at 15° C, and 10° C was a
thermal critical. Zhang et al. (2002) concluded that soil temperature below 15° C is a
limiting factor to soybean nodulation in Canada. Also, after study the effectiveness of
strains of Rhizobium, Herdian and Silsbury (2001) found that seeding growth and
nodulation were poorer at 10° C than at 15° C or 20° C in faba bean (Vicia faba L.) and
pea (Pisum Sativum L.). Therefore, at the time of the 7 June 2005 PSNT sampling date,
the clover was likely an N sink and not an N source.

Generally, relatively lower amounts of plant available nitrate were in the soil in
2003 and 2005 compared to 2004 which is likely due to the late 2004 PSNT sampling
date and environmental conditions.

We concluded that, in 2003, in WRSR treatments with manure, clover

signiﬁcantly increased soil nitrate levels. In the rest of treatments, clover did not have any

71

effect on soil nitrate levels. In WRSR treatments with clover, manure signiﬁcantly
increased soil nitrate levels. But in WRR treatments with clover, manure decreased soil
nitrate levels which can be related to possible lower spring soil temperature which
delayed N mineralization.

In 2004, in all treatments, clover did not affect soil nitrate levels and manure
decreased the amount of soil nitrate in WRR treatments with clover.

In 2005, in WRSR treatments with manure, clover signiﬁcantly increased soil
nitrate levels. In the rest of treatments, clover did not have any effect. And, in WRSR and
WRR treatments with and without clover, manure signiﬁcantly increased soil nitrate
levels which is likely due the higher amount of plant available N in 2005 manure (Table
2.4). In NWR treatments, manure did not decrease soil nitrate levels as it did in the wheat
residue systems. This further supports our conclusions that the relatively cooler soils
resulting from the wheat residues delayed manure N mineralization.

In every year, wheat residue affected soil nitrate levels. WRSR treatments with
and without clover and manure had signiﬁcantly lower soil nitrate levels than NWR
treatments with and without manure. In 2004 and 2005, WRSR and WRR with and
without clover and manure were not different. In 2003, WRR and NWR treatments with

and without manure were not different.

72

Table 2.4. Manure analysis during three years of application.

 

 

 

2002 2003 2005
Parameter kg M g'I
Moisture 653.40 - 662.60 - 564.50 -
Solids 254.60 - 245.40 - 343.50 -
Organic Matter (LOI) no - 225.81 - 291.19 -
Nitrogen, Total (N) 4.63 2.22* 2.81 1.45* 8.22 3.04*
Nitrogen (NH4-N) 1.41 1.41* 1.00 1.00* 1.32 132*
Nitrogen, Organic 3.22 0.81 * 1.81 0.45* 6.90 1.73*

Phosphorus (as P205) 1.36 1.36* 1.36 1.36* 4.09 409*
Potassium (as K20) 3.63 1.36* 4.54 4.54* 7.08 708*

’- First year availability (source: MWP — 18, Livestock Waste Facilities Handbook, 1993).

Effect of clover and manure on chlorophyll content in corn leaves
In 2004 and 2005, in the early to mid-stages of corn development, WRSR
treatments resulted in signiﬁcantly decreased chlorophyll content in corn leaves
compared with other treatments (Figures 2.6 and 2.7). However, by August 2 and July 5,
just prior to tasseling, the amount of chlorophyll was found to be similar in all treatments,

likely due to different N application rates based on PSNT results (Figure 2.8).

73

 

‘ _ Chlorophyll content ' _ _

Figure 2.6. Effect of treatments on leaf chlorophyll content in 2004.

 

.—-o—WRR

—I—WRRand
Clear

_._WRRch
andManure

—-n—WRRand
Manure

--e--MNR

 

 

 

 

--'-- NWRand
Marrure

—a—WRSR

Chlorophyll content

 

 

‘\

, ‘ ---A—--WRSRand
..I Cher

l--- v' - ***** * 1% +WRSR

718 7/18 "”28 0mm
Manure
Date - -o— - WRSR and

_2. _22_ - _ . .- m.

 

 

 

 

 

 

Figure 2.7. Effect of treatments on leaf chlorophyll content in 2005.

 

 

 

 

 

55 1— -— - - 2 ~ . _._WRR

-—a-—WRR and
Clowr

+WRR Clover
and Manure

+ WRR and
Manure

+NWR

 

/' .".

. .I' —-.--NWRand
35 2 .I" _.I’ Manure
11+WRSR
30 1 x" 1 =
[1--x—-WRSRand

1 Clover

l
25 1 22 , — ,2 - r»" 22 t ,1 !—-o--WRSRCIO\671

6121 6/25 6/29 7/3 1 and "am”

pm 1+WRSR and
‘ Manure

 

 

q a
\

 

Ir
1
I

 

 

 

74

Figure 2.8. 2004 SPAD readings plotted versus soil nitrate levels in 2004.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

July8
55
5o 1 .4 R2=0.395
45 '“ . ‘. 0 Ah A A v
D 40 1 ‘..A." 1‘0;
535- :- ..; 12: _2
(I) 30 _. "I: u 1' 1 I NWR
25~ 1 *WRR
20~ . 1 r2WRSR2
15 1 1
0 100 200 300
Nitrate, kglha
Augustz l
551 ~ ~ 6
5O ‘ . O I‘ I 222 ' l
' 45. W ' 1 1
D40”: 0’“ ' 1 2-2 E1 1
E 35 " WRR 1 1 1
"’ 30 . l I
25 R2=0.107 , 1 NWR 1
20 1 . M2825 1
151 + + l 1
0 100 200 300 ;
Nitrate, kglha

75

In 2004, in WRSR and WRR treatments with and without manure, clover did not
affect chlorophyll content in corn leaves on 8 July and 15 July. On 26 July, corn leaves,
in WRSR treatments with clover and either with or without manure, had signiﬁcantly
higher amounts of chlorophyll than corn leaves in WRSR treatments without clover and
with or without manure. This could be explained by either the effect of added N fertilizer
and/or N supplying effect of the clover.

In WRSR and WRR treatments with and without clover, manure did not have an
effect on chlorophyll content in corn leaves at all studied dates. But, in NWR treatments,
manure decreased chlorophyll content of corn leaves in all studied dates. This was likely
a result of lower soil temperature and lower rate of mineralization of soil and manure N
in the wet and cold growing season of 2004.

In 2005, clover and manure did not affect chlorophyll content in corn leaves on 21
June. On the 28 June and 5 July chlorophyll sampling dates, manure had a signiﬁcant
positive effect on corn chlorophyll levels. This may be attributable to the cold May of

2005 resulting in the PSNT underestimating the N contribution from the manure.

76

Effect of treatments on corn grain moisture and test weight

In all years, WRSR treatments had signiﬁcantly higher corn grain moisture at
harvest than NWR treatments (Table 2.5). This is likely due to delayed emergence of
corn observed in 2003 and 2005 and delayed time of tasseling of corn observed in all
three studied years.

In 2003, in WRR treatments without manure, clover signiﬁcantly increased corn
grain moisture. In the rest of the treatments, clover did not have an effect on corn grain
moisture. Also, manure did not affect grain moisture of corn in all the treatments.
Residue signiﬁcantly affected corn grain moisture. NWR treatments without manure had
signiﬁcantly lower corn grain moisture than WRSR and WRR treatments without clover
and manure.

In 2004, clover and manure did not have any effect on corn grain moisture.
Residue was the only factor that increased corn grain moisture. WRSR treatments with
and without clover and manure had signiﬁcantly higher corn grain moisture than NWR
and WRR treatments with and without clover and manure. NWR and WRR treatments
were not different.

In 2005, clover signiﬁcantly increased corn grain moisture in WRSR and WRR
treatments with and without manure. Also, manure signiﬁcantly increased corn grain

moisture in the all treatments.

77

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78

Wheat residue also increased corn grain moisture. WRSR treatments without
clover and manure had signiﬁcantly higher corn grain moisture than NWR and WRR
treatments without clover and manure. NWR and WRR treatments were not different
from each other.

In 2003 and 2005, WRSR treatments had signiﬁcantly lower corn test weight at
harvest than NWR treatments (Table 2.5). This is likely due to delayed emergence of
com (2003 and 2005), delayed time of tasseling of corn, and lower amount of soil plant
available N that is result of microbial immobilization of N. In 2004, there were no
differences between treatments which is likely due to the late planting date of corn and
relatively quicker and more consistent emergence patterns.

In 2003, in WRSR treatments with manure and WRR treatments without manure,
clover signiﬁcantly reduced corn test weight. Manure did not have effect on corn test
weight. Residue signiﬁcantly decreased test weight of corn. WRSR treatments without
clover and manure had signiﬁcantly lower corn test weight than NWR and WRR
treatments without clover and manure that were not different between each other.

In 2005, in WRSR and WRR treatments with and without manure, clover
signiﬁcantly reduced corn test weight. Also, in all treatments, manure signiﬁcantly
reduced corn test weight. Residue also decreased corn test weight. WRSR, WRR, and
NWR treatments without clover and manure were signiﬁcantly different from each other.

And, in WRSR treatments corn had the lowest test weight.

79

Effect of treatments on corn yields

The treatments can be viewed as four management practices. The ﬁrst practice
consists of N management strategy only with nitrogen application according to PSNT
results (Figure 2.9). This management system includes NWR, WRR, and WRSR
treatments. PSNT management of the two wheat residue treatments (WRR and WRSR)
was effective in two of the three years, 2003 and 2004. But, in 2005, the PSNT
management practice was not effective and both WRR and WRSR had lower yields than
the NWR treatment.

The second practice consists of N management strategy with nitrogen application
according to the PSNT results and clover as a cover crop (Figure 2.10). This management
system consists of WRR and Clover and WRSR and Clover treatments. Similar to the
ﬁrst system, the second system was effective in 2003 and 2004. But in 2005 both WRR
and Clover and WRSR and Clover treatments had lower yields than NWR.

The third practice consists of N management strategy with nitrogen application
according to the PSNT results and manure application (Figure 2.11.). This management
system consists of NWR and Manure, WRR and Manure, and WRSR and Manure
treatments. This system was effective in all three studied years. In all three years, the
yield of WRR and Manure was not signiﬁcantly lower than the yields of NWR
treatments. Also, in all three years, the yields of WRSR and Manure treatments were
similar to the yields of NWR treatments.

The fourth practice conSists of N management strategy with nitrogen application
according to the PSNT results, clover as a cover crop, and manure application (Figure

2.12.). This practice includes WRR Clover and Manure and WRSR Clover and Manure

80

treatments. This system was effective in 2003 and 2004 years, with yields of both WRR
Clover and Manure and WRSR Clover and Manure treatments being not lower than the
yields of NWR and NWR and Manure treatments. However, the system was not effective
in 2005. Yields, in both WRR Clover and Manure and WRSR Clover and Manure
treatments, were signiﬁcantly lower than the yields of NWR and NWR and Manure
treatments.

One of the possible reasons that in 2005 the systems were not effective could be
much lower corn populations as compared to 2003. In WRR and Clover, WRSR and
Clover, and WRR Clover and Manure treatments the corn population in 2005 was more

than 20% lower than the population in the control treatment.

Table 2.6. Decrease in corn population (%) compared to NWR (control)

 

Treatment 2003 2005 Strategy
WRR 2 4 PSNT

WRSR 8 12

WRR and Manure 6 l4 PSNT+ Manure
WRSR and Manure 9 16

WRR and Clover 3

21 PSNT + Clover
WRSR and Clover 12 22 1
WRR Clover and Manure 7 27 PSNT + Clover + Manure

 

81

Figure 2.9. Management practice: PSNT.

WRR System

     

 

1

g 12 1 ns ns a b 1nWRR1 1

5'” 1o " T ' 1

3 8‘ 1

E 61 1
>' 41

C

- 21 1 1

5 o- 1

2003 2004 1

Year 1

++++ 1

WRSRSystem 1.NWR 1 1

12 ns ns a b EWBSB‘ 1

‘ 2; 1o 1 1

E 8‘ 1

E 6‘ 1

3": 41 1

.5 2, 1

1

5 0.1 .1 1- , 1 1

2003 2004 2005 1

Year 1

82

Figure 2.10. Management practice: PSNT and clover cover crop.

G rain Yield (Mglh

Grain Yield (Mg/ha)
O N A O)

12

12

ONAO)

ns

 

2003

ns

2003

WRR System

2004

Year

2005

WRSR System

0Year

83

2005

1" T
lWRRand Clover

.,,, 1, W

I WRSR and Clover ‘

Figure 2.11. Management practice: PSNT and manure.

11
1
1
1
1
1

WRRSystom [NWR

e ab a b b b a b a b 1°m‘“‘"“""'°1
E 15 ' 1DWRRand Manure 11

1 1
5 1° 1
E 5 1
0 2003 2005

Year
WRSRSystem 1.1m ’
10 MR and Manure
i? 12 "S b a b 1DVYRSRand Manure
g 10 1 + + 1
5 3'
E 6‘
s‘-.’ 4 1
.E 2~
2 1
o o. 1
2003 2005
0Y04ear

84

 

Figure 2.12. Management practice: PSNT, manure, and clover.

 

 

 

 

 

, WRR System
:5; '12 ns b b a
g to
U 8 Iﬂ ia—1:1
E 6
>' 4
§ 2
5 o ,
2003 2004 2005
WRSR System
31: ns ns b a c
5 10
U!
E, 3
g a
; .1
E 2
<3 0 1 . 7
2003 2004 2005
Year
1INWR 1
1 l3 NWR and Manure 1
1 u WRSRCIover and Manure 1

85

N management practices effect corn growth and development

Effect of clover and manure on corn date of emergence

In 2003, residue was the only factor that signiﬁcantly affected corn emergence,
with delayed corn emergence observed in wheat residue treatments (Table 2.6). All
WRSR treatments were signiﬁcantly different in corn emergence compared with NWR
and WRR treatments regardless of their manure and clover levels. The negative effect of
wheat residue on corn emergence can be related to the relatively early planting of com
(30 April) in 2003. As we discussed earlier, soil temperature in WRSR treatments was
lower compared to NWR and WRR treatments, thus being a reason for the delayed corn
emergence.

In 2004, because of the very wet and cool spring, corn was planted relatively late
(29 May). Higher soil temperatures observed in late May and early June promoted
germination of corn, thus potentially being the reason for the same corn emergence time
in all treatments in this year.

In 2005, the presence of wheat residue, clover and manure delayed emergence of
corn. In all WRSR treatments, NWR treatments with manure, and WRR treatments with
clover and manure corn emerged signiﬁcantly later compared to NWR treatments without
manure. In WRSR and WRR treatments with and without manure, clover signiﬁcantly
delayed corn emergence that is likely due to a heavier clover stand in 2005. Heavy clover

residue after herbicide bumdown insulated soil and prevented it from warming up.

86

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In NWR treatments, WRSR and WRR treatments with and without clover, manure
delayed corn emergence compared to NWR treatments without manure. As with the
heavy clover residue, the layer of manure acted as an insulator in the early spring season
delaying the warm up of the soil. Only, in WRR treatments with clover, manure did not
affect corn emergence. Negative inﬂuence of manure and clover can be related to spring
manure application and high percent of clover standing which, as we stated above,

reduced soil temperature.

Effect of clover and manure on corn plant stands and date of tasseling

Generally, in 2003 and 2005, NWR had higher corn plant stands than WRR and
WRSR treatments regardless of their manure and clover levels (Table 2.6). In contrast, in
2004, the lowest population of corn had NWR treatments without manure.

In 2003 and 2004, in all treatments, manure and clover did not affect corn
population. The exception is 2004 when WRR treatments with clover and manure had
higher com population than treatments without manure. In 2005, clover and manure
affected the population of corn. In WRSR and WRR treatments with and without manure,
clover signiﬁcantly reduced corn population. Manure signiﬁcantly reduced corn
population in WRR without clover and WRSR with clover treatments. The corn plant
population trends resemble those observed with corn date of emergence.

In 2003, tasselling of corn was signiﬁcantly delayed in WRSR treatments as
compared with NWR treatments, but not signiﬁcantly different from WRR treatments,
regardless of their manure and clover levels (Table 2.6). In 2004, all WRSR treatments

were signiﬁcantly different as compared with the rest of the treatments. In 2005, in

88

WRSR treatments, NWR and WRR treatments with clover and manure, VT stage of corn
was signiﬁcantly later as compared to NWR treatments with clover and manure.

In 2003, in all treatments, manure and clover did not affect VT stages of corn. In
2004, in WRSR treatments with manure and clover corn had later VT stage. In NWR
treatments without clover, presence of manure signiﬁcantly delayed VT stage of corn. In
2005, in WRSR and WRR treatments with and without manure, presence of clover
signiﬁcantly delayed VT stage of corn. The delay in reaching VT stages of corn may be
attributable to the heavy levels of clover residue in 2005 which delayed soil warm up.
Also, in WRSR, NWR, and WRR treatments without clover, manure signiﬁcantly

delayed VT stage of corn as compared to treatments without manure.

Effect of clover and manure on height of corn
In 2003, corn plants in WRSR treatments and WRR treatments with and without
clover and manure were signiﬁcantly shorter compared with corn plants in NWR

treatments (Figure 2.13).

89

Figure 2.13. Height of com in 2003 treatments.

  
  

1 2.11

7/9 7/13 7/17 7121
Date

Figure 2.14. Height of corn in 2004 treatments.

Helght, m

90

2.3. ; a ,,;,,7:5, W W,

T _._‘ m TWR’R'

+ WRR and
Clover
+ WRR Clover
and Manure
+ WRR and
Manure
—a— NWR

—-.-- NWRand
Manure
—+—WRSR

—-a-—WRSRand
Clover
—-¢-—WRSRC|o1er1

andManure
--+~-WRSRand

 

 

 

Manure

 

_._.W WEE

+WRR and
C|over
+WRR Clowr
and Manure
—x—WRR and
Manure
—-a— NWR

—o-— NWR and
Manure
--+— - - WRSR

---a---WRSR and
Clover

-'t-- WRSR Clover
and Manure

—-o—- WRSR and
Manure

 

In 2004 and 2005, corn height was signiﬁcantly lower in WRSR treatments with
and without clover and manure than in the other treatments, especially in early stages of
corn development (Figures 2.14 and 2.15).

We concluded that, in 2003, manure and clover did not affect height of corn in the
all studied treatments that can be related to poor clover stands and fall manure application
that barely affected soil temperatures, especially in WRSR and NWR treatments (Table
2.2).

In 2004, in WRSR treatments without manure, clover did not affect height of corn
in all studied dates. In WRR treatments without manure, clover signiﬁcantly reduced
height of corn in the early stage of corn development (20 July and 28 July). It can be
related to lower soil temperature that was decreased by clover residue that probably
affected soil and manure net N mineralization (Table 2.2). In WRR treatments with
manure, clover signiﬁcantly decreased height of corn on 20 July. On the rest of the dates,
there were no clover effects. Also, manure affected height of corn. In NWR treatments,
manure signiﬁcantly decreased height of corn on the early dates (20 July and 28 July)
that that can be explained by lower soil temperature in the early growing season that
probably affected soil and manure net N mineralization. In WRSR treatments with and
without clover manure did not affect height of corn in all dates.

In 2005, in WRSR treatments with and without manure, clover signiﬁcantly
decreased height of corn only in the early measured date (20 June). In the rest of the dates
there were no effects of clover. In WRR treatments with and without manure, clover
signiﬁcantly decreased height of corn in all dates that is likely due to lower soil

temperature that was decreased by clover in the early growing season (Table 2.2).

91

Manure decreased corn height in WRSR and WRR treatments with and without clover in

the early sampling date (20 June).

Figure 2.15. Height of corn in 2005 treatments.

1 1.71-- 3* “:2,
w
1 1.5 1

1.3 1 I /

 

 

 

1 Date

92

 

1+NWRand 11
11—4—WRSR 1
1 —a———WRSR aid
1.

-. ---a-~WRSRClover

 

_._" “with“ "“1

+WRR and
Clear
+WRR Clover
and Manure
—x——WRR and
Mantle
—a—— NWR

 

Manure 1

Claw

and Manure
- -o - -WRSR and
Manure

W __.__-._W11

 

CONCLUSION

Despite decreased soil temperature, later corn emergence, reduced corn
populations, delayed VT stage, decreased leaf chlorophyll content and plant height in the
early stages of corn development a PSNT nitrogen strategy was effective in maintaining
corn grain yields in wheat residue systems equivalent to yields in no-wheat residue
systems in 4 of 6 site years. Similar results were obtained for PSNT plus clover cover
crop and PSNT plus manure plus clover cover crop N management systems. Using PSNT
and manure system equalized high wheat residue corn yields to no-wheat residue in 6 of

6 site years.

Table 2.8. Summary of nitrogen management strategies effectiveness in overcoming

wheat residue antagonism on corn grain yield.

Nieoge‘n Management Strategy '

Success Rate (%)
Residue PSNT PSNT + PSNT + PSNT +Clover + Manure
System Clover Manure
WRR 66 66 100 66
WRSR ' 66 66 100 ’ 66

93

 

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99

APPENDIX

Table A 1. 2003 mean volumetric soil moisture values (%) ................................. 101
Table A 2. 2004 mean volumetric soil moisture values (%) ................................. 102
Table A 3. 2005 mean volumetric soil moisture values (%) ................................. 102
Table A 4. Summary of clover and manure effect on soil moisture ........................ 103
Table A5. 2003 means of soil temperature (0 C) in treatments .............................. 104
Table A6. 2004 means of soil temperature (° C) in treatments .............................. 105
Table A.7. 2005 means of soil temperature (0 C) in treatments .............................. 106

Table A 8. Effect of treatments on height of corn (m) during 2003-2005 growing
seasons .............................................................................................. 107

Table A 9. Effect of the treatments on the amount of chlorophyll in corn leaves observed
during 2004 and 2005 growing seasons ......................................................... 108

100

 

 

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Table A 2. 2004 mean volumetric soil moisture values (%).

 

 

 

Treatment Date
16-Apr 22-Apr 29-Apr 6- May 13-May 27-May 6-June
WRR 18.3 bci' 17.9 bc 16.4 be 20.5 a 26.1 a 30.1 a 20.8 a

WRR and Clover 16.8 a 16.4 a 13.8 a 21.2 ab 26.4 a 30.7 ab 24.9 c
WRR Clover and 19.3 ed 19.0 cd 15.4 ab 22.7 bc 27.5 abcd 31.4 ab 24.9 c
Manure

WRR and Manure 20.1 de 19.7 d 19.4 de 24.3 cde 26.7 abc 31.4 ab 23.9 be
NWR 17.6 ab 17.4 ab 16.6 be 20.5 a 25.8 a 30.4 a 21.7 a
NWR and Manure 21.0 e 20.3 d 20.6 e 24.2 cde 28.3b cde 32.3 b 25.6 c
WRSR 19.9 de 19.5 d 18.8 de 24.7 de 29.4 e 30.5 a 25.5 c
WRSR and Clover 18.2 be 17.6 be 17.6 cd 22.8 bcd 26.5 ab 30.7 a 24.2 bc
WRSR Clover and 20.3 de 19.9 d 19.5 e 23.7 cde 27.0 abcd 30.8 ab 25.4 c
'Manure

WRSR and Manure 20.7 e 20.3 d 19.6 e 24.8 e 28.5 cde 31.0 ab 25.6 c

 

T-Means within each column followed by the same letter are not signiﬁcantly different (Fisher

protected LSD, P<0.05)

Table A 3. 2005 mean volumetric soil moisture values (%).

 

 

Treatment l8-Apr 29'API' 5 -May 10-May 18-May 26-May

WRR 18.9 aT 18.2 a 16.0 a 15.6 a 19.5 c 18.7 b
WRR and Clover 19.3 a 18.3 a 15.8 a 15.3 a 17.5 b 15.5 a

mm“ and 22.3 be 21.4 bcd 18.9 be 18.3 be 22.0 fg 20.3 c

WRR and Manure 21.6 b 20.7 b 18.4 b 17.7 b 24.3 i 24.0 ef

NWR 18.6 a 17.5 a 15.2 a 14.9 a 16.2 a 17.9 b

E“ and 22.4bcd 20.9bc 18.9bc 17.9b 21.1 def 21.8d
allure

WRSR 22.6bcd 21.8bcd 19.1bc 18.1 b 20.5 cde 21.4cd

WRSR and 22.8 bcd 21.5 bed 18.7 be 18.0 b 21.5 ef 22.8 def

Clover

W RSR 00"“ 24.2 cd 22.9 cd 20.5 be 19.3 be 24.71 24.7 f

and Manure

3R” and 24.4 d 23.6 d 21.0 c 20.3 c 23.0 h 24.0 ef
allure

 

T-Means within each column followed by the same letter are not signiﬁcantly different (Fisher

protected LSD, P<0.05)

102

Table A 4. Summary of clover and manure effect on soil moisture.

 

 

 

 

 

Treatment 2003 2004 2005

Effect of clover

WRSR without manure 8 from 9 no effect 4 from 7 decreased 6 from 6 no effect
WRSR with manure 8 from 9 no effect 7 from 7 no effect 5 from 6 no effect
WRR without manure 9 from 9 no effect 4 from 7 no effect 4 ﬁ‘om 6 no effect
WRR with manure 6 ﬁ'om 9 no effect 6 from 7 no effect 4 from 6 no effect
Effect of manure

WRSR without clover 8 from 9 no effect 7 from 7 no effect 3 from 6 no effect
WRSR with clover 9 ﬁom 9 no effect 4 from 7 no effect 5 from 6 no effect
NWR 7ﬁ’om9noeffect 6from7increased 6ﬁ'om6increased
WRR without clover 4 from 9 increased 5 ﬁ'om 7 increased 6 ﬁom 6 increased
WRR with clover 8 ﬁom 9 no effect 5 from 7 decreased 3 from 6 increased

 

103

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