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EFFECTS OF GYPSUM, COMPOST AND COVER CROPS
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EFFECTS OF GYPSUM, COMPOST AND COVER CROPS ON SOIL NUTRIENT
AVAILABILITY, CORN YIELD AND QUALITY AND SOIL QUALITY

By

Marcia LaCorbiniere-JnBaptiste

A DISSERTATION
Submitted to
Michigan State University
in partial fulﬁllment of the requirements
for the degree of
DOCTOR OF PHILSOPHY

Crop and Soil Sciences

2009

ABSTRACT

EFFECTS OF GYPSUM, COMPOST AND COVER CROPS ON SOIL NUTRIENT
AVAILABILIY, CRON YIELD AND QUALITY AND SOIL QUALITY

By
Marcia LaCorbiniere-Jn-Baptiste

The recent and growing interest in the use of gypsum (CaSO4- 2HzO) by
Michigan farmers, and the lack of documentation on the effect of gypsum on Michigan
soils, warrant investigation on its effect on various soil and plant growth parameters.

This study investigated the effects of gypsum and its interaction with compost and cover
crops on soil nutrient availability, yield and quality of sweet corn (Zea mays var. rugosa),
and soil quality. The objective was to study the effects of gypsum alone, or combined
with compost and cover crops on 1) extractable Ca and Mg, 2) sweet corn growth, yield
and quality, and 3) soil quality. The treatment design involved three factors: gypsum
application at 0 and 2.24 Mg ha", poultry compost at O and 2.7 Mg ha", and four cover
crops, plus a no cover treatment. The four cover crops were oilseed radish (Raphanus
sativus), oriental mustard (Brassicajuncea L), red clover (T rifolium pratense), and cereal
rye (Secale cereale), or wheat (T riticum aestivum) and no cover. Corn was sown in the
spring of each year and cover crops were sown in the spring of 2005 and both spring and
fall of 2006. An early cover crop treatment was planted in early spring and a late cover
treatment planted after sweet corn was harvested in the fall of 2006. The statistical model
included the three factors and all interactions among them as fixed effects and replication
as a random effect. Gypsum had minimal (positive) effect on extractable Ca in spring of
2007 but had a negative effect on extractable Mg in 2006 and 2007 (both spring and fall).

Compost application increased Ca by up to 44% and resulted in signiﬁcant transfer of

extractable Mg to lower depths. Our results suggest that sweet corn has a higher demand
for both Ca and Mg than the cover crops studied and that sweet corn requirement of Ca
may be genetically/variety dependent. Cover crops may have potential to increase
availability of both Ca and Mg ((1 = 0.05) to soil. Gypsum application decreased both
corn plant biomass at the V8 (8-leaf stage) growth stage and corn yield; had no effect on
number of corn ears, and no combined treatment effect on number of corn ears per
hectare. Cover crops affected the number of sweet corn ears only in 2006 (a = 0.05).
Both cover crops and compost had a positive effect on sweet corn growth, yield and
quality. Gypsum had no effect on the quality components investigated. Compost
application significantly enhanced aggregate stability and reduced bulk density over the
three years of study. This increase corresponded with the active organic matter (AOM)
test which showed a fair rating of soil quality compared to the non compost treatment.
Generally there was no effect (a = 0.05) of cover crops on the soil quality components
studied. Mustard negatively inﬂuenced water stable aggregate (W SA), bulk density and
nematode population. This study may have economic implications to Michigan and other

farmers.

DEDICATION

This work is dedicated ﬁrst to my husband for his unwavering support and love and for
his dedication to the completion of my studies and research; my two sons- Ishmerai and

Hasadiah for their patience, understanding and love.

Also, to the memories of my parents, Leonard and Flavienne LaCorbiniere and the

memories of my four siblings, Peter, Nicholson, Gregory and Veronica.

ACKNOWLEDGEMENT

For granting me the opportunity to work on this wonderful research project; for
his guidance, his generous accommodation and patience, and for the funding
opportunities towards my research and other career enhancement activities, I would like
to extend special thanks and appreciation to Dr. Darryl Warncke. For the willingness to
serve on my graduate committee, provide assistance with my proposal, take time to edit
my dissertation and make critical recommendations, I would like to thank Drs. Sieglinde
Snapp, Mathieu Ngouajio and Brian Teppen. Many thanks and appreciation to the Crop
and Soil Sciences Department, the Ofﬁce of Diversity and Pluralism, C SS Mott
Foundation and the Graduate College for the various funding opportunities. Special
thanks to Dr. Lee Jacob for accommodating my Future Academic Scholar Training
(FAST) project, and to Dr. Smucker for his guidance and advice throughout my stay at
MSU. Thanks for the help and support of the many friends I made here at MSU. Finally,
my family both here and abroad who constantly extended their support and their love,

Thank you.

TABLE OF CONTENTS

CHAPTER 1: LITERATURE REVIEW ........................................................ 1
Soilamendinents 3
Gypsum as a soil amendment ............................................................... 3
Compostasasoil amendment... 6

Covercropsassoilamendments8

CHAPTER 2: EFFECTS OF GYPSUM ALONE OR COMBINED WITH

COMPOST AND COVER CROPS ON CALCIUM AND MAGNESIUM-
AVAILABILITY ............................................................................................................. 18
INTRODUCTION .. A 19
SITE DESCRIPTION AND EXPERDVIENTALDESIGN 23
Soil Measurements .25
STATISTICAL ANALYSIS” 26
RESULTSANDDISCUSSION 26
Residual effects on CaandMg from prior treatments 26
Treatment effects on exchangeable Ca... 28
Treatment effecton exchangeable Mg32
SUMMARY AND CONCLUSION37

CHAPTER 3: EFFECTS OF GYPSUM ALONE OR COMBINED WITH
COMPOST AND COVER CROPS ON CORN YIELD AND QUALITY.... ......... 64
MATERIALS AND METHODS 68
Sweet Corn Measurements68
Nutrientanalysis... .. 68
RESULTSANDDISCUSSION ... 69
Treatment Effects on Sweet Corn Growth and Development .......................... 69
Treatment Effects on Sweet Corn Yield .................................................. 78
Treatment Effects on Sweet Com Quality ................................................ 80
SUMMARY AND CONCLUSIONS85

vi

CHAPTER 4: EFFECTS OF GYPSUM ALONE OR CONIBINED WITH

COMPOST AND COVER CROPS ON SOIL QUALITY ...........................

ABSTRACT.
INTRODUCTION

Organic Matter .
Soil Aggregation and Aggregate Stability
Bulk Density... .
Microbial Biomass and Nematode Population

MATERIALS AND METHODS ......................... -

Soil Measurements...
Soil Organic Matter: A Simple Soil Quality Test
Bulk Density and Aggregate Stability
Microbial Biomass” .. . ... ..
Nematode Population ..
RESULTS AND DISCUSSION

Active organic matter. .

Treatment Effects on Bulk Density

Treatment Effects on WSA“

Treatment Effects on Microbial Biomass Carbon and Nematode

Population. ..
SUMMARY AND CONCLUSIONS
REFERENCES... .
GENERAL CONCLUSIONS AND RECOMMENDATIONS

vii

..... 114

1.14

W.......115
......117
........118
........119
.....120
....122
.....123
......123
.....124
.....126
.....128
....128
..128
......129
...131

.....132
.....134

.....155
...159

LIST OF TABLES

CHAPTER 2: EFFECTS OF GYPSUM ALONE OR COMBINED WITH
COMPOST AND COVER CROPS ON CALCIUM AND MAGNESIUM

AVAILABILITY
Table 2.1. Planting schedule for cover crops and sweet corn (2005-2007) ............. 39
Table 2.2. Nutrient composition ofpoultry compost... .....40
Table 2.3. Statistical signiﬁcance of gypsmn, compost, depth and cover crops, and
corn effects on soil extractable Ca and Mg For 2005 soil sampling ........ 41
Table 2.4. Effects from gypsum, compost depth and cover crops and corn on mean
soil extractable Ca and Mg in the top 20 cm for 2005 soil sampling... ...4]
Table 2.5. Effects form compost by previous crop effects on extractable soil Mg.
Table 2.6. Effects from compost plus depth interaction effects on mean extractable
Ca and Mg for spring 2005 ....................................................... 43
Table 2.7. Effects from treatment interactions on mean extractable Ca, and Mg in
Fall 2005 ........44
Table 2.8. Statistical signiﬁcance of gypsum, compost, depth, corn and cover
crops effects on extractable Ca and Mg... ...45
Table 2.9. Effects from gypsum, compost, depth and cover crops on mean
extractable Ca and Mg in the top 20 cm in 2005 .............................. 46
Table 2.10. Effects from gypsum plus depth and compost ”plus depth on extractable
Ca,andMgfor2006... . . 47
Table 2.11. Statistical signiﬁcance of gypsum, compost, depth, com and cover crops
on extractable Ca and Mg for 2007 ............................................. 48
Table 2.12. Effects from gypsum, compost, depth and cover crops on mean
extractable Ca and Mg (2007)... ...49
Table 2.13. Effects from treatment interactions on extractable Ca, and Mg (2007.. . .50
Table 2.14. Effects from compost and cover crops on mean extractable soil Ca for

viii

Table 3.1.

Table 3.2.

Table 3.3.

Table 3.4.

Table 3.5a.

Table 3.6b.

Table 3.6.

Table 3.7.

Table 3.8.

Table 3.9.

Table 3.10.

Table 3.11a.

Table 3.11b.

Table 3.12.

Table 13a.
Table 13b.

Statistical signiﬁcance of gypsum, compost and cover crops for CMRs in
2006 and 200786

Effects of gypsum, compost and cover crops on corn density, height,
biomass and CMRS (V8) for 2006 and 2007 .................................. 87

Statistical signiﬁcance of gypsum, compost and cover crops, on plant
height, biomass and corn ears .................................................... 88

Effect of combined interactions of compost and cover crops on plant
He1ght89

Statistical signiﬁcance of gypsum compost and cover crops on nutrient
concentration of plant biomass (V8 stage) ...................................... 90

Statistical signiﬁcance of gypsum compost and cover crops on nutrient
concentration ofplant biomass (V8 stage) .....91

Means of plant (V 8) nutrient concentration as affected by the various
treatment factors92

Effects of gypsum, compost, cover crop interaction on N and Mg
concentration on plant biomass at the V8 stage ............................... 93

Statistical signiﬁcance of gypsum, compost and cover crops, on number
and weights ofsweet corn ears for 2006 and 2007... ...94

Effect of gypsum, compost and cover crops on yield and quality .......... 95

Signiﬁcance of gypsum, compost and cover crops on sweet corn ear
lengths, weights anddlameter96

Statistical signiﬁcance of gypsum compost and cover crops on nutrient
concentrationofcom cars. 97

Statistical signiﬁcance of gypsum compost and cover crops on nutrient
concentrationofcom ears98

Means of nutrient concentration of corn ears as affected by gypsum,
compost and cover crops .......................................................... 99

Effects of treatment interaction on N concentration in com ears ......... 100
Effects of treatment interaction on Ca, N and K concentration in corn

earSIOI

Table 4.1.

Table 4.2.

Table 4.3a.
Table 4.3a.

Table 4.4.

Table 4.5.
Table 4.6.

Table 4.7.

Table 4.8.

Table 4.9.

Table 4.10.

Table 4.1 1.

Table 4.12.

Table 4.12.

Statistical signiﬁcance of gypsum and compost active soil organic

matter for fall 2007134
Effects of gypsum and compost on active soil organic matter ............. 134
Soil quality ﬁeld chartl37
Soil quality active organic matter (AOM) and available N color
Signiﬁcant effect of gypsum, compost and cover crops on mean bulk
Effect of gypsum, compost and cover crops on mean bulk density ....... 139

Statistical signiﬁcance of gypsum, compost, depth and cover crops on soil
WSA determined by the rain simulator method (2005-2007) ............. 140

Effects ﬁ'om gypsum, compost, depth and cover crops effects on
mean WSA determined by the rain simulator method (2005-2007) ...... I41

Statistical signiﬁcance of gypsum, compost, depth, cover crops, and corn
on soil Microbial biomass (MB) for fall 2006... 142

Statistical signiﬁcance of gypsum, compost, depth, cover crops, and com
on soil Microbial biomass (MB) for fall 2007... 143

Effects from gypsum, compost, depth, over crops and corn on
microbial biomass (fall 2006)]44

Effects from interactions of corn and mustard plus depths on
microbial biomass; fall 2006144

Statistical signiﬁcance of gypsum, compost, depth, corn and cover crops
effects on nematode population... 145

Effects of gypsum, compost and cover crops nematode community
(measured on a lOOcm3 soil basis) ............................................. 142

LIST OF FIGURES

CHAPTER 2: EFFECTS OF GYPSUM ALONE OR COMBINED WITH
COMPOST AND COVER CROPS ON CALCIUM AND MAGNESIUM

AVAILABILITY
Figure 2.1. Representation of a typical block of the experiment design ................. 52
Figure 2.2. Effects of cover crops and corn on extractable Ca ............................ 53
Figure 2.3. Effects of cover crops and corn on extractable Mg ............................ 55
Figure 2.4. Effects of compost and gypsum on extractable Ca ............................ 57
Figure 2.5. Effects of compost and gypsum on extractable Mg ........................... 58
Figure 2.6. Effects ofdepths on extractable Ca...... ......56
Figure 2.7. Effects of depths on extractable Mg ............................................. 56
Figure 3.1. Representation of a typical block of the experiment design... 102
Figure 3.2. Effects of cover crops on plant height ......................................... 103
Figure 3.3. Effects of compost and gypsum on plant height ............................. 104
Figure 3.4. Corn growth and development as affected by compost application. . . 105
Figure 3.5. Effects of cover crops on whole corn plant biomass at the V8 Stage ..... 102
Figure 3.6. Effects of compost and gypsum on whole corn plant biomass at the

V8 Stage (2006 and 2007)... 107
Figure 3.7. Effects of cover crops on corn yield, presented in number of corn ears..106
Figure 4.1. Representation of a typical block of the experiment design... 147
Figure4.2. Rain simulator... ...148
Figure 4.3. Effects of compost on bulk density .............................................. 149
Figure 4.4. Effects of cover crops on bulk density ......................................... 150
Figure 4.5. Effects of compost on water stable aggregates (W SA) ..................... 151
Figure 4.6. Effects of corn and cover crops on water stable aggregates (WSA). . . I 52
Figure 4.7. Microbial biomass and nematode population with reference to soil

xi

CHAPTER 1

LITERATURE REVIEW

INTRODUCTION

One of the major issues dominating the global agenda for the agriculture sector
over the past three decades is the need for sustainable production (management) systems
(Bird, 2003). Prior to the dawn of agriculture, the hunter—gatherer lifestyle supported
approximately 4 million people globally; modern agriculture now feeds over six billion
people (Tilman et al., 2002). Yearly, global food crops have increased consistently
throughout the 19th and 20th century, though at a more rapid rate during the latter
(Krishna, 2002). Agricultural practices determine the level of food production and, to a
great extent, the state of the global environment (Tilman et al., 2002) and consequently
human health and wellbeing. Sustainability is a multifaceted concept, which ensures that
management and use of natural resources does not diminish their capacities to meet
economic, environmental, social and aesthetic needs and presents opportunities of present
and future generations (Dalal et al., 2003). Agricultural sustainability therefore,
envelopes environmental soundness, economic viability, social responsibility, service for
the present and future generations, with emphasis on the welfare of all species of the
biosphere (Allen et al., 1991). This sustainable view of agriculture presents a mandate
for researches to reevaluate the agricultural practices which have adversely impacted the
environment, and to adopt new management methods that will lessen potential risk to the

environment and human health. Therefore, sustainable agricultural will be manifested

only when farming practices seek to manage soils with an agro-ecological approach,
since the most important link between agricultural productivity and agricultural

sustainability is the health or quality of the soil (Gregorich, I995, Cochrane, 2003). .

The concept of soil quality is not a new topic, having been used as early as the
19505, especially by pedologists. Soil quality refers to a 5011’s capacity to perform
speciﬁc functions. The term SQ envelopes both a soil’s productive and environmental
capabilities (Wander, et, al, 2002). Concerns with soil degradation worldwide, and the
growing need for sustainable soil management in agro-ecosystems has renewed scientiﬁc
attention to characterize soil quality (Carter, 2001; Sénchez-Maraﬁén etal., 2002).
Additionally, intensiﬁed crop production to meet world food demands, and the pressure
on nonrenewable resources, have imposed a mandate for sustainable agriculture which
has become a global agenda, as it offers long term focus for soil quality goals (Ditzler, et
al., 2002; Sénchez-Maraﬁon et al., 2002). In 1993, in an effort to assist with the
conservation of natural resources and the environment, the United States Department of
Agriculture (USDA), through. the Natural Resources Conservation Service (N RCS)
identiﬁed soil quality as an emphasis area, and established the Soil Quality Institute
(SQI). The primary mission of the SQI is to develop and dissemination soil quality
information and technology in cooperation with various partners (Ditzler, et al., 2002). A
reduction in soil quality as a consequence of human activities can be deﬁned as soil
degradation (Cassman, 1999). Soil quality can be enhanced by the use of various soil

amendments in crop production systems.

Soil Amendments

Soil amendments are added to improve soil status and can be either fertilizers,
added for their nutrient values, or conditioners used for their beneﬁcial impact on the
biological, chemical and physical status of the soil, but have limited amount of nutrients.
Soil amendments can be naturally occurring or synthetic, and either organic or inorganic.
Since the 19508 soil conditioners have been used extensively in agriculture (Li et al.,
2000). Soil amendments for the purpose of making nutrients available to crops and
improving soil quality must be carefully examined. The misuse of soil amendments can
result in adverse impacts on both crops and soils with consequences to environment and
human health (Brown et al., 2004). Organic amendments include but are not limited to
crop residues, green manures, and cover crops, food processing by-products, biosolids,
sawdust and wood ash. Inorganic amendments include vermiculite, perlite, lime,
gypsum, manures and compost. The most common form of soil amendment is granular
inorganic fertilizer, NPK. Among those mentioned, gypsum, compost and cover crops

are of interest here, and will be discussed further.

Gypsum as a soil amendment

Gypsum (CaSO4—2HZO) is a natural mineral and a source of readily available
calcium (Ca) and sulphur (S) amendment that is sufﬁciently soluble to move rapidly into
the soil when surface applied. Large quantities of gypsum are also produced by various
processes. For example, phosphogypsum is the main byproduct of phosphoric acid

production resulting from the mixing of phosphate rock with sulfuric acid (Soratto and

Crusciol, 2008; El-Mrabet et al., 2003; Hao et al., 2003; Zvomuya at al., 2005). Another

type of gypsum, FGD (ﬂue gas desulfurization), is a byproduct of the process which

removes sulfur (502) from the flue gas in coal-ﬁred power plants for sulfur emissions

reduction when coal is burned for energy (EPA, 2008; Chen et al., 2008; Punshon et al.,
2001). FGD, commonly referred to as by-product gypsum contains less impurities than
other commercially produced gypsum (EPA, 2008; Chen et al., 2008), and is of the
identical chemical structure as mined gypsum (EPA, 2008). Gypsum (calcium sulfate
dehydrate) contains 23- 32% Ca, 16—1 8 % S and 45-50% non-gypsum material and is a
valuable input for rapidly replenishing the’soil proﬁle with Ca (Ritcher and Sunffer,

2002, Warncke, 2003, and Tisdale et, al, 1996).

Since the 19703 the beneﬁts of gypsum on crop yield have been reported,
particularly as they relate to amending sodic and acid soils. Throughout the world,
extensive losses of topsoil and agricultural productivity from surface runoff is known to
occur; this is caused mainly by low inﬁltration rate (IR) from surface seal due to falling
raindrops (Y 11, et, al. 2003, & Warrington et, al., 1990). Gypsum was found to reduce
erosion rate by 50%, in inﬁltration and erosion studies done by Yu et a1. Gypsum has
been used extensively in reclamation of sodic soils with inﬁltration problems, to improve
the soil physical conditions by promoting ﬂocculation, enhancing aggregate stability,
thereby increasing the inﬁltration rate. Norton (1997) reports that gypsum could reduce
surface sealing and improves inﬁltration to reduce erosion. According to Libron et al.,
(2002), these observations had no scientiﬁc documentation or quantiﬁcation to support
the actual assembling of the soil particles at the aggregate level. However, in an

experiment to study the effect of gypsum on aggregate size and geometry of three sodic

4

soils under reclamation, Libron et al., reported that presence of gypsum in soil columns
prevented the breakdown of aggregates in proportion to the amount of gypsum added.

They found that the more gypsum added, the less break-down of aggregates.

In another study to examine the effect of various surface-incorporated
amendments on plant growth in Ca and aluminum (Al) mobility in acidic mine spoil
material, Willert and Stehouwer (2003) found the use of gypsum with or without other
amendments only improved conditions for root growth in the amended layer, but not
subsoil conditions. However, they found signiﬁcant increase in extractable subsoil Ca in
treatments that received gypsum or limestone or both. Reports have also indicated that P
sorption capacity of soils can be increased by the addition of gypsum (Adler and Sibrell,
2003). Ritchey and Snuffer (2002) found that gypsum in the presence of dolomitic
limestone improved yields, and gypsum alone negatively impacted soils and magnesium
(Mg) concentrations, though yields were not depressed. In addition, plants in higher

gypsum treatments had higher concentrations of P and K.

Management practices to ameliorate subsoil acidity by applications of gypsum
have been widely applied. Gypsum application is known to increase exchangeable Ca,
while reducing exchangeable A]; thus enhancing deep root exploration (Tomma et al.,
1999; Reeve and Sumner, 1972). Recently, gypsum has been used as a source of Ca for
developing peanut pods (Sumner, 1993). Gypsum has been shown to increase corn yield
and that of other crops, alone, and combined with other soil amendments. Gypsum is a
' valuable input for rapidly replenishing the soil proﬁle with Ca (Ritcher and Sunffer,

2002, Warncke, 2003, and Tisdale et, a1, 1996); may alleviate hidden sulfur (S)

deﬁciencies and consequently improve N uptake (Shel jazkov et al., 2006), resulting in

increases in yields.

There are controversies over the actual beneﬁts of gypsum in crop production,
particularly in nutrient availability and soil quality aspects, and there seems to be limited
documented research on the effect of gypsum in these areas. Ritchey and Snuffer (2002)
reported that gypsum increased P and K uptake, whereas, Warncke (2003) reports that K
uptake may be reduced by gypsum. Some researchers suggest that gypsum improves soil
structure; others refute that. Scott (2004) contends that adding gypsum to sandy or non-
sodic soils is a waste of money, and can result in negative impacts on plant, soil, and
ecosystem health, by leaching aluminum and iron into ground water. What is apparent is
that gypsum impacts different soils in different ways. The need for adopting sustainable
agricultural systems has renewed interest in the use of gypsum as a soil amendment and
therefore, the necessity and opportunities for research. Documented beneﬁts of gypsum
have been on soil conditions which are either limited, or non-existent in Michigan

(W amcke and Dahl, 2004).

Compost as a soil amendment

Epstein (1997) deﬁnes composting as “the biological decomposition of organic
matter under controlled, aerobic conditions to a humus-like stabled product. Animal
manures are composted mainly for odor reduction, to reduce the incidence of
contamination by pathogens, and the incidence of antibiotics entering surface waters from

manure application (Dolliver et al, 2008; Davis et al., 2006). Additionally, composting

allows for ease of handling, storage, transport of animal manures (Dolliver et al., 2008),

and kills viable weed seeds (Eghball and Power, 1999; Lamey and Blackshaw, 2003).

The use of compost as a soil amendment is as old as farming, and continues to be
used to enhance soil quality. Several beneﬁts of compost applications have been
established, such as weed suppression and soil organic matter addition, nutrient cycling,
and improved soil structure. The use of compost to manage nutrient inputs for crop
production presents certain challenges (Singer et al., 2004). Much research in the uses of
compost is being done to study the environmental implications of indiscriminate compost
uses, particularly accelerated eutrophication of surface waters from high application of
poultry and other manures (Preusch et al., 2002; Reddy et al., 2008; Singer et al., 2004).
Compost (and manure) application to meet N for corn potentially increases soil levels of
P (and other ions) because the N/P ratios of beef cattle feedlot manure and composted
manures are signiﬁcantly smaller than N/P uptake of most crops (Eghball and Power,
1999). Both organic and plant available forms of N (NOLNH4) and P205 are found in
compost (Eghball, and Power, 1999). Singer, et al., (2007) found that com grown on
compost treated plots accumulated more P (19 %) and K (21 %) than corn plants from
non compost plots. Nutrients bound in organic forms, though lower than in raw manure

and waste are slowly released, offering the beneﬁt of nutrients being available long term.

Soil physical property is critical to soil health and its ability to support optimum
crop production. Compost supplies organic matter to the soil, which improves soil
structure, enhances water-holding capacity and aeration. Hudson (1994) reported that
water-holding capacity more than doubles as soil organic content increases from 5 g/kg''

to 30 g/kg". Singer, et al. (2004), reported that soil organic matter content in compost

7

plots was 63 g kg”1 compared with 56 g kg’1 in the no-compost plots ﬁ'om corn, soybean
and wheat plots. Compost application rates were 61.6, 74.7, 54.1, and 22.3 Mg dry
matter ha“1 in 1998, 1999, 2000, and 2001, respectively. An increase in organic matter
and inﬁltration rate was reported by Butler and Muir (2006) from application of dairy
compost. Compost application has also been found to decrease soil bulk density. Johnson
et al., (2006) found decreases of up to 5.6 % with increased top-dressed application and
Aggelides and Londra (2000) reported signiﬁcant reductions of bulk density in clay and
loamy soils of 17 % and 20 %, respectively. In a study to stabilize Loess-derived soils of
the northern Paris basin, where soils are highly prone to degradation because of low clay
and organic matter content, compost application caused a reduction in runoff and soil loss

and improved the structural stability of seedbeds (Bresson et al., 2001 ).

Cover crops as soil amendments

Cover crops are plants grown primarily as ground covers to reduce erosion, cycle
nutrients as green manures, add organic matter, suppress weeds and diseases and control
the loss of nutrients through leaching (Mutch and Martin, 1998; Hutchinson McGiffen,
Jr. 2000; Wang et al., 2008). All cover crops provide protection to the soil in the absence
of cash crops. The cover prevents soil from being eroded by wind and the impact of rain
drops. Additionally, runoff is controlled and inﬁltration is enhanced. The beneﬁts of
cover crops have been known for decades (Odland, and Knoblauch, 193 8; De Bruin et al,
2005), and there is evidence of a growing interest in the use of cover crops as soil

amendments to reduce the use of chemical inputs for economic reasons and

environmental stewardship (Mutch and Snapp, 2003; Ngouajio and Mutch, 2004, 2004;
Mutch, 2007). However, cover crops adoption in farming systems remains low. Only

1 1% of producers in the com-belt used cover crops between 2001 and 2005, with others
citing cost, lack of knowledge of cover crops, time consumption, among other reasons for
not adopting (Singer et al., 2007; Mcdonald et al., 2008). The potential to improve soil
quality, enhance soil fertility, and increase crop yields, are among the many reasons for
using cover crops in farming systems, and also offers opportunities for scientiﬁc research
(N gouajio and McGriffen, 2002). The cover crops used in the this study were cereal rye,

wheat, red clover, oriental mustard, and oilseed radish.

Cereal rye is commonly grown as a cover crop for its multiple functions in a
cr0pping system. It is an excellent scavenger of residual N03-N. Kessavalou and
Walters (1997), reported an average of 34 kg N Mg'I of rye dry matter. Rye (and wheat)
has the potential for reducing the leaching of nitrates (Kessavalou and Walters, 1997;
Strock et al., 2004, De Briun et al., 2005; Duiker and Curran, 2005); is winter tolerant
and can be planted late in fall (De Briun et al., 2005; Kessavalou and Walters 1997),
making it a very attractive cover crop in the North-Eastem and Mid-western states (Ruffo
et al., 2004; Duiker and Curran, 2005). However, cereal rye (and wheat), has the
potential to reduce corn yield, because of N immobilization, and the alleleopathic
phytotoxic compounds produced by these plants and their residues (Raimbault et af.,
1990; Tollenaar, et al., 1993). Cereal rye and wheat reslease phenolic compounds such as
ferulic acid (4-hydroxyl~3-methoxy-cinnamic acid), p—coumaric acid (4-hydroxycinnamic
acid), and vanillic acid (hydroxybenzoic acid). These compounds inhibit the germination

of some species of both monocot and dicot plants.

Oriental mustard and oilseed radish, both belong to the Brassicaceae family, and
are attractive for their production of glucosinolates, which are secondary metabolites
known for their activities on weeds, nematodes, and diseases (Snapp et al., 2005;
Ngouajio and Mutch, 2004). Members of the Brassicacea family do not associate with
arbuscular mycorrhizal fungi (AMF) to form mycorrhiza, which plays an important role
in plant root development, nutrient availability (Wright, et a1 1996). It is also important
for the mobilization of certain nutrients, particularly, phosphorous and trace metals such
as zinc and copper. Arbuscular mycorrhizal fungi produces glomalin —- a soil glycoprotein
(a glue) which contains about 30-40 % carbon, and may be responsible for soil clmnping
and carbon and nitrogen sequestration. In addition, reports relate glomalin to aggregate
stability across a number of different soil types and management practices (Wright,
1996). Various researchers (Ryan, et al., 2001, Wright, et al., 2001, and Fraser et al.,
2005) have documented signiﬁcantly higher levels of mycorrhizal colonization and crop
yield after, or in combination with AM forming plants, compared to Brassica plants

which are non- AM compatible plants.

Brassica green manures and cover crops have the potential to provide biological
control of several common soil pests, including soil borne diseases, nematodes, and
weeds. Recent preliminary research involving the use of oriental mustard (Brassica
jum'ca L) as a soil biofumigant has been effective for the control of certain soil borne
fungal diseases. Phythium ultimim, F usarz'um solani and Rhizocatonia solam' were
suppressed by 67-100% and enhanced tubers and root health by 65 — 88% (Date and
Snapp, 2004). These two different traits of Brassica present opportunities to obtain the

beneﬁts of Brassicas and avoid their potential negative impact on soil—plant continuum in

10

cropping systems. Oilseed radish has a large, deep root system; is an excellent scavenger
of nitrates, grows rapidly, and produces a large amount of biomass in a short time,

making a good cover for wind erosion control. Oilseed radish established quickly and is
tolerant to moderate drought. Additionally, the large roots create channels for improved

aeration and inﬁltraton after decomposition (N gouajio and Mutch, 2004).

Red clover, a legume, is an important forage crop in North America (Steiner and
Aldermna, 1999), and is Michigan’s most common cover crop, mostly grown in non-
leguminous rotation systems (Mutch and Martin, 1998). It is attractive for its beneﬁt in
supplying nitrogen, ease of establishment, tolerance of seedlings to frost, and effective
ground cover for reducing erosion (Mutch and Martin, 1998; Singer et al., 2005). Vyn et
al., (2000) reported that presidedress NO3—N concentrations were at least 24% higher
after red clover, and that grain corn yield indicated enhanced N availability to corn than
other cover cr0ps studied. Winter wheat, which is grown in com- soybean-wheat rotation
(Kravchenko and Thelen, 2007), is being encouraged as an early spring forage (Thelen

and Leep, 2006;) and as a good weed suppressor (Singer et al., 2007).

The growing interest in the use of gypsum by Michigan farmers (Warncke, 2003 ),
and in cover crops for improving soil quality and nutrient enhancement (Mutch et al
2003, Snapp et al., 2005, and Ngouajio et al, 2003), warrants continued research in these
areas. The main objective of this study was to investigate whether gypsmn can be
beneﬁcial to cropping systems in Michigan, when applied alone, or in combination with
compost and in association with cover crops. The study was a three part investigation to
assess those treatment effects on 1) soil Ca and Mg availability, 2) sweet corn growth,
yield and quality, and 3) soil quality of a Kalamazoo loam in southwest Michigan.

11

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17

CHAPTER 2

EFFECTS OF GYPSUM ALONE OR COMBINED WITH COMPOST AND

COVER CROPS ON CALCIUM AND MAGNESIUM AVAILABILIY
ABSTRACT

Nutrient availability is viewed from both soil and plant perspectives. The recent
and growing interest in the use of gypsum (CaSO4- 2H20) by Michigan farmers, and the
lack of documentation on the effect of gypsum on Michigan soils warrant investigation of
its effect on various soil and plant growth parameters. This study investigated gypsum
and its interaction with poultry compost and cover crops on extractable soil Ca and Mg.
Sweet corn (Zea mays var. rugosa) was the index crop. The treatment design involved
three factors: gypsum application at 0 and 2.24 Mg ha", poultry compost, at 0 and 2.7 Mg
ha", and four cover crops plus a no cover treatment. The four cover crops were oilseed
radish (Raphanus sativus), oriental mustard (Brassica juncea L.), red clover (Trzfolium
pratense), and cereal rye (Secale cereale), or wheat ( T riticum aestivum). The data
presented here are for soil sampling for spring and fall of each of the three year (2005 and
2007) study. The statistical model included the three factors and all interactions among
them as ﬁxed effects, and replication as a random effect. Gypsum had no effect in 2006;
minimal effect on extractable Ca only 2007, but had a negative effect on extractable Mg
in 2006 and 2007 (both spring and fall). Compost application increased Ca by up to 44%
and resulted in signiﬁcant transfer of extractable Mg to lower depths. Our results suggest
that sweet corn has a higher demand for both Ca and Mg than the cover crops studied

Cover crops have potential to supply both Ca and Mg (0. = 0.05) to soil.

18

INTRODUCTION

Soil mineral resources are the key to optimal crop growth and harvest (Krishma,
2002), but are useless unless they are made available to plants when needed. Nutrient
availability as deﬁned by Bridgham et al., (2001), is the rate of replenishment (or the
buffer capacity) of the dissolved inorganic nutrient pool. It is a function of soil chemical
and mineralogical properties which control exchange reactions, nutrient concentration,
nutrient diffusion, and mineralization (Sherrod et al., 2002). Reduction in yield potential
due to mineral deﬁciency can vary widely from 20- 80 % of actual possible yield when
balanced nutrition is unavailable to plants (Binkely and Vitousek, 1989). Nutrient
availability can be viewed ﬁ'om a soil perspective and from the standpoint of plant
productivity. From the soil perspective, the ﬂux of nutrients from unavailable to
accessible pools, represents the nutrient supply rate. From the plant productivity
standpoint, individual plants or entire ecosystems can be affected by nutrient limitations
(Binkely and Vitousek, 1989). Although nutrient availability is the most important aspect
which inﬂuences crop productivity, quantifying available nutrients is a challenge because
of the complexity of nutrient cycles and the limitations of methods for this purpose.
Besides, the importance of individual pools and their transformation varies among
nutrients (Bridgham et al., 2001). Soil nutrients are found in large numbers of pools that

vary in availability to plants, and plants affect nutrient availability in a number of ways.

Total elemental composition of a soil is generally of little use in assessing the

availability of these elements to plants. Example, the iron (Fe) and magnesium (Mg)

19

deﬁciency in plants commonly occurs despite their relatively high levels in soils
(McBride, 1989). Nutrient supply to plants in most part depends on the mobility of the
ions and plant root density, and is most often limited by the availability of solutes rather
than by root intrinsic absorption capacity. Hence, the limiting factor in the uptake of
certain ions moving to the roots (as in non-mobile ions, such as phosphorus, P) is not
usually due to the absorption ability of the roots, but the inability of ions to move to the
roots. On the contrary, the absorption of mobile ions such as nitrates, may be limited by

plant root ability to assimilate this element (Lavelle and Spain, 2001).

Many soils in which plants suffer from micronutrient deﬁciencies contain about
1,000 times the amount of the deﬁcient element the crop needs (Leeper, 1985). The
nutrient interaction within the soil-plant continuum is complex, and nutrient balances
among both macro and micronutrients are essential; however, the latter is more difﬁcult
to maintain given that some of the plant enzyme systems dependent on micronutrients,
require more than one element to function. For example, plants require both manganese
and molybdenum for the assimilation of nitrates; some plants require both zinc and
phosphorus for optimum use of manganese. Yet, other plants require sufﬁcient amount
of zinc for copper utilization which in turn is favored by adequate manganese (Brady and
Wei] 2002). Therefore, management programs must, in order to be cost effective, take
into account the nutrient requirements of crops to be grown as well as the nutrient status
of the soil (W arncke et al., 2004). Even the best methods cannot account for all the
ﬂuxes (Binkely and Vitousek, 1989). Consequently, any method for determining nutrient
availability must be considered an index, since plant growth is an indirect measure of

nutrient availability as it is a response to nutrient availability (Bridgham et al., 2001).

20

For a sustainable crop production management system nutrient removal must be
offset by nutrient replacement to avoid soils being depleted of their fertility. When this
relationship is not ideal, optimum productivity is not obtained, and there is potential for
loss of nutrients to the environment, resulting in air, water and soil degradation, if
replacement exceeds removal and need (Grant et al, 2002). A healthy soil will provide
sufﬁcient nutrients for growth and development of healthy crops with the ability to resist
diseases. Many researchers have suggested that the liberal use of chemical fertilizers can
decrease plant resistance to insect pest (Altieri and Nicholls, 2003). Soil nutrient
availability has been found to affect both the amount of damage that plants receive from
herbivores and the ability of plants to recover from herbivory (Myer, 2000). Altieri and
Nicholls (2003) contend that, although more research is needed to investigate the effect
of fertilization on plant resistance to diseases and herbivory, preliminary results indicates
that nutritional imbalances in crops can make them more susceptible to insect disease
pressures. In a 2-year study, Brodbeck et al. (2001) found signiﬁcantly higher
populations of the thrips Frankliniella occidentalis on tomatoes that received higher rates
of N fertilization. Nutrient management for crop production requires knowledge of the
growth and physiology of the crops to be grown and their nutrient requirement coupled
with knowledge of the soils on which they grow. There is an intricate relation between
nutrient management, the speciﬁc crops grown, and soil quality, where the latter can be
positively or adversely impacted by the other parameters. The nutrients of interest in this
study were calcium (Ca) and magnesium (Mg). In the past, researchers suggested a need
for a speciﬁc CazMg ratio necessary to facilitate uptake of other nutrients and for

optimum plant grth and productivity (Bear and Toth, 1945; Sanik et al. 1952; McLean,

21

1977). This view promoted the “ideal balance ratio” (65% Ca, 10% Mg, and 5% K) for
cation exchange capacity (CBC) and stipulated that plants cannot obtain optimum growth
and yield outside of that ratio. Some research continues to promote the concept of the
“ideal balance ratios” (Osemwota et al., 2007; Tisdale et al., 1999). The divergent view
and research have established that no set “basic cation saturation ratio” exists to obtain
optimum growth and yield, but supplying sufﬁcient amounts of these nutrients regardless
of ratios will result in optimum growth and yield; that is, the “sufficiency level of
available nutrients” (SLAN) concept. Therefore, the Ca, Mg, and potassium (K) status
and fertility can be maintained across a range of ratios for maximum plant productivity
(Kopittke and Menzies, 2007, Favaretto, 2008; Mc Lean et al., 1983; Eckert and Mclean,
1981; Lanyon and Heald, 1982; Liebhardt, 1981). Calcium and Mg requirements vary
for different crops, and under different soil conditions, speciﬁcally as they relate to soil
pH (Favaretto et al, 2006; Sartain, 1993; Christenson etal., 1973). The objective of this
phase of the study was to assess the effects of gypsmn applied alone, or combined with

compost and cover crops on soil Ca and Mg availability.

22

SITE DESCRIPTION AND EXPERIMENTAL DESIGN

A study was established at the Kellogg Biological Station in Kalamazoo County,
South West Michigan, on a Kalamazoo loam (fme-loamy, mixed, mesic Typic
Hapludalfs). The treatment design was a randomized, incomplete block design with four
blocks in a 2x2x5 factorial. The designed was a type of split-split-split plot composed of
the following three factors: gypsum with two levels (with and without), compost with
two levels (with and without), and cover crops with ﬁve levels (four covers and a no
cover). The layout of the design is illustrated in ﬁgure 2.1. Within each block, each
gypsum level was randomly assigned to one 79.5 m x 5.3 m strip, and each compost level
was randomly assigned to one 10.7 m x 13.3 m plot, resulting in three compost plots for
each block with gypsum and no gypsum treatment. Each compost plot was split into
three 10.7 m x 4.4 m sub-subplots. The assignment was such that every whole plot
(compost level) had two subplots. Within each subplot were three sub— subplots with two
cover crops and one with no cover. Each individual cover crop was randomly assigned to
the sub-subplots; each with two gypsum sub-sub-subplots (5.3 m x 4.4 m). The system
was managed in a cover crop-sweet corn rotation such that for each growing season both
corn and cover crops were grown (Figure 2.1). A representation of block (rep) one for

cover crops assignments is presented in ﬁgure 2.1.

23

MATERIALS AND METHODS

In 2005, two sets of cover crops were grown. One set included oilseed radish and
mustard along with no-cover. The other set included cereal rye, red clover, and no-cover.
In 2006, there was a two-phase planting of cover crops. One set of cover crop which
included red clover, oilseed radish and mustard was the early phase. The second set was
the same as the previous year with cereal rye being replaced by wheat (Figure 2. 1 b). No
cover crop was grown in 2007 (Figure 2.1c). The planting schedule for cover crops and
sweet corn is given in table 2.1. For each planting season, six rows of corn were planted
in each sub-subplot about 0.76 m apart. In June of 2005 a 72 day maturing sweet corn
variety (Temptation) was seeded on one whole plot (compost and no compost) and cover
crops were grown on two whole plots (two composts; two non-composts). In 2006, sweet
corn was grown on plots where cover crops were grown in 2005 and cover crops on
sweet corn plots. An 82 day maturing sweet corn variety, Serendipity hybrid, was seeded
at approximately 59,280 seeds/ha, and all cover crops were seeded at 28 kg ha‘1 for each
year. Planting of sweet corn was done on May 24‘h of 2006 which facilitated a two phase
planting of cover crops. One phase (early) was planted in July and the second phase
(late) in October, about one month after the sweet corn was harvested. Sweet corn grown
on compost treated plots were harvested two days earlier (August 9‘”) than those on no-
compost plots (August 11‘”). Adequate N can speed up the maturity of crops and permit
an earlier harvest (Tisdale et al., 1999). In 2007, all plots were seeded with BC 0805
sweet corn on May 18 and harvested August 10. Prior to seeding sweet corn and cover

crops, gypsum and a poultry manure-oak leaves compost were incorporated at 2.24 Mg

24

hail and 2.7 Mg ha-'respectively; N-P-K fertilizer was broadcasted at 0.2 Mg/ha'l on
plots not receiving compost treatments. The poultry compost contained approximately
4g/kg and 45 g/kg of Mg and Ca respectively. The nutrient list and content of the poultry
compost on a dry weight basis is presented in table 2. Gypsum was applied each year
prior to planting; compost was applied only in the ﬁrst year (2005) of this study, but had
been applied to these same plots in the previous three years. Soil samples taken in the
spring of 2005 prior to the application of this study reﬂects the crop treatments of the
previous study. The previous crops were green bell pepper, cabbage and corn which
followed cereal rye, red clover and no-cover crop. Each crop was grown on a compost

plot, comprised of two levels (compost and no compost).

Soil Measurements

Soils were sampled at two depths; 0-10 cm (0-4”) and 10-20 cm (4-8”) with a 3
cm diameter soil probe, in spring, prior to planting, and fall after harvest. Six cores were
taken from each gypsum treatment, giving four samples for each sub-subplot with either
compost or no compost (Figure 2.1). Soil samples were air dried and ground to pass a 2.0
mm mesh. Extractable Ca, Mg, and K extracted with 1M NH40Ac at pH 7, as speciﬁed
by the modiﬁed North Central Region -13 method described by Warncke and Brown
(1998). This method involves a 1:10 soil to extracting solution ratio; 2g of soil and 20.0
ml extraction solution was used. The solution was shaken for 5 minutes at 200 rpm and

the suspension ﬁltered through Whatman No. 2 ﬁlter paper. The extractants were sent to

25

the Soil Testing Laboratory (MSU), where K, Ca and Mg were measured by an atomic

absorption spectrometer.
STATISTICAL ANALYSES

The data analysis was conducted in PROC MD(ED (SAS Inc, 2002). The
statistical model included the three studied factors; compost, cover crops and gypsum,
and all the interactions among them as ﬁxed effects, and replication as a random effect.
The error terms used in this model associated with the strips were used to test the gypsum
effect; errors associated with the plots were used to test the compost effect, and the
interactions between strips and plots were used to test the gypsum plus compost
interaction effect. Multiple comparisons among the various treatment means were
conducted using t- tests when respective factors, interactions or slicing effects were found

to be statistically signiﬁcant at a = 0.05.

RESULTS AND DISCUSSIONS
Residual effects on Calcium and Magnesium from prior treatments

In the spring of 2005 prior to the application of treatments for this study, soil
samples collected reﬂected prior corn and cover crops treatments effects. ANOVA for
signiﬁcant treatment effects for Ca and Mg are presented in table 2.3 and means for
extractable Ca and Mg are presented in tables 2.4, 2.5 and 2.6 respectively. The previous
crops were sweet peppers, cabbage and corn which followed cereal rye, red clover and

no-cover crop. In the spring the effects that were signiﬁcant for Ca availability, were

26

compost (P < 0.001), cover crops (P _<_ 0.01), soil depth and the interaction of compost
and depth (P < 0.001 ). Generally, mean Ca concentrations were highest following
cabbage regardless of the previous cover crop, followed by com, then sweet peppers.
Compost application increased Ca concentrations by 35% (1200 mg/kg”) compared to no
compost (891 mg/kg") application. Extractable Ca was 10% higher at the 0-10cm depth
(1086 mg/kg") than the 10-20 cm depth (1005 mg/kg'l). The mean of compost plus
depth interaction wa312% greater at the 0-10 cm depth than the 10-20 cm depth (Table
2.6). There was no difference in Ca between the two depths when compost was not

applied.

The effects found to be signiﬁcant for Mg were compost (P < 0.001), cover crops
(P < 0.001), depth (P < 0.01), and the interactions of compost plus cover crops (P < 0.01)
and compost plus depth (P < 0.001). Cover crop effects for Mg followed a similar
pattern as Ca, with the greatest extractable Mg from cabbage plots followed by com, then
pepper, regardless of the preceding cover crop (Table 2.4). The mean for extractable Mg
in the top 20 cm was 17 % greater for non compost treated plots (170 mg/kg") the
compost treatment (145 mg/kg“). The mean of extractable Mg for the 10-20 cm depth
(153.9 mg/kg") was 17% greater than 0-10 cm depth (1 31 mg/kg“). For the interaction
of compost with cover crops, generally, the means for extractable Mg were greatest from
cabbage plots followed by com, then peppers irrespective of previous cover crop and
compost treatment (Table 2.5). For the compost plus depth interaction, the greatest
concentration of Mg was found in plots with no compost regardless of depth. When
compost was applied, the Mg content of the 0-10 cm depth was 11 % greater than of the

10-20 cm depth (Table 2.6).

27

Treatment effects on exchangeable Ca concentration in soil

In 2005 cover cr0ps were seeded about one month after com, and incorporated
two months aﬁer seeding (Table 2.1). For each growing season both corn and cover
crops were grown on separate plots. Corn was grown on one compost plot (with a
compost and non compost subplot), and cover crops were grown on two compost plots.
(Figure 2.1). For post-harvest soil sampling in the fall of 2005 the effects that were found
to be signiﬁcant for extractable Ca, were crops (PS 0.01), compost (P5 0.001), depth (PS
0.001), the interactions of gypsum and depth (PS 0.01) and compost and depth (PS
0.001). ANOVA for soil Ca concentration as affect by cover crops and corn is presented
in table 2.3. The mean of extractable Ca was similar for soils from all cover crops, which
were no different from means for no-cover crop plots (Table 2.4: Figure 2.2). Soils ﬁ'om
sweet corn plots had the lowest mean of extractable Ca (1081 mg fkg‘l); 9% less than no-
cover crop (1180 mg/ kg”). This seems to indicate a higher Ca demand and removal
ﬁ'om corn compared to the cover crops after cover crops were incorporated. There was
no difference between the Ca in soils from no-cover and cover crops, indicating that
cover cr0ps did not supply nor sequester any signiﬁcant Ca to soil after incorporation.
Compost application increased soil Ca concentration (1374 mg/ kg") by 38% compared
to no compost (996 mg /kg—') and Ca was higher at the 0-10 cm (1247 mg/ kg") by 11%
than the 10-20 cm (1122 mg /kg_'). From the interactions of compost plus depth, the

mean of Ca was signiﬁcantly greater at the 0-10 cm depth by 15% and 6 % than the 10-

28

20 cm depth ﬁom compost and non compost treated plots respectively (Table 2.7; Figure
2.6). At each depth the compost treatment had signiﬁcantly higher Ca means than no
compost. At the 0-10 cm depth, Ca from compost application was 44% (1469.8 mg
/kg-') greater than the no compost application (1024.2 mg /kg"). Extractable Ca
decreased with depth from both compost and non compost treated plots. However,
compost application increased Ca in the 10-20 cm depth by 32 % compared to no
compost, supporting other reports that compost and broiler liter enhances subsoil Ca
(Zheljazkov , et al., 2006; Adeli et al., 2008). From the interaction of gypsum plus depth
the mean of Ca was signiﬁcantly greater at the 0-10 cm depth by 15% and 7 % than the
10-20 cm depth from compost and non compost treated plots respectively. There was no

difference in Ca between the two depths from gypsum or non gypsum plot (Table 2.7).

The effects found to be signiﬁcant for soil Ca concentration from soil sampled in
both spring and fall of 2006 (Table 2.8) were compost (P 5 0.001), crops (P S 0.05 S
0.01), depth (P 5 0.001) and the interaction of compost plus depth (P 5 0.001; P S 0.01).
Corn was grown on the plots where the previous cover crops were grown in 2005. In the
spring (2006) effects of the previous cover crops on soil Ca availability was as follows:
mustard (1130 mg/kg") = oilseed radish (1074 mg/kg") 2 cereal rye (1062 mg/kg") = red
clover (10286 mg/kg"). In the spring of 2006, the lowest soil extractable Ca was from
corn plots (983 mg/kg") which was signiﬁcantly lower than no-cover crop
(1072 mg/kg'l), mustard and oilseed radish (Table 2.9; ﬁgure 2.2). Corn is among the
crops with high calcium needs (Tisdale et al., 1999), and it seems to suggest that com
demand and removal of Ca was higher than for the other cover crops, as occurred in the

fall of 2005. Additionally, there is more rapid cycling of nutrients from cover crops

29

incorporated in the fall, opposed to corn. Sweet corn ears, which are a signiﬁcant source
of Ca were harvested and corn remaining stover takes much longer to decompose and
cycle nutrients. In the fall of 2006 the means of extractable Ca for soils under crops was
the reverse (from fall 2005) with the mean from corn plots signiﬁcantly higher than the
three cover crops grown; mustard, oilseed radish and red clover. The effect was as
follows: corn (1 1 14 mg/kg") > mustard (1033 mg/kg") = oilseed radish (1012 mg/kg") =
red clover (1010 mg/kg'l). Compost application increased Ca availability by 35% and
37% in the spring (1214 mg/kg") and fall (1204 mg/kg") respectively compared to no-
compost (902mg/kg'l and 880.2 mg/kg"). The poultry compost used in this study was a
signiﬁcant source of Ca; it contained 45g/kg'I Ca (Table 2.2). Other studies have found
that poultry manures, and sludge signiﬁcantly increased exchangeable Ca content
compared to controls (Siddique and Johnson, 2003 Parsons et al., 2007); compost was
found to signiﬁcantly increase Ca > 55 % relative to the control (Eghball et al., 2002). In
both spring and fall, Ca was signiﬁcantly higher at the 0-10 cm depth than the 10-20cm
depth by 11% and 12 % respectively. Extractable Ca for compost plus depth interaction
followed a similar pattern in both spring and fall. The mean extractable Ca at the 0-10
cm depth was signiﬁcantly higher than 10-20 cm for compost treatments; 1310 mg/kg‘l at
0-10 cm vs 1118 mg/kg’l at 10-20 cm in the spring and 1290 mg/kg'l vs 1118 mg/kg'I in
the fall. There was no difference in extractable Ca between the two depths when compost
was not applied, and compost application had signiﬁcantly higher available Ca than non
compost plots at both depths (Table 2.10: Figure 2.6). Kingery et al., (1994) found that

poultry liter and compost supplied signiﬁcant amounts of K, Ca and Mg, and that

30

IF““"m—n

extractable Ca was greatest at shallower depths. As much as 800 mg kg-' more Ca was

reported in the upper 15 cm of litter treated soils than non-littered soils.

Cover crops (late) were grown on plots where corn was harvested in the fall of
2005. For soil sampled in the spring of 2007 following early planted cover crops, the
effects found to be signiﬁcant for Ca availability were compost application (PS 0.001),
depth (PS 0.001), the interaction of compost plus depth (P_<_ 0.001), and gypsum plus
depth (PS 0.05). Effects found to be signiﬁcant following late planted cover crops were
compost (PS 0.001), depth (P5 0.001), the interactions of compost and cover crops (PS
0.05) and compost and depth (P: 0.001). ANOVA of signiﬁcant treatments for both
spring and fall are presented in table 2.11; and means of treatment effects in tables 2.12,
2.13 and 2.14. Compost application increased Ca in soil by 37% compared to no
compost regardless of cover crop planting time (Table 2.11: Figure 2.4). Means of
extractable Ca were 11% (1026.3 mg/kg'l vs 923.6 mg/kg") and 9 % (1101 mg/kg'l vs
1009 mg/kg") higher at the 0-10 cm depth than 10-20 cm depth respectively following
early and late planted cover crops (Table 2.12). Extractable Ca from the combined effect
of compost and depth from spring sampling was greater at the 0-10 cm depth (1212
mg/kg") by 17% more than the 10-20 cm depth (1040 mg/kg") ; 44% and 29% greater at
the 0-10 cm (841 mg/kg") and 10-20 cm (808 mg/kg") depths respectively, from
compost compared to non compost plots, following early planted cover crops (Table
2.13). Following late planted cover crops the 0-10 cm depth was 13% (1297 mg/kg")
greater than the 10-20 cm depth (1 147 mg/kg'l). Following late planted cover crops,
extractable Ca was 36% (1297 mg/kg" vs 905.6 mg/kg") and 31 % (1147 mg/kg" vs

847) greater at the top 10 cm depth and 10-20 cm depth, respectively, from compost

31

treatment than non compost. There was no difference between the two depths when

compost was not applied.

From the gypsum plus depth combination extractable Ca was about 12% (1066
mg/kg'l vs 943.5 mg/kg") and (I 146 mg/kg'I vs 1026 mg/kg") greater at the 0-10cm
than the 10-20 cm following early and late early planted cover crop in both cases. There
was no signiﬁcant effect on Ca at the 10-20 cm depth from gypsum application,
indicating that gypsum application did not enhance Ca in the 10-20 cm. The interaction
of compost with cover crops affected Ca following late planted cover crops only. The
effect was as follows: wheat (1298.2 mg/kg") = red clover (1242 mg/kg") = oilseed
radish (1199 mg/kg") 2 mustard (1187.3 mg/kg") = no-cover (l 184 mg/kg"). There was

no difference in Ca following cover crops when compost was not applied.

In the fall of 2007, signiﬁcant effects (Table 2.11) for Ca availability following
corn harvest, were gypsum (P S 0.05), compost (P 5 0.001), depth (P 5 0.001), and the
interactions of compost plus depth (P5 0.05). When gypsum was applied Ca
concentration in soil was 12% (1131 mg/kg") higher than no gypsum application (1005
mg/kg'l). Ca in soils to which compost was applied averaged 33% (1220 mg/kg")
greater than in non-compost treated soils (916 mg/kg"). At the 0-10 cm depth (1 118
mg/kg") available Ca was 10% greater than the 10-20 cm depth (1018 mg/kg").
Extractable Ca was 12% (1289 mg/kg" vs 1151 mg/kg") and 9 % (948 mg/kg" vs 884
mg/kg") higher at the 0-10cm depth than 10-20 cm depth from compost and none
compost treated plots respectively (Table 2.12: Figure 2.6). Calcium was 36 % and 31%
greater from compost than non compost treated plots, at the 0-10cm and 10-20 cm depth,
respectively.

32

Treatment effect on exchangeable Mg concentration in soil

In the fall of 2005 the effects that were found to be signiﬁcant for Mg availability,
were cover crops (PS 0.01), depth (P5 0.001), the interactions of compost plus depth (PS
0.001), and cover crops plus depth (P3 0.01). ANOVA for treatment effect on
extractable Mg for fall 2005 is presented in table 2.3. Extractable Mg was signiﬁcantly
different following the various cover crops and following corn. Mean soil Mg level from
corn plots (179 mg /kg_') was 8% lower than the means of the various cover crops
compared to no-cover (193 mg/ kg"). Among the cover crops only cereal rye and
mustard were signiﬁcantly different, with soil after mustard having 8% less Mg than soil
after cereal rye (Table 2.4; Figure 2.3). This seems to indicate as in the case of Ca that
com has a higher demand for Mg, than the cover crops, and among the cover crops cereal
rye had the lowest demand for Mg. The mean soil Mg at the 0-10 cm (197 mg /kg“')

depth was greater than at 10-20 cm (188 mg /kg") (Table 2.4).

Generally, the means of extractable Mg from the combined effects of compost
plus depth were greater when no compost was applied and in that case there was no
difference in Mg between the two depths. Extractable Mg wale % greater at the 0-10
cm (193mg/ kg“) than the 10-20 cm (173 mg/ kg") depth when compost was applied
(Table 2.7). For the combined effect of cover crop plus depth the mean of extractable Mg
was signiﬁcantly lower from corn plots than the various cover crops, and there was no
difference between the two depths. At 0-10 cm depth the mean from corn plots was (177

mg/ kg”) 14% less than no-cover (202 mg/ kg”). Among the cover crops, cereal rye

33

f‘F‘ “ 'Wm

resulted in the highest mean of Mg at the two depths, with the 0-10cm depth 12% greater
than the 10-20 cm depth; there was no difference among the other cover crops compared
to no- cover crop. Crops plus depth (0-10cm) combination effects were as follows:
Cereal rye (213mg/kg'l) 2 no cover (202 mg/kg") = oilseed radish (197 mg/kg'l= red

clover (197 mg/kg") > com (177 mg/kg").

In the spring 2006 (Table 2.5) the effects found to be signiﬁcant for Mg were
compost (P5 0.01 ), the combined effects of gypsmn plus depth and compost plus depth.
When compost was applied, extractable Mg was 19% less (146 Mg/kg") than non
composed (174 mg/kg") plots (Table 2.9). For the combined effect of compost plus
depth, mean of Mg was greater when no compost was applied, regardless of depth. The
means of Mg were 11% and 27 % greater at the 0-10cm depth and 10-20 cm depth
respectively, when compost was not applied compared to compost treated plots (Table
2.10). When compost was applied Mg was 5% lower at the 10-20 cm (142 mg/kg")
depth than the 0-10 cm depth (149 mg/kg'l). The mean of Mg for the combined effect of
gypsum plus depth was greater at the 10-20 cm depth when gypsum was applied (163
mg/kg") than the 0-10 cm depth (154 mg/kg"); there was no difference between the two

depths ﬁ'om non gypsum plots (Table 2.10).

The effects found to be signiﬁcant for soil Mg concentration from soil sampled in
the fall of 2006 (Table 2.8) were compost (PS 0.01), crops (PS 0.01), depth (PS 0.001)
and the interaction of compost plus depth (P_<_ 0.01). Fall extractable Mg (2006) followed
a similar pattern as Ca with the highest mean obtained from corn plots. The mean
extractable Mg from corn plots was the greatest, and there was no difference among

cover crop means. The effects were as follows: com (151 mg/kg") > red clover (145

34

mg/kg'l) = mustard (142 mg/kg") = oilseed radish (142 mg/kg'l). The table means of
treatment and interaction effect are presented in Tables 2.9 and 2.10 respectively. The
mean of Mg concentration from compost was 18% less than non compost treated plots.
Extractable Mg was greater in the 10-20 cm depth (153 mg/k") than the 0-10 cm (140
mg/kg") depth (Figurel 0). For the combined effect of compost plus depth, extractable
Mg was greater from non compost plots than compost treatment regardless of depth, and
greater within in the 10-20 cm depth (170 mg/kg") than the 0-10 cm depth (148 mg/kg"),

by 15% (Table 2.10).

For soil samples taken in 2007, ANOVA for extractable Mg is presented in table
2.11. Cover (PS 0.01), compost (PS 0.01), depth (P5 0.01) and the interaction of compost
plus depth (PS 0.01) were the effects found to be signiﬁcant for Mg from soil samples
following early planted cover crops and. Mean of Mg concentration (Table 2.12: Figure
2.3) ﬁom red clover plots was 11% greater than both mustard (138 mg/kg") and oilseed
radish (138 mg/kg"). Compost application depressed soil Mg concentration by 23% (128
mg/kg") compared to none compost (158 mglkg") plots (Table 2.12; Figure 2.5). From
the interaction of compost plus depth, when no compost was applied, extractable Mg was
18% and 29% greater at the 0-10 cm and 10-20 cm depth respectively than compost
treated plots, and 10% greater at the 10-20 cm depth than the 0-10 cm depth. There was
no difference in Mg concentration between depths when compost was applied (Table

2.13).

Compost application (P5 0.05), depth (P5 0.001), and the interactions of both
gypsum and compost plus depth (P5 0.01), were signiﬁcant treatment effects following

late planted cover crops. When compost was applied the mean extractable Mg (Table

35

""1!

2.10) wasl 8 % (140 mg/kg'l), less than the mean from non compost treated plots (166
mg/kg'l). Extractable Mg at the 0-10 cm depth (148 mg/kg") was less than in the 10-20
cm depth (157 mg/kg'l). For the combined effect of gypsum plus depth, extractable Mg
was 10 % greater at the 10-20 cm depth (156.0 mg/kg-l) than the 0-10 cm depth (142
mg/kg-l) ﬁ'om gypsum application (Figure 2.5). This extractable Mg at the 10-20 cm
depth ﬁom applied gypsum was similar to extractable Mg when no compost was applied
regardless of depth (Table 2.10). This seems to indicate a displacement of Mg from the
exchange complex to lower soil depths when gypsum was applied. Other researchers
have reported this effect of gypsum on Mg (Peregrina et al., 2008; Ritchey et al., 2004;
Toma et a1. 1999; Sumner, 1993). Evidence of the preference for Ca over Mg on the soil
exchange sites is ﬁ'equently demonstrated (DeSutter et al., 2006; Bladel et al., 1980;
Cutin et al., 1998). Extractable Mg was greater ﬁom non composted plots than compost
plots by 15% and 22 % at the 0-10 cm and 10-20 cm depth respectively. When no
compost was applied, the 10-20 cm depth was 9% (172 mg/kg") greater in extractable
Mg than the 0-10 cm (159 mg/kg") depth (Table 2.13). The observed greater extractable
Mg when no compost was applied and within the 10-20 cm depths ﬁ'om compost
application is evidence of Mg displacement by Ca from compost application as seen to
occur when gypsum was applied. There is limited focus/research on soil

available/extractable Mg and Ca, with relation to soil amendments, including compost.

Only corn was grown on all plots for the 2007 growing season. For post harvest
soil sampling, the effect found to be signiﬁcant for extractable Mg were compost (PS
0.01), depth (PS 0.01) and the interactions of gypsum plus depth (PS 0.01) and compost

plus depth (PS 0.01). When compost was applied, Mg was depressed by 22% compared

36

to non compost application; a similar pattern as the two previous growing seasons. Mean
of Mg was greater (Table 2.12; Figure 2.7) for 10-20 cm depth (154 mg/kg'l) than the 0-
10 cm depth (147 mg/kg"). Mean of Mg for the combined effects of gypsum plus depth
was greater by 9 % at the 10-20 cm depth (150.9 mg/kg ") than the 0-10 cm depth (138
mg/kg'l). At the 0-10 cm depth, extractable Mg when gypsum was applied was 13% less
than non gypsum treatment, and there was no difference between the gypsum and non

gypsmn treatments at the 10-20 cm depths (Table 2.14).

SUMMARY AND CONCLUSION

Compost increased extractable Ca by up to 38% within the top 20 cm depth
compared to control plots. Extractable Ca levels within the 0-10 cm depth ranged from
42-44 % greater from compost plots compared to non compost plots. Evidence of
enhanced Ca ﬁ'om increases of 28% - 31% within the 10-20 cm depths was observed, but
no signiﬁcant difference in the three year study or between spring and fall of each year.
Conversely, compost application resulted in Mg displacement of up to 18% from the
top10 cm depth. The decrease of up to 29 %, of Mg in the10-20 cm depth from compost
application is evidence of Mg displacement by Ca below the 10-20 cm depth. Generally,

Mg levels were greater by 23 % when compost was not applied.

Gypsum’s inﬂuence on extractable Ca was minimal, with 6% and 15% increases
within the top 10 cm depth in 2005 (fall) and 2007(spring) respectively, and 12% in the
top 20 cm depth in 2007 (fall). Gypsum application did not enhance Ca levels within in

the 10-20 cm depth. Evidence of Mg displacement by Ca from gypsum application was

37

observed in the top cm depth. These decreases were observed in 2006 (spring) and 2007
(spring and fall) within ranges of 8-13% %. There were no changes in Mg levels from

non gypsum plots.

In the fall of 2005 signiﬁcantly lower soil Ca levels from corn plots than all the
cover crop plots, seemed to indicate a greater Ca need and removal by com than the
cover crops studied. In spring of 2006, Ca from corn, cereal rye and red clover plots
were similar, but signiﬁcantly lower than the other cover crops, which may be due to
slower rates of nutrient cycling. Signiﬁcantly higher soil Ca levels from corn plots than
cover crops in fall 2006 and from corn plots in the previous year may be due to. the
difference in sweet corn varieties grown. Calcium uptake is genetically controlled
(Tisdale et al., 1999), and corn hybrids vary in their efﬁciency to utilize and mobilize
nutrients (Hatlitligil, et al., 2005; Heckman et al., 2006). Generally, Mg concentration in
corn plots remained the same, but the Mg in cover crop plots decreased over time. One
explanation is a decrease in biomass production, which would in turn decrease the
amount of nutrients for cycling. Some of the cover crops in this study may have potential

as sources of soil Mg and Ca in cropping systems.

38

Table 2.1. Planting schedule for cover crops and sweet corn (2005-2007)

 

2005

 

Planting Harvest

Planting Harvest

Planting Harvest

Planting Harvest

 

Cover crops
Mustard
Oilseed radish
Red clover
Cereal rye
Wheat

Sweet corn
Temptation
Serendipity

BC805

7/29

7/29

7/29

7/29

6/30

10/11

10/11

8/09

..... Early-----

7/11

7/11

5/24

10/05
10/05
5/4

15/4

8/11

----late -----

9/01 10/05
9/01 10/05
9/01
9/01

5/18

4/30

4/30

8/10

 

39

Table 2.2. Nutrient composition of poultry compost

 

 

Nutrients % g/kg
Nitrogen 0.9 9.1
Sulfur 0.2 1 .6
Phosphorous 0.6 6.1
Potassium 0.4 4.0
Magnesium 0.4 4.0
Calcium 4.5 45.1
Sodium 0.2 2.0
Zinc 0.02 0.2
Manganese 0.1 0.6
Iron 0.6 6.3
Copper 0.002 0.02
Aluminum 0.6 6.2

 

Poultry compost was applied only in spring of 2005 at

2.7 Mg/ha-lValues are given on a weight basis

40

Table 2.3. Statistical signiﬁcance of gypsum, compost, depth and cover crops, and corn effects on Ca and
Mg for the sprig 2005 pre—treatment soil sampling

 

 

 

 

2005

Sources Ca Mg

Spring F-value P-Value F -value P-Value
Gypsum 0.02 ns 0.05 ns
Compost 79.55 *** 65.43 **"'
Gyp*comp 0.02 ns 0.05 ns
Crops 2.57 ** 11.87 ***
Gyp*crops 0.02 ns 0.04 ns
Comp*crops 1.73 ns 2.66 **
Gyp‘comp*crops 0.02 ns 0.04 ns
Depth 25.32 *** 10.65 **
Gypsum*depth 0.09 ns 0.08 ns
Comp*depth 13.96 "“" 13.34 ***
Gyp*Comp*depth 0.09 ns 0.08 ns
crops *depth 1.19 ns 1.20 ns
Gyp“ crops *depth 0.08 ns 0.07 ns
Comp“ crops ‘depth 0.40 ns 0.33 ns
Gyp*comp* crops *depth 0.08 ns 0.07 ns

Fall
Gypsum 0.26 ns 3.41 ns
Compost 57.94 *"”“ 4.45 ns
Gyp*comp 0.03 ns 0.28 ns
Crops 3.40 *"' 3.80 **
Gyp“ crops 1.55 ns 0.44 ns
Comp“ crops 2.27 ns 1.09 ns
Gyp‘comp" crops 0.21 ns 0.04 ns
Depth 50.95 *** 11.53 ***
Gypsum*depth 7.03 ** 2.38 ns
Comp*depth 14.88 *** 34.38 ***
Gyp*Comp*depth 0.02 ns 1.74 ns
Crops*depth 1 .39 ns 3 .38 **
Gyp" crops *depth 1.59 ns 0.56 ns
Comp“ crops *depth 0.78 ns 0.91 ns
Gyp*comp"' crops *depth 0.16 ns 0.28 ns

"' P s 0.05
*" P 5 0.01
*** P <0.001

ns Not signiﬁcant at (1:005 Abbrev: Gyp = gypsum; comp = compost

41

Table 2.4. Effects from gypsum, compost, depth, cover crops and corn on mean soil extractable Ca and
Mg in the top 20 cm for 2005 soil sampling

 

 

 

 

 

Sprilg 2005 Fall 2005

Treatments Ca Mg Treatments Ca Mg
-1
mg/kg

Cereal “'3 1164a 184a Corn 1081b 179s
Red °'°V°"B 1124a 175a N0 °°Ver 1180a 193ab
N°'°°Ve' '3 1075ab 1763 “"5”” 1257a 190b
Cereal WC'C 1084ab 157b Oilseed radish 1187a 193ab
Red “NFC 1050abc 152b Red “10"“ 1180aa 196ab
NW0” 'C 107lab 154b Cem' We 1223a 205a
Ccm' 9’” 945.0e 141C - - -
Red clover-P 958bc 143bc - _ ,
No-cover -P 942C 13 8 c - _ _
Compost 1200a 145b - 1374a 183a
No compost 891 b 170a - 996b 202a
Gypsum - - - 1 199a 201 a
No gypsum - - - 1171a 184a
Depth 0-10cm 1086a 131b - 1247a 1975a
Depth 10-20 cm 1006b 154a - 1123b 188b

 

Means within the same column and groups followed by the same letters are not signiﬁcantly

different at a=0.05

Abbrev. B- cabbage; C- corn; P- green bell pepper, followed by cereal rye (grain cover crop); red clover
(legume); no-cover crop

42

Table 2.5. Effects from compost by previous crop on mean extractable soil Mg. Spring 2005

 

Previous crops and cover crops

 

Cabbage Corn Pepper

 

Crops*compost BG BL BN CG CL CN PG PL PN

 

Magnesium mg/kg‘l

 

 

Compost 174bc 167bc 145d 142de 141de 150d 127e 134e 1296
No compost 193a 184b 207a 172bc 162C 157cd 155d 151d 146d

Stdr l8 l7 _ 18

 

Means within rows and columns followed by the same letters are not signiﬁcantly different at (1:005

The cash crops were followed by cereal rye (grain cover crop); red clover (legume); No cover crop
Abbrev. B- cabbage; C- corn; P- green bell pepper; C- cereal rye; L- Red clover; N-no cover

Table 2.6. Effects from compost plus depth interaction on mean extractable Ca and

 

 

 

 

 

Mg for spring 2005
Ca '- Mg
Compost*depth Compost No compost Compost No compost
-1
mg/kg
0-10 cm 12703 902C 153a 169a
10-20 cm 1130b 880.c 138b 1703
Stdr 79 17

 

Means within groups followed by the same letters are not signiﬁcantly different at (1:005

43

Table 2.7. Effects from treatment interactions on mean extractable Ca and Mg in Fall 2005

 

 

 

 

 

 

 

 

 

 

 

 

 

Ca Mg
Compost*depth Compost No compost Compost No compost
mg/kg-l
0-10 cm 14708a 1024c 1933 200a
10-20 cm 1278b 967d 172b 2053
Stdr 97 16
Ca Mg
Gypsum*depth Gypsum No gypsum Gypsum No gypsum
0-10 cm 1284a 121083 203a 1903
10-20 cm 1114b 1132b 1993 1783
Stdr 97 16
Magnesium
Crops ‘depth No cover Mustard O/radish R/clover C/rye Corn
Magnesium mg kg-1
0-10 cm 2023b 192b 197b 197b 2133 177.0c
10—20 cm I85C 188bc 189bc 195b 196b 180C
Stdr 16 16 16 16 16 16

 

Means within the same rows followed by the same letters are not signiﬁcantly different

at a=0.05

O/radish = oilseed radish
R/cover = red clover
C/rye = Cereal rye

44

Table 2.8. Statistical signiﬁcance of gypsum, compost, depth, corn and cover crops effects on

 

 

 

 

Extractable Ca and Mg
2006

Sources Ca Mg

Spring F -value P-Value F -value P-Value
Gypsum 0.99 ns 0.03 ns
Compost 69.60 *** 13.23 **
Gyp‘comp 0.39 ns 1.52 ns
Crops 2.69 "' 0.58 ns
Gyp*Crops 0.24 ns 0.50 ns
Comp*crops 1.80 ns 0.15 ns
Gyp*comp*crops 0.06 ns 23.00 ns
Depth 50.96 *** 3.48 ns
Gypsum*depth 1.93 ns 6.36 **
Comp‘depth 22.93 **"' 26.47 ***
Gyp‘Comp*depth 0.05 ns 0.85 ns
Cover*depth 0.1 1 ns 0.86 ns
Gyp“ crops *depth 0.07 ns 0.10 ns
Comp“ crops*depth 0.45 ns 0.24 ns
Gyp*comp* crops*depth 0.07 ns 0.1 1 ns

Fall
Gypsum 0.8 ns 1.95 ns
Compost 173.3 *** 25.28 **
Gyp*comp 0.03 ns 0.06 ns
Crops 6.34 ** 5.28 **
Gyp*crops 0.12 ns 0.02 ns
Comp*crops 0.56 ns 0.09 ns
Gyp*comp*cover 0.06 ns 0.07 ns
Depth 28.69 *** 18.43 ***
Gypsum*depth 0.48 ns 0.76 ns
Comp*depth 7.38 ** 10.58 **
Gyp‘Comp*depth 0.02 ns 0.05 ns
Cover*depth 0.01 ns 0.26 ns
Gyp‘crops*depth 0.03 ns 0.12 ns
Comp*cover*depth 0.05 ns 0.13 ns
Gyp*comp"‘crops*depth 0.05 ns 0.04 ns

* P s 0.05
" P S 0.01

"* P $0.001; ns Not signiﬁcant at (1:005 Abbrev: Gyp = gypsum; comp = compost

45

Table 2.9. Effects from gypsum, compost, depth and cover crops on mean extractable
Ca and Mg in the top 20 cm.

 

 

 

 

 

Sprig2006 Fall 2006
Sources Ca Mg Ca Mg
g/kg'l
Corn 982.5b 154.83 1113.53 1563
Cover crops
Mustard 11303 1643 1033b 142b
Oilseed radish 1074a 1593 1012b 142b
Red clover 10283b 1583 1010b 145b
Compost 1214a 146b 1204a 134b
No compost 902b 1743 880b 1593
Gypsum 1077a 1593 ‘ 1053a 1433
No gypsum 1039a 1603 10313 1503
Depth 0-10cm 11163 1583 1099a 14%
Depth 10-20 cm 1000b 1623 985b 1533

 

Means within columns and groups followed by the same letters are not signiﬁcantly
different at a: 0.05

46

Table 2.10. Effects from gypsum *depth and compost‘depth on mean extractable Ca, and Mg

 

 

 

 

 

 

 

 

 

 

for 2006.
Spring 2006 Ca Mg
Gypsum*depth Gypsum No gypsum Gypsum No gypsum
-1
mg/kg
0-10cm 11453 10863 154b 1613
10-20 cm 1008b 993b 1643 1603b
Stdr 66 18
2006 Ca Mg
Compost‘depth Compost No compost Compost No compost
-l
------------- mg/kg -----------
Spring
0-10 cm 13103 921C 149C 1661b
10-20 cm 1118b 883C 142.2d 1813
Stdr 66 18
Fall
0-10 cm 12903 908. 132C 148b
10-20 cm 11 18% 852c 135c 1703
Stdr 66 16

 

Means within rows and groups followed by the same letters are not signiﬁcantly different at a: 0.05

47

Table 2.11. Statistical signiﬁcance of gypsum, compost, depth, corn and cover crops on
extractable Ca and Mg for 2007.

 

 

 

 

2007
Sources Ca Mg
Spring F-value P-Value F-value P-Value
------------- Early-----------
Gypsum 0.59 ns 0.16 ns
Compost 61.96 *** 60.72 ***
Gyp*comp 0.08 ns 0.55 ns
Cover 0.18 ns 6.53 **
Gyp“ cover 0.09 ns 0.27 ns
Comp“ cover 1.10 ns 1.90 ns
Gyp‘comp“ cover 0.50 ns 0.13 ns
Depth 128.53 ** 11.00 **
Gypsum*depth 4.85 * 1 .94 ns
Comp*depth 58.35 *** 9.21 **
Gyp‘comp*depth 1.56 ns 0.57 ns
Cover*depth 0.38 ns 0.04 ns
Gyp“ cover *depth 1.15 ns 1.81 ns
Comp“ cover *depth 1.69 ns 0.14 ns
Gyp‘comp" cover *depth 1.74 ns 2.49 ns
--------------- Late--------------

Gypsum 1.05 ns 0.54 ns
Compost 123.66 *** 8.87 *
Gyp*comp 0.38 ns 0.27 ns
Cover 0.18 ns 0.76 ns
Gyp“ cover 0.15 ns 0.24 ns
Comp" cover 2.72 "‘ 0.74 ns
Gyp*comp"' cover 0.22 ns 0.14 ns
Depth 36.66 *** 21.2 ***
Gypsum*depth 3.17 ns 5.83 *
Comp*depth 14.07 *** 5.85 *
Gyp*comp*depth 0.36 ns 0.89 ns
Cover*depth 0.15 ns 1.25 ns
Gyp" cover *depth 0.26 ns 0.58 ns
Comp“ cover *depth 0.35 ns 0.57 ns
Gyp*comp* cover *depth 0.11 ns 0.33 ns

Fall
Gypsum 12.66 * 2.78 ns
Compost 219.92 *" 16.79 **
Gyp*comp 0.76 ns 0.00 ns
Depth 33.58 *** 7.94 **
Gypsum*depth 3.77 ns 7.99 **
Comp‘depth 4.66 * 14.53 **
Gyp‘Comp*depth 1 .49 ns 0.45 ns

"' P s 0.05
** P S 0.01;

”“ P $0.001; ns Not signiﬁcant at (1:005 Abbrev: Gyp = gypsum: comp = compost

48

Table 2.12. Effects from gypsum, compost, depth and cover crops on mean extractable C3

 

 

 

 

 

and Mg (2007).
2007 Spring Early Spring Late Fall Late
Sources Ca Mg Ca Mg Ca Mg
-1
mg/kg
No Cover _ _ 10423 1503 _ _
Wheat _ _ 1068a 1573 _ _
Mustard 9773 138b 10623 1553 _ _
Oilseed radish 9663 138b 1055a 1493 _ _
Red Clover 9823 1533 10483 1533 _ _
Compost 1126a 128b 12223 13% 12203 136b
No compost 824b 1583 888b 1663 916b 1673
Gypsum 10053 1413 10863 1493 11313 1453
No gypsum 9453 1453 1024a 1563 1005b 1573
Depth 0-10 cm 10263 13% 11013 148b 1119a 147b
Depth 10-20 cm 924b 1473 1009b 1573 1018b 1543

 

Mean within the columns and groups followed by the same letters are not signiﬁcantly different
at a= 0.05

49

Table 2.13. Effects from treatment interactions on mean extractable Ca, and Mg (2007).

 

 

 

 

 

 

 

 

 

 

 

Ca Mg
Compost*depth Compost No compost Compost No compost
Spring mg/kgil
Early
0-10cm 12123 841C 128C 150b
10-20 cm 1034b 808C 128C 1593
Stdr 78 19
Late
0-10 cm 1297a 9060 138C 15%
10-20 cm 1147b 870c 141bc 1723
Stdr 70 17
Fall
0-10 cm 12893 948C 138c 158b
10-20 cm 1151b 884d 134c 1733
Stdr 57 18
Ca Mg
Gypsum*depth Gypsum No gypsum Gypsum No gypsum
-1
Spring mg/kg
Early
0-10 cm 1067a 986b 1363 1423
10-20 cm 944bc 903C 1463 147a
Stdr 85 17
Late
0-10 cm 11463 10573 142b 1543
10-20 cm 1026a 9923 156a 1583
Stdr 74 17
Fall
0-10cm 11983 103b 138b 1573
10-20 cm 1063b 972C 1513 157a
Stdr 59 18

 

Means within the same columns and rows followed by the same letters are not signiﬁcantly different

at a=0.05

50

Fr.”

Table 2.14. Effects from compost and cover crops on mean extractable soil Ca for spring 2007

 

 

 

 

 

Spring 2007
Cover*compost N W M O R
Early mg/kg']
Compost - - 11043 112783 11463
No compost - - 849b 8.4b 819b
Stdr - - 80 80 80
Late
Compost 1184b 12983 1 187b 1 1983b 12423b
No compost 899C 839C 9370 911C 854C
Stdr 75 77 77 77 77

 

Means within the same columns and groups followed by the same letters are not
signiﬁcantly different (1:005

Abreva = no-cover; W= wheat; M= mustard; 0 = oilseed radish; R= red clover

51

FIGURES

Figure 2.1. Representation of a typical block of the experiment design.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

b. 2006
3.2005 Early Late c. 2007
Cover crop sub-subplot
N CN _ CN 10.7m x4.4m
(35’X14.5)
M CN M CN
0
Compost
10.7 m x 13.m
(35’x43.5’)
Compost
Levels

 

 

9
z
z
9

 

> No compost

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CN R CN
Gypsum No gypsum Gypsum No gypsum
Sub-sub-subplots 79.5 m x 5.3 (261 x 17.5’)

5.3m x 4.4 m(17.5’x 14.5)

Abbrev.: N= No cover; C= Cereal rye; W= Wheat; R= Red clover, O= Oilseed radish;
M=Mustard; CN= Corn

52

Figure 2.23. Effect of cover crops and corn on extractable C3, 2005 and 2006.

 

N

 

_—I

 

 

 

I 2005 Fall
1400.0 -
a a

°° 1200.0 - a a a
"3‘, b
5 1000.0 —
1::
8
g 800.0 -
8
= 600.0 ~
8
«I
0 400.0 ~

200.0 ~ . —r—— —-—r

No-cover Cereal Mustard Oilseed Red Com
rye radish clover
Cover crops
b I2006 spring
1400.0 - 332006 Fall
3;) 1200.0 1
$11 1000.0 ~
8
_5 800.0 —
1?, 600.0 ~
§ 400.0 .
a 200.0 7
U
0.0 '
No cover ard Oilseed
rye radish clover
Cover crops

 

 

 

53

Figure 2.2b. Effect of cover crops and corn on extractable C3, 2007.

 

 

 

l 2007 early spring
1! 2007 late spring
1400 -
5. 1200 -
'30
f5 1000
E 800
_o
E 600
t:
3 400
8
as 200
U
0 E
No cover Wheat Mustard Oilseed Red clover
radish
Cover crops

 

 

 

54

Figure 2.33. Effect of cover crops and corn on extractable Mg 2005, and 2006

 

 

 

 

   

a
250 - '2005 Fall

200 - ab 1, ab
1‘ C
'30
i, 150
E
8
'g 100 ~
1:
=
g 50
8
E“

o «L —e —
No cover Cereal Mustard Oilseed Red Corn
rye radish clover
Cover crops
b l 2006 spring
~ 2006 F311

250.0 -
3,? 200.0 —
g” a
:: 150.0 -
'8
I:
1:: 100.0 ~
3
8
E 50.0 —

0.0 ._‘L
No cover Cereal rye Mustard Oilseed
radish
Cover crops

 

 

 

55

Figure 2.3b. Effect of cover crops and corn on extractable Mg 2007

 

Mg concentration mg/kg“)

 

250

 

I 2007 early spring
3 2007 late spring

 

No cover Wheat Mustard Oilseed Red clover
‘ radish

Cover crops

 

56

 

Figure 2.4. Effect of compost and gypsum on extractable Ca.

 

0)

Ca concentration (mg kg 1)

16000 7
14000 1
1.. 000

10000

3000 *1.
6000 a,
400.0 1
2000 01

FallOS

Spring 06

I Compost
i No compost

SpringO Fall
late

Fall 06 SprillgO

eall'v
Seasons

 

5'

Ca concentration (mg/kg")

 

1600.0 4,
1400.0 1

1200.0»; 3 ,3.

I

0.0 1» «5

111110111
800.0 1
600.0
400.0
200.0 1

Fall 05

SpringOG

I Gypsum
‘5'" No gypsum

a a

Fall 06

a
33 I30 b

SpringOG Spring06
early late

Fall 07

Seasons

 

57

 

Figure 2.5. Effect of compost and gypsum on extractable Mg.

 

  

 

     

 

 

   

 

a ICompost
250 . nNocompost

12

g; 200 ~

5 150 11 a raj”

{:1 b b

g .

g 100 — a;

.30 50 1. . ,5;

o ...“ . ..., 4 1 “‘1'“ ' -. ".33... .-- ..
FallOS Spring 06 Fall 06 Spring 07 Spring 0"
early late
Seasons
b IGypsum
250 * eNogypsum

3'2 200 « a

\

m

E

:t 150~ a a 3

o

'5‘

a
' E 100 <

11,)

2

8 so —

DD

2

0 ~, I.-. _T_ ..-]
FallOS Spring06 FallOG Spring06 Spring06 Fallo7
early late
Seasons

 

 

 

58

Figure 2.6. Effect depths on extractable Ca.

 

C a concentration (mg/kg")

 

1400.0 ~

1200.0

1000.0

800.0
600.0 -
400.0 -
200.0 ,

0.0

 

 

Fall 05 Spring 06 Fall 06 Spring 07 Spring 07 F31107

Seasons early late

 

Figure 2.7. Effect depths on extractable Mg.

 

Mg concentration (mg/kg“)

 

250

 

I 0-1OCm
l 10-20cm

 

F31105 Spring 06 F31106 Spring 07 Spring 07 Fall 07
early late

Seasons

 

59

 

 

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measurement in calcareous soils: ion—exchange resin bag, capsule, membrane,
and chemical extractions. Soil Sci. 167: 666-679.

Sumner ME. 1993. Gypsum and acid soils: the world scene. Advan. Agron. 51 :1-32.

62

Tisdale, L.S., W. L. Nelson, J. D. Beaton., J. L. Havlin. 1999. Sixth Ed. Soil Fertility and
Fertilizers. Macmillan. New York, NY.

Toma, M., M. E. Sumner, G. Weeks, and M. Saigusa. 1999. Long-term effects of
gypsum on crop yield and subsoil chemical properties. Soil Sci. Soc. Am. J. 63:
891-895.

Warncke , D., and J .R Brown. 1998. In Brown, J .R (ed). Recommended soil test
procedures for the North Central Region. Research publication No.22] (revised).
N.D. Agric. Exp. Stn., Fargo, ND.

Warncke, D., and J. Dahl. 2004. Nutrient recommendations for vegetable crops in
Michigan. Ext. Bull. E-2934, Mich. State Univ., East Lansing, MI.

William C. Liebhardt. 1981. The basic cation saturation ratio concept and lime and
potassium recommendations on Delaware's coastal plain soils. Soil Sci. Soc.
Am. J. 45: 544-549.

Zheljazkov, V. D., T. Astatkie, C. D. Caldwell, J. MacLeod, and M. Grimmett. 2006.
Compost, manure, and gypsum application to Timothy/red clover forage. J.
Environ. Qual. 35: 2410-2418.

63

CHAPTER 3

EFFECTS OF GYPSUM ALONE OR COMBINED WITH COMPOST AND
COVER CROPS ON CORN YIELD AND QUALITY

ABSTRACT

This phase of the study investigated gypsum and its interaction with compost and
cover crops on growth, yield and quality of sweet corn (Zea mays var. rugosa). The
treatment design involved three factors: gypsum application at 0 and 2.24 Mg ha'1,
poultry compost, at 0 and 2.7 Mg ha'1, and four cover crops plus a no cover treatment.
The four cover crops were oilseed radish (Raphanus sativus), oriental mustard (Brassica
juncea L.), red clover (T rifolium pratense), and cereal rye (Secale cereale), or wheat
(Triticum aestivum). Sweet corn was sown in the spring of each year and cover crops in
the spring of 2005 and both spring and fall of 2006. The data presented here are for two
years (2006 and 2007) of a three year study. Gypsum application decreased both corn
plant biomass at the V8 growth stage and corn yield; had no positive effect on the total
number of marketable corn ears per hectare either alone or combined. Gypsum plus
compost interaction reduced corn yield per hectare when red clover was the previous
crop. Cover crops affected the number of sweet corn cars per hectare in 2006 (a = 0.05).

Both cover crops and compost had a positive effect on sweet corn growth, yield and

quality.

64

INTRODUCTION

Gypsum has been shown to increase corn yield and other crops when applied
alone, and combined with other soil amendments. These yield increases have been
observed mostly when subsurface acidity was treated with gypsum in highly weathered
soils of the southeastern USA (Sumner et al., 1986; Tomma et al., 1999) and that of
tropical and subtropical soils which are highly leached and variable charged which
impedes root penetration (Reeve and Sumner, 1970; Harnmel et al., 1985. Sumner et al.,
(1986) reported increased yield in alfalfa (Medicago sativa L.) in the southeastern USA
due to improved root development as a consequence of improved physical condition in
the subsoil. Yield increases by com (20—50%) and alfalfa % in response to gypsum were
shown to be directly correlated to improved water extraction ﬁom the subsoil through
decreased Al toxicity to roots, throughout a sixteen year study in Georgia (Tomma et al.,
1999). Similarly, signiﬁcant improvement in corn and soybean yields reported by
Harnmel et al., (1985) was due to increases in Ca levels and a consequent decease in Al
toxicity which allowed for deeper penetration and root proliferation and increased water
uptake from the subsoil. Gypsum is a valuable input for rapidly replenishing the soil
proﬁle with Ca (Ritchey and Sunffer, 2002; Warncke, 2003 and Tisdale et al., 1996); may
alleviate hidden sulfur (S) deﬁciencies and consequently improve N uptake (Shelj azkov
et al., 2006), resulting in increases in yields. Sulfur deﬁciency frequently encountered in
alfalfa management was corrected with addition of gypsum, and resulted in a slight yield
increase in soybean (Glycine max L.), and up to 40% increase in alfalfa (Chen et al.,
2005) in Ohio. Also, clay-textured soils amended with gypsum, were shown to increase

sugar yields of ratoon sugarcane in Louisiana (Breithaupt et al., 1991).

65

Reports of responses from compost application to soil nutrient and soil physical
properties are abundant in the literature, but information on compost effect on crop
growth and yield is limited. Singer et al., (2004) found signiﬁcant increases in soil P and
organic matter when compost was applied to soybean plots and increases in both corn and
soybean yield. In a two year study to assess the effects of compost and tillage on corn
growth and nutrient accumulation in corn grain, Singer et al., (2007) also found increases
in P (19%) and K (21%) from compost application compared to non compost in corn.
Bow et al., (2008) reported increases in both grasses and legumes from compost

application due to increase soil P levels.

Traditionally, cover crops are used for erosion control (Andraski and Bundy 2005
Zheng et al., 2004; Kessavalou and Walters. 1999) and weed and disease suppression
(Snapp et al., 2005; Ngouajio and Mutch, 2004, Date and Snapp, 2004 ), through
alleopathy. Although a considerable amount of research into the beneﬁts of cover crops
have been done in recent years, the adoption of cover crops in crop production systems is
still low. Several studies have documented both beneﬁcial and unfavorable reports of
their uses. For example, yield increases of corn grain following winter rye (Secale
cereale L.) have been observed by Moschler et al.,1976; Andraski and Bundy, 2005 and
Clarke et al., 2007 and also, following winter killed oat (Avena sativa L.) and triticale (x
T riticosecale Wittmack) compared to control (Clarke et al., 2007). Conversely,
Mcdonald et al., (2008) reported signiﬁcant decreases (5 to 22%) in corn grain yield
following winter rye, winter wheat (T riticum aestivum L.), and triticale compared to
control plots. Hively and Cox (2001) reported signiﬁcantly lower corn grain yields

following annual rye plots compared to control plots, and interceeding red clover and

66

chickling vetch did not affect corn yield when com was planted at various densities
(Baributsa et al., 2008). Additionally, a signiﬁcant delay in soybean pod maturity and a
decrease in dry matter were observed following winter rye compared to control plots
(W estgate, et al. 2005). When soybean was interceded with rye, yield was greatly
reduced due to moisture stress (Thelen et al., 2004). In a study to investigate N
availability to corn in south-central Ontario, Vyn et al., (2000) found corn grain yield
responses to red clover substantially enhanced available N, but oilseed radish, oat, and
rye cover crops did not. In order to obtain the beneﬁts from cover crops for subsequent
cash crops, continued research is needed for the suitability of the various cover crops

within speciﬁc cropping systems in all aspects of production.

Taking into account the lack of information on the use of gypsum in Michigan
cropping systems and the limited documentation on compost and cover crop with regards
to crop growth and quality aspects, this study assessed the response of sweet corn growth
(and development) yield and quality to gypsum, and the synergistic effects with poultry

compost and the various cover crops studied.

67

MATERIALS AND METHODS

Site description and experimental design are explained in chapter two (p. 22).
Description of treatments and plot layout are given in the materials and methods of

chapter two (p. 23).
Sweet Corn Measurements

Plant stand, plant height, and whole corn plant samples were taken at the 8‘11 leaf
stage, about one month after sowing each year. Three corn plants were randomly
selected from each of two rows in each gypsum treatment, giving two samples per
subplot; a gypsum and a non-gypsurn sample. Chlorophyll meter readings (CMRs) were
taken when tassel emerged with a Minolta SPAD(soi1-plant analysis development)
chlorophyll meter (Spectrum Technologies, Inc., Plainﬁeld, IL). Readings were taken on
20 randomly selected uppermost fully developed leaves, midway between the leaf tip and
base and between the leaf margin and mid-rib, as described by Zhang et al., 2008, Varvel
et al., 2007; and Shanahan et al., 2001. Corn ears were harvested ﬁom 3.05 m (1011) of
the two middle rows from each subplot, and each gypsum treatment. All harvested corn
ears from each gypsum treatment were sorted into marketable and non marketable ears,
and weighed. From the marketable ears, ten were randomly selected, and their

(combined) weights, lengths and diameters measured.

Nutrient analysis

Five of the ten husked ears were selected and 7.6 cm mid-section sample taken for

68

nutrient analysis. All plant tissues were dried at 60 0C for 72 hrs, then ground with a
Wiley Mill and sent to A & L Great Lakes Laboratory Inc., Fort Wayne, Indiana for total
nutrient analyses. The nutrients analyzed were nitrogen (N), sulfur (S), phosphorus (P),
potassium (K), sodium (N a), boron (B), zinc (Zn), manganese, (Mn), iron (Fe), copper

(Cu), aluminum (Al), magnesium (Mg), and calcium (Ca) (A&L Great Lakes Lab., Inc).

RESULTS AND DISCUSSIONS
Treatment effects on Sweet Corn Growth and Development

For both 2006 and 2007, visual observations made up until visible tassel, corn
plants following oilseed radish had the darkest green color followed by mustard, then
corn followed by red clover. Corn which followed cereal rye or wheat was less green in
color (or similar) than corn which followed no- cover crop treatments. This was
especially noticeable in the plots where compost was applied, although compost
interaction with cover crops was not statistically signiﬁcant (P>0.05) for CMRs. The
degree of greenness generally reﬂects the level of nitrogen available in the soil for plant
uptake. ANOVA and means for CMRs are presented in tables 3.1 and 3.2 respectively.
CMRs were taken about the time of tassel emergence (VT) but prior to silking (RI). Only
cover crops inﬂuenced CMRs for corn plants. Results of CMRs in 2006 showed
signiﬁcant differences (P $0.01) among cover crop treatments in the following order:
cereal rye (55.5) = Oilseed radish (55.1) = red clover (55.1) = mustard (54.6) > no cover
(53.3). CMRs indicate the relative amount of chlorophyll in plant leaves; readings are in

SPAD units and are dimensionless (Zhang et 31., 2008). In 2007 when com followed

69

early planted cover crops, means of CMRs for red clover was signiﬁcantly higher (47.7),
than for corn after oilseed radish (45.5) or mustard (42.6). Visual observations for corn
which followed late planted cover crops in 2007 were similar to the visual observations in
2006, and CMRs in 2007 were reﬂective (numerically) of the visual observations. The
order of CMRs readings in corn following late cover crops were: oilseed radish (43.8) =
Mustard (43.7) = red clover (43.1) = wheat (42.5) > no cover (41.0). CMRs following
cereal rye were expected to be similar or less than corn following no cover crops. It was
not expected that the CMRs of corn following cereal rye (2006) would be similar to
CMRs of corn following other cover crops particularly for oilseed radish and mustard,
since visual observations indicated that the color intensity (greenness) was lowest for
corn following cereal rye. CMRs for cereal rye Were expected to be similar or less than
corn following no cover crops. The reason for the disparities between visual observations
and CMRs could be due to: l) Immobilization and mineralization time for the cereal rye
was different ﬁom the other cover crops. This is because mineralization occurred much
later in the season for cereal rye than mustard and oilseed radish which were winter
killed. Conversely, red clover (and other leguminous cover crops) can ﬁx atmospheric N
which can increase available N during decomposition (Kuo and Sainju, 1998). During
the early stages of the corn growth since cereal rye was incorporated in the early spring,
N immobilization exceeded N mineralization while the residue was being decomposed.
Net N immobilization generally occurs for the ﬁrst couple months after winter cereal
cover crops are incorporated (Snapp et al., 2005; Malpassi et al., 2000). Vyn et al.,
(2000) also found low spring concentrations of NO3-N following annual rye indicating a

low N availability to succeeding corn compared to other cover crops and no-cover crop

70

treatment. During the decomposition of crop residue, N immobilization can reduce soil
N (NI-14+ and N03) concentrations to very low levels (Tisdale et al., 1999). 2) When
mineralized N was made available from cereal rye later during the growing season, this
resulting in higher CMRs for corn than from the other cover crops. 3) It is also possible
for corn following cereal rye to have higher levels of chlorophyll and N concentration
than the other cover crops. This is because cereal rye (or wheat) killed in the early spring
while still young has lower biomass than if killed after reaching or approaching
physiological maturity, but will have higher N concentration and a low C/N ratio (Reiter
et al., 2008). Young cereal rye plants have a UN ratio of 14:1 compared to cereal rye at
mid-boot which is 40:1(Boswith, 2006). The C/N ratios for oilseed radish, red clover,
and mustard are 28:], 21 :1 (V yn et al., 1999) and 26:1 respectively. Additionally, rye has
shown superior ability to scavenge residual soil N than some cover crops (Ranells and

Waggner 1997; Shipley et al., 1992).

In 2006 cover crops (PS 0.001), compost (PS 0.001) and the combined effects of
compost and cover crops (PS 0.05) signiﬁcantly affected corn height at the V8 stage.
ANOVA and means of plant height are presented in tables 3.2, 3.3 and 3.4. Plant height
was greatest when com followed oilseed radish (70.3 cm) and mustard (68.7); there was
no signiﬁcant (Figure 3.23) difference between red clover (60.2 cm) and no-cover (59.6
cm). Cereal rye had the lowest mean compared to no-cover (57.1 cm). In 2007, there
was no difference in mean height when com followed early planted cover crops. Mean
plant height when com followed late cover crops (Figure 3.2b) was higher ﬁ'om oilseed
radish (62.3 cm) and mustard (62.0 cm) than red clover (58.5 cm), and wheat (54.2 cm).

Plant height in no-cover plots (61.0cm) was similar to that following oilseed radish and

71

mustard. More vigor and growth from these cover crop treatments can be directly related
to their capacities to cycle N to the surface soil. Oilseed radish has a deep root system
and is an excellent scavenger of nitrates; produces a large amount of biomass in a short
time (N gouajio and Mutch, 2004). Collins et al., (2007) reported 36 kg N ha“1 from
decomposition of mustard residues from a study to evaluate N cycling from mustard
cover crops to potato. In both years, corn following cereal rye (2006) and wheat (2007)

had the lowest mean heights even compared to no-cover.

Compost application increased plant height in 2006 (P <0.001) and in 2007 (PS
0.01) from early cover crops; both compost (PS 0.01) and cover crops (PS 0.001)
inﬂuenced height of corn following late planted cover crops (Figure 3.33; tables 3.2, 3.3,
and 3.4 ). When compost was applied in 2006, plant height increased by 19 % (47cm)
compared to no-compost treatment (39.5 cm). In 2007, plant height from compost
treatment was 12 % greater (63 cm) than no-compost (56 cm). Compost treated plots
developed tassels much earlier than no-compost (Figure 3.43 and 3.4b), and sweet corn
from compost treated plots were harvested two days before non compost treated plots
because of earlier maturity. Singer et al., (2004), reported that soil organic matter content
in compost plots was 63 g kg’1 compared with 57 g kg’1 in the no-compost plots.
Organic matter enhances soil physical properties and water holding capacity,
consequently affecting crop grth and development. Corn plants growing in compost
treated soil accumulated more P and K than plants growing in non compost soils (Singer
et al., 2007). Table 3.5 shows that com plots accumulated more Ca, P and K from
compost soils than from compost treated soils. Adequate P in the early stages of plant

growth is important for development of productive parts. K is vital for activation of

72

enzymes which are abundant in meristematic plant tissues where rapid cell division
occurs and primary tissues are formed. Tisdale et al., (1999) reported more advanced

development of small grains receiving P, compared to control.

When compost and cover crops interacted, the greatest effect on plant height was
from compost application with oilseed radish (74 cm) and mustard (72 cm), followed by
red clover (68 cm), then cereal rye (65 cm). There was no statistical difference in plant
height between cereal rye and no-cover (66 cm). Gypsum application had no effect on
plant height in both years (Figure 3.3b). Corn grown on gypsum plots regardless of
compost treatments developed tassels later than no-gypsum plots. However, no—gypsum
plots which were compost treated developed tassels earlier than gypsum plots which had
no compost applied. Trends for soil available P ﬁ'om Mehlich-3 anaylsis indicated that P
concentrations were lower for gypsum than non-gypsum treated plots, although
differences were not signiﬁcant. Gypsum supplies additional C3 to the soil, which may
result in phosphorous (P) being less available for plant growth at the critical early stages
of development. Gypsum application was found to reduce dissolved reactive P (DRP)
concentration by converting readily desorbable soil P to less readily soluble Ca—P
compounds (Favaretto, et al., 2006; Stout et al., 2000). It seems that delayed tassel
development of corn from gypsum treated plots may be a consequence of reduced P
availability at the critical growth stage, or rather more P available from compost

treatments when no gypsum was applied which resulted in earlier tassel development.

Only cover crops and compost inﬂuenced whole plant biomass at the V8 stage in
both years. ANOVA and means of plant biomass are presented in tables 3.2 and 3.3.
Cover crops signiﬁcantly affected plant biomass in 2006 (P<0.001) and in 2007(P S

73

0.05) when com followed late planted cover crops. Mean for corn plant biomass at the
V8 stage in 2006 were as follows: oilseed radish (0.68 Mg/ha'1) = mustard (0.64 Mg/ha’1)
> red clover (0.51Mg/ha'1 ) = no-cover (0.50 Mg/ha'1) = cereal rye (0.44 Mg/ha'1). Mean
weight for corn plant biomass where cover crops were incorporated in 2006 (Figure 3.53)
were signiﬁcantly higher than for 2007 (Figure 3.5b). One reason for this difference in
biomass may be higher temperatures in 2007 than 2006 which resulted in drier soil
conditions that affected growth at early stages of growth. In 2007 mean for plant biomass
when com followed oilseed radish and mustard, were similar to no-cover; wheat had the
lowest mean. There was no signiﬁcant difference among means of plant biomass
following early planted cover crops, mostly because early cover crops did not include no-

cover treatment and cereal rye or wheat.

Compost application had a positive effect on whole plant biomass for both years
(Figures 3.63). The mean from compost treatment was 26% greater than no-compost in
2006 (PS 0.001). When corn followed early planted cover crops in 2007 (PS 0.001) the
mean of plant biomass ﬁom compost application was 48% higher than no-compost
application, and 45 % higher following late cover crops (PS 0.01) . This is noteworthy,
since NPK fertilizer was applied to no-compost plots. Other studies have reported
increased biomass yield due to residual plant-available N provided by compost (Lynch et
al., 2004; Tejada and Gonzalez, 2006), when compost alone was applied compared to
controls. Still other studies have reported unexplained yield increases from compost
application. In a study comparing compost treatments with tillage management, Singer et
al., (2007) reported greater yield responses from no-till. There was no apparent reason

for this, since the data suggested that N was not responsible. Although gypsum

74

application did not signiﬁcantly affect plant biomass (Figures 3.6b); numerically, corn
plant biomass from gypsum application was 9% lower than no-gypsum in 2006. In 2007
mean of corn plant biomass from gypsum application was 14% lower than no-gypsum,
following early cover crops (Table 3.2). This trend was not statistically signiﬁcant and

was not observed in 2007 following late cover crops.

Nutrient (Ca, Mg, N, P and K) concentrations of plant biomass were signiﬁcant
for gypsum, compost and the combined effects of gypsum and compost, and of compost
and cover crops. Effects of the various treatment factors (ANOVA) on whole plant
nutrient concentrations are presented in Table 3.53 and 3.5b; their means in Tables 3.6
and 3.7. In 2006, mean of Ca concentration in corn biomass was 7 % higher for compost
(3.6 g/kg'1) than no-compost (3.4 g/kg'1) application. In 2007, C3 was 11% higher with
compost than no-compost when com followed early planted cover crops and 6 % higher
when com followed late planted cover crops. Cover crops signiﬁcantly (PS 0.001)
inﬂuenced Ca concentration of plant biomass in 2006. Red clover incorporation resulted
in the highest Ca concentration (3.7 g/kg'1); mustard was the lowest (3.2 g/kg'1),
compared to no-cover (3.5g/kg'1). When corn followed early planted cover crops in
2007, the order of effect was: red clover (4.52 g/kg'1)> mustard (4.0 g/kg'1) = oilseed
(4.0g/kg'1). No cover crop effect was observed following late planted cover crops in
2007. Gypsum signiﬁcantly affected Ca concentration in plant biomass only in 2006 and
2007 when com followed late planted cover crops. Calcium concentration was 8%
higher (4.3 g/kg'1) from gypsum application compared to no-gypsum (3.9 g/kg'1).
Faveratto et al., (2008) reported higher Ca concentrations in corn shoots when gypsum

was applied compared to control plots.

75

Magnesium concentration was signiﬁcantly affected in both years by compost and
cover crops and in 2007 by the combined effect of compost and cover crops (Tables 3.53
and b, 3.6 and 3.7). Magnesium concentration of corn plant biomass was signiﬁcantly
depressed when compost was applied, a direct opposite to the effect on Ca concentration
in plant biomass. Compost application resulted in 23% decrease of Mg compared to no-
compost in 2006, and similar decreases in 2007 when corn followed both early and late
planted cover crops. The combined effect of compost and cover crops had a signiﬁcant
effect on Mg following early planted cover crops (Table 3.7). When compost was
applied compared to no compost application, corn following red clover had the largest
decrease in Mg (1.2 g/kg'1), followed by mustard (0.8 g/kg’1), then by oilseed radish (0.5
g/kg'1). The application of both gypsum and compost resulted in increased Ca and
decreased Mg concentrations; conversely, when neither compost nor gypsum was added,
Mg concentration in plant biomass increased. Magnesium and Ca existence in plant
tissue is sensitive in relation to each other. Too much of one results in the reduction and

possibly, an insufﬁciency of the other (Vitosh et al., 1994; Faveratto et al., 2008).

Nitrogen concentration in corn biomass was enhanced by the effects of cover
crops (P S 0.001), and the interactions of cover crops and compost (PS 0.001) in 2006
(Tables 5, 6 and 7). The order of cover crop effects were: oilseed radish (25.6g/kg) > red
clover (24.1 g/kg) = cereal rye (23.9g/kg) > mustard (22.0g/kg) = no cover (21.9g/kg). A
similar trend was observed in 2007 (P S 0.001), when com followed both early and late
cover crops. The combined effects of compost and cover crops were signiﬁcant in 2006
(P S 0.001) and following late cover crops in 2007(PS 0.05). The mean of N

concentration in plant biomass when cover crop plots received compost application in

76

2006 (Table 3.7) was highest following cereal rye and red clover (25.0 g/kg'1), followed
by oilseed radish (24.0g/kg'1), then mustard (20.9g/kg'1) which was similar to no-cover
(21.5g/gk’1). When corn followed late cover crops, application of compost to no-cover
plots increased N concentration by 10% compared to no-cover plots without compost.
There was no difference among other compost-cover crop interactions. Gypsrun
application had no effect on N concentration of plant biomass in 2006 but had a
signiﬁcant negative (P S 0.05) effect in early 2007. When corn followed early cover
crops in 2007, gypsum decreased N by 6%, but had no effect with late cover crops.
There was a signiﬁcant effect from the combined application of gypsum and compost on
N content of plant biomass only from early planted cover crops in 2007. There was a
10% decrease in N when gypsum was applied to no-compost plots compared to compost
plots when neither gypsum nor compost was applied. No gypsum effect on N content of

plant biomass was observed when com followed late cover crops (Table 3.5b).

Phosphorous concentration in plant biomass was inﬂuenced by cover crops in
2006 (P S 0.05) and 2007 (P S 0.001), and by compost in 2006 (P S 0.01). In 2006,
when com was grown on oilseed radish plots, P concentration of plant biomass was the
lowest (3.0 g/kg'1); there was no difference among the other cover crops compared to no-
cover (3.5g/kg'1). The highest mean of P in 2007 from early planted cover crops, was for
corn grown on red clover plots (3.9 g/kg'1); there was no signiﬁcant difference between
oilseed radish (3.5 g/kg'1) and mustard (3.4 g/kg'1). A similar trend was observed in 2007
(as 2006) when com followed late planted cover crops; oil seed radish resulted in the
lowest P (3.9 g/kg'1), and there was no difference among the other cover crops including

no-cover (4.3 g/kg'1). When compost was applied in 2006, biomass P increased by 11 %

77

compared to no-compost application. There was no compost effect in 2007 and gypsum
had no effect on P concentration of plant biomass. Singer et al, (2007) reported that com
plants growing in compost treated soil accumulated more P and K than plants growing in
no-compost soils. Cover crop effect on P was generally the direct opposite of N.
Mustard and oilseed radish, resulted in the highest N concentrations, with no difference

between wheat, and no-cover (Table 3.6).

Effects found to be signiﬁcant for K concentration in corn biomass were compost
(P S 0.05) in 2006 and 2007, and cover crops (P S 0.001) in 2007. Compost application
increased K by 8% compared to no-compost in 2006. When corn followed late planted
cover crops, K was increased by 8%, but no compost effect was observed following early
planted cover crops in 2007. Cover crops had no signiﬁcant effect on K concentrations in
2006 (P > 0.05), but inﬂuenced K in 2007 (PS 0.001). When corn followed early planted
cover crops, the highest K concentration was following oilseed radish (46.4 g/kg'1),
followed by mustard (44.1 g/kg'1), then red clover (37.8 g/kg'1). There was no signiﬁcant
difference in K when com followed late cover crops (Table 3.6). There is limited
information in the literature on effect of these soil amendments on corn whole plant
nutrient concentration; most studies focus on soil nutrient status, and treatment effect on

soils.

Treatment Effects on Sweet Corn Yield

In 2005, corn yield data was not meaningful due to heavy infestation by

European corn borer. ANOVA and means for corn yield in 2006 and 2007 are presented

78

in Tables 3.8 and 3.9 respectively. Only cover crops signiﬁcantly (P > 0.01) affected the
number of marketable corn ears in 2006. Oilseed radish resulted in the highest number of
total marketable ears per hectare; cereal rye was the lowest, and similar to no—cover
(Figure 3.73). There was no signiﬁcant difference (P > 0.05) in number of ears ﬁ'om
early or late treatments of similar cover crops (mustard, oilseed radish and red clover)
(Figure 3.7b). Overall, there was no signiﬁcant difference in the percentage of
marketable corn ears among cover crops (Table 3.9). Generally, the number of corn ears
was higher in 2006 than 2007 across cover crop treatments, partly due to lower plant
densities in 2007. Cereal rye (2006) and wheat (2007) generally resulted in the lowest
corn yield (and biomass), even compared to no-cover. We hypothesize that, this was due
partly to N immobilization (Tollenaar et al., 1993; De Bruin, 2005), which reduced
available N for plant growth. Also, lower growth, development and corn yield can be
caused by rye and wheat through alleopathy from phytotoxic compounds secreted by the
roots, or produced by decomposition of their residues (Tollenaar et al., 1993; and

Raimbault, 1990). Ear weights were not signiﬁcantly affected by treatments in 2006.

In 2007, only compost had a positive signiﬁcant effect (P S 0.01) on ear weights.
When corn followed late cover crop treatments, mean weight of corn ears was 11.78
Mg/ha'l for compost and 9.49 Mg/ha'1 for no—compost. There was no effect from the
early planted cover crops. Singer et al, (2004) reported that compost increased wheat
yield ntunerically by 5% and 4% (2001 and 2002), though differences were not
statistically signiﬁcant. They also reported increased yield in ﬁeld corn by 6% (2000),
8% (2001), and 13% (2002), from compost, compared to no-compost treatments. Dorivar

et al., (2008) reported signiﬁcantly higher grain yields in ﬁeld corn from poultry compost

79

compared with control plots, and Endale et al., 2008, reported 18% yield increase in ﬁeld
corn from compost compared to mineral fertilizer. Neither gypsum nor any of the
combined treatments affected number of marketable corn ears. Number of marketable
corn ears though not statistically signiﬁcant, was numerically higher for no-gypsum plots
than gypsum treated plots for both years. There was a 4% increase in 2006; 6% and 5%
increases from early and late cover crops in 2007 respectively when gypsum was not

applied compared to gypsum application (Table 3.9).

Treatment Effects on Sweet Corn Quality

The quality of sweet corn was evaluated by the physical measurements of
weights, lengths and diameters, and the nutrient concentrations of 10 randomly selected
corn ears (combined). ANOVA and means for treatment effects on physical
measurements of sweet corn ears are presented in Tables 3.10 and 3.9 respectively. In
2006 lengths and weights were signiﬁcantly affected by both cover crop incorporation (P
S 0.001) and compost application (P S 0.05) but there was no treatment effect on ear
diameter (P > 0.05). Effect of cover crops on means of combined lengths of the ten corn
ear were as follows: cereal rye > red clover= no cover> mustard =oilseed radish (table
3.9). Generally, means for lengths of corn ears follow a similar pattern with
corresponding ear weights. Corn ear lengths and weights were inversely correlated with
the plant densities of corn and the number of corn ears following respective cover crops

(Tables 3.2 and 3.9). Compost application signiﬁcantly increased both lengths (P S 0.05)

and weights (P S 0.01) of corn ear in 2006. When compost was applied, corn ears were

80

longer (by 4 cm) and heavier (by 0.2 kg), than no—compost. In 2007, lengths, weights and
diameters were signiﬁcantly inﬂuenced by compost and cover crops. When corn
followed early planted cover crops only compost (P S 0.01) application was signiﬁcant
for corn ear weights (P S 0.01); both compost (P S 0.01) and cover crops (P S 0.05) were
signiﬁcant for corn ear diameter. Mean corn ear weight was 5% higher and diameter was
4 % higher when compost was applied, compared to no-compost. Mustard cover crop
(46.9 cm) resulted in the largest diameter mean followed by red clover (46.5 cm), then
oilseed radish (45.6 cm) when com followed early cover crops. When corn followed late
planted cover crops, means of lengths (P S 0.01), weights (P S 0.001) and diameters (P S
0.01) were signiﬁcantly higher from compost application compared to no-compost.
Cover crops inﬂuenced corn ear weight and diameter, but had no signiﬁcant (P > 0.05)
effect on length. The order of effect on mean corn ear weight ﬁom late cover crops was:
Oilseed radish (2.03 kg) kg) = no cover (2.02 kg) mustard (1.94 kg) = red clover (1.92kg)
Z wheat (1.88 kg). Cover crops (late) except wheat, resulted in an increase in ear

diameter, compared to no-cover.

Generally, mean corn ear lengths were higher across treatments in 2006 than
2007, but diameter means were greater in 2007 than 2006. The growing season in 2007
was hotter and drier, which may have caused a reduced number of kernels per row,
consequently reduced ear lengths. Kernels per row can be strongly inﬂuenced by severe
stress such as drought conditions ocCurring about two weeks prior to pollination (J anes
and Rosati, 2002). Low soil moisture can result in low K availability to plant roots
because diffusion and mass ﬂow are responsible for most of the K adsorbed by plants.

Potassium also provides most of the osmotic pull drawing water into plant roots.

8]

Potassium can be available, but if soils are to dry, K can become positionally unavailable.
When this happens many plant physiological processes are impacted, including the
development of meristematic tissues where cell division takes place (Tisdale, et al.,

1999)

Concentrations of Ca, Mg, N, P, and K of the corn ears were determined.
ANOVA for treatment effect on nutrient concentrations in corn ears is presented in Table
3.113 and 3.1 lb, and means of nutrient concentrations from the various treatment factors
and their interactions are presented in Tables 3.12, 3.133 and 3.13b, respectively. In
2006, C3 concentration in corn ears was affected only by compost (P S 0.05) and the
combined effect of gypsum and compost (P S 0.05). Compost application increased Ca
concentration in corn ears (0.17 g/kg'1) by 31% more than no-compost (0.13 g/kg‘1).
When both compost and gypsum were combined, Ca concentration (0.21 g/kg'1) was 75%
higher than gypsum application alone (0.12 g/kg'1), 50% higher than compost application
alone (0.14 g/kg'1) and 50 % higher ﬁom plots where neither gypsum nor compost (0.14
g/kg'1) was applied (Table 3.13b). This may indicates a synergic effect between gypsum
and compost for enhanced Ca accumulation in sweet corn ears. No treatment factor had

an effect on C3 concentration in corn ears in 2007.

In 2006 (Table 3.1 lb), N was inﬂuenced by gypsum (P S 0.05), cover crops (P S
0.001), and the combined effect of compost and cover crops (P S 0.01). When gypsum
was applied, mean N concentration (15.1 g/kg'1) was decreased by 3.3% compared to no
gypsum (15.6 g/kg'1). There was no gypsum effect on corn ear N concentration in 2007.
Cover crops effect on N concentration of corn ears in 2006 was as follows: oilseed radish
(15.7 g/kg'1) = mustard (15.7 g/kg'1) Z cereal rye (15.4 g/kg'1) 2 red cover (15.1g/kg'1) =

82

no cover (15.0 g/kg'1). There was no signiﬁcant difference among cover crop treatment
on N concentration of corn ears in 2007. The combined effect of compost and cover
crops on N concentration in corn ears was signiﬁcant (P S 0.01) in 2006. The highest
increase was observed from compost interaction with cereal rye (7.4%), followed by
mustard and oilseed radish (4%), then red clover, which was similar to no-cover
(14.9g/kg'1) plots when compost was applied (Table 3.13b). Only compost application
inﬂuenced N concentration of corn ears in 2007 when com followed early planted cover
crops, with a 5% increase compared to no compost. There was a signiﬁcant (P S 0.05)
three way interaction among compost, gypsum and cover crops when com followed late

cover crops in 2007 (Table 3.13b).

Means of N concentration were similar when either compost (19.2 g/kg'1) or
gypsum (19.1 g/kg'1) was applied to red clover plots. When both compost and gypsmn
were applied to plots following red clover, N concentrations remained the same as red
clover plots with neither compost nor gypsum applied (18.0 g/kg'1); a 6.4% less N (Table
3.13b). It appeared that interaction of gypsum and compost with red clover exhibited a
negative effect on N concentration in corn ears. Legumes generally have a relatively
high S requirement (Mckell et al., 1971; (Sathyarnoorthi et al., 2007) for the formation of
nodules and nitrogen ﬁxation (V itosh et al., 1994; Tisdale et al., 2005). Compost
application potentially increases soil levels of P (Eghball and Power, 1999). In a study to
evaluate the effect of S and P on mung bean, Aulahk and Pasricha (1977) reported an
antagonistic relationship between S and P uptake and utilization especially when applied
together. This may explain the reason for the decrease in N concentration in corn ears,

when compost and gypsum interacted with red clover. The effect of compost application

83

to no-cover crop plots was similar to the effect of gypsum plus compost application (18.7
g/kg'1), but signiﬁcantly higher (7.5 %) than gypsum application alone to the no-cover
crops (17.4 g/kg'1). There was no signiﬁcant difference between gypsum application
alone (17.4 g/kg'1) and when both gypsum and compost were not applied (17.8 g/kg'1).
No signiﬁcant compost by gypsum three-way interaction was observed with wheat and

mustard.

Phosphorous concentration in corn ears was inﬂuenced only by cover crop
treatments in 2006 (P S 0.05), and their effects followed a similar trend to N
concentrations. Mustard (3.4 g/kg'1) and oilseed radish (3.5 g/kg'1 ) resulted in the
highest increases in P concentration which were signiﬁcantly higher than following red
clover (3.3 g/kg'1) and cereal rye (3.5 g/kg'1). Corn ear P concentration following cereal
rye and red clover were not different from no-cover crop (3.3 g/kg'1). Potassium was
only inﬂuenced by cover crops (P S 0.001) in 2006 and the combined effect of compost
and cover crops (P S 0.01) when com followed early planted cover crops in 2007 (Table
3.12). The effect of cover crops on K followed an opposite trend to their effects on N and
P. The mean corn ear K concentration (Table 12) following oilseed radish (10.6 g/kg'1)
and mustard (10.7 g/kg'1) were the lowest; following no-cover crop (l 1.1 g/kg'1) was the
highest, followed by cereal rye (11g/kg'1), then red clover (10.9 g/kg'1). When corn
followed early planted cover crops (2007), the corn ear K means following mustard (9.5
g/kg) and oilseed radish (9.6 g/kg-l) were 9% and 6% higher respectively, when
combined with compost than their means with no compost applied. The mean ear K
following red clover combined with compost was 5% lower than no—compost (Table

3.133).

84

SUMMARY AND CONCLUSION

This study indicates that, cover crops and compost alone or combined, have
potential to increase the quality and yield of sweet corn. Oilseed radish and mustard offer
great potential for increases in sweet corn yield and ear quality. Cereal rye and winter
wheat are not good choices for improving yield. There is indication that combining
gypsum and compost application can have a negative interaction effect on sweet corn
yield when red clover is the previous crop. In some cases, gypsum applied alone and in
combination with compost and various cover crops used in this study had a negative
effect on corn growth, yield and/or quality. Generally, sweet corn yield was lower when
gypsum was applied alone or in combination with cover crops or compost. If the desired
beneﬁt is for increasing yield and improving quality, the use of gypsum was not
beneﬁcial in sweet corn production on a Kalamazoo sandy loam. Long term studies are
necessary to investigate the effect of gypsum on crop yield for different soils across

Michigan and elsewhere.

85

Table 3.1. Statistical signiﬁcance of gypsum, compost and cover crops for CMRs in 2006 and

 

 

 

 

2007
2006 2007

Sources of variations F-value P-value F-value P-value F-value P-value
2006 Early Late

Gypsum 1.47 ns 0.55 ns 0.55 ns

Compost 3.1 1 ns 0.90 ns 3.89 ns

Gypsum * compost 0.32 ns 0.97 ns 0.20 ns
Cover 4.72 ** 38.04 *** 6.17 **"‘
Gypsum "‘ cover 0.13 ns 1.68 ns 1.16 ns
Compost * cover 0.38 ns 1.35 ns 0.73 ns
Gypsum * cover * compost 1.09 ns 0.01 ns 0.41 ns
** P S 0.01
***P S 0.001

ns Not signiﬁcant at a=0.05

86

Table 3.2. Effects of plant compost, gypsum and cover crops on corn density, height, biomass, and CMRS,
concentration (V 8) for 2006 and 2007

 

 

 

 

 

Treatment Plant density Plant height Corn Biomass CMR ’
-1 -1
Plants/Ira cm Mg/ha Reading
2006
No cover 74915c 57b 1.00b 53.3c
Mustard 75992b 693 1.283 54.63
Oilseed radish 762073 703 1363 55.13
Red clover 71040b 60b 1.03b 55.13
Cereal rye 67596c 57c 0.88c 55.53
Compost 723323 693 1.283 54.43
No compost 740543 56b 0.94b 55.13
Gypsum 731933 633 1.063 55.03
No Gypsum 731933 633 1.163 54.53
Early
2007
Mustard 525273 613 0.373 42.6c
Oilseed radish 533883 623 0.433 45.5b
Red clover 505893 593 0.423 47.73
Compost 538183 633 0.523 45.03
No compost 505893 56b 0.30b 45.63
Gypsum 516663 613 0.383 45.53
No Gypsum 527423 603 0.443 45.03
Late

No cover 527423 623 0.403 41.0c
Mustard 533883 623 0.433 43.73
Oilseed radish 536033 623 0.413 43.83
Red clover 512353 59b 0.37ab 43.13b
Wheat 514503 54c 0.3 3b 42.53b
Compost 516663 623 0.433 43.33
No compost 531733 58b 0.34b 42.3b
Gypsum 520963 593 0.393 43.03
No Gypsum 529573 613 0.393 43.03

 

Means within the same column and groups followed by the same letters are not
signiﬁcantly different a=0.05 .

87

Table 3.3. Statistical signiﬁcance of gypsum, compost and cover crops, on corn plant height, biomass and

 

 

 

 

corn ears
2006 2007
Sources of variations F-value P-value F-value P-value F-value P-value

Plant height(V 8) Early Late
Gypsum 0.01 ns 0.05 ns 0.13 ns
Compost 70.53 *** 41.52 '1'" 15.10 **
Gypsum *x compost 2.77 ns 0.08 ns 0.76 ns
Cover 34.80 *** 0.42 ns 10.18 ***
Gypsum * cover 0.68 ns 0.52 ns 0.64 ns
Compost * cover 3.28 * 0.92 ns 1.54 ns
Gypsum "' cover *compost 0.14 ns 0.71 ns 1.23 ns

Plant Biomass (V 8) Early Late
Gypsum 6.34 ns 0.94 ns 0.00 ns
Compost 72.08 *** 29.57 "'1' 16.11 **
Gypsum '1' compost 2.05 ns 0.08 ns 0.86 ns
Cover 27.55 '1'" 0.81 ns 2.50 *
Gypsum * cover 1.28 ns 0.23 ns 0.36 ns
Compost * cover 0.93 ns 0.10 ns 1.98 ns
Gypsum * cover * compost 0.03 ns 0.10 ns 0.97 ns

Corn Ears Early Late
Gypsum 1.04 ns 0.11 ns 0.14 ns
Compost 0.61 ns 0.23 ns 2.68 ns
Gypsum '1' compost 0.00 ns 0.14 ns 0.16 ns
Cover 3.98 ** 0.55 ns 0.85 ns
Gypsum "‘ cover 0.12 ns 0.25 ns 0.17 ns
Compost“ cover 0.60 ns 0.12 ns 0.52 ns
Gypsum * cover "' compost 0.70 ns 0.23 ns 0.31 ns

I"PS0.05

"PSODI

*"PS0.001

us Not signiﬁcant at (1:005

88

Table 3.4. Eﬁect of combined interactions of compost and cover crops on mean corn height

 

 

 

 

Treatments N C/W M O R
2006 cm

Compost 66b 65b 72a 74a 69ab

No compost 53c 42d 66b 67b 54c
2007 ---------------- Early ------------------

Compost - - 66a 66a 63ab

No compost - - 56b 57b 54b

-----------------Iate
Compost 64a 54c 65a 64a 61 a
No compost 60b 55c 59b 61ab 56bc

'MEans wiﬁml the same treatments groups followed by the same letters are not signiﬁcantly—

different at a=0.05

Abrev.: Abrev.: N= No cover; C=Cereal rye; W= Wheat; M= mustard; O= Oilseed radish; R: red clover

89

Table 3.5a. Statistical signiﬁcance of gypsum, compost and cover crops on Ca and Mg concentration of

 

 

 

 

Corn plant biomass (V 8 stage)
Treatments Ca Mg
2006 F-value P-value F-value P-value
Gypsum 8.88 * 0.15 ns
Compost 26.04 ** 121.54 ***
Gypsum“ compost 4.53 ns 0.97 ns
Cover 9.43 **"‘ 3.11 *
Gypsum‘cover 0.25 ns 1 .90 ns
Compost*cover 1.07 ns 0.87 ns
Gypsum*cover*compost 1.13 ns 0.51 ns
2007 -«-------------Early--------------
Gypsum 4.71 ns 1.38 ns
Compost 24.28 ** 22.46 **
Gypsum“ compost 3.46 ns 0.19 ns
Cover 16.41 *** 40.83 ***
Gypsum*cover 0.08 ns 0.72 ns
Compost‘cover 0.47 ns 0.32 *
Gypsum*cover*compost 0.54 ns 0.30 ns
Late
Gypsum 9.96 * 1.69 ns
Compost 6.08 * 31.31 **
Gypsum“ compost 1.95 ns 0.55 ns
Cover 1.07 ns 2.97 *
Gypsum*cover 0.36 ns 1 .39 ns
Compost‘cover 0.97 ns 1.07 ns
gypsum*cova*compost 0.73 ns 0.70 ns

 

* P S 0.05
** P S 0.01

*** P $0.001
ns Not signiﬁcant at (1:005

90

Table 3.5b. Statistical signiﬁcance of gypsum, compost and cover crops on nutrient concentration of
plant biomass (V 8 stage)

 

 

 

 

 

Treatments N P K
2006 F -val ue P-value F-value P-value F -value P-value
Gypsum 2.21 ns 0.67 ns 0.00 ns
Compost 1.02 ns 18.41 ** 8.18 *
Gypsum“ compost 2.21 ns 2.05 ns 0.30 ns
Cover 11.70 *** 3.11 * 2.01 ns
Gypsum‘cover 0.50 ns 2.00 ns 0.35 ns
Compost*cover 5.69 *** 1.14 ns 0.86 ns
Gypsum*cover*compost 0.45 ns 1.40 ns 0.50 ns
2007 -------------------Early ----------------
Gypsum 14.40 * 0.03 ns 0.04 ns
Compost 4.25 ns 2.56 ns 0.21 ns
Gypsum“ compost 6.70 * 1.53 ns 0.52 ns
Cover $1.46 *** 16.95 *** 23.17 ***
Gypsum*cover 0.21 ns , 0.68 ns 1.08 ns
Compost*cover 1.06 ns 0.28 ns 1.18 ns
Gypsum*cover*compost 0.37 ns 0.12 ns 1.17 ns
Late

Gypsum 1.52 ns 3.83 ns 0.09 ns
Compost 1.23 ns 0.81 ns 6.84 *
Gypsum“ compost 0.12 ns 0.00 ns 0.33 ns
Cover 6.24 *** 1.65 ns 1.43 ns
Gypsum*cover 0.62 ns 0.64 ns 1.20 ns
Compost*cover 2.53 * 0.75 ns 2.27 ns
Gypsum‘cover*compost 0.90 ns 0.66 ns 0.26 ns
* P S 0.05

** P s 0.01

*** P $0.001

ns Not signiﬁcant at a=0.05

91

Table 3.6. Means of corn plant nutrient concentration as affected by the various treatment factors at the V8

 

 

 

 

 

 

 

 

growth stage
Treatment C3 Mg N P K
-1
2006 g/kg
No Cover 3.5b 2.7bc 21 .9c 3.53 43.53b
Mustard 3.2c 2.6c 22.0c 3.4ab 41 .93b
Oilseed radish 3.4b 2.8ab 25.63 . 3.1c 42.23b
Red Clover 3.7a 2.9a 24.1b 3.4ab 43 .03b
Cereal rye 3.6ab 2.8ab 23.9b 3.3abc 45.63
Compost 3.6a 2.4b ‘ 23.33 3.5a 4503
No Compost 3.4b 3.13 23.73 3.2b 41.5b
Gypsum 3.63 2.7a 23.83 3.43 43.33
No gypsum 3.4b 2.8a 23.23 3.3a 43.23
Early
2007 .
Mustard 4.01, 3.1 b 27.8b 3.4b 44.13
Oilseed radish 3.8b 2.90 32.03 3.5b 46.4a
Red clover 4_ 53 4.03 34.23 3.93 37.8b
Compost 4.43 3.01) 30.88 3.63 43.03
NO Compost 3.9b 183 31.93 3.73 42.328
Gypsum 4.3a 3.23 30.3b 3-63 42-68
No gypsum 403 3.43 32.33 3.73 42.93
Late
No Cover 4.23 3.1b 25.4c 4.3a 42.33
Mustard 4.03b 2.8c 28.53 4.13b 42.53
Oilseed radish 4.03b 3.1b 27.6ab 4.0b 43.83
Red Clover 4.23 3.23 26.9b 4.0b 40.63
Wheat 4.1 ab 3 .0b 26.4bc 4.23 41.73
Compost 4.23 2.6b 27.23 4.13 43.83
No Compost 4.0b 3.53 27.63 4.03 40.5b
Gypsum 4.263 3.03 26.43 4.03 42.43
No gypsum 3.92b 3.133 27.43 4.23 42.23

 

Means within the same columns and group followed by the same letters (within treatment groups)
are not signiﬁcantly different at a=0.05)

92

Table 3.7. Effects of gypsum, compost, cover crop interaction on N and Mg concentration on mean plant
biomass at the V8 stage

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Compost*cover crop N C/W M O R
Nitrogen
g/kg“
2006
Compost 21 .5cd 25 .0b 20.9d 24.0b 25%
No Compost 22.3cd 22.3cd 23.1 be 27.23 23.1bc
2007 Early
Compost 26.83 31.53 34.23
No Compost 28.83 32.53 34.33
Latek
Compost 26.7ab 26.23b 28.23 27.43 27.53
No Compost 24.0b 26.6b 28.83 27.83 26.23b
_ Magnesium
2006
Compost 2.353 2.413b 2.33b 2.53b 2.43b
No Compost 3.053 2.413 2.93 3.13 3.33
2007 Early
Compost _ __ 2.7c 2.6d 3.4b
No compost _ _ 3.5b 3.1bc 4.63
Late
Compost 2.7ab 2.53b 2.53b 2.83b 2.73b
No Compost 3.5b 3.5b 3.23b 3.43b 3.73
Nitrogen
Gypsum *compost Compost No Compost
2006
Gypsum 23.33 24.33
No gypsum 23.33 23.13
2007 Early
Gypsum 30.4b 30.2b
No gypsum 31.1b 33.63
--——Late—-—-——
Gypsum 26.63 26.33
No msum 27.83 27.13

 

Means within the same groups followed by the same letters are not signiﬁcantly different at

a=0.05

Abrev.: Abrev.: N: No cover; C=Cereal rye; W= Wheat; M= mustard; 0: Oilseed radish; R= red clover

93

Table 3.8. Statistical signiﬁcance of gypsum, compost and cover crops, on number and weights of sweet

 

 

 

 

corn ears for 2006 and 2007
2006 2007
Sources of
variations F -value P-value F-value P-value F-value P-value
Number of Ears ---E3rly---- "ﬂaw---
Gypsum 1.04 ns 0.11 ns 0.14 ns
Compost 0.61 ns 0.23 ns 2.68 ns
Gypsum*com post 0.00 ns 0.14 ns 1.06 ns
Cover 3.98 ** 0.55 ns 0.85 ns
Gypsum *cover 0.12 ns 0.25 ns 0.17 ns
Compost*cover 0.60 ns 0.12 ns 2.52 ns
Gypsum *cover *compost 0.70 ns 0.23 ns 0.31 ns
Ear Weights ----E3rly---- -----[ate -----
Gypsum 0.63 ns 0.60 ns 0.85 ns
Compost 5.07 ns 3.45 ns 14.90 "”"
Gypsum *compost 0.21 ns 0.01 ns 1.42 ns
Cover 2.35 ns 0.32 ns 1.82 ns
Gypsum*cover 0.16 ns 0.38 ns 0.30 ns
Compost *cover 0.45 ns 0.02 ns 2.27 ns
Gypsum*cover *compost 0.34 ns 0.62 ns 0.08 ns
"' P s 0.05
** P _<. 0.01
"* P 50.00]

ns Not signiﬁcant at (1:005

94

Table 3.9. Effect of gypsum, compost and cover crops on yield and quality. Yield is presented in
percentage of marketable ears, weight and number of cars. Quality is presented in lengths, diameter and
weights of ten selected husked ears.

 

 

 

 

 

 

 

 

 

Yield Quality
Marketable corn ears Diamter Length Weight
-1 -1
Treatment Dozens/ha Mg/ha Percentage ---cm-—-- kg
2006
No cover 4541bc 13.593 813 413 203b 1.91b
Mustard 49673b 15.203 82.3 423 199C 1 .93 b
Oilseed radish 5079a 15.723 833 423 199C 1.9%
Red clover 4967ab 15.973 85.3 413 203b 1.93b
Cereal rye 4294c 15.103 83 .3 413 2083 2.153
Compost 47113 15.843 823 423 2043 2.083
No compost 48283 14.393 853 413 201 b 1.88b
Gypsum 4693a 14.853 843 423 2033 1 .963
No gypsum 48463 15.383 833 413 2023 2.003
2007
Early
Mustard 36773 1 1.403 903 47a 1733 2.013
Oilseed radish 35093 11.003 893 463b 1753 1.973
Red clover 3576a 11.003 853 45b 1753 1.923
Compost 36103 12.003 903 47a 1733 2.053
No compost 35653 10.503 853 45b 1753 1.88b
Gypsum 34753 1 1 .003 87a 46a 1743 1 .943
No gypsum 3699a 11.523 873 47a 1733 1.993
Late

No cover 34583 10.613 833 46a 1733 2.023
Mustard 3486a 10.743 843 463 1723 1 .943b
Oilseed radish 34753 10.933 833 46a 1803 2.033
Red clover 33183 10.243 833 46a 1733 1.923b
Wheat 31723 9.233b 843 45b 1793 1.88b
Compost 34863 11.163 863 47a 1813 2.063
No compost 32783 9.57b 813 45b 170b 1.85b
Gypsum 3297a 10.013 833 463 1743 1.963
No gypsum 3468a 10.663 843 46a 1753 1.963

 

Values within the same columns and groups followed by the same letters are not signiﬁcantly
different at a = 05

95

Table 3.10. Signiﬁcance of gypsum, compost and cover crops on sweet corn ear lengths, weights
and diameter

 

 

 

 

2006 2007
Sources of variations F-value P-value F-value P-value F-value P-value
Lengths ----E3rly--- ----Late----
Gypsum 0.18 ns 0.25 ns 0.49 ns
Compost 11.35 * 1.79 ns 28.15 **
Gypsum*compost 0.75 ns 0.99 ns 1.39 ns
Cover 9.34 *** 0.53 ns 2.29 ns
Gypsum "' cover 0.16 ns 1.37 ns 1.30 ns
Compost" cover 0.89 ns 0.54 ns 0.82 ns
Gypsum *cover *compost 1.25 ns 0.81 ns 0.69 ns
Weights
Gypsum 0.14 ns 1.29 ns 0.05 ns
Compost 22.60 ** 18.38 ** 52.73 ***
Gypsum *compost 0.25 ns 1.24 ns 0.21 ns
Cover 3.98 ** 1.84 ns 3.80 **
Gypsum * cover 0.28 ns 0.70 ns 0.39 ns
Compost *cover 0.38 ns 1.28 ns 0.59 ns
Gypsum*cover*compost 0.37 ns ‘ 0.08 ns 0.24 ns
Diameters
Gypsum 0.04 ns 1.84 ns 0.88 ns
Compost 1.91 ns 25.91 ** 26.54 **
Gypsum *compost 0.92 ns 3.48 ns 0.02 ns
Cover 0.31 ns 3.51 * 4.35 **
Gypsum *cover 0.12 ns 0.39 ns 0.51 ns
Compost *cover 0.64 ns 0.63 ns 0.23 ns
Gypsum * cover * compost 0.93 ns 0.05 ns 0.13 ns
* P S 0.05
** P s 0.01
*** P $0.001
ns Not signiﬁcant at (1:005

96

Table 3.113. Statistical signiﬁcance of gypsum, compost and cover crops on nutrient
concentration of corn ears.

 

 

 

 

 

 

 

Ca Mg
Treatments F-value P-value F-value P-value
2006
Compost 6.12 * 0.77 ns
Gypsum" compost 6.89 * 0.63 ns
Cover 1.26 ns 0.30 ns
Gypsum‘cover 0.53 ns 0.43 ns
Compost*cover 0.07 ns 0.40 ns
Gypsum*cover*compost 0.58 ns 0.78 . ns
2007 ---—- Early
Gypsum 3.71 ns 0.00 ns
Compost 0.49 ns 0.13 ns
Gypsum“ compost 2.07 ns 0.13 ns
Cover 0.33 ns 2.64 ns
Gypsum*cover 0.06 ns 0.59 ns
Compost*cover l .67 ns 1 .41 ns
Gypsum*cover*compost 2.84 ns 0.58 ns
—-.-— Late
Gypsum 0.03 ns 2.00 ns
Compost 0.14 ns 0.03 ns
Gypsum“ compost 0.02 ns 0.06 ns
Cover 0.93 ns 0.10 ns
Gypsum*cover 1.98 ns 2.05 ns
Compost*cover 0.41 ns 0.21 ns
Gypsum*cover*compost 0.58 ns 1 .54 ns
"‘ P s 0.05
** P s 0.01,
*" P $0.001,

ns Not signiﬁcant at (1:005

97

Table 3.11b. Statistical signiﬁcance of gypsum, compost and cover crops on nutrient concentration of

 

 

 

 

 

 

 

corn ears.
N P K
Treatments F-value P-value F-value P-value F-value P-value
2006
Gypsum 9.49 * 4.90 ns 0.22 ns
Compost 0.06 ns 1.42 ns 0.22 ns
Gypsum“ compost 0.95 ns 0.00 ns 0.19 ns
Cover 5.80 *** 3.15 * 6.72 ***
Gypsum*cover 0.13 ns 0.46 ns 0.54 ns
Compost*cover 4.58 ** 0.58 ns 1.28 ns
Gypsum*cover*compost 1.00 ns 0.23 ns 0.39 ns
2007 ------------------Early
Gypsum 1.88 ns 0.45 ns 0.01 ns
Compost 10.05 * 5.11 ns 4.25 ns
Gypsum“ compost 1.00 ns 0.00 ns 0.27 ns
Cover 2.76 ns 0.34 ns 0.55 ns
Gypsum*cover 2.1 1 ns 0.40 ns 0.71 ns
Compost*cover 1.55 ns 1.86 ns 7.41 **
Gypsum*cover*compost 1.67 ns 0.59 ns 0.95 ns
Late
Gypsum 1.07 ns 0.22 ns 0.51 ns
Compost 4.91 ns 3.89 ns 3.78 ns
Gypsum“ compost 0.55 ns 0.13 ns 0.09 ns
Cover 1.69 ns 0.58 ns 0.08 ns
Gypsum*cover 0.76 ns 2.61 ns 0.65 ns
Compost*cover 1.54 ns 0.47 ns 0.76 ns
Gypsum*cover*compost 2.73 * 1.90 ns 1.56 ns
* P S 0.05
** P S 0.01
*** P $0.001

ns Not signiﬁcant at (1:005

98

Table 3.12. Means of nutrient concentration of corn ears as affected by gypsum, compost
and cover crops

 

 

 

 

 

Treatment Ca Mg N P K
-1
2006 Ma
No Cover 0.153b 1.203 15.0b 3.3b 1 1.13
Mustard 0.13b 1.243 15.63 3.403 10.7bc
Oilseed radish 0.143b 1.233 15.73 3.53b 10.6c
Red Clover 0.153b 1.243 15.1b 3.3b 10.9ab
Cereal rye/wheat 0.19.3 1.223 15.43b 3.3b 1 1.03
Compost 0.173 1.213 15.43 3.33 10.73
No Compost 0.13b 1.243 15.43 3.33 10.83
Gypsum 0.173 1.233 15.1b 3.33 10.93
No gypsum 0.143 1.223 15.63 3.43 10.83
2007 -—---------------E3rIy----------------
Mustard 0.113 1.243 18.23 3.53 9.23
Oilseed radish 0.123 1.293 18.73 3.63 9.33
Red clover 0.133 1.293 18.93 3.63 9.33
No Compost 0.113 1.273 18.1 b 3.53 9.13
Gypsum 0.133 1.273 18.83 3-63 93a
No gypsum 0.113 1.273 18.43 3.73 9.23
L3te------------------
No Cover 0.113 1.273 18.23 3. 6a 9.23
Mustard 0.133 1.273 18.73 3.53 9.33
Oilseed radish 0.103 1.263 18.43 3.63 9.23
Red Clover 0.123 1.273 18.53 3.63 9.33
Cereal rye/wheat 0.133 1.253 18.13 3.53 9.33
Compost 0.123 1.263 18.83 3.63 9.33
No Compost 0.113 1.263 18.43 3.53 9.23
Gypsum 0.123 1.253 18.53 3.53 9.23
NO gypsum 0113 1.278 18.28 3.63 9.33

 

Means within the same columns and treatment groups followed by the same letters are not
signiﬁcantly different

99

Table 3.133. Effects from treatment interaction on Ca, N and K concentration

 

 

 

 

 

 

 

 

 

 

in corn ears
Nitrogen
Compost‘cover N C M O R
-1
2006 an
Comp 14.9b 16.03 15.53b 15 .63b 15.0b
No comp 15.1b 14.9b 15.73 15.83 15.3b
2007 Early
Comp 18.93 19.23 19.13
No comp 17.63 18.23 18.73
late
Comp 18.73 18.13 18.93 18.63 18.53
No comp 17.63 17.93 18.43 18.03 18.63
Potassium
2006
Comp 11.03 11.13 10.73 10.43 10.93
No comp 11.83 10.83 10.73 10.73 10.83
2007
Comp 9.53 9.63 9.0b
No comp 8.80 9.1b 9.53
Comp 9.43 9.33 9.53 9.523 9.33
No comp 9.13 9.33 9.03 9.013 9.353
Calcium
Gypsum‘compost Gypsum No gypsum
2006
Compost 0.213 0.14b
No compost 0.12b 0.14b
2007 ---------- Early-num-
Compost 0.153 0.123
No compost 0.123 0.113
Late
Compost 0.123 0.123
No compost 0.123 0.113

.Means within rows and groups followed by the same letters are not signiﬁcantly—
different a=0.05)
Abrev.: N= No cover; C=Cereal rye; M= mustard; O= Oilseed radish; R= Red clover

100

Table 3.13b. Effects from treatment interaction on N concentration in corn ears.

 

 

 

Gypsum No gypsum

Gyp*comp*cover Compost No compost Compost No compost
2006 g/kg'l

No cover 14.53 15.13 15.13 15.13

Mustard 15.53 15.43 15.53 15.53

Oilseed Radish 15.63 15.53 15.63 16.13

Red clover 14.83 14.93 15.13 15.73

Cereal rye/W heat 15.73 14.53 16.33 15.03
2007 Early

No cover

Mustard 19.33 17.6b 18.6ab 17.5b

Oilseed Radish 19.03 18.2b 19.43 18.1b

Red clover 20.03 18.8ab 18.23 18.6ab

Cereal rye/W heat

Late

No cover 18.73 17.4b 18.73 17.8b

Mustard 19.43 18.3ab 18.4ab 18 .53

Oilseed Radish 18.83 18.53b 18.73 17.6b

Red clover 18.0b 19.23 19.13 17.9b

Cereal rye/W heat 18 .43b 18.23b 17.9b 17.6b

 

 

 

 

 

 

 

Means within columns and groups followed by the same letters are not signiﬁcantly

different (a=0.05)

101

FIGURES

Figure 3.1. . Representation of a typical block of the experiment design.

b. 2006

a. 2005 Early Late c. 2007

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cover crop sub-subplot
10.7m x4.4m
(35’X14.5)
Compoatw
10.7 m x 13.m
(35’x43.5‘)
Compost
Levels
CN M M CN % No compost
CN 0 CN
./
Gypsum No gypsum Gypsum No gypsum
Sub-sub-subplots 79.5 m x 5.3 (261 x 17.5’)

5.3mx4.4 m(17.5’x14.5)

Abbrev.: N= No cover; C= Cereal rye; W= Wheat; R= Red clover, O= Oilseed radish;
M=Mustard; CN= Corn

102

Figure 3.2. Effects of cover crops on corn height, 2006 and 2007..

 

 

 

  

 

 

a. 2006
80 -
70 g a a
A _ b C b
g 60
j 50 ~
‘51)
.c:
E 30 -
c
U 20 ~
10 -
O _
No cover Cereal rye Mustard Oilseed Red clover
radish
Cover Crops
b. l 2007 Early
80 ~ a 2007 Late
E
8
in
0
4:
E
o
O
is" v . ..
No cover Wheat Mustard Oilseed Red clover
radish
Cover Crops

 

Mean comparisons in 2007 are by cover crop planting time

103

 

Figure 3.3. Effect of compost and gypsum on corn height, 2006 and 2007.

 

 

  

 

 

 

 

a. I Compost
70
a I No compost
a a
60 — b
50
E 40
8’
35”,, 3o
.2
E 20
8
10
0 _
2006 2007 Early 2007 Late
Years
b. I Gypsum
1‘. No gypsum
70
”ET
8
in
0
4:
E
o
O
2006 Years 2007 Early 2007 Late

 

Mean comparisons in 2007 are by cover crop planting time

 

Figure 3.4. Com grth and development as affected by compost application.

 

     

b. Corn grown on oilseed radish plots
with compost applied. Photo: 07/17/07

 

 

Images in this dissertation are presented in color

105

Figure 3.5. Effects of cover crops on whole corn biomass at the V8 Stage,

 

 

 

2006 and 2007.
3- l2006
:73 1.5 — a
g b
b
a 1 C
§
".8 0.5 »
E
o
O
0 _.
No cover Wheat Mustard Oilseed Red clover
Cover crops radish
b. .2007 Early
~ 2007 Late

1.5 -

Corn biomass (Mg/ha'l)

    

 

No cover Wheat Mustard Oilseed Red clover

radish
Cover crops

 

 

 

Mean comparisons in 2007 are by cover crop planting time

Figure 3.6. Effects of compost and gypsum on whole corn plant biomass at the
V8 Stage, 2006 and 2007.

 

 

 

 

 

 

a. ICompost
0.7 _ nNo compost
'2 0.6 ~
B a
g 0.5 —
,,, a
"’ 0.4 ~
E b b
5 0.3 ~
5 0.2 -
0.1 -
0 a
2006 2007 Early 2007 Late
Years
b. lepsum
0.7 - 1‘ No gypsum
0.6
é, 0.5
E 0.4
§
5 0.3
.2
..D
0.2
E
O 0.1
0
2006 2007 Early 2007 Late
Year

 

 

 

Mean comparisons in 2007 are by cover crop planting time

107

Figure 3.7.

Dozens ears/ha'l

Effect of cover crops on corn yield, presented in number of
corn ears.

 

6000
5000
4000
3000
2000

1000

I 2006

be

 

 

No cover Cereal Mustard Oilseed Red
rye radish clover
Cover crops

 

Dozens ears/ha"l

 

5000

 

I 2007 Early
- 4’5 2007 Late

 

No cover Wheat Mustard Oilseed Red
radish clover

 

Cover crops

 

Mean comparisons in 2007 are by cover crop planting time

108

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113

CHAPTER 4

EFFECTS OF GYPSUM ALONE OR COMBINED WITH COMPOST AND
COVER CROPS ON SOIL QUALITY

ABSTRACT

Water stabled aggregate (W SA), bulk density, microbial biomass and nematode
population, along with the simpliﬁed active organic matter (AOM) test were used to
determined soil quality. The treatment design involved three factors: gypsum application
at 0 and 2.24 Mg ha", poultry compost, at 0 and 2.7 Mg ha", and four cover crops plus a
no cover treatment. The four cover crops were oilseed radish (Raphanus sativus),
oriental mustard (Brassicajuncea L), red clover (T rrfolium pratense), and cereal rye
(Secale cereale), or wheat (T riticum aestivum). Soil samples were taken the spring and
fall of each of the three years (2005- 2007). The statistical model included the three
factors and all interactions among them as ﬁxed effects, and replication as a random
effect. Gypsum did not improve any soil quality component investigated. Compost
application signiﬁcantly enhanced aggregate stability and decreased bulk density over the
three year study. These increases corresponded with the ADM test which showed a fair
rating for the soil quality compared a poor rating for the non compost treatment.
Generally there was no positive effect ((1 =0.05) of cover crops on the soil quality
components studied. Mustard negatively inﬂuenced WSA, bulk density and nematode

population.

114

INTRODUCTION

Among the many factors for consideration in addressing management practices
for sustainable agriculture is soil quality (SQ). The concept of soil quality is not a new
topic, having been used as early as the 19503 especially by pedologists. However, it has
been viewed with a different approach — the ecosystem concept — since the late 19805
(L31, 1998) when addressing sustainability issues and is considered a key element of
agricultural sustainability (Carter, 2001). Concerns with soil degradation and the
growing need for sustainable soil management in agro-ecosystems has renewed scientiﬁc
attention to characterize soil quality (Carter, 2001). Soil quality refers to a soil’s
capacity to perform speciﬁc functions and includes both a soil’s productive and
environmental capabilities (Wander et al., 2002). Hence, with respect to agricultural
production, SQ is a soil’s ability to sustain agricultural productivity (Johnson et al., 1997
and L31, 1998). If an agricultural system is unsustainable it is due in part to decline in SQ
overtime (L31, 1998). A reduction in soil quality due to human activities can be deﬁned

as soil degradation (Cassman, 1999).

Soil quality has two aspects — its inherent and dynamic properties. Its inherent
properties are a function of its geology, acted upon by intrinsic factors, such as climate,
topography and hydrology. It is mainly static; showing little change over human time
scales. Hence, each soil has an inherent capacity to function; for example, a loamy soil
has a higher inherent water holding capacity than a sandy soil. Dynamic properties on
the other hand, can change over short time periods, and examples are as soil
macroporosity, structure and soil organic matter (SOM) content (Carter, 2002). Though a

loamy soil has an inherently higher water holding capacity, under certain management

115

practices, this capacity can become limited due to compaction, reduced aggregate
stability and other factors (Maushbach, 1996). The focal point for assessment of SQ (also
referred to as soil health) in agricultural production is soil dynamic properties, which are
greatly inﬂuenced by agronomic practices (Lal,1998; Rachman, 2003; Moebius-Clune,
2008). Although SQ cannot be measured directly, its capacity to function is reﬂected in
many measurable soil (quality) indicators and is a combination of physical, chemical, and
biological aspects that are reﬂective of soil processes and management practices (Detzler
and Tugel, 2002; Schindelbeck,et al., 2008). Therefore, due to a soils’ multifaceted
nature, SQ determination requires that biological, physical, and chemical attributes of a

soil be considered simultaneously (Wander and Bollero, 1999; Brejda, et al., 2000).

Physical attributes of SQ are those qualities that are derived from primary and
secondary soil particles, and void pore spaces between then. These attributes facilitate
functions such as soil capacitance (ability to store and transmit liquid and gases), soil
strength, and their interactions (T opp et al., 1997). The chemical properties of soil
function are to provide nutrients for crop growth. A soil’s chemical properties include
but not are limited to cation exchange capacity (CEC), electrical conductivity (EC),
exchangeable sodium percentage (ESP), organic matter (OM) content, mineralogy, and
soil pH (Heil and Sopsito, 1997). The biological aspects of soil quality include the living
organisms and their derivatives; those components and processes related to soil organic
matter cycling. Examples of these are total carbon, total nitrogen, microbial biomass,
enzyme activities (Gregorich et al., 1997), arbuscular mycorrhiza (AM) fungi, and
glomalin. Presumably, glomalin a newly discovered insoluble soil glycoprotein, is

produced by the arbuscular mycorrhizal fungi (AMF) which grow symbiotically on plant

116

roots. Glomalin contains about 30-40 % carbon, and may contribute to clumping (Wright
et al., 1996). Such ﬁnding warrants the inclusion of glomalin in studies regarding SQ.
Glomalin may be an important speciﬁc cementing agent involved in the process of
aggregation (Wright et al., 1996; Wright and Upadhyaya, 1996). The soil quality
indicators studied were organic matter, aggregate stability, bulk density, microbial

biomass and nematode population.

Organic matter

Soil organic matter is made up of humic substances and biochemical compounds,
such as peptides, proteins, polysaccharides, and sugars, which are derived ﬁom
decomposed animal and plant residues. Organic matter inﬂuences biological and
chemical properties of the soil (Pierzynski et al., 2000; Sparling et., al 2006), resulting in
an array of beneﬁts that enhance soil quality. Most recently, organic matter has been
promoted as having both direct and indirect impact on environmental quality (Sparling et
al., 2006; Carter, 2000; Pullman, 2000) and global climate through carbon sequestration
(L31, 2001). Addition of organic matter improves soil structure, increases cation
exchange capacity, buffering capacity against pH change, the soil’s chelating ability, and
supplies C and energy sources for microorganism (Pierzynski et al., 2000; Sparling et al.,
2006). A linear positive relationship has been established by researchers between organic
matter and soil quality (Jansen, et al 1997 ) where a decline in organic matter correlates

with a decline in soil quality, and vice versa. The active portion of soil organic matter is

117

the most important component indicator of soil quality, because of the susceptibility to

further decomposition (Islam and Wright, 2003)

Soil aggregation and aggregate stability

A soil aggregate is an assemblage of particles of various sizes, shapes,
orientations, and chemical composition, which contains amorphous substances,
particularly OM, attached to the mineral grains — ﬂocculation plus cementation (Hillel,
2004). Factors affecting the process of soil aggregation are biotic, abiotic and
environmental; also, chemical, biological and physical (Marques et al., 2004).
Aggregation is important because it increases the macroporisity of soils, thereby
facilitating gas exchange, inﬁltration, percolation, seedling emergence and root
exploration. Hence, soil aggregation is a particularly good indicator of management
practices' inﬂuence (N issen and Wander, 2003), and a major factor for assessing SQ
(Marques et al., 2004). Soil aggregation process is a means to both conserve and protect
SOM and allow the stored OM to function as a reservoir of plant nutrients and energy
(Carter, 2002). Soil aggregate stability is a measure of a soil’s vulnerability to externally
disruptive forces, as it expresses the resistance of aggregates to breakdown when
subjected to potentially disruptive forces (Hillel, 2004). Although soil aggregate
formation and aggregate stability have been hypothesized as being crucial in SQ and
productivity, yet many questions still exist with regards to the processes by which
aggregates are formed and stabilized. Tisdall and Oades (1982), contend that though

polysaccharides play an important role in soil aggregate formation and stability, they are

118

not involved with stabilizing large aggregates but only those less than 50 pm in

diameters, and have less importance with soils high in OM.

Aggregate stability has been strongly correlated with soil OM, and decreases in
OM have been shown to correspond with decreases in aggregate stability, upon
cultivation (Chen et al., 2000). Soil organic matter compounds were generally believed.
to bind the primary particles in the aggregate, physically and chemically, and this in turn,
increases the stability of the aggregates and limits their breakdown during the wetting
process. McLauchlan and Bailey (2004) found positive relationships which indicated that
labile soil organic carbon, (SOCL) increased with total soil organic matter (SOCT). Gale
et al., (2000) contends that little is known about the dynamics of the particulate organic
matter (POM) fraction or its role in aggregate formation. However, recent investigations
have demonstrated that soil aggregate formation, stability and soil tilth are directly
inﬂuenced by the presence of glomalin, which is a glycoprotein produced in abundance
by AM fungi (Wright et al., 1996; Wright et al., 1998, wright et al., 1999). Glomalin and
its relation to soil aggregate stability, inﬂuence of plant roots and other soil interactions

aspects, needs further investigation (Wright et al., 2001).

Bulk density

A soil’s bulk density is the ratio of the soil’s solid weight to its bulk volume, is

inversely related to its porosity, and is an indicator of 3 soil’s compaction. Bulk density
ranges from 1.2 g/cm'3 in loamy soils to 1.6 g cm'3 in sandy soils depending on a number

of factors including, texture, structure and degree of compaction (Blake and Hartge,

119

1986; Carter and Ball, 1993; Hillel, 2004; Lampurlanes and Martinez, 2003; Assouline,
2006). Compaction inﬂuences the physical, chemical and biological processes of a soil
through inﬁltration, evaporation, seedling emergence, root penetration and development,
among others. Increases in bulk densities can occur from both natural processes such as
root penetration, shrink -swe11 cycles and artiﬁcial processes such as humans and tractor
movement (Assouline, 2006). As the soil becomes compressed ﬁ'om the weight of
humans and farm vehicles, soil pores are reduced and bulk density increases. Bulk
density has also been shown to have strong correlations with organic matter, decreasing
as organic carbon increases (Alexander, 1980). Generally, bulk density increases with
depth because of reduced soil pores due to reducd organic matter, root penetration, and
aggregation in the subsoil. The ability of a soil to offer structural support, water solute
and air movement impact the soil’s health (Brady and Weil 2002; Kuykendall, 2008);
hence, bulk density measurements is a useful indicator of the physical component of soil
and ecosystem ﬁmctioning, and impacts both the biological and chemical properties.
Measurements of bulk density can be done through various methods- the core (cylinder),

clod, excavation and radiation methods.

Microbial biomass and Nematode population

Soil microorganisms play an important function in maintaining soil quality
because they play a central role in the decomposition of organic matter and the cycling of

nutrient. (Parkinson and Paul, 1982; Anderson and Domsch, 1985; Dick 1992; Byre et al.,

2003) and bacterial polysaccharides may enhance soil aggregation. Although microbial

120

biomass is only approximately 1-3 % of organic carbon (Anderson and Domsch, 1989;
Gregorich et al., 1997), the fast turnover time gives microbial biomass its central role in
nutrient cycling (Suman et al., 2006; Gregorich et al., 1997). For this reason, soil
microbial population has been widely used as a useﬁil indicator of soil quality (health).
Soil microbial biomass is sensitive to an array of ecological factors, including
temperature, soil structure, plant communities and moisture levels, which make it a good
indicator of soil quality (Suman et al., 2006). Microorganisms inhibit soil pore spaces
(Brye et al., 2003 ); consequently, soil aggregation and bulk density as affected by
management practices will impact the microbial community. Bacteria and fungi are the
major components of the soil microbial biomass (Byre et al., 2003; Parkinson and Paul,
1982), and their combined population represents a large fraction of the total microbial
biomass. Therefore management practices will reﬂect the population ratio of soil fungi
and bacteria Soil that are less intensely managed are dominated by fungi, while more

intensely managed soils are dominate by bacteria (Bardgett et al., 1999).

Soil microfauna which includes nematodes are major determinants of soil
processes that affect soil fertility and soil structure. Therefore their abundance, diversity
and activities are useful indicators of soil quality (Gregorich et al., 1997). Nematodes are
threadlike, un-segmented worms that are ubiquitous in every ecological niche, and are the
second most abundant soil faunal group in terms of numbers and biomass after protozoa.
Of the more than 10,000 described species, the vast majority are predators on bacteria
and fungi living in soils and water — fresh and marine (Gundy, 1982). Some nematodes
are deﬁned by humans as beneﬁcial to the soil environment and plant health while others

are not. Plant parasitic nematodes are pathogens that may cause yield and quality losses

121

for many vegetable and ﬁeld crops where suitable management practices are not in place.
For example, lesion nematodes (Pratylenchus spp.) have approximately 400 different
crop and weed species that serve as hosts, and root-knot nematodes (Meloidogyne spp.)
can reduce production for more than 2000 species of plants, including forage crops, small
grains, fruits, vegetables, ﬁeld crops, nursery crops, turfgrasses, and weeds. (Kratochvil et
al., 2004). Several management practices for the control of plant parasitic nematodes
have been utilized. These include crop rotation, the use of resistant cultivars, green
manure crops, organic soil amendments, among others (Johnson and Motsinger, 1990;

Kratochvil et al., 2004).

Due to 3 soil’s multifaceted nature, SQ determination requires that biological,
physical, and chemical attributes of a soil be considered simultaneously. Therefore, we
investigated the effects of the various treatments applied in this study (gypsum poultry
compost, and the various cover crops) on several quality parameters (physical and
biological) - bulk density, aggregate stability, active organic matter, nematode population

and microbial biomass.

MATERIALS AND METHODS

Site description and experimental design are explained in chapter two (p. 22).
Description of treatments and plot layout are given in the materials and methods of

chapter two (p. 23).

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Soil Measurements
Active organic matter: a simple soil quality test

Soil samples for organic matter determination were sub-samples from soils used
for nutrient analysis. Soils samples from a depth of; 0-10 cm (0-4”) taken with a 3 cm
diameter soil probe, in the fall of 2007 after sweet corn harvest. Six cores were taken
from each gypsum treatment, giving four samples for each sub-subplot with either
compost or no compost. Soil samples were air dried and ground to pass a 2.0 mm mesh.
Samples were sent to the Agricultural Research and Development Center at Ohio State
University for soil quality analyses. Active organic matter (AOM) was used as a measure
of soil quality with the “Simple Soil Quality Test” developed by Dr. Raﬁq Islam of Ohio
State University. The method employed the use of potassium permanganate (KMnO4)
which preferentially oxidizes the active fraction of soil organic matter. The soil quality is
based on the degree of color loss from the purple solution which can be determined on a
pre-established index. As the soil quality improves, the purple color decreases. This
method is used to determine both the AOM and available nitrogen in the soil (Islam and

Sandermeirer, 2003; Weil et al., 2003; Islam, 2008).

The test is based on the premise that active soil organic matter (SOM) is the most
important component of, and most widely accepted soil quality indicator. Soil (OM) has
no deﬁnite chemical composition; therefore, soil organic carbon (SOC) which is the
dominant component of SOM is more commonly measured (W eil et al., 2003). Air dried
soil (5 g) was shaken for about 2 minutes in 20.0 ml KMnO4 solution (0.2M KMnO4 in

1M calcium chloride, CaClz, adjusted to pH to 7.2) with 2.0 ml of 0.1M sodium

123

hydroxide. The CaClz serves to stimulate soil ﬂocculation and settling to speed the
clearing of the supernatant. The mixture was allowed to settle for 10 minutes. An aliquot
(1.0 ml) of the supernatant was transferred to in 3 test tube and placed in a Hach, single
parameter, portable colorimeter (550 wavelength) to obtain the absorbance reading. This
wave length was adopted because it always “resulted in the lowest slope and highest
regression coefﬁcient (Weil et al., 2003 ).” The absorbance reading was used to estimate
soil quality (Tabhe 4.1); both active organic matter (AOM) and the soil available N
(Table 4.2b). These values can checked against the color chart developed for the quick
ﬁeld test for soil quality (Tables 4.33 and 4.3b). The lighter the color of the supernatant,

the greater the active organic matter content of the soil, and the better the soil quality.

Bulk density and aggregate stability

Soils were sampled with 3 coring tube (cylinder) driven in the soil with a drop
hammer, as described by Blake and Hartge, 1986. The coring tube was 7.6 cm diameter
(3.0”) x 7.6cm high (3.0”); a total volume of 344.6 cm3. Care was taken to avoid
compressing the soil in the cylinder to preserve the structure. Soil samples were taken in
the fall of 2005 ﬁ'om no-cover crop plots, and in the spring (2006 and 2007) from all
cover crop plots (including no-cover), prior to planting of cover crops and corn on all
plots. Weights of soil samples were recorded prior to and after drying. Weights were
taken about three times, until weights became stable, then bulk densities were calculated.

Units are presented in g/cm3 .

Bulk density (pb) = Wt soil (3) /T0tal volume (cm3)

124

Aggregate stability measurements were made ﬁ'om soil cores used for bulk
density measurements. Soil samples were remoistened with a low pressure mist of
deionized water, gently crumbled and air dried. Each sample was sieved into six size
fractions (<1, 1-2, 2—4, 4—6.3, 6.3—9.5, and >95 m), using stacked sieves and a catch
pan. The samples were shaken for] minute with 3 Tyler Coarse Sieve mechanical shaker
(Mentor, OH) and stored at room temperature in tightly sealed plastic containers. The 6.3
to 9.5 mm fraction size aggregates were used to determine water-stabled aggregation
using a portable rainfall simulator designed at Cornell University (Ogden et al., 1997; van
Es et al., 1991; Moebius et al., 2007). The apparatus was set up as described by Moebius
et al., 2007 (Figure 4.2). The rainfall simulator was hanged above the sieve stand, and
ﬁlled with deionized water up to 43 cm. Single layers of aggregates (30 g sample) were
spread on a 4-mm mesh sieve placed 0.5 m below the 0.25m diameter rainfall simulator
and calibrated to deliver 1.0 J of energy over a 300 —s (5 min) period to each sample (set
of aggregates). An automatic shut-up valve allowed the water to stop ﬂowing after 5
minutes. The rainfall simulator was reﬁlled after every 300-s to maintain the ﬂow rate
which is a function of the hydraulic head. This calculation was based on the ﬂow rate,

which was 0.6 kg (605 ml) for 300-s (5 min).

KE= l/2 mvz, where V = \JZgh

KE = '/2 (0.6 kg x 3.1m/s)

KE= 0.6x3.1/2=0.93~ 1.01

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For each sample processed, the slaked soil material which fell through the sieve
was collected in a pre-weighed 1000 ml beaker, dried and weighed. Stones and other
solid materials were also weighed and the water stabled aggregate (W SA) fraction was
calculated from the equation below. The respective variables, W.,...“ , Wstabrc, W.,lam, and
Wmm, are the dry weights of the total aggregates tested, the stabled aggregates that
remained on the sieve, aggregates slaked through the sieve and the stones (Moebius et al.,

2007).

WSA: Wstable,/ Wtotal, where

Wstable = Wtotal ‘ (Wslaked + Wstones)

Microbial biomass

For microbial biomass determination, soil sampling was done in the fall of 2006
and spring and fall of 2007. The cover crop treatments selected for microbial biomass
measurements were cereal rye/ wheat, mustard and no-cover crop. Soils were sampled at
two depths; 0-10 cm (0-4”) and 10-20 cm (4-8”) with a 3 cm diameter soil probe, and
stored in 15°C. Ten cores were taken from each gypsum treatment, giving four samples
for each sub-subplot with either compost or no compost (Figure 4.2). The chloroforrn-
ﬁrmigation—incubation method described by Parkinson and Paul, 1982; Horwath and
Paul, 1994 was employed. The soil samples were passed through 3 6.35m sieve to
remove roots and stones. Two replicated sets (one for fumigation, one control set) of 40
g soil from each treatment and depth were weighed into a 50 ml beaker. Each replicated

set was placed in a large vacuum desiccator lined with moist tissue paper to protect

126

samples from drying. A few zeolites granules were placed in a 100 ml beaker with 50-ml
alcohol-free chloroform (CHC13) placed in a desiccator for fumigation. Samples were
evacuated four times until CHC13 boiled vigorously, allowing 2 minutes for the last
boiling. The valves on the desicators with fumigated samples and controls were closed
and desicators kept in darkness for 18-24 at 25°Ch. The moist paper and CHCl3 were
removed and the desicator evacuated 8 times for three minutes allowing air to circulate
through after each evacuation. This allowed for removal of residual CHCL3 from the soil
samples. Each fumigated sample was inoculated with approximately 1 g of its
corresponding unﬁrmigated sample and thoroughly mixed. All samples, (fmnigated and
unfumigated) were adjusted to 55% of the soil’s water holding capacity then placed in a
l-L air-tight sealed mason jar lined with moist paper and incubated for 10 days in
darkness. A septum was inserted in the cover of each mason jar to accommodate the
extraction of C02. After the incubation period C02 measurements were made using an

Infrared Gas Analyzer (Analytical Development Co Ltd, Series 225, Mk3).

This process is based on the premise that the respiration rate of the soil prior to
fumigation is greater than the rate immediately after fumigation, and that a temporary
ﬂush of C02 occurs after the ﬁrmigant is removed. The ﬂush of C02 is largely the result
of the decomposition of microbial cells killed by the fumigation process. Hence it has
been proposed that a measure of the CO2 evolved is the approximate size of the soil
microbial biomass (Parkinson and Paul, 1982). After the incubation period
measurements of C02 evolved were measured using a C02 infrared gas analyzer. The

micorbial biomass of each sample calculated using the following:

127

Total microbial biomass B = F/K, where K =0.4l , where

CO2-C evolved from fumigated soil - CO2-C evolved from non-fumigated soils (F)
B =

 

Fraction of biomass C mineralized to C02 over 10-day incubation period (K)
Nematode population

Soil sampling was done in the spring and fall of 2007. The cover crop treatments
selected were red clover, mustard and no-cover crop. Ten cores were taken from each
gypsum treatment, giving two samples for each sub-subplot with either compost or no
compost (Figure 4.1). Soils were sampled at approximately 20.0 cm depth (8”) with a 3
cm diameter soil probe, and stored at 15°C. The nematode extraction and counting was
done by the Michigan State University (MSU) Nematology Laboratory using the
centrifugal-ﬂotation technique (Jenkins, 1964). Nematodes were identiﬁed at 40 to 60x
magniﬁcation and the number of nematodes was expressed per 100 cm3 soil basis. The
nematode population reported in this study were for two plant parasitic nematodes; the
lesion (Tylenchorhynchus sp), lesion (Pratylenchus sp), and bacterial feeders which are
beneﬁcial nematodes. The stunt nematodes are ecto-parasites while the lesions

nematodes are endo-parasites.

RESULTS AND DISCUSSION
Active organic matter Tests

Soil samples for active organic matter (AOM) determination were from soils
collected after corn harvest in the fall of 2007. ANOVA and means for treatment effects

are presented in tables 4.1 and 4.2. Signiﬁcantly different effects for active organic

128

matter were found only from compost treatments (P < 0.01). Compost application
resulted in a fair rating for soil quality compared to poor soil quality when no compost
was applied (Tables 4.2). These ratings correspond with low (> 0.25 -— 0.50) and
extremely low (> 0 — 0.25) absorbance readings respectively, from the color chart (Tables
4.33 and 4.3b). For soils rated with a poor quality, the AOM range is 0- 448kg/ha-l (>0 -
400 lbs/a); for soils rated fair the range is 488 gk/ha'l — 896 kg/ha'l (>400 - 800 lbs/a).
Neither gypsum nor previous cover crop affected AOM. According to Islam, this method
of evaluating soil quality is not only inexpensive but also simple and requires little time
to measure. Because soil organic matter is widely accepted as the most sensitive
indicator of soil quality, measuring the active fraction of organic matter gives early
indication of the soil’s response to management practices which impacts soil quality
(Alvaro-Fuentes et al., 2008; Islam, 2008; Franzluebbers et al., 2000; Wander and
Bollero, 2000). Among the various treatment applied in this study, compost had the
biggest inﬂuence on corn yield and 311 quality components measured, on bulk density,

WSA and extractable and Ca and Mg.

Bulk density effects

For soils sampled in 2005 (no cover crop plots), there were no signiﬁcantly
different effects when either compost (P > 0.9) or gypsum (P > 0.4) was applied.
ANOVA and the table of means are presented in Tables 4.4 and 4.5; Figure 4.3. The
bulk densities for soils from both compost and gypsum treated plots were 1.50 g/cm3 with

or without treatments. Effects found to be signiﬁcant in 2006 and 2007 were cover crops

129

and compost (Table 4.4). In 2006, compost application (P S 0.01) resulted in a lower
(4%) bulk density (1.40 g/cm3) than non compost plots (1.46 g/cm3), and a 7 % decrease
compared to compost treatment in 2005. In 2007 bulk density ﬁ'om compost treated plots
was 3.5 % lower (1.43 g/cm3) than non compost plots (1.48 g/cm3). Other studies have
shown improved bulk densities from compost application. Johnson et al., (2006) reported
5.6% lower bulk density from composted dairy manure, compared with the control within
one year. Spargo et al., (2006) also found signiﬁcant improvement from both composted
and non composted poultry litter applied to silt-loam soils. As much as 19.7% and 16.7
% reduction in bulk density was observed from application of town-waste compost to

loamy and clay soil respectively (Aggelides and Londra, 2000).

Cover crop treatment effects for 2006 were as follows: Mustard (1.46g/cm3) =
oilseed radish (1.44 g/cm3) 2 red clover (1.42g/cm3) = cereal rye (1.42g/cm3) = no-cover
(1 .41 g/cm3). The bulk density of soils from mustard plots was 4 % greater than soils
from no—cover crop plots. There was no difference in bulk density among red clover,
cereal rye and no-cover crop plots (Table 4.5; Figure 4.43). This result seems to suggest
that mustard negatively affects soil bulk density. Cover crop effects for 2007 showed
signiﬁcant differences in bulk densities in soils from both early and late planted cover
crops. Generally, wheat and red clover resulted in lower bulk densities than mustard and
oilseed radish. The effects from early planted cover crops were as follows: Mustard (1 .52
g/cm3) = oilseed radish (1.48 g/cm3) 2 red clover (1.46g/cm3). The effects from late
cover crops were: oilseed radish (1.47 g/cm3) = no-cover (1.45 g/cm3) = mustard
(1.43g/cm3) > wheat (1 .42g/cm3) > red clover (1.41 g/cm3). The bulk density of soils

from late planted mustard and red clover plots were 6% and 4 % lower than these early

130

planted cover crops respectively, but their bulk densities were not signiﬁcantly different
from soils in no-cover plots (Table 4.5; Figure 4.4b). A possible contributing factor to
the higher bulk densities of mustard and oilseed radish, which is consistent for both years,
is that brassica cover crops do not form mycorrhizae. Possibly, as a result soil
aggregation was negatively inﬂuenced and consequently, bulk density increased.
Various researchers (Ryan et al., 2001; Wright et al., 2001, and Fraser et al., 2005) have
documented signiﬁcantly higher levels of mycorrhizal colonization and crop yield after,
or in combination with AM forming plants, compared to Brassica plants. Bulk densities
of soils from red clover and wheat were also generally lower than mustard and oilseed
radish, but not signiﬁcantly. During the growing periods, large amounts of organic
materials are exuded from roots of cover crops plants (Goodﬁiend et al., 2000). The
roots of winter cover crops remain active during the winter and continue growth in
spring, as opposed to cover crops that are winter killed such as mustard and oilseed
radish. There was no difference in soil bulk densities between early or late planted

oilseed radish plots.

Treatment Effects on WSA

In the fall of 2005 aggregate stability samples were taken only from no cover
plots with both gypsum and compost treatments. In 2006, and 2007, aggregate stability
measurements were done on soil from selected cover crop treatments (mustard, cereal
rye/wheat, and no-cover crop), with and without gypsum and compost. There was no

signiﬁcant treatment effect on aggregate stability in 2006 (P > 0.05). The effects found

131

to be signiﬁcant for increased water stable aggregation (fraction size 6.3 to 9.5 mm) in
2007 were compost (P 5 0.05) and cover crops (P S 0.05). ANOVA and table of means
for treatments effects on aggregate stability are presented in Tables 4.6 and 4.7. Compost
application increased aggregate stability by 21.5 % compared to non compost treatment.
The statistically signiﬁcant difference observed with cover crops was between early and
late planted mustard. There was a 29 % decrease in stabled aggregates when mustard
was planted early compared to late planted mustard. The non- AM forming relationship
of brassicas negatively inﬂuences soil aggregation (Ryan et al., 2001, Wright et al., 2001;
and Fraser et al., 2005). There was no signiﬁcant difference in water WSA from soils in
late planted mustard, and wheat when compared to no-cover crop plots. Generally,
higher percentages of stabled aggregates were found in cover crop plots than no-cover

plots although the differences were not statistically signiﬁcant for either year.

Effects on Microbial Biomass Carbon and nematode population

For microbial biomass determination, soil sampling was done in the fall of 2006
and spring and fall of 2007. The soil samples selected for microbial biomass
measurements were from cereal rye/wheat, mustard, no-cover crop and corn plots. Soils
were sampled at two depths; 0-10 cm (0-4”) and 10-20 cm (4-8”). In the fall of 2006
(Table 4.8 and 4.9), the effects found to be signiﬁcant for soil microbial biomass (or the
C02 evolved) were depth (P5 0.05) and the interaction between crops and depth (PS
0.05). Microbial biomass was 34% greater at the 0-10 cm (91 mg/kg'l) depth than the 10-

20 cm (68 mg/kg") depth (Table 4.10). For the crop plus depth interaction (Table 4.11),

132

microbial biomass in the top 10 cm depth of corn plots was 79% (104 mg/kg") greater
than the 10-20 cm (58 mg/kg"). Below the 10 cm depth microbial biomass decreased
signiﬁcantly under corn but did not change under mustard within the top 20 cm depth. In
the spring and fall of 2007, the only factor with signiﬁcantly different microbial biomass
was depth (PS 0.001). In the top 10 cm depth of the soil, microbial biomass was 43 %
(82 mg/kg'l vs 58 mg/kg") and 29% (74 mg/kg'1 vs 57 mg/kg") greater than the 10-20 cm
for spring and fall respectively (Table 10). It was expected that microbial activities
would decrease with depth which is consistent with other ﬁndings that as organic matter
decrease within the subsoil, so does the microbial activities. However, it was also
expected that microbial biomass would increase with cover crop treatment when
compared to no-cover crop or fallow (Mendes et, al- 1999; Upendra et al., 2005), which

was not the case here.

Soil sampling for nematode population count was done in the spring and fall of
2007 from red clover, mustard and no-cover crop plots of both compost and gypsum
treatments. Samples were taken at the 0—20 cm (8”) depth. For both parasitic nematodes
stunt, and lesion), the effects found to be signiﬁcant (Table 4.12) was cover crops (P=
0.001 and (P<0.0001). Neither gypsum nor compost signiﬁcantly inﬂuenced nematode
population. Although studies have reported antagonism between the lesion nematodes
and poultry litter (Kratochvil et al., 2004), this evidence was not observed with this study.
Signiﬁcantly greater numbers of both stunt and lesion nematodes were found in plots of
early planted mustard compared to late planted mustard, early and late planted red clover.
An increase of 281 % (77 per100 cm3 ) and 264% (50 per100 cm3) in stunt and lesion

nematodes were found in mustard plots compared to no-cover (20.2 and 13.0 per100

133

cm3) respectively. This may suggest that mustard potentially serve as a host to both stunt
and lesion nematodes, and early planting provide an extended energy source encouraging
the population to build compared to late planted mustard. There was no difference in the
stunt nematode population among no-cover crop, late planted mustard, early and late
planted red clover plots. However, the lesion nematode population was signiﬁcantly
lower (45%) in early planted (7 per100 cm3 ) than late planted (1 1 per100 cm3) red clover
plots (Table 4.13). Taylor and Queensberry (1999) reported on documented research
ﬁndings that red clover is a good host of the lesion nematode. The results suggest that
early planting of red clover may potentially suppress the lesion nematode. Only compost
signiﬁcantly inﬂuenced bacterial feeders (P 50.0001). When compost was applied
bacterial feeders increased by 43% (371 cm3 soil) compared to non compost treatment
(258.8). Among the nematodes counted bacterial feeders dominated (Table 4.13),
indicating a high bacterial population (Goodfriend et al., 2000). The literature is scarce

on the subject of cover crops inﬂuence on nematode population.

SUMMARY AND CONCLUSIONS

Active organic matter (AOM) is widely accepted as the most sensitive indicator of
soil quality. At the end of the three year study, measurements of AOM from the
simplified soil quality test showed enhanced soil quality from poor to fair which was
inﬂuenced by compost application. The ﬁrst year following the application of the poultry
compost a 7 % decrease in bulk density was observed. Neither gypsum nor cover crops

affected soil AOM. A 4% and 3.5% decrease in bulk density was observed from compost

134

plots in 2006 and 2007 respectively, compared to non compost treated plots. Generally,
cereal rye and wheat resulted in higher percentages of stabled aggregates than mustard
and red clover. Mustard negatively inﬂuences soil aggregation when planted early. The
percentage of stable aggregates increased over time with application of compost which is
consistent with the AOM soil test. Although microbial biomass was not signiﬁcantly
(a=0.05) different between compost and non compost treatments numerically, compost
treatment showed greater microbial activity, suggesting that compost has the potential to
enhance microbial activity in soil. Microbial activity in corn plots was greater within the
top 10cm depth and decrease signiﬁcantly in the 10-20 cm depth, but in mustard plots
there was no decrease in microbial activity within the top 20 cm depth. The cover crops
planting time inﬂuenced the population of both parasitic nematodes, but had no effect on
the beneﬁcial nematodes. When compost was applied bacterial feeders were signiﬁcantly
increased. The evidence in this study seem to suggest that mustard increases the
population of both stunt and lesion nematodes if planted early in the season and red

clover planted early in the season may reduce the lesion nematode population.

135

Table 4.1. Statistical signiﬁcance of gypsum and compost on active soil organic

 

 

 

matter for fall 2007
Fall 2007
Active carbon
Sources F-value P-value
Gypsum 6.5 ns
Compost 125.3 **
Gypsum *compost 1.3 ns

 

 

** P S 0.01; ns Not signiﬁcant at a=0.05

Table 4.2. Effects from gypsum and compost on active soil organic matter

 

 

 

(fall 2007).
Fall 2007
Active
Sources SOM Soil qualig rating
---mg/kg--
Compost 6583 Fair
No compost 567b Poor
Gypsum 6363 Poor
No gypsum 5853 Poor

 

Mean within columns and groups followed by the same letters
are not signiﬁcantly different at a= 0.05.

136

Table 4.33. Soil quality ﬁeld chart

 

Extremely low

 

 

 

 

 

 

Poor Fair Good Excellent
>0 - 0.25 >0.25 - 0.50 >050 — 0.75 >0.75 - 1.0
Soil quality index scale

 

 

 

Table 43b. Soil quality, active organic matter (AOM), and available N
color chart

 

 

*
Soil quality quality soil quality quality
>0to400 >400t0800 >800t01600 >1600
AOM lbs/A AOM lbs/A AOM lbs/A AOM lbs/A
> 0—12 lbs > 12—26 lbs > 26—40 lbs > 40 lbs
Available N/A Available N/A Available N/A Available N/A

 

 

 

 

 

Tables above show colorcomparison of KMnO4 solution aﬁer shaking with soil

Copyright © 2008, The Ohio State University

137

 

Table 4.4. Signiﬁcant effects of gypsum, compost and cover crops on bulk density

 

 

 

 

 

Bulk density
2005 2006 2007

Sources F -value P-value F-value P-value F-value P-value
Gypsum 0.89 ns 0.54 ns 0.09 ns
Compost 0.00 ns 27.50 ** 18.92 **
Gyp*comp 0.38 ns 0.03 ns 0.00 ns
Cover " ' 2.45 * 3.73 **
Gyp*cover ' ' 0.37 ns 0.45 ns
Cover*comp ' " 1.81 ns 0.75 ns
Gyp*cover*comp ' " 0.45 ns 0.46 ns

"' P s 0.05

** P s 0.01

*** P $0.00]

us Not signiﬁcant at u=0.05
Abbrev: Gyp = gypsum; comp = compost

138

Table 4.5. Effects from compost, gypsum and cover crop on mean bulk density

 

 

 

 

Bulk density

2005 2006 2007

Sources Early Late
-------------g/cm3-----------

Mustard - 1.463 1.523 1.43bc
Oilseed radish - 1.443b 1.48ab 1.47b
Red clover - 1.42b 1.46b 1.41c
cereal/wheat - 1.42b N/A 1 .42c
No cover - 1.41 b 1.45bc
Compost 1.503 1.40b 1.43b
No compost 1.503 1.463 1.483
Gypsum 1 .503 1 .423 1.463
No gypsum 1.503 1.433 1.453

 

Mean within columns and groups followed by the same letters are not signiﬁcantly
different at a: 0.05 (2005 and 2006), and mean within group (early and late) followed
by the same letters are not signiﬁcantly different at a: 0.05 (2007)

139

Table 4.6. Statistical signiﬁcance of gypsum, compost, depth and cover crops on soil
WSA determined by the rain simulator method (2005-2007)

 

 

 

 

 

Fall 2005 Spring 2006 Spring 2007
Sources Aggregate Stability
F-value P-value F-value P-Value F -va|ue P-value
Gypsum 0.00 ns 0.29 ns 2.11 ns
Compost 1.22 ns 2.76 ns 9.26 *
Gyp‘comp 0.97 ns 0.46 ns 0.27 ns
Cover ' ' 2.21 ns 3.31 *
Gyp*cover " ' 1.37 ns 0.74 ns
Comp*cover " ' 0.02 ns 0.56 ns
Gyp*comp*cover " ' 0.34 ns 1.27 ns
* P S 0.05

** P <_ 0.01

*"'* P $0.001

ns Not signiﬁcant at a=0.05

140

Table 4.7. Effects from gypsum compost depth and cover crops on mean WSA
determined by the rain simulator method (2005-2007)

 

Fall 2005 Spring 2006 Spring 2007

 

 

Sources Aggregate Stability

%

Mustard _ 27a
Early _ _ 3 lb
Late _ _ 40a
Rye/wheat - 34a 4 23
NO COVCI _ 273 383
Compost 243 323 423
No compost 24a 27a 34b
Gypsum 273 303 353
No gypsum 273 303 403

 

Means within the same column and groups followed by the same letters are not signiﬁcantly
different at a=0.05

141

Table 4.8. Statistical signiﬁcance of gypsum, compost, depth, cover crops, and corn on soil
microbial biomass (MB) for fall 2006.

 

Fall 2006

Microbial Biomass

 

 

 

Sources F-value P-value
Gypsum 0.50 ns
Compost 3.50 ns
Gyp*comp 0.71 ns
Crops 0.02 ns
Gypsm*crops 0.82 ns
Comp*crops 0.1 1 ns
Gyp*comp*crops 0.14 ns
Depth 7.70 *
Gypsum‘depth 0.59 ns
Comp*depth 0.00 ns
Gyp*Comp*depth 0.56 ns
crops *depth 6.27 *
Gyp“ crops *depth 1.06 ns 8
Comp“ crops *depth 0.89 ns
Gyp*comp* crops *depth 0.30 ns
* P s 0.05
** P s 0.01
*" P $0.001

us Not signiﬁcant at (1:005

Abbrev: Gyp = gypsum; comp = compost

142

Table 4.9. Statistical signiﬁcance of gypsum, compost, depth, corn and cover crops effects on
microbial biomass.

 

2007

Microbial Biomass

 

 

 

Sources F-value P-Value

Spring
Gypsum 0.29 ns
Compost 3.28 ns
Gyp*comp 0.06 ns
Cover 1.56 ns
Gyp*cover 0.18 ns
Comp*cover 0.89 ns
Gyp*comp*cover 0.30 ns
Depth 60.38 ***
Gypsum*depth 0.88 ns
Comp*depth 2 13 ns
Gyp‘Comp*depth 0.04 ns
Cover*depth 0.37 ns
Gyp*crops*depth 0.30 ns
Comp*cover*depth 0.22 ns
Gyp*comp*crops*depth 1 .26 ns

Fall
Gypsum 1.24 ns
Comp 0.37 ns
Gypsum*comp 0.55 ns
Depth 42.99 ***
Gypsum*depth 0.03 ns
Comp*depth 0.04 ns
Gyp*Comp*depth 0.52 ns

* P 5 0.05
** P S 0.01

*** P $0.001; us Not signiﬁcant at (1:005

Abbrev: Gyp = gypsum; comp = compost

143

Table 4.10. Effects from gypsum, compost, depth, cover crops and corn on mean microbial
biomass (fall 2006)

 

Microbial biomass

 

 

 

 

Sources Fall 2006 Spring 2007 Fall 2007
-1
mg/kg
Corn 823 - -
Cover Crops
Mustard 793 - -
Early - 643 -
Late - 713 -
Wheat - 723 -
No cover 723 -
Compost 89a 693 683
No compost 713 713 64a
Gypsum 763 623 703
No gypsum 843 663 623
Depth 0—10 cm 913 823 74a
Depth 10-20 cm 68b 58b 57b

 

Means within the same column and groups followed by the same letters are not signiﬁcantly different at
u=0.05

Table 4.1 1 Effects from interactions of corn and mustard
plus depths on mean microbial biomass; fall 2006

 

Microbial Biomass

 

 

Crops *depth Corn Mustard
-1
-------mg/kg ........
0-10 cm 1043 803b
10-20 cm 58b 783b
Stdr 7 12

 

Means within the same column followed by the same letters are not
Signiﬁcantly different at (1:005

144

Table 4.12. Statistical signiﬁcance of gypsum, compost and cover crops effects on nematode population

 

Nematode population

 

Stunt Lesion Bacterial feeders

 

F-value P-value F-value P-value F-value P-value

 

 

Spring 2007
Gypsum 1.86 ns 0.30 ns 1.71 ns
Compost 2.60 ns 2.46 ns 5.87 *
Gyp‘comp 1.83 ns 0.89 ns 0.33 ns
Cover 6.11 "‘** 12.98 *** 0.88 ns
Gyp‘cover 0.25 ns 1.50 ns 0.35 ns
Comp*cover 2.05 ns 0.13 ns 0.49 ns
Gyp*comp*cover 0.72 ns 0.42 ns 0.78 ns
Fall 07
Gypsum 0.01 ns 0.75 ns 0.18 ns
Compost 0.01 ns 4.62 ns 0.03 ns
Gyp*comp 1.58 ns 0.08 ns 2.03 ns
* P s 0.05
** P s 0.01
*** P $0.001
us No significant at a=0.05

Abbrev: Gyp = gypsum; comp = compost

145

Table 4.12. Effects ﬁ'om gypsum, compost and cover crops on nematode community
(Measures on a 100 cm 3 soil basis)

 

 

 

 

2007
Nematodes
StuntT LesionT Bacterial Feeders:
Sources Spring Fall Spring Fall Spring Fall

 

100cm3 (soil)

 

 

Mustard
Early 77a - 503 2993 -
Late 1 1b - 22b 3373 -
Red clover
Early 21 b - 7c 2573 -
we 33b - 11b 388a -
N0 “W" 20b - 13b 293a -
Compost 253 323 253 27a 3713 2753
No compost 403 323 173 183 259b 2843
Gypsum 263 323 233 243 2853 2693
No gypsum 39a 33a 193 213 3453 2903

 

Means within the same columns and groups followed by the same letters are not
signiﬁcantly different at a=0.05

TPlant parasitic nematodes
IBeneﬁcial nematodes

146

Figure 4.1. . Representation of a typical block of the experiment design.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

b. 2006
a. 2005 Early Late c. 2007
Cover crop sub-subplot
10.7m x4.4m
(35’X14.5)
Compost
10.7 m x 13.m
(35’x43.5’)
Compost
Levels
CN M M CN % No compost
CN R CN
Gypsum No gypsum Gypsum No gypsum
Sub-sub-subplots 79.5 m x 5.3 (261 x 17.5’)

5.3m x 4.4 m(17.5’x 14.5)

Abbrev.: N= No cover; C= Cereal rye; W= Wheat; R= Red clover; 0= Oilseed radish;
M=Mustard; CN= Corn

147

Figure 4.2. Rain simulator

Entire apparatus: rain simulator with sieve stand

Delivery tu I -.,

 

Aggregate sample before rain simulation Sample during simulation

Images in this dissertation are presented in color

148

Figure 4.3. Effect of compost on bulk density, 2005 - 2007

 

I Compost
ﬂ No compost

Bulk density (g/cm3)

  

 

 

2005 2006 2007 Early 2007 Late
Years

 

 

149

 

Figure 4.4. Effect of cover crops on bulk density, 2006 and 2007

 

 

 

 

 

 

a I2006

1.6 -

1.5 - a
r: 3" b b
{5, 1.4 -
39
g» 1.3 -
m
5
'U 1.2 ~
X
'3
m 1.1 —

1 _ _7
Mustard Oilseed Red clover Cereal rye No cover
radish
Cover crops
b 1 6 I 2007 Early
' I 2007 Late

"‘3
U
E
E
(I)
E
'U
2‘
'3
m

 

 

Mustard Oilseed Red clover Wheat No cover
radish

Cover crops

 

150

 

Figure 4.5. Effect of compost on water stable aggregates (W SA) 2005 -2007,

 

 

 

50 _ ICompost
INo compost
4o -
... 30 -
o3.
2’3 20 ~
3
10 ~
0 ..
Fall 2005 Spring 06 Spring 2007
Years

 

 

 

151

Figure 4.6. Effect of corn and cover crops on water stable aggregates (W SA)

 

 

a ISpring06
50 a
40 _.
s .0-
<
m
3 20-
1o-
0 ~._ _1'

 

 

No cover Mustard

Cover crops and com

 

 

 

b I Spring 2007
50 -
4° ‘ a
g 30 -
<
U)
3 20 -
1o -
o -e
No cover eat E/mustard I/mustard
Cover crops

 

 

 

Abbrev.: E = Early planted cover crops; L = Late planted cover crops

152

Figure 4.7. Microbial biomass with reference to soil depth, 2006 and 2007.

 

60~

40—

Microbial Biomass (mg/kg“)

 

 

Fall 06 Spring 07 Early Spring 07 Late

Years/season

I 0-10cm
a 10-20cm

    

Fall 07

 

Figure 4.8. Effect of cover crops on nematode population, 2006 and 2007.

 

100.0

Nematode (per 100 cm'3 soil)

 

7

 

EfMustard L/Mustard E/Red cloverL/Red clover

Cover crops

I Stunt
.4- Lesion

 

No—cover

 

Abbrev.: E = Early planted cover crops; L = Late planted cover crops

153

 

 

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GENERAL CONCLUSIONS AND RECOMMENDATIONS

It is apparent that gypsum impacts different soils in different ways. This research

provided critical information for gypsum effects on a Kalamazoo sandy loam. When

gypsum was applied (2.24Mg/h'l) applied Ca was four times that applied through

compost (2.24Mg/h'l), yet extractable Ca from gypsum treated plots was not different

from non-gypsurn plots for all years. Generally, gypsum did not increase the soil
extractable C3. Compost increased extractable C3 by up to 38% within the top 20 cm
depth compared to control plot. Therefore, in a Kalamazoo sandy loam, gypsum
application is not recommended if the intended beneﬁt is to increase Ca. Additionally,
according to Warncke, (2003), soil test levels at and above 35 ppm and 350 ppm for Mg

and Ca respectively are adequate for optimum production on sandy textured soils.

This study showed, that both cover crops and compost, alone or combined, have
potential to increase the quality and yield of sweet corn. Sweet corn yield was generally
lower when gypsum was applied alone or in combination with cover crops or compost
and in some cases, gypsum applied alone and in combination with compost and cover
crops had a negative effect on com growth, yield and/or quality. If increasing yield and
improving quality is the intended beneﬁt, gypsum may not be an economical choice for a

Kalamazoo sandy loam.

If one desires to improve soil quality, gypsum application is not a good choice of
amendments, but compost application showed evidence of reducing bulk density over
time. Some of the cover crops show potential to reduce bulk density and increase

aggregate stability over time especially if planted later in the season. A mustard (late)

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cover crop reduced WSA and seemed to be 3 good host for both the stunt and lesion
nematode, especially when planted early. The latter observation contradicts the common

view and documented research that Brassica cover crops suppress nematode population.

Further research to study the beneﬁt of gypsum across Michigan is recommended,
since farmers have interest in its use. Such studies can be developed collaboratively with
other research institution across the north central regions due to the growing interest in
gypsum in these regions also. Secondly, building on this study (long term) would be a
good way forward especially to investigate the status of the C a as affected by gypsum
application. Where did all that C3 go? In this study, soil samples were taken within the
top 20 cm depths and only one rate of gypsum was used. Sampling lower depths and
applying more than one rate of gypsum would give a better understanding of the gypsum
effects. Thirdly, I would also recommend complete designs that would accommodate all
cover crops in each block and for each season. This would allow for a better assessment
of cover crops effects on the following cash crops. Finally, a good addition to this study
would be to investigate the effect of the various treatments on glomalin. Several reports
on glomalin indicate a positive relationship with increases in soil gomalin and improved
soil quality, especially as it relates to soil aggregate formation. Studies have also linked

low glomalin levels and corresponding poor soil quality with Brassicas.

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