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I LIBRARY
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University

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This is to certify that the
dissertation entitled

THE IMPACTS OF CONTINUOUS CORN AND A CORN-
CORN-SOYBEAN-WHEAT ROTATION GROWN UNDER
VARIOUS MANAGEMENT SCHEMES ON NITRATE
LEACHING, SOIL PHYSICAL CHARACTERISTICS, AND
NET RETURNS

presented by
Jeffrey Smeenk

has been accepted towards futﬁllment
of the requirements for the

m. decree in W

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6/01 c:/CIRC/DateDue.p65—p. 15

THE IMPACTS OF CONTINUOUS CORN AND
A CORN-CORN—SOYBEAN—WHEAT ROTATION GROWN UNDER VARIOUS
MANAGEMENT SCHEMES ON NITRATE LEACHING, SOIL PHYSICAL
CHARACTERISTICS, AND NET RETURNS
By

Jeffrey Smeenk

A DISSERTATION
Submitted to
Michigan State University
in partial ﬁIlﬁllment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY
Department of Crop and Soil Sciences

2003

ABSTRACT
THE IMPACTS OF CONTINUOUS CORN AND
A CORN-CORN-SOYBEAN—WHEAT ROTATION GROWN UNDER VARIOUS
MANAGEMENT SCHEMES ON NITRATE LEACHING, SOE PHYSICAL
CHARACTERISTICS, AND NET RETURNS
By
Jeffrey Smeenk

Nitrate leaching, maintenance of soil quality, and economic viability are major issues
associated with row crop agriculture and are inﬂuenced by the production strategies
chosen by the farm manager. These strategies include rotation sequence, source of
nutrient inputs and the use of cover crops. A long-term rotation study on Oshtemo and
Kalamazoo sandy loams (coarse-loamy, mixed, mesic Typic Hapladaulfs) at the Wig
Kellogg Biological Station near Hickory Corners, MI was established in 1993 to compare
various physical and economic parameters of a corn-com-so -wheat rotation to those
of continuous corn under various management systems. The organic (O) and integrated
compost (IC) systems used compost as the external nutrient source while the integrated
fertilizer (IF) and conventional (C) systems used synthetic fertilizers. All management
systems except C have cover crops interseeded at various points of the rotation. Corn
yields were highest in 1" year corn. In the O and IC systems, when 1" year corn followed
wheat+red clover yields were the same as for fertilized corn. Without the preceding red
clover cover crop, yields of 1" year corn crops in O and IC were signiﬁcantly lower.
Wheat yields were lower in the O and IC treatments. No signiﬁcant differences were seen

in soybean yields. The leaching patterns of a crop was very dependent upon the climatic

conditions. Both systems receiving compost had lower nitrate leaching rates than the

systems using fertilizer. In the IC system 1" year corn leached more nitrate (50 kg N ha'
lyr") than 2"d year com (35 kg N ha"yr") , soybean (34 kg N ha"yr“) continuous corn
(26 kg N ha‘1yr"), or wheat (17 kg N ha"yr"). In the IF system the nitrate leaching rates
of 1It year com (59 kg N ha"yr"), 2" year com (67 kg N ha'1yr“), and continuous com
(57 kg N ha‘1yr") were greater than the leaching rates of soybean (39 kg N ha"yr") or
wheat (20 kg N ha'1yr"). Bulk density was lowest following ﬁrst year corn and highest
following wheat but the inﬂuence of management was not signiﬁcant. Water holding
capacity, while statistically signiﬁcant, was not agronomically signiﬁcant (41-43%).
Aggregate stability was highest in wheat interseeded with red clover and lowest in the
soybean plots that did not receive cover crops at any point of the rotation. The
management systems receiving compost tended to have higher inﬁltration rates than those
receiving synthetic fertilizer but these differences were not signiﬁcant due to the high
variability. The resistance to penetration tended to be higher in wheat than in the other
crops but the differences were not consistent nor signiﬁcant. Net returns to land and
management expertise were highest in the 0 treatments (33 59-398 ha") due to the
premium prices associated with organic crops. Within the normally priced crops the IF
com-com-soybean-wheat rotation without cover crops had the highest net returns ($155
ha") followed by the IF rotation with cover crops ($128 ha") and the C rotation ($116 ha'
‘). The IC continuous corn had the lowest net returns both with cover crops ($15 ha")
and without cover crops ($10 ha"). This research demonstrated that a corn-corn-soybean-
wheat rotation had higher net returns than continuous corn while building soil quality and
reducing environmental impact from nitrate leaching. The use of compost enhanced the

soil quality effects but would not be eﬁ‘ective in rotations with multiple years of corn.

Dedicated to Gottlieb “Goodie” Streicher

iv

ACIGVOWLEDGMENTS

Thank you Dr. Harwood

PREFACE

Chapter 1 in this dissertation was written in the style required for publication in the
Journal of Environmental Quality. Chapter 2 was written in the style required for
publication in the Journal of Soil and Water Conservation. Chapter 3 was written in the

style required by the Agronomy Journal.

TABLE OF CONTENTS

LIST OF TABLES .................................................. viii
LIST OF FIGURES ................................................... ix
CHAPTER 1: INFLUENCE OF CROP ROTATION AND NUTRIENT SOURCE
ON NITRATE LEACHIN G ............................................ 1
Abstract ....................................................... 1
Introduction .................................................... 2
Materials and Methods ............................................ 5
Results and Discussion ........................................... 10
Conclusions ................................................... 20
References .................................................... 23

CHAPTER 2: THE INFLUENCE OF FARMING SYSTEM ON SELECTED SOIL

PHYSICAL CHARACTERISTICS ..................................... 34
Abstract ...................................................... 34
Introduction ................................................... 35
Materials and Methods ........................................... 38
Results and Discussion ........................................... 44
Conclusions ................................................... 52
References .................................................... 54

CHAPTER 3: AN ECONOMIC ANALYSIS OF CORN-CORN-SOYBEAN-
WHEAT ROTATIONS AND CONTINUOUS CORN PRODUCED UNDER

VARIOUS MANAGEMENT SYSTEMS. ................................ 66
Abstract ...................................................... 66
Introduction ................................................... 67
Materials and Methods ........................................... 70
Results and Discussion ........................................... 76
Conclusions ................................................... 85
References .................................................... 88

vii

LIST OF TABLES

CHAPTER I: INFLUENCE OF CROP ROTATION AND NUTRIENT SOURCE
ON NITRATE LEACHIN G

Table 1. Characteristics of management schemes ........................... 25
Table 2. Leachate volumes compared to precipitation over seven years .......... 25
Table 3. Nitrate available for crop growth ................................ 26

CHAPTER 2: THE INFLUENCE OF FARMING SYSTEM ON SELECTED SOIL
PHYSICAL CHARACTERISTICS

Table 1. Characteristics of management schemes ........................... 57
Table 2. 1999 Total carbon levels in the 0-25 cm proﬁle by management scheme . . 57
CHAPTER 3: AN ECONOMIC ANALYSIS OF CORN-CORN-SOYBEAN—
WHEAT ROTATIONS AND CONTINUOUS CORN PRODUCED UNDER
VARIOUS MANAGEMENT SYSTEMS

Table 1. Eight year averages of yield, gross income and net returns by crop and

management ................................................ 92
Table 2. Eight year averages of production expenses per hectare by crop and

management ................................................ 92
Table 3. Generalized table of operations by crop and management .............. 93
Table 4. Average crop prices .......................................... 93

Table 5. Average annual net returns to landed management under various crop price
scenarios compared to standard prices ............................ 94

Table 6. Average annual net returns to landed management under various input cost
scenarios compared to standard costs ............................. 95

viii

LIST OF FIGURES

(Figures are in color)

CHAPTER 1: INFLUENCE OF CROP ROTATION AND NUTRIENT SOURCE

ON NITRATE LEACHIN G
Figure 1. Lysimeter diagram ........................................... 27
Figure 2. Plot layout with lysirneters ..................................... 27
Figure 3. Daily leaching volumes: Integrated Compost ....................... 28
Figure 4. Daily leaching volumes: Integrated Fertilizer ....................... 28
Figure 5. Nitrate concentrations in leachate over the season: Integrated Compost . . . 29
Figure 6. Nitrate concentrations in leachate over the season: Integrated Fertilizer . . . 29
Figure 7. Daily nitrate leaching rates over the season: Integrated Compost ........ 30
Figure 8. Daily nitrate leaching rates over the season: Integrated Fertilizer ........ 30
Figure 9. Annual nitrate leaching (by crop) over seasons 2-7: Integrated Compost . . . 31
Figure 10. Annual nitrate leaching (by crop) over seasons 2-7: Integrated Fertilizer . . . 31
Figure 11. Inﬂuence of management on annual leaching ....................... 32
Figure 12. Will nitrate leaching under rotational crop compared to continuous corn by
management ................................................ 32
Figure 13. CVs of cumulative years ....................................... 33
Figure 14. CVs of cumulative seasons based on lysirneter size ................... 33

CHAPTER 2: THE INFLUENCE OF FARMING SYSTEM ON SELECTED SOIL
PHYSICAL CHARACTERISTICS

Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.

Figure 14.
Figure 15.

1997 and 1998 soil bulk density by crop and management ............. 58
1999 soil bulk density by crop .................................. 58
1999 soil bulk density by management ............................ 59
1998 soil water holding capacity by management .................... 59
1999 soil water holding capach by management .................... 60
1998 soil water holding capacity by crop .......................... 60
1999 soil water holding capacity by crop .......................... 61
1998 soil aggregate stability by management ........................ 61
1999 soil aggregate stability by management ........................ 62
1998 soil aggregate stability by crop .............................. 62
1999 soil aggregate stability by crop ............................. 63
1999 water inﬁltration rate by management ........................ 63
1999 water inﬁltration rate by crop ............................... 64
Resistance to penetration by soil associated with each crop ............. 64
Resistance to penetration by by soil at each sampling date ............. 65

CHAPTER 3: AN ECONOMIC ANALYSIS OF CORN-CORN-SOYBEAN—
WHEAT ROTATIONS AND CONTINUOUS CORN PRODUCED UNDER
VARIOUS MANAGEMENT SYSTEMS

CHAPTER 1
Inﬂuence of Crop Rotation and Nutrient Source on Nitrate Leaching

ABSTRACT
Nitrate leaching is a signiﬁcant problem in the upper Midwest. Row crop agriculture,
especially corn, has been implicated in the nitrate contamination of ground water. This
study looked at the inﬂuence of compost and fertilizers on the nitrate leaching rates of
both a diverse rotation and continuous corn. The inﬂuence of lysimeter size on the
estimation of nitrate leaching was also evaluated. Fifty six 30.5 cm and four 91 cm intact
core lysimeters were installed in a long-term rotation study on Oshtemo and Kalamazoo
sandy loams (coarse-loamy, mixed, mesic Typic Hapladaulfs) at the Kellogg Biological
Station near Hickory Corners, MI. A com - corn - soybean - wheat rotation was
compared to continuous corn under various management systems. The organic (O) and
integrated compost (IC) systems used compost as their external nutrient source while the
integrated fertilizer (IF) and conventional (C) systems used synthetic fertilizers. All
management systems except C had cover crops interseeded at various points of the
rotation. The O and IC systems had similar nitrate leaching rates. The IF and C nitrate
leaching rates were Similar to each other and both were greater than the IC and O leaching
rates. In the IC system 1" year corn leached more nitrate (50 kg N ha") than 2Ml year
com (35 kg N ha") , soybean (34 kg N ha") continuous com (26 kg N ha"), or wheat (17
kg N ha"). In the IF system the nitrate leaching rates of 1" year com (59 kg N ha"), 2"‘1
year com (67 kg N ha“), and continuous com (57 kg N ha") were greater than the
leaching rates of soybean (39 kg N ha“) or wheat (20 kg N ha"). The lower leaching

rates of IC 2MI year and continuous corn corresponded with grain yields that were also

about 15% lower. The coeﬁcient of variation (CV)S of the nitrate leaching rates from the
large (91.5 cm) lysimeters were greater than the CVs of the small (30.5 cm) lysimeters for
the last 5 of the 7 leaching seasons reported. When the leaching data were aggregated
over the seven years, the resulting CV of the small lysimeters was 67% and the CV of the
large lysimeters was 59%. A highly productive corn system using compost did not leach
more nitrate N than a fertilized system with comparable yields. Wheat and soybeans
leached less nitrate N than fertilized com. A rotation including soybeans and wheat should
leach signiﬁcantly less than continuous corn. The leaching patterns of a crop were very
dependent on the climatic conditions. Growing crops with different seasonal leaching
patterns will decrease the impact of adverse climatic conditions on the total nitrate
leaching of a farm since ﬁelds with diﬂ‘erent crops will vary in their sensitivity to high

rainfall events in any given season.

INTRODUCTION
In southwest Michigan, as in many regions, nitrate leaching is an important factor in
designing sustainable farming systems that operate in areas with signiﬁcant suburban
encroachment. The combination of sandy soils, nearby surface water, and an increasing
number of residential and community wells in this mixed usage area, mandates effective
nitrate management. Since nitrate readily leaches, agronomic crops receiving fertilizer are

often implicated in increasing nitrate levels in ground and surface water.

Non-point nitrate losses can be reduced through optimization of fertilizer usage and

replacement of some continuous row crop acreage with alternative crops that have longer

periods of active rooting (Mitsch et al., 1998). One mechanism of accomplishing both of
these goals is through the use of crop rotations that include legumes and/or cover crops.
Not only is the active rooting period, and thus time for plant nitrate uptake, longer in a
rotation with cover crops than in continuous corn (Zea mays L.), the release of nitrogen

can be manipulated to reduce the amount of added N fertilizer necessary for high yields.

Of the major crops grown in the upper Midwest, corn receives the most fertilizer N per
hectare. Much of this N is susceptible to loss by leaching. Owens et al. (2000) reviewed a
number of tile eﬁluent studies and summarized that NO3-N concentrations under
conventionally grown corn typically ranged from 10 to 60 ppm and were similar under
several multiple cropping systems. The lysimeter studies he reviewed showed even higher
nitrate concentrations. A Minnesota study showed that leachate concentration varied from
52 to 116 ppm NO3-N and represented 27-43% of applied N. An Ohio study with much
higher fertilization rates yielded leachate concentrations that ranged from 44 - 73 ppm,
NO3-N representing 40% of the N applied in the fertilizer. A Pennsylvania study with
corn (Jemison and Fox, 1994) reported loss rates equivalent to 24 to 55% of the nitrate

applied at optimum economic rates of around 190 kg/ha.

A com - soybean (Glycine max L.) rotation has lowered N fertilizer inputs compared to
continuous corn and would be expected to have lower N leaching loss. Klocke et al.
(1996), Weed and Kanwar (1996), and Randall et al. (1997) reported lower leaching rates
under a corn - soybean rotation than under continuous corn. Owens et al. (1995) reported

that less nitrate leached under a corn - soybean/rye cover rotation than under continuous

corn. with no cover crop. A reduction in the amount of fertilizer applied to the corn in the
rotation can also result from nitrogen credits from the soybeans (Owens et al., 2000). In
the corn - soybean - wheat (T riticum aestivum L.) rotation common in southwest
Michigan, corn typically receives 157 kg N ha", wheat typically receives 84 kg N ha",
and soybean is usually not fertilized with nitrogen. A rotation of corn-com-soybean-
wheat would be expected to receive 398 kg N ha'1 over the four years while over the same
period continuous corn would receive 628 kg N ha". The actively growing winter wheat
crop should also decrease late fall and winter leaching following soybeans both by
increasing transpairation and by scavenging residual soil nitrate prior to winter, the period

of greatest leaching loss in Michigan.

Alternative management systems using compost and leguminous cover crops as the sole
external nutrient source gave similar 1" year corn yields as were seen with synthetic
fertilizer and no cover crops (Jones et al., 1998) A soil with an enhanced (both quantity
and quality) pool of mineralizeable N is likely to provide adequate N for crop growth
(Sanchez, 2002). Much of the N from a red clover (T rifolium pretense L.) cover crop

* goes into the soil to be released in ﬁrture years (Harris et a1, 1994). This increase in
mineralization potential and the possibility of the cover crop to leach N over several years
highlights the need for careful N management in alternative systems as well as

conventionally fertilized systems.

The major objective of this study is to compare nitrate leaching under a system that used

compost and cover crops to supply nutrients with a system that used synthetic fertilizer

and cover crops. Concurrently, the rate of N leaching under a com-com-soybean-wheat
rotation was compared to that of with continuous corn, and whether the size of the

lysimeter inﬂuenced the stability of the data.

MATERIALS AND METHODS
Site Description, Lysimeter Construction and Operation
During the summer of 1992, sixty intact core lysimeters (Fig. l) were installed in the sandy
soils of “The Living Field Laboratory”, a com-corn-soybean-wheat rotation study (Fig.
2), at the WK. Kellogg Biological Station near Hickory Corners in southwest Michigan.
Soils are Oshtemo and Kalamazoo sandy loams (coarse-loamy, mixed, mesic Typic

Hapladaulfs). The climate is temperate with an average annual precipitation of 890 mm.

A long-term mixed stand of alfalfa and grass hay was sprayed with glyphosphate prior to
lysimeter establishment. The Ap horizon above the lysimeter was removed and set aside
prior to lysimeter installation. A truck-mounted pile driver was used to press the 61 cm
segment of 30. 5 cm (ID) PVC pipe through the Bt horizon and subsequent layers until the
leading edge of the core was into the sand-gravel layer that underlies the entire ﬁeld. The
soil around the north side of the pipe was pulled away and the intact core of soil was
removed. The ends of the PVC pipe were occluded with a large clamp that also served as
a ﬁtting connection. The pipe with the soil core was inverted and plumbed. A layer of
ﬁberglass tile drain cloth was inserted with a 3 cm layer of ﬁne stones held in place with a
6.6 mm screen. A PVC pipe end cap with a small 90° elbow inserted in its center diverted

the leachate into the storage reservoir (a 20 liter carboy) placed below and adjacent to the

lysimeter. A surface access tube was also plumbed into the carboy and the entire
assembly was buried in the plot. The Ap horizon was then replaced over the lysimeter. In
the conventional continuous corn plots this process was also repeated with a 91.5 cm (ID)

steel pipe installed about 2 m south of the small lysimeter at the same depth and with

similar plumbing.

Installation of the 60 lysimeters was completed by Nov. 1992. All accumulated leachate
was pumped ﬁom the reservoirs and discarded. Following this initial emptying the
reservoirs were emptied and sampled approximately monthly. The leachate was removed
from the reservoir by inserting a thin tube through the PVC access tube (1.9 cm ID). The
thin tube was connected to a graduated cylinder to which a vacuum was applied. The
volirme was recorded and a sample of the leachate was stored for laboratory analysis. The
concentrations of N as nitrate and ammonium were determined using a Lath auto-

analyzer (Lachat Instrument Co., Milwaukee, WI).

Prior to primary tillage the lysimeters were emptied, the access tube removed, and the
buried portion of tube was capped. A metal end cap along with a steel collar facilitated
the use of a metal detector to relocate the buried pipe for re-connection. Since all parts
of the lysimeter were buried well below the depth of tillage, commercial scale farm
equipment (6-row) was used for all ﬁeld operations. Following ﬁnal cultivation of corn
and soybeans in late June the access tubes were re-installed and the lysimeters were
sampled. The access tube terminated 10-20 cm above the soil surface to prevent surface

water ﬁ'om entering the carboy. The access tube was unobstructed to prevent the

lysimeter from becoming vapor-locked. Although rain had the opportunity to enter the
access tube, the actual amount of rain that fell into the tube was negligible compared to

the amount that leached into the lysimeter.

Experimental Design and Layout

The entire experiment was a split-split-plot design, with management system as the main
factor (4 treatments), crop as the split-plot (5 treatments) and cover crop as the split-split
plot (2 treatments). There were four replications. Each crop in a com- com - soybean -
wheat rotation, along with continuous corn, was present under the four different
management systems. Each crop plot was further divided into a cover crop side and a no-
cover crop side. Table 1 outlines the major differences between the management
treatments. The conventional plots, due to their full coverage herbicide program, do not

receive cover crops. Figure 2 illustrates the layout of the lysimeters within the

experiment.

Crop Management

Corn Compost was applied to the Organic (0) and Integrated Compost (IC) plots in
April prior to tillage at the following rates: 4,500 kg/ha on 1" year and
continuous corn and 9,000 kg/ha on 2ml year com. All plots were chisel
plowed and disced at least a week prior to planting. On the day of planting all
plots were ﬁeld cultivated and planted (69,000 seeds/ha) in 76 cm rows. A
starter fertilizer (10-20 kg N ha'1 either granular or liquid) was applied in the

Integrated Fertilizer (IF) and Conventional (C) treatments and a pre-emerge

Soybean.

grass herbicide (Dual H) was banded over the row in the IC and IF treatments
and broadcast in the C treatments at planting. Continuous and 2'“1 year corn
received a banded soil insecticide for corn rootworrn control. Mechanical
weed control in 0, IC, and IF usually consisted of two rotary hoeings, a
cultivation with the rolling shields down and a ﬁnal aggressive cultivation prior
to canopy closure (Table 1). Nitrogen, initially as ammonium nitrate and in the
last two seasons as liquid 28% N, was usually sidedressed at rates
recommended for a 9.4 Mg/ha yield goal by the pre-sidedress nitrate test
(PSNT) in the IF and C treatments. The fertilizer was incorporated in the ﬁnal
cultivation. Immediately following ﬁnal cultivation crimson clover (T rrfoliwn
incarnatum) was banded at 19 kg/ha between the corn rows in 1" year and
continuous corn and annual ryegrass (Lolium multrﬂorum) was banded at 30
kg/ha in 2"“ year corn. Yield data were recorded from the center 2 rows of the

entire length of the 15.3 m plots alter the boarder plants were removed.

All plots were chisel plowed and disced at least a week prior to planting.
Neither compost nor fertilizer was added to these plots in this point of the
rotation. On the day of planting all plots were ﬁeld cultivated and planted
(370,000 seeds/ha) in 76 cm rows. Mechanical weed control in 0, IC, and IF
usually consisted of two rotary hoeings, a cultivation with the rolling shields
down and a ﬁnal aggressive cultivation prior to row closure. In the early years
of the experiment, pre-emerge herbicides were used, and more recently post-

emerge herbicides were used. Round-up resistant varieties were used in the

Wheat.

last three years with two applications of glysphosphate at low rates. Yield data
were recorded from the center 2 rows of the entire length of the plots alter the

boarder plants were removed.

Compost was applied (4,500 Kg/ha) in the O and IC plots immediately
following soybean harvest. At planting, the plots were disced or ﬁeld
cultivated and then planted (5,000,000 seeds/ha). In early spring 84 kg/ha
nitrogen (as urea) was applied to the IF and C plots. At the same time
‘Michigan Mammoth’ red clover was frost seeded (18 kg/ha) into the wheat.
The wheat was harvested in July using a plot combine and the straw was baled
and removed. The plots were clipped in September to stimulate the clover

cover crop and/or to control weeds.

Statistical Methodology

Of the 2900 lysimeter readings taken from April 1993 - April 2000, six values were

missing and were approximated using SAS (SAS Institute) Least Square Means (LS-

means). The' measured leaching interval of March 24, 1995 - July 24, 1995 was divided

into two smaller intervals (March 24 - April 12 and April 12 - July 24) using a ratio of

daily leaching volumes determined for this period by the other six years of leaching

volumes. Dividing this long interval into to two smaller intervals facilitated assigning the

early interval leaching to the 1994-1995 leaching season and the latter interval to the

1995-1996 leaching season. The volume and concentration curves were generated using

LS—means rather than the actual means to compensate for the high variability of the actual

data.

The volume and concentration data set was converted into kg per ha N as nitrate. Nitrate
accumulation from the ﬁrst pumping of the lysimeters following access tube opening in the
spring until the last pumping prior to access tube closure in the following spring was
summed to estimate annual leaching. To attribute the nitrate leaching to the crop
associated with it the “leaching year” was deﬁned as the period from access tube closure

prior to spring planting until the date of access tube closure in the following spring.

When the calculated N leaching rates were ranked, there were six individual leachate
values that were more than 10 standard deviations from the resulting mean with them
removed. These six calculated leaching rates were removed, treated as missing values,
and approximated using SAS-generated least squared means (LS- means). The resulting
annual values were normalized using a natural log transformation. The means reported are
the least square means of the un-transforrned data (kg/ha) while the signiﬁcant differences
between treatments are always determined based on the transformed data set (In kg/ha)

using SAS’S MDIED model (SAS, 1999).

RESULTS AND DISCUSSION
Leaching patterns over the season
While individual readings of lysimeter volumes varied from no leachate captured to

volumes that represented 300% of rainfall, when the data were aggregated over

10

replications and seasons the leachate volume averages were remarkably similar. Thirty six
percent of the annual precipitation was represented as leachate captured at 80 cm depth
(Table 2). The leaching volumes of the various management systems were fairiy
consistent within seasons but there were large differences between years. The slightly
higher year to year variability seen with the O and C management compared to the IC and
IF treatments may be due to fewer data points in the averages, or they may represent a
stronger crop inﬂuence. The O and C managements have lysimeters only in continuous
corn and one point in the rotation while the IC and IF management have lysimeters in the

continuous corn and all four points of the rotation

Daily leaching volumes, determined by dividing the volume pumped by the number of days
since last pumping, varied throughout the season. During the mid- and late-growing
season the average leaching volumes decreased to about 15 ml per day (Figs. 3 and 4).
Average daily leaching volumes increased through the late fall and early winter reaching a
peak of about 120 ml per day in early spring. From May until September evapo-
transpiration exceeds rainfall (Cavigelli et al., 1998) and, with the exception of preferential
ﬂow following major rain events, the majority of precipitation never leeches beyond the
root zone. From October to April precipitation exceeds evapo-transpiration and the
proﬁle has a chance to recharge and then leach excess soil water. From December until
March signiﬁcantly greater volumes usually leached ﬁom the corn plots than from the
soybean and wheat plots. Except for 1" year corn in the late winter leaching period, the
differences between the leachate volumes for crops under IC management and the crops

under IF management were not signiﬁcant.

11

The leachate nitrate concentration data is also highly variable (Figs. 5 and 6). The lowest
concentration measured was 0.8 ppm N as nitrate and concentrations of over 200 ppm
were recorded from several lysimeters. Toth and Fox (1998) identiﬁed and removed a
value of 180 ppm, attributing it to possible rodent activity. In our data set 200 ppm was
the upper end of a continuum rather than an outlier. Most of the nitrate concentration
patterns in the IC management systems were Similar to those in the IF systems. A notable
exception was continuous corn. In the IC plots the continuous corn leachate NO,-N
concentration was usually more dilute than those of the rotation crops, while in the IF
plots the continuous corn leachate NO3-N was more concentrated than the rotation crops.
These differences were signiﬁcant in the heavy leaching periods of fall and winter. Similar
patterns were observed in the seasonal soil nitrate levels in these plots (Sanchez, 2000). In
IC continuous corn plots average soil nitrate levels from April to December remained
fairly constant at around 4-7 ppm throughout the season while the soil nitrate levels in IF
continuous corn plots ranged ﬁ'om 4 ppm in April to a maximum of 28 ppm in August and

then returned to 8 ppm in December.

The seasonal leaching loss curves are driven by the leaching volume curves since the
seasonal concentrations are relatively stable (Figs. 7 and 8). During the winter and early
spring, when leaching is at it highest, the average daily nitrate N leaching rates for all of
the IC corn treatments ranged from 0.15 to 0.25 kg N ha" per day. Conversely, the corn
grown with fertilizer ranged ﬁom 0.28 to 0.45 kg N ha‘1 per day for the same period.
These differences were signiﬁcant in the Feb-March heavy leaching period. The leaching

rate for IC 1‘' year corn signiﬁcantly increased to 0.17 kg N ha" per day in Oct-Nov

12

period while all other IC corn treatments remained in the 0.06 kg N ha‘1 per day range.
This increase probably reﬂects the higher August soil nitrate levels present with 1" year
corn and its preceding red clover cover crop (12 ppm N as N03) compared to the lower

levels (5 ppm) associated with IC 2ml and continuous corn treatments (Sanchez, 2000) .

Annual leaching losses over the six seasons: Integrated Compost and Integrated
Fertilizer

In the ﬁrst year of the experiment leaching was high, because the alfalfa/grass hay crop
that preceded it (Jones et al., 1998), and the data were removed from the analysis. The
hay had been baled in mid-summer of 1992 to facilitate lysimeter instalation resulting in
high N mineralization. In four of the last six seasons IC 1" year corn leached more nitrate
per year than IC 2ml or continuous corn (Fig. 9). Soybean leaching was very erratic under
compost. In the 1995-1996 and 1996-1997 seasons the levels of nitrate leached under
soybeans were the second highest and in the 1997-1998 season they were the highest. In
the 1998-1999 season soybean nitrate leaching was less than all other crops and in the
1999-2000 season it was next to least. It was noted that heavy nitrate leaching under
soybean occurred when excessive rains fell in late spring/early summer, before the
soybeans reached the late vegetative stage. Precipitation later in the soybean growing
season was not associated with heavy leaching. This lack of leaching may have been due
to greater transpairation associated with larger plants or that as the soybeans reached
maximum grth rates they took up most of the mineralized N. The April-April leaching
year concept works well with corn crops but there were problems with the soybean and

wheat leaching seasons. The leachate during the winter following soybeans was

13

confounded with the fall-planted wheat present in that plot. The nitrate leached was
arbitrarily attributed to soybean but it may actually have been associated with the newly
planted wheat crop. Lower October soil temperatures probably resulted in minimal
mineralization of the compost that was applied prior to wheat planting. The low October
nitrate levels probably caused the fall planted wheat to act as a N scavenger further
decreasing the winter leaching from the ‘soybean’ plots. The wheat plots under IC

management were consistently in the middle or low leaching range each season.

In the fertilizer treatments some of the same patterns were observed (Fig. 10). Wheat
again was consistently in the middle or low leaching range and soybean leaching was very
erratic. Some seasons soybean leaching was greater than corn leaching and in other
seasons it was less than corn leaching. The IF wheat was not fertilized in the fall so, like
the IC wheat treatment, the wheat may act as a nitrate scavenger crop until it is fertilized
in the spring. In most leaching seasons the leaching from IF soybean is very similar to the
leaching of IC soybean. The major diﬂ‘erence between the annual IC and IF nitrate
leaching patterns was that under IF management, 1" year corn did not consistently leach
more nitrate than 2'“1 year or continuous corn. In most seasons, there were only slight
differences between the nitrate leaching amounts from each of the corn crops. Unlike the
IC corn, no IF corn crop consistently leached nitrate more than any other corn crop.
Similarities in IF corn leaching patterns were expected since all three treatments were
fertilized to the same yield goal using PSNT. The elevated corn leaching rates in the
1996-1997 leaching year were probably associated with a mid and late season drought.

Following side-dress N application in early July there was insigniﬁcant rainfall until

14

October. In late fall, intact ammonium nitrate granules could be found in the soil and were

probably the source of the elevated leaching rates for the season.

Leaching Losses over the six seasons

When the yearly data were aggregated the amount of nitrate leached under IC 1" year corn
following wheat/red clover is similar to the amounts leached under all the IF corn
treatments and greater than the amounts leached under IC 2" year and IC continuous corn
(Fig. 11). As shown in Table 3, the estimate of N available to IC 1" year corn is very
similar to the estimate of N available to IF 1" year corn and both are greater than the
estimate of N available to IC continuous corn (F ortuna et al., 2002). First year corn from
both IC and IF managements leach similar amounts of nitrate as IF continuous corn in
spite of estimates of available N that are 33% and 28% lower respectively. These
differences cannot be explained on a basis of yield alone since the 0.1 Mg/ha lower yield of
IF continuous corn only accounts for 18 kg N ha“. Sanchez et al. (2001) found that
mineralization in the IC 1" year corn plots in the presence of corn roots was 50% higher
than in the soil in these plots without com. This would increase the estimate of N
available to IC 1" year corn to 309 kg N ha" which is similar to the estimate of 306 kg N
ha'1 available for IF continuous corn. Unfortunately, we do not have any data on the corn
root inﬂuence on the N mineralization of soils without compost or clover residue.

Another possibility for this incongruity is that the timing of N availability may be more

important to crop production and N leaching than the actual amounts of N in the system.

15

The leaching losses measured for corn were lower than some reported in the literature
(Owens, 1987; Chichester, 1977; Jamison and Fox, 1994; Yadav, 1997). One possible
explanation is that the levels of N inputs used in this study were lower than in the levels
used in the above studies. The Oshtemo and Kalamazoo soils in southern MI have
historical grain yield averages of 8.2 Mg/ha with 9.4-11 Mg/ha attainable, weather
permitting. We fertilize for yield goals of 9.4 Mg/ha using PSNT. Many trials reported in
the literature fertilize to signiﬁcantly higher yield goals. The 56 kg N ha" annual leaching
rate measured under fertilized corn was more than the 16 kg N ha'1 that Sogbedji et al.

(2000) reported when also using PSNT to set fertilizer rates on a coarse textured soil.

Soybean leached similar amounts of nitrate regardless of management system. Based on
150 day laboratory N mineralization potentials Fortuna et al. (2002) calculated that the IC
soil (25 cm depth) prior to soybean planting could have 161 kg N ha'1 available while the
IF soil ahead of soybeans could have 124 kg N ha". The higher mineralization potential of
the IC management system may not be realized in-situ since there were no signiﬁcant

diﬂ‘erences between yields or annual leaching over the six years.

Although it does not appear signiﬁcantly different on the graph of LS-means of the un-
transformed kg/ha data, after the natural log transformation necessary to normalize the
data, the amount of nitrate leached by IC wheat was signiﬁcantly (a=0.05) less than the
amount leached by IF wheat (Fig 11). The majority of this leaching occurred in the winter
following harvest. During the wheat’s active growing season there was very little nitrate

leached from the system. Even though the soil nitrate levels averaged 8 ppm for the

16

fertilized wheat (Sanchez, 2000) ﬁ'om April to June the leaching rate for this period was
only about 0.06 kg N ha“ per day. The majority of precipitation into an actively growing
wheat ﬁeld is lost as transpiration, so in spite of higher soil N levels in the IF wheat,

leaching was minimal.

Leaching Losses over all four managements

The leaching patterns of the 0 management lysimeters were very similar to those seen in
the IC management. The O rotation plots usually leached more nitrate than their IC
counterparts (signiﬁcant at a=0.05 in 1996-1997). The leaching pattern for 0
continuous corn was usually similar to the pattern of IC continuous corn. In the 1995-
1996 season continuous corn from the 0 management leached signiﬁcantly more than the
continuous corn from IC, and in 1996-1997 IC continuous corn leached more than 0
continuous corn. When the six seasons were combined (Fig. 12) the annual amount of N
leached under the rotation crops was greater in the 0 plots than in the IC plots. This
diﬂ‘erence is perplexing since management operations between these treatments are very
similar. The major difference between these treatments is a 30 cm band of herbicides in
the corn and soybean crops. Possibly, the greater weed pressure (mainly summer annuals)
seen in the 0 treatment may be associated with the diﬂ‘erence in leaching rates. Another
possibility is that the differences are associated with the smaller dataset of O and C
leaching values. There is a lysimeter in only one rotation plot in the O and C
managements while the IC and IF results are the averages of lysimeters in each of the four

plots.

l7

TheleachingpanernsofthelyﬁmetasmtheCmmagananwa'evaysinﬁhrmﬂmseof
theIFmanagement. Theamomrtsofnitmteleachedundertherotationplotswerenot
signiﬁcantlydiﬂ‘erent(a=.05)betweentheIFandeanagements. Infourofthesix
mareponeitherewaemdiﬁ‘aenoesmtheninateamoumueachedunder
continuous corn. Inthe 1997-1998 leachingyearIFcontimrousoomleachedsigniﬁcantly
morenitratethandidtheCcontinuouscom 'I'hissituationwasreversedinthefollowing
season Whenthecropsoverthelastsixyearsarecombinedovermanaganernsystems
(Figs. l2),themamgememsystansreceivingferﬁﬁzer(IFde)leachedsigmﬁcamly
morenitratethanthemanagementsystemsreceivingcompostﬂCandO). This
observaﬁonnmybeaﬁmcﬁonoftherdaﬁvdyslowmuiemwleasecompostthatwe
applied. Fortuna(2003)indicatedthatthesteadystatemeanresidencetimeofthe
mhaalizablemMcpoolofsoﬂNwasabomWAbngermsdectedplotsreceivmg

compost than in the corresponding fertilized plots.

Cover Crop inﬂuence
Ihaemesewralrepoﬂshtheﬁterahneofusingmnlryegrassaﬁawmasadﬁate
catchcropﬂsseetal, 1999, Vynetal., 1999). Inboththe1993-19943easonandthe
1997-1998leaclﬁngseasontherotaﬁonsequencehadferﬁﬁzedZ"yearcornwithanmal
ryegrass(IF)andfertﬂizedZ‘yearcornwithoutacovercrop(C)abovethelysimeters.
OvaﬂreseMoseasothediﬁ‘ermcemleacMngbaweenmewmwhhmnmlryegrass
(55 ngha“) andthe comwithno cover crop (67 ngha")wasnot signiﬁcant. It is
possible that with more observations this difference would become signiﬁcant. We also

sawmdiﬂ‘erencemleachingmnoum8assodatedunththecﬁmsondoverwva’crop

18

under continuous corn versus continuous corn with no cover crop (both 61 kg N ha")

under similar (IF and C) fertilizer inputs.

Comparisons of Coefficients of Variations (CV s)

As indicated by the stars in Fig. 13, the CVs (Std Dev / mean) of the continuous corn
plots of all management systems changed each year. Initially, there was a trend towards
decreasing CVS, but since the 5‘' season the average of the CVs remained between 25-
65%. The trend lines in Fig. 13 indicate that aggregating the annual leaching data
decreases and stabilizes the CVS at 60-90%. This inﬂuence may have been more
mathematical than biological. In the 1993-1994 season there were only four values (reps)
for each CV while by the 1999-2000 season the cumulative CVs were composed of 28
values (7 seasons ‘ 4 reps each). The increase in observations going into the CV estimate

decreased the standard deviation while the mean remained fairly constant

The small (30 cm) lysimeters and large (91 cm) lysimeters in the continuous corn plots
under C management were within 2 m of each other in the same corn row. The stars in
Fig. 14 indicate that the CVs for individual seasons were actually lower for the small
lysimeters than for the large lysimeters for these continuous corn comparisons, using equal
observation numbers. In the 1" season (93-94) the CV for the small lysimeter was 105%
but for seasons 3-7 the CVs have averaged around 30%. The annual CVs for the large
lysimeters averaged around 60%. As the data were aggregated over seasons the small
lysimeter CV trend line decreased while the large lysimeter CV trend line remained stable

at around 60%.

19

The choice of lysimeter size and design involves a series of tradeoﬂ‘s. Designs that have
a lip above the soil level eliminate surface ﬂow into and out of the fetch area. This lip also
eliminates the proper use of farm scale equipment over the lysimeter. Large undisturbed
monolith lysimeters necessitate such extensive soil disturbance around them that plot data
outside the lysimeter may be meaningless. Reconstructed proﬁle lysimeters may have
different water patterns than would be seen in the undisturbed proﬁle. The buried quartz
lysimeters have minimal soil disturbance but do not measure water ﬂow rates. The 30.5
cm buried intact core lysimeters were as stable in their estimates of nitrate leaching as the

91 cm lysimeters despite having a much smaller fetch area.

CONCLUSIONS
It is important to measure leachate during the winter Since that is when the majority of
leaching occurs in the Michigan agroecosystem. Studies that only measure nitrate
leaching after rain events during the growing season would miss the majority of leaching

events in the Michigan system.

The use of 30.5 cm PVC pipe allowed 56 lysimeters to be installed in one summer to
facilitate a good estimate of the same season’s effect on different crops and management
systems. Increasing the size of lysimeter to 91.5 cm did not decrease the CVS of the data
despite the higher cost and increased complexity involved in the installation of the four

large lysimeters.

20

Agronomic systems with enhanced active N pools such as the compost with cover crop
management seen by 1" year corn can have similar yields as fertilized systems and have
nitrate leaching that is the same or less than those fertilized systems. The 60% higher
mineralization potentials seen in 1" year com the compost treatments with a preceding red
clover cover crop probably resulted in higher percentages of N coming from the soil than .
in the treatments that were fertilized. In spite of the higher mineralization potentials, the
compost treatments did not leach more N than did the lower N mineralization potential

treatments that were fertilized.

Manure disposal challenges are a limiting factor in the expansion of area livestock
operations. Composting the manure and applying it to a neighbor’s row crop land may
beneﬁt both operations. Sanchez (2000) showed that the addition of clover to a
conditioned soil increased in-sr'ru mineralization more than the addition of compost. Thus,
red clover is also an important component of a productive system. Other portions of our
current cover crop scheme need to be adjusted to capture excess fall nitrate. The annual
ryegrass currently used is not aggressive enough to scavenge the residual soil N in the

small window of opportunity between corn maturity and winter freeze

To spread out labor demands and minimize risk most farms have each crop in the rotation
every year. The expected annual leaching load from the farm would be less in a com-
soybean—wheat rotation than from a continuous corn operation. The late season drought
in 1996 that was associated with excessive N leaching under corn did not affect wheat

yields or leaching. Crop diversiﬁcation may be a way for a farm to decrease the risks

21

associated with the crop x season interactions. Since wheat leaches less nitrate than corn,
any ﬁelds that are planted to wheat should decrease the total farm’s average leaching
loads. Unfortunately, throughout the duration of the trial, nitrate concentrations in all of
our lysimeters were well above the 10 ppm maximum in the Federal Drinking Water

Standard.

A highly productive system using compost and red clover preceding 1" year corn, no
supplementary N for soybeans, and spring applied fertilizer for wheat could be expected to
maximize yields while keeping the same nitrate leaching rates. This would be expected to
decrease the amount of fertilizer inputs and provide the soil quality beneﬁts associated

with an enhanced active pool of soil N.

Excess nitrate, regardless of source (red clover vs. fertilizer), is subject to leaching. A
rotation with organic inputs can leach as much nitrate as a rotation that uses synthetics
fertilizers. If soil N levels are adequate for high corn productivity there is the risk that N
will be leached. An important corollary is that production systems that have increased soil
mineralization potentials need to have an actively growing crop present to capture the N

as it is mineralized or that N will likely leach.

22

 

REFERENCES

Cavigelli M.A., S.R Deming, L.K. Probyn, and RR Harwood (eds). 1998. Michigan
Field Crop Ecology: Managing biological processes for productivity and
environmental quality. Michigan State University Extension Bulletin E-2646,
92 pp.

0 Chichester, F.W. 1977. Effects of increased fertilizer rates on nitrogen content of runoﬂ‘
and percolate ﬁ'om monolith lysimeters. J. Environ. Qual. 6:211-217.

. Fortuna, A.M., RR. Harwood, K. Kizilkaya, and EA Paul. In Press. Optimizing nutrient
availability and potential carbon sequestration in an agroecosystem. Soil
Biology and Biochemistry.

. Harris, G.H., O.B. Hesterman, EA Paul, S.E. Peters, and RR Janke. 1994. Fate of
Legume and fertilizer Nitrogen-15 in a long-term cropping systems experiment.
Agron. J. 86:910-915.

Isse, AA, AF. MacKenzie, K. Stewart, D.C. Cloutier, and D.L. Smith. 1999. Cover

crops and nutrient retention for subsequent sweet corn production. Agron. J.
91:934-939.

6 Jamison, J .M. and RH. Fox. 1994. Nitrate leaching from nitrogen-fertilized and manured
corn measured with zero tension pan lysimeters. J. Environ. Qual. 23:337-343.

Jones, M.E., RR. Harwood, N.C. Dehne, J. Smeenk, and B. Parker. 1998. Enhancing soil
nitrogen mineralization and corn yield with overseeded cover crops. Soil and
Water Cons. 53:245-249.

*1 Klocke, N.L., J .P. Schneekloth, and DC. Watts. 1996. Potential for reducing leaching by
managing water and crop rotations. J. Soil and Water Cons. 51:84-90.

Mitsch, W.J., J.W. Day, J.W. Gilliam, P.M. Groﬂinan, D.L. Hey, G.W. Randall, and N.
Wang. 1998. Reducing nutrient loads, especially nitrate-nitrogen, to surface
water, ground water, and the Gulf of Mexico: topic 5, report for the integrated
assessment on hypoxia in the Gulf of Mexico. US. Dept. of Commerce,
National Oceanic and Atmospheric Administration, Coastal Ocean Program
Publishing Agencies, Silver Springs MD, 118 p.

- Owens, LB. 1987. Nitrate leaching losses from monolith lysimeters as inﬂuenced by
nitrapyrin. J. Environ. Qual. 16:34-38.

\ Owens, L.B., RW. Malone, M.J. Shipitalo, W.M. Edwards, and J .V. Bonita. 2000.

Lysirneter study of nitrate leaching ﬁom a com-soybean rotation. J. Environ.
Qual. 29:467-474.

23

l Owens, L.B., W.M. Edwards, and M.J. Shipitalo. 1995. Nitrate leaching through
lysimeters in a com-soybean rotation. Soil Sci. Soc. Am. J. 59:902-907.

Randall, G.W., D.R Huggins, M.P. Russelle, D.J. Fuchs, W.W. Nelson, and J .L.
Anderson. 1997. Nitrate losses through subsurface tile drainage in
conservation reserve program alfalfa, and row crop systems. J. Environ. Qual.

26: 1240-1247.
c Sanchez, J .E. 2000. Managing cropping systems to enhance the active soil nitrogen pool
and control its mineralization. Ph D. dissertation - Michigan State University.

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

Sanchez, J.E., E.A Paul, T.C. Willson, J. Smeenk, and RR Harwood. 2002. Corn root
effects on the nitrogen supplying capacity of a conditioned soil. Agron. J.

94:391-396.
SAS Institute. 1999. The SAS system for Windows. Release 8.0. SAS Inst, Cary, NC.

0 Sogbedji, J .M., H.M. van Es, C.L. Yang, L.D. Geohring, and FR Magdoff. 2000. Nitrate
leaching and nitrogen budget as aﬂ’ected by maize nitrogen rate and soil type.

J. Environ. Qual. 29:1813-1820.

0 Toth, JD, and RH. Fox. 1998. Nitrate losses from a com-alfalfa rotation: Lysirneter
measurement of nitrate leaching. J. Environ. Qual. 27: 1027-1033.

Vyn, T.J., K.J. Janovicek, M.H. Miller, and EC. Beauchamp. 1999. Soil nitrate
accumulation and corn response to preceding small-grain fertilization and

cover crops. Agron. J. 91 : 17-24.

Weed, DA]. and RW.Kenwar. 1996. Nitrate and water present in and ﬂowing from
root-zone soil. J. Environ. Qual. 25:709-719.

. Willson, T.C., E.A. Paul, and RR Harwood. 2001. Biologically active soil organic matter
fractions in sustainable cropping systems. Agric., Ecosyst. Environ. 16:63-76.

Yadav, SN. 1997. Formulation and estimation of nitrate-nitrogen leaching from corn
cultivation. J. Environ. Qual. 26:808-814.

24

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25

Table 3: Nitrate available for crop growth

 

 

 

 

ﬁPotential
Min. N Sum N Crop
Applied N (kgha) in Soil ‘ Inputs Yield
Compost Starter Sidedress ﬁgN/ha) (kgﬂha) (Mg/ha)
Integrated Compost
1" Corn 4 203 207 7.8
Soybean O 161 161 2.4
Cont. Corn 4 143 147 6.2
Integrated Fertilizer
1" Com 16 77 127 220 7.9
Soybean 0 0 124 124 2.2
Cont. Corn 16 160 130 306 6.9

 

‘ Data from Fortuna, 2000

26

 

 

5K "c966. .6 69 . End: to "onus: e
82 .93 Dem 022..

23.533 5.3 5336.“. u .2“.

>850
.05 ON

Em

 

OOESQQ

80 2w ck _ «am
cs 0.8

 

 

E0 0.0”

 

 

 

 

 

 

 

 

 

.xfrs: .,

 

E29... Sac—=33 _. .9".

27

Flg. 5 Nltrate Concentrations in Leachate over the Season

99'“ WW mun-ta

 

15
Apnrm Aug-Sept Oct-Nov nee-Jan Feb-Mar April

Fig. 6

 

April-July Aug-Sept oer-Nov nee-Jan Fob-Mar April

Hg. 7 Daily Nitrate Leaching Rates over the Season

Ks M my
0.45

Integrated Compost sas m

0.4
0.35
0.3
0.25
0.2
0.15 g
0.1

  

o j I. . I - V . ‘ .
AprlHuIy Aug-Sept Oct-Nov Dec-Jar Fab-March Apr.

Fig- 8 Daily Nltrate Leachlng Rates over the Season

:2?“ ”'3’ Integrated Ferllllznr sas Bran-m

- 1st-eorn

0.4

0.35

0.3

0.25

0.2

0.15 ~,

 

o . . ' ‘ ‘
April-July Aug-Sell Oct-Nov Dec-Jar Fob-HIM Apl'll

Flg. 9 Annual Nitrate Leaching (by Crop) over Seasons 2-7

'1?“ |nt_egrated Compost

+ 1st-com
+ 2nd-oom
_. -—-Soybem
+Wheat

4.5....

I H
17].].3I If If

 

 

 

4_

3.5

 

 

 

 

   

'98-'97 ‘97:” ‘ﬂ-‘O’ '99-“

Flg.1o Annual Nitrate Leaching (by Crop) over Seasons 2-7
Inlstglha

5

4.5

4

3.5

s

25 .........

'94-'95 '5-‘90 '98-'97 '97-“ 'S-‘SO '90-'00

31

Flg. 11 Inﬂuence of Management on Annual Leaching

Flg.

KgII-Ia Averaged over seasons 2-7

70 Evarycrop, everyyaar

I Int Comp
El Int Fert

 

1st Corn 2nd Com Soybem Wham Cont. Corn
12 Annual nitrate leaching under rotational crop
compared to continuous corn by management
Kgfl-la

Averaged over last 6 seasons
00
asslgned based

on transformed data

El

 

Org. Int Comp Int Fart Conv.

32

Flc- 13 CVs of Cumulative Years

"9: (Includes cv: for Individual Years)

    
      

'93-'04 '94-'05 '05-'00 '00-'07 '07-” '00-'00 ”W

Fls- 14 CVs of Cumulative Seasons
% based on lysimeter size
110

 

'.,._,¢ _

 

 

 

 

 

 

   

 

+ small Lyslmeter :
-°-LargeLyslmeter . . , . .

1° ' T N A.” ’1 I." > " " ' 5’ J :- -- '. "~z- ~.‘

'93-'34 '94-'35 '95-“ “'97 '97-'93 ”JD. ”3”

 

 

 

33

CHAPTER 2
The Influence of Cropping System on Selected Soil Physical Characteristies
ABSTRACT

Selected soil physical characteristics were determined on an Oshtemo and Kalamazoo
sandy loam following six and seven years of cropping systems trials. Continuous corn
systems were compared to a com-com-soybean-wheat rotation each with and without
cover crops. These cropping systems were grown under a variety of management
schemes, and all crops in the rotation were grown every year. The organic and integrated
compost systems received supplemental nutrient inputs from compost and the integrated
fertilizer and conventional systems received synthetic fertilizer. Bulk density was lowest
following ﬁrst year corn and highest following wheat. The inﬂuence of management
schemes on bulk density were not signiﬁcantly diﬂ‘erent. Water holding capacity
diﬂ‘erences, while statistically signiﬁcant, were probably not agronomically signiﬁcant (41-
43%). Aggregate stability was highest in wheat interseeded with red clover and lowest in
the soybean plots that did not receive cover crops at any point of the rotation. The double
ring inﬁltration rate data was highly variable. The management systems receiving compost
tended to have higher inﬁltration rates than those receiving synthetic fertilizer (10 cm/hr
vs. 8 cm/hr) but these differences were not signiﬁcant (P= 0.05). The resistance to
penetration tended to be higher in wheat than in the other crops but the differences were
not consistent or signiﬁcant. Although there was a general trend towards improving soil
quality through the use of compost and/or cover crops the differences due to management
were not always signiﬁcant. Differences may be masked through the highly variable soil

and the diﬂiculty of changing the physical characteristics of a sandy loam.

34

INTRODUCTION
Soil quality as deﬁned by Doran and Parkin (1994) is the capacity of a soil to function
within ecosystem boundaries to sustain biological productivity, maintain environmental
quality, and promote plant and animal health. The status of the physical characteristics of
a soil is an important aspect of the total quality of the soil. The physical characteristics of
the soil inﬂuence the ﬂora and fauna in the soil which in turn ﬁlrther inﬂuence the physical
characteristics of the soil. Management choices of cropping system, use of cover crops
and the addition of organic amendments inﬂuence the soil’s physical characteristics. Some
of the basic physical characteristics include bulk density, aggregate stability, water holding
capacity, inﬁltration capability, and the resistance to penetration. Measurements of these
physical characteristics can give an indication of a soil’s suitability to grow crops and can

identify some management problems.

Numerous studies have looked at the diﬂ‘erences in soil physical qualities seen in
‘alternative’ production systems compared to ‘conventional’ systems. Islam and Weil
(2000) saw no diﬂ'erence in the cropping system’s inﬂuence on soil bulk density in organic
vs. conventional systems which included a no-till corn-soybean-wheat rotation and
conventionally tilled continuous corn. The bulk density from a continuous grass system
was signiﬁcantly less than any of the armual cropping systems evaluated. Wei] et al.
(1993) also found no diﬂ‘erences in cropping systems except all annual systems were

greater than continuous grass on a sandy loam.

35

Studies that applied sewage sludge at agronomic rates generally see little affect on bulk
density (Kaheel et al., 1983). Where organic matter is applied at disposal rates (10 -300
t/ha) as compost (Porter et al., 1999) or as sludge the decreases in bulk density seen may
be simple mechanical dilutions (Kaheel et al., 1983, Metzger and Yaron, 1987, Lindsay,
1998). MacRae’s (1985) review of cover crop’s inﬂuence on soil properties found that
ﬁve of the seven studies reported decreases in bulk density associated with the
incorporation of green manures. Power et al. (1998) also reported a decrease in bulk
density associated with cover crops. Although tillage regimes strongly inﬂuence bulk
density, the bulk densities of a silt loam managed organically for over 70 years were not
signiﬁcantly different from those of nearby conventionally managed ﬁelds (Reganold,

1988)

Biological processes are the major inﬂuences in the process of soil aggregate stabilization
in most agricultural soils. Earthworm activity and physical enmeshment by roots and
fungal hyphae contribute to aggregate stability by physically holding the particles in close
proximity (Brady and Well, 1999). The production of organic binding agents by
microorganisms then acts to aggregate the particles together (Lynch and Bragg, 1985).
Species differences are seen in the efﬁcacy of roots assisting the formation of stable
aggregates with sod, pasture, or hay crops being more effective than annual ﬁeld crops
(Bullock, 1992). Hay crops increase aggregate stability more than short rotations of grain
crops. This is due to the species involved, greater time periods in the ﬁeld, absence of
tillage for a longer period of time (Harris et al., 1966) and simultaneously occurring

conditions for enhanwd aggregate formation and stabilization (Allison, 1968). Including

36

sod grasses or legumes as winter crops or in short term rotations with summer grains can
also increase aggregate stabilization (Smith et al., 1987). Rasse (1997) reported that the
addition of alfalfa shoots increased aggregate stability on a Kalamazoo sandy loam more
than the addition of alfalfa roots but both increased aggregate stability relative to soil with
no alfalfa addition. Islam and Weil (2000) also reported that conservation practices such
as reduced tillage, crop rotation and the use of cover crops can increase aggregate stability

relative to a conventionally managed cash grain (corn and soybean) system.

The literature presents a mixed picture of the inﬂuence of cropping systems on water
holding capacity (WHC). The addition of organic matter as cover crops (MacRae and
Mehuys, 1985), peat humus (McCoy, 1998), sewage sludge (Lindsay and Logan, 1998,
and Metzger and Yaron, 1987), or manure (Martens and Frankenberger, 1992) has been
shown to increase the water holding capacity of sandy soils. Alternatively, Weil et al.
(1993) found that diﬂ‘ering cropping systems and tillage management did not signiﬁcantly

inﬂuence WHC on a sandy loam.

Increases in inﬁltration rate have been associated with winter cover crops ( Smith et al.,
1987, and Unger and Vlgil, 1995) and interseeded corn (Smeltkop et al., 1997). Increases
in inﬁltration rates are also associated with the addition of relatively high rates of organic
matter as manure or sludge (Smith et al., 1937, Albrecht and Sosne, 1944, Kaheel et al.,

1981, Martens and Frankenberger, 1992).

37

Soil resistance to penetration does not seem to be strongly inﬂuenced by rotation (Pikul
and Aase, 1996, and Harnmel, 1989). Chen and Heenan (1996) observed a crop
diﬂ'erence with higher resistance to penetration under a barley grain than under canola,

ﬁeld peas, or Lupin but these differences were only signiﬁcant at the 5-10 cm depths.

The objective of this study is to determine the inﬂuence of various farming systems,
managed using accepted ‘best management practices’, on selected soil physical
characteristics. The characteristics should give insight to the farming system’s long-term

inﬂuence on soil quality.

MATERIAL AND METHODS
Site Description
A long-term com-com-soybean-wheat rotation study was established in “The Living Field
Laboratory‘ ’ at the WK. Kellogg Biological Station (Hickory Corners, MI). The site is a
glacial till composed of Oshtemo and Kalamazoo sandy loams (coarse-loamy, mixed,
mesic Typic Hapladaulfs). The climate is temperate with an average annual precipitation

of 890 mm.

Experimental Design and Layout

The experiment was a split-split-plot design, with management as the main factor (4
treatments), crop as the split-plot (5 treatments) and cover crop as the split-split plot (2
treatments). There were four replications. Each crop in a corn- com - soybean - wheat

rotation along with continuous corn was present lmder the four diﬂ‘erent management

38

systems. Each crop plot was further divided into a cover crop side and a no-cover crop

side. Table 1 outlines the major differences between the management treatments. The

conventional plots, due to their full coverage herbicide program, did not receive cover

crops. Data were collected over a three year period. Further information of this site is

available at the WK. Kellogg Biological Station Long-Term Ecological Research data

website hmJ/Itenkbsmsuedyz

Crop Production

Corn.

Compost was applied to the Organic (0) and Integrated Compost (IC) plots in
April prior to tillage at the following rates: 4,500 kg/ha on 1" year and
continuous corn and 9,000 kg/ha on 2"l year com. All plots were chisel plowed
and disced at least a week prior to planting. On the day of planting all plots
were ﬁeld cultivated and planted (69,000 seeds/ha) in 76 cm rows. A starter
fertilizer (10-20 kg N ha‘1 either granular or liquid) was applied in the
Integrated Fertilizer (IF) and Conventional (C) treatments and a pre-emerge
grass herbicide (Dual 11) was banded over the row in the IC and IF treatments
and broadcast in the C treatments at planting. Continuous and 2‘" year corn
received a banded soil insecticide for corn rootworm control. Mechanical
weed control in 0, IC, and IF usually consisted of two rotary hoeings, a
cultivation with the rolling shields down and a ﬁnal aggressive cultivation prior
to canopy closure. Nitrogen, initially as ammonium nitrate and in the last two
seasons as liquid 28% N, was sidedressed at rates recommended for a 9.4

Mg/ha yield goal by the pre-sidedress nitrate test in the IF and C treatments.

39

The fertilizer was incorporated in the ﬁnal cultivation. Immediately following
ﬁnal cultivation crimson clover (T nfolr'um incarnalum) was handed at 19 kg/ha
between the corn rows in 1" year and continuous corn and annual ryegrass
(Lolium multrﬂorum) was banded at 30 kg/ha in 2"" year corn. Yield data were
recorded from the center two rows of the entire length of the 15.3 m plots

following removal of the boarder plants.

Soybean All plots were chisel plowed and disced at least a week prior to planting.

Wheat.

Neither compost nor fertilizer was added to these plots in this point of the
rotation. On the day of planting all plots were ﬁeld cultivated and planted

(3 70,000 seeds/ha) in 76 cm rows. Mechanical weed control was similar to
that of corn. In the early years of the experiment, pre-emerge herbicides were
used and more recently post—emerge herbicides were used. Round-up resistant
varieties were used in the last three years with two applications of
glysphosphate at low rates. Yield data were recorded from the center two rows

of the entire length of the 15.3 m plots following removal of the boarder plants.

Compost was applied (4,500 Kg/ha) in the O and IC plots immediately
following soybean harvest. At planting, the plots were disced or ﬁeld cultivated
and then planted (5,000,000 seeds/ha). In early spring 84 kg/ha nitrogen (as
urea) was applied to the IF and C plots. At the same time ‘Michigan
Mammoth’ red clover was frost seeded (18 kg/ha) into the wheat. The wheat

was harvested in July using a plot combine and the straw was baled and

40

removed. The plots were clipped in September to stimulate the clover cover

crop and/or to control weeds.

Bulk Density Protocol

Corn and wheat samples were taken in November of 1997, 1998, and 1999 and soybean
mples were taken in early October prior to tillage in preparation for wheat planting. The
samples from the corn and soybean plots were taken in the crop row. A ﬂat shovel was
used to remove the top 1-2 cm of soil and crop residue from each of ﬁve measurement
sites in each plot. A double-cylinder, harnmer-driven core sampler was used to remove an
uncompressed core of soil (7.6 cm height and 7.6 cm diameter). The soil was dried,
weighed, and sieved to remove stones. Samples where stones comprised more than 10%

of the weight were removed from the analysis.

Infiltration Protocol

Samples were taken in October and November of 1998 and 1999. Segments of aluminum
irrigation pipe (20 and 30 cm diameter, 3.2 mm wall thickness) were driven at least 7 cm
into the soil to form a double ring inﬁltration unit. Four layers of burlap were placed in
the bottom of the center ring to decrease surface soil disturbance when the water was
added. The soil in the inﬁltration rings was pre-saturated with at least 110-15 cm of water
two hours prior to the beginning of the test period. At the initiation of the measurement
period approximately 5-8 cm of water was poured into both rings. At 20 minute intervals

the height of the water column in the center ring was measured and the water loss was

41

replaced to maintain a relatively constant head pressure. Measurements were made for at

least two hours from each of three inﬁltration units in each plot.

Aggregate Stability Protocol

A modiﬁcation of Gruver and Weil (1998) was used. Air dried soil from the bulk density
cores was dry sieved for 10 seconds to collect aggregates greater than 4 mm diameter.
Since aggregates of this soil type are sensitive to rapid wetting they were brought up to
saturation over a period of 4-6 hours in a mist chamber. The saturated aggregates on a
0.5 mm mesh sieve were submerged in 2 cm of water and shaken (100 rpm) on a rotary
shaker for 120 seconds. The ‘Unstable’ soil that slaked oﬂ‘ the aggregates and passed
through the sieve during shaking was dried. The ‘Stable’ soil remaining on the sieve was
extruded through the sieve with slight ﬁnger pressure and dried. The ‘Debris’ that would
not pass through the sieve was also dried. Samples where the sum of ‘Stable’, ‘Unstable’,
and ‘Debris’ was less than 98% of the initial sample weight were discarded. The percent
of stable aggregates was determined using the formula,

% of Stable Aggregates = 100 * wt. Stable / (wt. Stable + wt. Unstable).

Water Holding Capacity Protocol

Drainage units were made by melting many holes in the bottoms of ‘5 02’ (approx. 130
ml) disposable plastic drinking cups and covering the bottom with non-absorbent ﬁlter
paper. The drainage units were wetted and allowed to drip away excess moisture prior to
use. The wet drainage units were ﬁlled with 130-150 g of air-dried soil ﬁom the 1998 and

1999 bulk density samples. The soil was wetted from the bottom by placing the units on a

42

tray with 1 cm of water. When the soil “glistened”, the drainage units with soil were
placed in a sealed 100% humidity chamber for a week. The sealed chamber allowed
gravimetric drainage but prevented the soil from drying out. Water Holding Capacity was
determined using the formula,

%WHC= 100 '- (Soil Final Wet wt. - SoilDrywt.)/SoilDrywt.

Resistance to Penetration Protocol
Soil resistance to penetration was determined in Fall 1997, Fall 1998 and Spring 1999
using a recording penetrometer (Pike Agri-Lab Supply Inc. Strong, Maine). Following
proﬁle moisture recharge, ten resistance/depth proﬁles were made for each plot. Corn and
soybean plots were sampled within the rows and wheat stubble plots were sampled
randomly. The stones in this glacial till inﬂuenced the resistance curves so the following
criteria were established to eliminate questionable data.
1. Initial readings must begin below 60 psi. If not, the curve will be deleted ﬁ'om
the data set.
2. Slope of the curve must be less than 20 psi per cm. If not, the data following
the rapid rise in slope will be removed from the data set.
3. Slope of the curve must be positive. A sudden negative slope in this glacial till

usually means that a stone obstruction has been pushed aside.

Least Square Means were generated from the processed data using the SAS Nﬁxed model

(SAS, 1999).

43

RESULTS AND DISCUSSION
Bulk Density
Mean bulk densities ranged from 1.18- 1.54 g/cc (Figs. 1-3). Although there were
differences in crops, management, and year, none of the plots approached the 1.80 - 1.85
g/cc levels of root inhibition in a sandy loam proposed by Bowden (1981), or Grossman
and Berdanier (1982). In the 1999 data where only wheat, 1" year corn and continuous
corn were sampled, the main effects of crop and management were signiﬁcant (P=0.05).
In the 1997-1998 data set where all plots were sampled there was a signiﬁcant (P=0.05)
crop x management interaction. The presence of cover crops was usually not signiﬁcant.
In the 1999 data the cover crop sub-plots usually had slightly lower (but not signiﬁcant)
bulk densities than the no-cover sub-plots. But in the 1997-1998 data there were a
number of instances where the cover sub-plots had higher mean bulk densities than their
no-cover counterparts. In the IF continuous corn plots the cover cropped sub-plots had
lower bulk densities than the no-cover sub-plots and signiﬁcantly (0.05) lower bulk
densities than the conventionally cropped continuous corn. Possibly, the use of a cover
crop in continuous corn could ameliorate some of the bulk density problems associated
with continuous corn. The lack of a strong cover crop inﬂuence on bulk density as
reported by MacRae and Mehuys (1985) and Power et al. (1998) may be due to the

moderate crimson clover residues returned in two of the four years of the rotation.

Over the three years sampled, there was a consistent pattern in bulk densities associated
with management. The organic plots had the lowest bulk densities and the conventional

plots had the highest bulk densities. This pattern also matches the pattern of increasing

soil carbon reported by Sanchez et al. (2003) in these plots (Table 2). These ﬁndings
agree with those of Logsdon et al. (1993), who found that the bulk density of an
organically managed ﬁeld (with ridge tilling) was less than that of a nearby conventionally
managed ﬁeld. Initially it was surprising that the organic plots, in spite of the highest
amount of traﬂic from ﬁeld operations, had the lowest bulk densities and the conventional
plots with the least traﬂic had the highest bulk densities. Our plot dimensions and
equipment size necessitated a form of controlled traﬁic where our wheel tracks were
always in the same location and the bulk density samples were not taken from the wheel
tracks. Logsdon et al. (1999) reported low bulk densities with both chisel plowing and
no-till systems when looking at a controlled traﬂic situation in a corn - soybean rotation
on silt loams. It is unlikely that these differences in bulk density are artifacts of sampling
or cultivation since the last cultivation in both corn and soybeans is aggressive. The
amount of settling of the top 10 cm from June to October is a function of rainfall, gravity,
and soil characteristics. Since rainfall and gravity are relatively uniform on the entire
experiment the diﬂ‘erences in bulk density between the various corn treatments and the

soybean treatment is probably due to differences in the soil characteristics.

We expected the bulk density in the IC plots to be lower than the bulk density in the IF
plots due to the addition of the lower bulk density compost. However, at the low annual
rate of 4,400 kg/ha in six years only 26,400 kg/ha was applied. Even if none of the
compost mineralized this amount is only 1.3% of the mass of a 16 cm furrow-slice (ave
bd= 1.30 g/cc). Kaheel et al. (1981) reported that when sewage sludge was applied at

agronomic rates generally little change on bulk density was seen.

45

The wheat plots had the highest bulk densities and the following 1" year corn crop had
signiﬁcantly lower bulk densities (Figs. 1 and 2). When wheat was sampled in the fall it
had been 13 months since the previous tillage while the corn and soybean plots had been
aggressively tilled only ﬁve months prior. Gravity and rainfall over the 13 months may
play a role in increasing the bulk density. Weinhold and Halverson (1998) found that bulk
densities in a wheat-fallow system, with tillage occurring every other year, were higher
than in annually cropped wheat under both conventional and no-till systems. The bulk
densities of the continuous corn plots were similar to their 1" and 2'“I year rotational
counterparts also possibly due to the aggressive ﬁnal cultivation which throws about 5 cm
of soil into the row. The differences between the continuous corn 1997-1998 data and

1999 data indicate the importance of the temporal eﬂ'ect on bulk density.

Water Holding Capacity

The procedure for determining water holding capacity was very repeatable. When the test
was performed on ﬁve aliquots of the same soil the results were within 1-2% of each
other. In both years the treatments that used compost and/or cover crops tended to have
higher water holding capacities than the treatments that used neither (Figs. 4 and 5). It is
unknown why IC with cover had relatively low WHC in 1999 when it received both

compost and cover crops and exhibited a higher WHC in the previous season.

In 1998, the WHC was highest following 1" year corn and decreased through the rotation
points reaching its lowest level with wheat (Fig. 6). It is likely that the increase in WHC is

not so much associated with corn as it is with the breakdown of the previous wheat roots

46

that were present in the 1" year corn soil. Likewise, WHC under wheat may be at its
lowest since the previous wheat roots had several seasons to break down and the current
wheat roots had not yet begun to break down. In 1999, there were no diﬂ‘erences
associated with the crops (Fig. 7) possibly indicating a stronger environmental inﬂuence
than crop inﬂuence on WHC. Although various treatment differences were statistically
signiﬁcant (P=0.05), the difference between a soil WHC of 39% and a soil WHC of 43%
may be negligible to plant water uptake. Field observations occasionally noted diﬂ‘erences
in moisture stress but they were usually more of a spatial nature than associated with

speciﬁc treatments.

Aggregate Stability

The 1998 data indicated that the management systems receiving compost and/or cover
crops tended to have a higher percentage of stable aggregates (Fig. 8). A notable
exception was IC with cover which, while having both compost and cover, was not
signiﬁcantly diﬂ‘erent from the conventional treatment which received neither. In 1999
the aggregate stability of each treatment (Fig. 9) was lower than it was in 1998 and
differences due to management were not signiﬁcant. With both grass and legume cover
crops and a relatively stable compost it is surprising that aggregate stability was not
uniformly higher in organic and compost managements than in the conventional and
fertilizer-no cover treatments. This lack of difference may be due to our uniform method
of primary tillage. It has been well documented that moldboard plowing reduces

aggregate stability compared to less disruptive forms of primary tillage. The use of the

chisel plow in our conventional treatment may be part of the reason that signiﬁcant

47

differences are not seen consistently. Martin (1942) found that properly composted
material did not increase the percentage of stable aggregates formed and concluded that
the composting process utilized the easily decomposable material, leaving the less
decomposable material that is not as eﬂ‘ective in aggregate stabilization. This observation
was supported by Diaz et al. (1994) who found that the addition of un-composted urban
refuse rapidly increased aggregate stability while the addition of a stable peat was not
eﬂ‘ective in increasing aggregate stability. Numerous studies reported increases in
aggregate stability associated with the application of sewage sludge (Metzger and Yaron,
1987, Lindsay and Logan, 1998) and animal waste (Martens and Frankenberger, 1992).
These materials have readily available food sources for bacterial and fungal production of
the polysaccharides and other microbial by-products associated with aggregate

stabilization.

The readily available by-products formed by the decomposition of cover crops is thought
to enhance the production of stable aggregates (Allison, 1968) but Benoit et al. (1962)
noted that several years of incorporating of ryegrass were necessary to signiﬁcantly
increase aggregate stability on a sandy loam. Conversely, Smeltkop et al. (1997) saw no
change in water stable aggregates associated with the use of sava snail medic cover crop in
corn. Although the treatments have experienced 6-7 seasons of cover cropping the
amount of biomass incorporated each year are not equal. The red clover cover crop
produced more biomass than annual ryegrass and, in most years, both produced more

biomass than crimson clover. It is possible that the cumulative biomass produced over the

48

rotation by the cover crops in this study is less than the biomass produced by the cover

crops in the published studies.

There were signiﬁcant differences in percentage of stable aggregates associated with crop
in both years (Figs. 10 and 11). Wheat had a higher percentage of stable aggregates than
all other crops. Our ﬁndings agree with those of Jordahl and Karlen (1993) and Bruce et
al. (1990) who found that the preceding crops had signiﬁcant effects on aggregate stability
and that preceding sod crops had a positive inﬂuence on aggregate stability. Martens
(2000) showed that the previous crop species has much to do with the aggregate stability
seen under the current crop. Our data does not support Martens’ ﬁnding that soybean
decreases aggregate stability more than corn. The aggregate stability measured in the
1998 soybean plots was not signiﬁcantly less than that of corn. These plots in 1999, when
measured under the standing wheat crop, had an aggregate stability ratio that was higher

than that of 1‘ year corn (previously wheat in 1998).

Our data did not support Raimbault and Vyn’s (1991) observation that winter wheat with
red clover had a greater inﬂuence on the aggregate stability seen in the next crop than
winter wheat alone. The percent of stable aggregation seen in 1" year corn following
frost-seeded red clover in wheat was not signiﬁcantly diﬁ‘erent from that seen in the 1“
year corn following wheat without clover (data not shown). Raimbault and Vyn also
noted that the percentage of stable aggregates was more in 1“ year corn following wheat
with red clover than was seen in continuous corn. In our trial there were no signiﬁcant

diﬁ‘erences seen between these treatments in either year.

49

Acrossalltreatmentsthepereentageofwaterstableaggregateswas greaterinl998than
inl999indicatingastrongtemporaleﬁ'ect. IslamandWeil(2000)proposedthat
Westabiﬁtymeaananansmaybeuseﬁﬂoomponansmsoﬂqmﬁtymdiceshnw
dataindieatesthedangeroftakingasetofmeasurementsonasingledate. Thevalueof
61%stableaggregatesseenmeonvenﬁonalmmaganuninl998,wlﬁletheloweﬂ
neatmeminl998,wasgreatertlmnalmostaﬂoftheUeamransvaluesinl999.
MmMsmkmeWaMVw(l991)mghuumemgm
hdicaedMWhﬂetheabwhnestabﬂﬁyofaggregmesﬂuMedwiddymghtheyear
merdaﬁvemnkingofmeneuman’saggregmestabiﬁﬁeswasquﬁesinnluthrmghGn

theyear.

Institution
ThemﬁlnaﬁonmeawremansshowedlngespaﬁﬂvaﬁaﬁmsagredngwithSnﬁthaal
(1937). Inﬁluationmeasuranansinthesameplot,sepmatedbyonly20an,someﬁmes
indieatedinﬁltrationratesthatdiﬁ‘eredbylW/o. 'I‘heactualmeaninﬁltrationratesranged
ﬁ'om7-15cm/lu'dependingontreatment. Whenthedatawasnormalizedusinganamral
log transformation there were signiﬁcant diﬁ‘erences in inﬁltration rates associated with
associatedwithcovercmpswereneithersigniﬁeantnorconsistentCFig 12). Thislackof
agreernentwith some ofthe publishedliteratme(Smithetal., 1987, UngerandVigil,
l995,andSmeltkopetal.,1997)maybeduetoourinﬁltrationsamplingdates. Latefall
mvayearlyspﬁngmaynmbetheopﬁmmﬁmetoseecmsistentneaumdiﬂ‘erences

duetocovercrops. Ourresultsindicatean'endtowardsgreaterinﬁln'ationratesinthe

50

management systems that use compost and/or cover crops than in the management
systems that do not use either. This supports the literature reports of high rates of organic
amendments being associated with increases in inﬁltration (Smith et al., 193 7, Albrecht
and Sosne, 1944, Kaheel et al, 1988, Martens and Frankenberger, 1992). Wheat,
soybean, and 2" year corn had higher inﬁltration rates than 1" year corn or continuous
com (Fig 13). It is unknown why 2“ year corn had inﬁltration rates that were so much
higher than the other treatments but these higher rates were seen across all management

systems.

Penetrometer

Wheat treatments usually required more force to penetrate than the corn or soybean
treatments (Fig. 14). These differences were signiﬁcant in the zone just below chisel
plowing (IS-l8 cm) for two of the three seasons. The diﬂ‘erences in resistance to
penetration associated with the various management systems were not signiﬁcant. The
lack of management inﬂuences agrees with Pikul and Aase (1995) and Harnmel (1989)
who saw tillage differences but saw no inﬂuence of crop rotation or previous cropping
history on resistance to penetration. Chen and Heenan (1996) observed higher resistance
to penetration under a barley grain than under canola, ﬁeld peas, or Lupin but these

differences were only signiﬁcant at the 5-10 cm depths.

As illustrated by the force-depth curves for continuous corn (Fig. 15), measurements of
resistance to penetration showed a strong temporal response. The force-depth curve

resulting from the Spring 1999 sampling was more similar to the Fall 1997 results than it

51

was to the Fall 1998 results taken only ﬁve months prior. These relationships were also
noted in the rotation crops (data not shown). This relationship is diﬂicult to explain since
the Spring 1999 and Fall 1998 determinations came from the same plots while the Fall
1997 determinations came from the same treatment but, due to rotations, diﬁ‘erent plots.
All determinations were made at soil moisture levels near ﬁeld capacity which should

allow season to season and within-season comparisons (Bradford, 1986).

CONCLUSIONS
The addition of an annual average of 4,500 kg/ha of compost was usually associated with
better soil physical characteristics. The inﬂuence of cover crops on the soil physical
characteristics examined was inconsistent in the treatments that received compost but in
the treatments that received fertilizer the presence of cover crops was associated with
improved soil physical characteristics. Unfortunately, with the high variability associated

with these glacial till soils, these differences were usually not signiﬁcant (P=0.05 level).

Winter wheat may play an important role in the rotation by maintaining good soil physical
characteristics. In the fall following wheat harvest, the soil’s bulk density, resistance to
penetration, and aggregate stability are all at the highest levels in the rotation and the
water holding capacity was at the lowest level in the rotation. In the following fall (aﬁer
1" year corn) when the wheat roots have had a chance to break down, bulk density was at
the lowest point in the rotation, water holding capacity was at the highest level in the
rotation, and aggregate stability was beginning a three-year decline through the rotation.

These soil enhancing characteristics may increase the long-term ﬁnancial value of having

52

 

wl

ch;

SO:

WE

dat

wheat in the rotation above the monetary value received for the grain and straw. Wheat
may be the point in the corn-corn-soybean-wheat rotation to improve soil physical

characteristics thus encouraging greater yields of the more ﬁnancially rewarding crops.

Soil physical characteristics ﬂuctuate throughout the rotation and, as shown by the
continuous corn plots, change from year to year. This highlights the potential problems of
evaluating a site against a series of static performance criteria with only a single sampling

date.

53

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crops and manuring. J. Am. Soc. Agron. 36:646-648.

Allison, RE. 1968. Soil aggregation - Some facts and fallacies as seen by a microbiologist.
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Benoit, RE, N.A. Willits, and W.J. Hanna. 1962. Eﬂ‘ect of rye winter cover crop on soil
structure. Agron. J. 54:419-420.

Bowden, RD. 1981. Alleviating mechanical impedance. In Modifying the root
environment to reduce crop stress, eds. G.F. Arkin and HM. Taylor, 21-57. St.
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Bradford, J .M. 1986. Penetrability. In Methods of soil analysis, Part 1. Physical and
Mineralogical Methods - Agronomy Monograph no. 9 (2”l Edition). Agronomy
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Brady, NC. and RR Weil. 1999. The Nature and properties of soils. 12" ed. Prentice-Hall
Inc. Upper Saddle River, NJ.

Bruce, RR, G.W. Langdale, and AL. Dillard. 1990. Tillage and crop rotation effects on
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Bullock, D.G. 1992. Crop Rotation. Critical Reviews in Plant Sciences, 11(4):309-326.

Chen, KY. and DP. Heenan. 1996. The inﬂuence of crop rotation on soil structure and
soil physical properties under conventional tillage. Soil & Tillage Research 37 :1 13-
125.

Diaz, E., A. Roldan, A. Lax, and J. Albaladejo. 1994. Formation of stable aggregates in
degraded soil by amendment with urban reﬁrse and peat. Geoderma 63:277-288.

Doran, J.W. and TB. Parkin. 1994. Deﬁning and assessing soil quality. In Deﬁning Soil
Quality for a Sustainable Environment. pp. 3-22. Soil Science Society of America
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Gruver, J.B., and RR Weil. 1998. Simpliﬁed method for determination of aggregate

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Madison, WI.

54

Harnmel, J. E. 1989. Long-term tillage anc crop rotation eﬂ‘ects on bulk density and soil
impedance rn northern Idaho. Soil Sci. Soc. Am. J. 53: 1515- 1519.

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inﬂuenced by conservation management. J. Soil Water Cons. 55:69-78.

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aggregate stability. Am. J. Alt. Agric. 8:27-33.

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Logsdon, S.D., J .K. Radke, and D.L. Karlan. 1993. Comparison of alternative farming
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55

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258.

56

Table 1: Characteristics of management schemes

Rotary Hoe Cultivation Herbicide Nutrient

 

Management Operations Operations Program Source

Organic (0) 3 3 None Compost
Integrated Compost (IC) 2 2 30 cm band Compost
Integrated Fertilizer (IF) 2 2 30 cm band Fertilizer
Conventional (C) 0 l Full spray Fertilizer

 

Table 2: 1999 Total carbon levels in the 0-25 cm proﬁle by management scheme1

 

Management mg C kg'l
Organic 1 1,310
Integrated Compost 10,210
Integrated Fertilizer 8,330
Conventional 6,740

 

V

1 Data ﬁom Sanchez et al. (2003'?)

57

Hg. 1 1997 and 1998 soil bulk denslty by crop and management

 

Com 1st Com 2nd Com Soybean Wheat

Hg. 2 1999 soll bulkdensﬂybycrop

 

 

  

 

 

 

 

 

 

 

 

glee
1.45 A
Contlnuoua
c Four Year Rotation
1.40
1.35
1.30
1.25 B
120 B
1.15
Corn 1st Corn Wheat

58

Fig. 3 199? soil bulk density by management

glee
1.45

1.40

1 .35

1.25

1.20

    

 

 

 

 

 

 

 

 

 

 

1.15 '
Cover No Cover Cover No Cover Cover No Cover No Cover
Organic Int. Compost Int. Fertilizer Conventional
Fig. 4 1998 soil water holding capacity by management
‘75 Moistue
44
A
‘3 '_ AB
AB
42 _— AB—
AB
BC
41
40 c —
as :3
l ' 7 . ‘ 1
Cover No Cover Cover No Cover Cover No Cover No Cover
Organic int. Compost int. Fertilizer Conventional

59

Fig.5 1999 soil water holding capacity by management

 

 

 

 

 

 

 

 

 

 

Cover
Organic int. Compost Int. Fertilizer Conventional

 

Fig.6 1998 soil water holding capacity bycrop

 

% m
44
mnwu' Four Year Rotation
‘3 Com

A

 

       

AB

42

 

 

AB

 

 

 

 

 

1st Corn 2nd Com Soybean Wheat

60

Fig.7 1”? soil waterholding capacity bycrop

15mm

‘3 Continuouﬂ 1

Corn Four Year Rotation

 

 

No Significant

differences

41—————————-——‘

 

 

 

 

 

 

 

 

 

 

 

 

38

 

Corn tatCom

Fig. 8 1998 soil aggregate stability by management

 

 

 

 

 

 

 

 

 

 

 

93$th
,2, ° Ratio Stable Mﬂnotalggm

A

AB

70
‘° ABC” ABC
66

Cover No Cover Cover No Cover Cover NoCover NoCover

Organic Int. Compost Int. Fertilizer Conventional

61

Fig. 9 i999 soil aggregate stability by management

% Stable
e4 Ratio Stable Aggregates : Total Agregates

 

 

 

 

 

 

 

 

Cover NoCover Cover NoCever Cover NoCover NoCaver
Organic Int. Compost int. Fertilizer Conventional

Fig. 10 ms soil aggregate stability by crop

 

 

1’25“” Ratio Stable ates : Total
Continuous
Com Four Year Rotation
70
so

 

 

 

 

 

   

1st Corn 2nd Com Soybeut Wired

62

Fig. it 199? soil aggregate stability by crop

%$tablo

 

 

 

 

 

 

 

 

   

 

 

u w
“align“ Four Year Reason

62

60

58

58

5‘ B

52

1st yr Com

 

Fig.12 i999 waterlnilltratlon rateby management

 

 

 

 

 

 

 

 

 

cmlhr
1s
14 A
basedon
In transfonneddata
12
AB
AB
10 AB
AB
s . tin-HI

 

 

Cover NoCover Cover NoCover Cover NoCover NoCover
Organic int. Compost Int. Fertilizer Conventional

63

Fig. 13 1999 water Infiltration rate by crop

cmlhr
1e

 

A Signiﬁcance based on
In transformed data

 

 

 
     

Continuous Four Year
Corn Rotation

 

 

10

 

 

 

 

 

Corn 1st Corn 2nd Com Soybeans Wheat

Fig. 14 Resistance to penetration by soil associated with each crop
Psi
100 I

Average
of 3 dates

 

 

 

 

 

 

 

 

 

 

Fig. 15 Resistancetopenetratlonbysollateach samplingdate

 

 

 

 

 

 

 

 

 

 

P8 /
100
Continuous o'
Corn 0'
I v'/
0"
g 00
8 /o’//
40 .’
o
I
I
I
'v
2| , —sepis7
0 —Dee”
I-OAW
it ‘ l ‘ ' ' ‘ Jun——
0 5 10 15 20 25 50 55 40 45

 

 

65

CHAPTER 3
Yields and Economic Returns from Eight Years of
Corn-Corn-Soybean—Wheat Rotations and Continuous Corn
Under Various Management Systems

ABSTRACT

Crop yields and net returns to land and management expertise resulting from continuous
corn systems were compared to those resulting from a corn-corn-so -wheat rotation

each with and without cover crops. These cropping systems were grown under a variety

 

of management schemes, and all crops in the rotation are grown every year. The organic
(O) and integrated compost (IC) systems received supplemental nutrient inputs from
compost and the integrated fertilizer (IF) and conventional (C) systems received
commacial fertilizer. Yields of 1" year corn following wheat+red clover were higher than
continuous corn and 2“ year corn. These diﬂ‘erences were signiﬁcant in the treatments
that received compost but not in the treatments receiving fertilizer. First year corn
following wheat with no cover crop, while better than 2" year and continuous corn in
each management treatment, did not equal the yields seen when 1" year corn followed
wheat+red clover. Wheat yields were lower in the treatments that received compost than
in the treatments with fertilizer. No diﬂ‘erence was seen in soybean yields. Net returns to
land and management expertise were highest in the 0 treatments ($3 59-398 ha“) due to
the premium prices associated with organic crops. Among the conventionally priced
crops, the IF corn-com—soybean-wheat rotation without cover crops had the highest net
returns ($155 ha") followed by the IF rotation with cover crops ($128 ha") and the C

rotation without cover crops ($116 ha"). The IC continuous corn had the lowest net

66

returns both with cover crops ($15 ha") and without cover crops ($10 ha“). Treatment
ranking was quite robust and changed only slightly with simulated increases in crop prices

and selected input costs.

Introduction

Cropping systems depend on the mix and sequence of crops or rotations that farmers
select (Francis and Clegg, 1990). Successful cropping systems utilize ‘biological

structuring’ (Harwood, 1985) where efﬁcient transfer of energy and growth factors along 1'

 

with altered population structure of pests, pathogens and their control agents within the
ecology of the production system reduces the need for additional inputs such as fertilizer

and pesticides.

It has been frequently reported that com in rotation yields more than does continuous corn
under various tillage systems (Peterson and Varvel, 1989, Lund et al., 1993, Raimbault
and Vyn, 1991, Singer and Cox, 1998a). Edwards et al., (1988) reported similar ﬁndings
in soybeans. The factors responsible for the yield increases seen with crop rotation are not
completely understood. Sometimes a nitrogen (N) contribution or a breaking of a pest
cycle is mainly responsible, but often no amount of pesticide or fertilizer can completely
compensate for crop rotation (Bullock, 1992). The increased yields of 1" year corn may
be associated with a general improvement of plant nutrition (Copeland and Crookston,

1992) or increased water use efﬁciency (Copeland et al., 1993).

67

There are management beneﬁts in addition to the biological beneﬁts of crop rotation.
While a more diverse complement of machinery is necessary (Colvin et al.,1990) for a
corn-soybean-wheat rotation than would be necessary for continuous com, peak labor
demands, crop yield rislg and marketing risk can be reduced through the crop diversity.
The scale of equipment can be smaller on a com-soybean-wheat rotation operation than is
necessary on an comparably sized continuous corn operation to complete ﬁeld operations V"
in a timely fashion. Crop yield risk and marketing risk are reduced by having a variety of

crops that are inﬂuenced differently by growing conditions and are marketed

 

independently. It is more likely that at least one of the several crops in the rotation will be j
L
proﬁtable than that the only crop grown will have both a productive season and a

favorable selling price.

Cover crops provide many services to agronomic systems including weed suppression
(Teasdale 1996), erosion control (Stocking, 1994), and increasing biodiversity. Cover
crops have been reported to increase aggregate stability and water holding capacity in
sandy soils (McRae and Mehuys, 1985, Smeenk et al., 2003?), maintain or increase the
organic matter levels in the soil (Smith et al., 1987), increase the rate of water inﬁltration
into the soil (Unger and Vigil, 1998) and reduce the amount of fall nitrate leaching (Isse et

al., 1999, Vyn et al., 1999).

The importance of legumes in crop rotations has long been recognized (Oakly, 1925).
Varvel and Peterson (1990) and Stute and Posner (1995) demonstrated that crop rotations

with legumes could reduce the N fertilizer needs compared to continuous corn. Corn

68

following a leguminous cover crop can exhibit even higher yields than corn that has
received proper amounts of N fertilizer (Jones et al., 1998). There are also potential
drawbacks to the inclusion of cover crops in the cropping system. These include possrble
loss of soil moisture prior to planting if not properly controlled, the additional costs of

cover establishment, and the additional expertise necessary to manage an additional crop.

Proponents of organic farming systems advocate that the ﬁelds are “healthier” while yields
can be similar to those of conventional farms (Stockstad, 2002). Mader et al. (2001)

found higher biological activity associated with soils managed organically than in . ti

 

conventionally managed soils while organic crop yields were only 20% lower than
conventional yields, and Clark et al. (1998) reported increases in organic matter associated
with organic productions compared to conventional systems. Delate et al. (2002) listed
several studies across various cropping systems that showed no statistical diﬁ‘erences

between organic yields and conventional yields.

Although farmers are very interested in high yields, they generate their income through net
proﬁts. The highest net proﬁts are not always associated with the highest yields.
Christenson et al. (1995) found that sugar beets yields were highest in four year rotations
but net returns were highest when beets were in a two year rotation. Chase and Duﬂ'y
(1991) reported higher net proﬁts with a com-soybean rotation ($366 ha“) than in
continuous corn ($324 ha") under chisel tillage. Liu and Duffy (1996) found that farmer
results across Iowa generally indicted that rotated corn had higher net returns per hectare

than continuous corn across a variety of tillage systems. In New York, Katsvairo and Cox

69

 

(2000) saw that under chisel plowed systems not returns and yields under high chemical
input continuous corn (ha“) were less than those seen of corn in a soybean-wheat/red
clover-com rotation ($156 ha") but the net returns to the soybean and wheat/red clover
portions of the rotation were only $7 ha‘1 and -$85 ha‘l respectively. Not all of the
beneﬁts of rotation are reﬂected in net returns. Reductions in pesticide use, nitrate
leaching and improvement of soil quality beneﬁt society but are not indicated in farm net
returns (Duﬂ‘y, 1991). Roberts and Swinton (1996) reported a lack environmental
evaluations in the 58 economic analysis they reviewed of crop production systems. They
suggested incorporating biophysical simulations with the economic optimization methods

to model both ﬁnancial and environmental system stability.

This study evaluates the yields and net returns to land and management expertise of a

com-corn-soybean-wheat rotation and a continuous corn cropping system produced under

a variety of management systems that range from organic to conventional.

MATERIALS AND METHODS

Site Description and Experimental Design

A long-term corn-corn-soybean—wheat rotation study was established in “The Living Field

Laboratory” at the WK. Kellogg Biological Station (Hickory Corners, MI). The soil is a
sandy loam and the county’s corn yield average is 8.1Mg/ha (130 bu/A). The experiment
was analyzed as a split-plot design with management as the main factor (7 treatments:

Organic (0), Integrated Compost (IC) and, Integrated Fertilizer (IF), each with and

without cover crops and Conventional (C) with no cover crops). and crop as the split-plot

7O

 

“fr: .-

 

(5 treatments: 1‘ year corn, 2" year corn, soybeans, wheat, and continuous corn). There

were four replications. Each crop in a com-corn-soybean-wheat rotation along with

continuous corn was present every year. The conventional management system, due to a

ﬁlll coverage herbicide program, did not have a cover crop component. All plots were

managed using the bea management practices appropriate to each treatment. Although

the three year com-so -wheat rotation is more typical in the region, a second year of

corn was added to the rotation with the objectives of increasing carbon inputs, nitrogen

demands, and proﬁtability of the entire rotation.

Crop Production

Corn

Compost was applied to the O and IC plots in April prior to tillage at the
following rates: 4,500 kg ha'1 on 1‘ year and continuous corn and 9,000 kg ha‘1
on 2""l year com. All plots were chisel plowed and disced at least a week prior
to planting. On the day of planting all plots were ﬁeld cultivated and planted
(69,000 seeds ha'l ) in 76 cm rows. A starter fertilizer (10-20 kg N ha'1 either
granular or liquid) was applied in the IF and C treatments and usually a pre-
emerge grass herbicide (Dual 11) was banded over the row in the IC and IF
treatments and broadcast in the C treatments at planting. Continuous and 2""
year corn received a banded soil insecticide for corn rootworm control when
indicated by prior sampling. Mechanical weed control in 0, IC, and IF usually
consisted of two rotary hoeings, a cultivation with the rolling shields down and
a ﬁnal aggressive cultivation prior to canopy closure. Nitrogen, initially as

ammonium nitrate and in the last two seasons as liquid 28% N, was usually

71

 

1

Wheat.

sidedressed at rates recommended for a 9.4 Mg ha'1 (150 bu/A ) yield goal by
the pre-sidedress nitrate test (Magdoﬁ; 1991) in the IF and C treatments. The
fertilizer was incorporated in the ﬁnal cultivation. Immediately following ﬁnal
cultivation hairy vetch (Vicia villosa), red clover (T rifolium pratense), crimson
clover (T rifolium incamatum) and/or annual ryegrass (Lolium multrﬂorum)
was applied. Yield data were recorded from the center 2 rows of the entire

length of the 15.3 in plots following removal of the boarder plants.

All plots were chisel plowed and disced at least a week prior to planting.
Neither compost nor fertilizer was added to these plots in this point of the
rotation. On the day of planting all plots were ﬁeld cultivated and planted
(370,000 seeds/ha) in 76 cm rows. Insect damage in 1999 necessitated
replanting all treatments. Mechanical weed control was similar to that of corn.
In the early years of the experiment, pro-emerge herbicides were used and,
more recently, post-emerge herbicides were used. Round-up resistant varieties
were used in the last three years with two applications of glysphosphate at low
rates. Yield data were recorded ﬁom the center 2 rows of the entire length of

the 15.3 m plots following removal of the boarder plants.

Compost was applied (4,500 Kg/ha) in the O and IC plots immediately
following soybean harvest. At planting, the plots were chisel plowed, disced or
ﬁeld cultivated, and then planted (5,000,000 seeds/ha). In early spring 84

kg/ba nitrogen (as urea) was applied to the IF and C plots. At the same time

72

‘Michigan Mammoth’ red clover was frost seeded (18 kg/ha) into the wheat
plots that received cover crops. The wheat was harvested in July using a plot
combine and the straw was baled and removed. The plots were clipped in

September to stimulate the clover cover crop and/or to control weeds.

Production costs 3
Published Michigan custom work rates (Dartt and Schwab, 2001) were used whenever
possible to avoid advantages that individual farmers may gain by aggressive purchasing

tactics and to factor in the value of labor and depreciation of capital equipment. For

 

operations with no published custom rates, the authors estimated rates based on the cost
of equipment and the similarity to tasks with published rates. Fertilizer costs were based
on a local supplier’s (The Andersons) 2002 prices and those published by USDA (2001).
Pesticide prices came from a variety of sources including various land grant university
websites, USDA (2001), and local retail prices. Where pesticide prices were unavailable,
the product was converted to another formulation on an active ingredient basis and the

equivalent price was substituted.

Gross Revenue

The national average annual corn, wheat and soybean prices from 1991 to 2000 reported
by the USDA National Agriculture Statistics Service were converted to 2001 dollar
equivalents by multiplying the reported annual prices by the respective Producer Price
Indexes for Major Commodity Groups for that year (2002), and then dividing the results

by the 2001 Producer Price Index. Gross revenue was determined by multiplying the grain

73

yield of each treatment by the average of the adjusted commodity prices. The average
prices used for the organic commodities determined by consulting a Michigan broker of
organic corn, wheat, and soybeans. Although the actual amount of straw removed ﬁ'om
the wheat plots was not measured, an estimate of 1.4 Mg ha'1 (2/3 ton/A) was used. The

$66 Mg"($60/ton) value of the straw is based on the local market.

Price and Cost Sensitivity

Prices received by the farmer and the costs incurred in producing the crops are constantly

[Li a~ a.

changing thus making diﬂ‘erences in net returns between treatments a relative

 

measurement for the conditions modeled. Within the arena of changing prices and
changing costs there are differing impacts of a increase in cost of a speciﬁc input on the
relative proﬁtabilities of the various management systems. For example, an increase in the
cost of pesticides has less of an impact on the net returns of the IC and IF systems which
band the herbicides and consequently use only 1/3 of the amounts used by the C
managements. Likewise an increase in the price of corn would have a much greater
impact on the proﬁtability of the continuous corn management systems than on the
rotation systems. When comparing the proﬁtability of different production systems it is
important to determine the sensitivity of net returns to various input costs and various
selling prices. A robust ranking of the management systems would not be expected to
have a major re-ranking of cropping system net returns with a slight modiﬁcation of a

single input cost, or a slight increase a single crop selling price.

74

An increase of one standard deviation of the adjusted annual commodity prices (1990 -
2000) was used in the model to determine the inﬂuence of corn, soybean or, wheat price
ﬂuctuations on the gross incomes and net retums of the various treatments. The organic
treatments were adjusted by increasing the average organic price the same proportion that

the corresponding commodity price had been increased using the following formula

 

Modiﬁed Average Average Std Dev of commodity price
Orgamc = Orgamc + Organic ‘ . .
Price Pnce Price Ave. commodity pnce

Each simulation was run with only one crop price modiﬁed at a time with the other prices

reset to the average prices determined previously.

Input cost sensitivities were simulated as drastic cost increases in the input cost being
modiﬁed. The modiﬁed pesticide simulation was a doubling of all of the base pesticide
prices and the modiﬁed nitrogen simulation was a doubling of the prices of urea,
ammonium nitrate, and liquid 28% N. The modiﬁed tillage simulation was a doubling in
the costs of both rotary hoeing and row cultivating. The modiﬁed compost simulations
were run at costs of $0 and $50 Mg" ($45 per ton) rather than the $16.5 Mg" ($15 per
ton) used in the standard conditions of the model. The $0 purchase price of compost
represents a situation where a large dairy operation with an inadequate land base would
haul the compost to the ‘buyers’ farm just to dispose of the material. The $50 Mg"
simulation price would be comparable to a situation where a dairy has a strong established

market for the compost such as the local landscape industry.

75

RESULTS AND DISCUSSION

Yields

The range of average annual yields within treatments was often greater than the range
between treatments in any one year (data not shown). These diﬁ‘erences were usually
associated with summer rainfall patterns. The corn yields in the ‘93-‘95 growing seasons
were much higher than the yields of the ‘96-‘99 seasons which were associated with '
sparse summer rains at critical corn growth stages. The July- August dry conditions seen
in the ‘96 season also lowered the soybean yields in all treatments. Wheat had completed

grain ﬁlling prior to the ‘96 dry conditions and yield was not aﬂ’ected.

 

In the plots that received compost (O and 1C) the average yields of 1" year corn were
signiﬁcantly greater than those of 2ml year or continuous corn (Table 1). Vifrthin the
treatments receiving compost, the yields of 1" year corn following wheat+red clover were
signiﬁcantly greater than the yields following wheat without a cover crop. These results
agree with those observed by Singer and Cox (1998a) and Peterson and Varvel (1989).
There were few differences in yield associated with cover crop in the 2"“ year or
continuous corn plots. The N contribution from the preceding red clover crop was
necessary to produce high yielding com when compost was the only nutrient input.
Although treatments of both 2‘“l year and continuous corn were planted following crimson
clover cover crops, soil nitrate levels were well below those following wheat+red clover

(Sanchez Thesis, 2000).

76

In the treatments receiving fertilizer (IF and C), 1" year corn also yielded more than 2"d
year and continuous corn but there was no difference associated with cover crop. The
yields of the fertilized 2"" year and continuous corn treatments were higher than the yields
of 2" and continuous corn treatments that received compost. All IF and C corn plots
were side-dressed by treatment at rates determined by the pre-sidedress nitrate test which
compensated for diﬁedng initial levels of soil N associated with previous crops and/or

cover crops (V ltosh, 1995).

The lower yields of soybeans from the 0 treatment were probably due to within-row weed
competition. The cultivator was adequate in controlling the weeds that emerged alter
rotary hoeing between the rows, but in many seasons the soil was not dry enough to
properly “ﬂow” into the soybean row and cover the weed seedlings without burying the
soybean seedlings. Post-emerge herbicides successﬁllly controlled within-row weeds in
the IC, IF, and C treatments. Our results diﬁ‘ered from Cox et al. (1999) who saw fewer

weeds in soybean than in corn following mechanical cultivation in chisel plowed systems.

The yields of wheat from treatments receiving compost were signiﬁcantly less than those
of the treatments receiving fertilizer. It is likely that the N associated with the compost is
notadequatelymineralizedinApriland earlyMayto ﬁlllymeetthewheat’aneedsin
these critical growth periods. In early April, cool soil temperatures limit mineralization
and in May and June mineralization in the wheat plots is limited by the low soil moisture
conditions caused by the heavy crop moisture demand. Previous research on this site

estimated that 40-50 kg N ha" yr" resulting from the current and former compost

77

applications was available for the entire growing season (F ortima et al., 2002). Sanchez et
al. (2002), also on this site, indicated that the soil in the rotation plots was less eﬁ‘ective in
nrineralizing the N from added compost than from added clover. Thus, the compost
treatments received less total N than the fertilized treatments and the N was not as

available during periods of peak demand.

Within a production year, the same variety of wheat was used under all management
treatments to keep the trial as statistically balanced as possible. It is possible that the

wheat yields in the O and IC treatments may have beneﬁtted from use of an alternative

 

variety that is better adapted to the low soil nitrogen levels seen in these treatments.

Production expenses

The production expenses associated with soybeans and wheat were less than the expenses
associated with corn (Table 2). Most machinery expenses in soybean production were
similar under all management systems with the C treatment receiving slightly less
secondary tillage. The slight decrease in machinery expense seen with C was more than
oﬂ‘set by the increase in input costs (mainly as broadcast herbicide). The production
expenses associated with wheat were also similar across management systems with the
diﬂ’erences being associated with the input costs of cover crop seed, compost and urea.
The machinery expenses associated with corn were very similar under O, IC, and IF
managements. The reduced machinery expenses of corn grown in the C treatment were

due to fewer secondary tillage operations (Table 3). The increased input costs associated

78

with 2"" and continuous corn mainly reﬂected increased fertilizer and pesticide costs

associated with corn following corn.

Gross Income by crop and management

The higher prices received for the organic products (Table 4) more than compensated for
crop yields that are occasionally lowertlrantheir IC, IF, or C counterparts. Thehighest 1"
average gross incomes for each crop were seen under the O managements (Table 1).

Within the conventionally priced treatments, the highest gross incomes were associated

 

with corn and the lowest gross incomes were associated with wheat. Although the

if

average price of conventional corn is about half of the price of soybeans and about 3/4 of
the price of wheat, the corn yield at this location is usually two to three times the yield of

soybeans and wheat.

Though the gross revenues with organic 2‘“l year and continuous corn appear attractive,
they are misleading because most organic certiﬁcation protocols require crops to be grown
in rotation so continuously grown corn could not be marketable as organic (USDA, 2001,
OGM, 2000). Fortunately, given the current pricing structure, average annual gross
income from an organic corn-soybean-wheat rotation ($806 ha") would be expected to be
only slightly less than the average annual gross income from a corn-corn-soybean—wheat
rotation ($822 ha") since the very high grossing 1" year corn crop would occure every

three years rather than every four years.

79

In the 19903 the commodity prices for corn, wheat, and soybeans generally increased ﬁom
1990 to 1995 and then decreased from 1995 to 2000. The 2000 commodity prices of corn
and wheat were very similar to the 1990 prices and the 2000 price of soybeans was less
than the 1990 price (Michigan Agricultural Statistics. The prices of organic commodity
crops is linked to the price structure of conventional commodity crops with an additional
premium paid for the organic crops above the conventional crop price. The premium paid
for organic corn and organic soybeans increased from 1995 to 1999 but decreased in 2000
and 2001. The premium paid for organic wheat ﬂuctuated widely ﬁom 1995 to 2000 with
2000 having the highest premium (Dimitri and Greene, 2002). Unfortunately for organic
crop producers, these premiums are paid on the basis of conventional crop prices, so
although the organic premiums were increasing the actual prices paid for the organic crops
has been decreasing in the last few years. The number of head of certiﬁed organic
livestock and poultry has been increasing from 1997 to 2001 (Greene and Kremen, 2002)

so it is likely that there will continue to be a demand for organic feed grains.

Net Returns to Land and Management Expertise by crop and management system
Since the value of land and the value of management expertise are constant between
treatments and are not included in the cost of production, Gross Income - Cost of
Production is properly called Net Return to Land and Management Expertise. For

purposes of this discussion, the term Net Return will be used instead.

Net returns were higher for all crops produced under the various 0 managements (Table

l). The higher gross incomes for each organic crop were not associated with

80

corresponding higher production expenses. Ifthe organic premiums are removed the
ranking changes completely. VVrthout the organic premiums the net returns of the rotation
are less than the net returns ofthe IC managements and the net returns ofthe continuous
corn are slightly higher than those of the IC managements (data not shown). Within the
conventionally priced commodity grains 1‘ year corn and soybeans usually had greater net
returns than did continuous corn, 2“" year corn and wheat. Katsvairo and Cox (2000)
using higher commodity prices reported negative net returns associated with the wheat-red
clover crop in rotation, low net returns associated with soybeans and relatively high net

returns associated with corn in a corn-soybean-wheat/red clover rotation under chisel

plow management.

Within the treatments receiving compost (O and IC) the use of cover crops was associated
with higher net returns in 1'’ year corn. Unfortunately, the cost of the red clover cover
crop that boosted the 1" year corn was associated with the previous wheat crop with
which it was planted. The cover crop cost that was calculated in the costs of production
with 1" year corn was the crimson clover planted to aid the following 2"" year corn crop.
Although these nuances inﬂuence the relative proﬁtability of individual crops within the
rotation, total proﬁtability is determined across the entire rotation which is only inﬂuenced

by total costs of all crops and total revenue from all crops.

Hesterman et al. (1992) reported N production of 94-188 1b/A from red clover when
frost-seeded into wheat. The N application rates recommended by the pre-sidedress

nitrate test in this trial were usually 40 kg N ha" less for 1't year corn following wheat+red

81

 

cloverthanfor l‘yearcornfollowingwheetalonc. UMerthepricestructureused,the
$21 ha"Nfaﬁﬁza'savingsassodatedwiththeprevimrsreddovacova'aopdoesnm
qrﬁtecompensateforthecostofthecoveraopseedanditsapplicaﬁonﬂﬂ ha"). Ina
non-fertilized systemtheina’easeincomyieldassociatedwiththeclovermorethanpays

for the cost ofthe cover crop.

'l'hcreareseveralwaysofevahratingalong-termrotationarperiment Onemethodwould
betoavaagethenetmcomeﬁomeachaopinﬂrerotaﬁoneachyearmdcompareﬂre

rearlﬁngrotationmeanwiththemeenofthecontimouscornplots. Tlismethodis

 

mbgoustocompaﬁngtheavaagewholefarmnetrennnpa'hectueofacominms E"
canopaaﬁonwiththeavaagewholefarmnctretmnperhectareofaneighbming
Wmthatisequﬂlypﬂﬁﬁmedhnol‘ywmfywmwybmmdm
Wrmunsmethodthevaﬁabiﬁtyassodatedwhheechseesonisequaﬂyappﬁedtoﬂn
treatmentsintheappropriateyear. Therotationmeansandthecontirarouscornmeansfor

eachteatmﬂcanbeavaagedovathedglnsusomtodetanﬁneagrandmeanforthe

rotationandagrandmeanforcontimrouscornforeechmanagement.

Thedternaﬁvemcthodoflookingmtheromﬁmnialwmﬂdbewfoﬂowmdividudplom
thrwghthedghtyemsofthearpaimanandavaagethcammalnamcomcgmaatedby
eechindividualplot. Sincethistrialhadeverypointoftherotationpresenteveryyeer,for
eachmanagememaeatmem,thaearefmndiﬁ‘eraneight-yearmeannetincomes

correspondingwiththefourentrypointsintherotationeveryyear. Thesefoureight-year

meannetincomescanbeavcragedtomﬁveatagrmdmeanformtaﬁonwitlﬁneech

82

management which can then be compared with the eight-year means for continuous corn.
Unfortunately, each eight-year mean also contains eight variance components associated
with seasons and when the four entry points are averaged the resulting grand means have
very different variances from the treatment means of continuous corn. Both the method

that focuses on seasons and the method that follows plots through the rotation give the

same results for mean net income for each management system. For the sake of simplicity

"”91

the season-based method was used for the following analysis.

When the rotation means and the continuous corn means were ranked, all net returns

 

“ir—

associated with the organic management were much greater than any net returns
associated with the other management systems (Table 5). Again, this is mainly a ﬁlnction
of the premium prices awarded organic crops during this period. Within the normally
priced crops the rotation treatments of IF had the highest net returns. The net return of
the IF rotation without cover crops was higher than the net return of the IF rotation with
cover crops due to similar yields between the two treatments and the cost of the cover
crops associated with the IF rotation with cover. Both the IF rotations had higher net
returns than the IF continuous corn returns. The C rotation treatment also had a slightly
higher net return than C continuous corn treatment. These results agree with those of
Singer and Cox (1998b) who found that when the sale of straw is included in the net
returns, a fertilized corn-soybean-wheaHred clover rotation had higher net returns than
did continuous corn. The net returns of 1C rotations with and without covers was less
than those of both 1F rotations. One explanation is that the yields of 2'“I year corn

produced in the systems receiving compost and the resulting negative net returns brings

83

down the average net yield of the rotation. The low yields associated with continuous
corn treatments of the IC management treatments resulted in the lowest net returns of all

treatments.

Sensitivity to ﬂuctuations in crop prices and selected input costs

The ranking of net returns of rotations and continuous corn by the various management
systems was very robust. Even when the prices of commodity corn, soybeans, or wheat
were increased one standard deviation above their average price, none of the net retruns of
conventional crops approached the net returns generated by organic crops without an
increase in organic crop prices. A 15.6% increase in the value of organic corn
(comparable to the increase in conventional corn) caused a re—ordering of the ranking.

The previous $20.00 ha" advantage of the O rotation with cover crops over the 0
continuous corn with cover seen under standard model conditions (all normal crop prices
and all normal production expenses) became a $29.00 ha'l deﬁciency when the price of

organic corn was increased.

Within the conventionally priced crops there was slight treatment re-rariking associated
with a higher price of corn. Increasing the price of corn one standard deviation was not
enough to raise the ranking of continuous corn produced under IC management. In
general, raising the value of corn only slightly increased the ranking of three of the ﬁve
normally priced continuous corn treatments when compared to the treatment ranking seen
with standard prices and expenses. Increasing the price of soybeans or wheat also resulted

in only minor re-ranking of the treatments.

84

When the cost of pesticide was doubled the 0 treatments were not aﬂ'ected and the IC and
IF treatments that receive banded herbicide were only slightly aﬂ‘ected. The C continuous
corn treatment, which received broadcast herbicide every year and banded soil insecticide
most years, was highly affected by the increase in pesticide cost. This treatment dropped
from a relatively high ranking (#6) under standard price and expense conditions to the
lowest net return (#14) under the high pesticide price scenario. The ranking of the IC .-
treatments was quite sensitive to the price of compost. When there was no cost
associated with the purchase of compost (only the application cost) the rank of the IC

rotations improved over all IF treatments. In an alternate scenario where the cost of

 

compost was tripled, all of the IC treatments had lower net returns than any of the other

conventionally priced treatments.

CONCLUSIONS
At the prices prevailing in Michigan during 2001, the organic rotation was a very
proﬁtable system. Although organic soybean and wheat yields were slightly reduced, net
returns were far greater than those of conventional crops. Although the market for
organically-produced grains appears to be strong as demand for organic products
increases, if the premiums paid for organic commodity crops decrease ﬁrture net returns

may not be as attractive as the non-organic production alternatives.

From a net retum standpoint, the yield beneﬁts over the entire rotation associated with
cover crops do not compensate for the cost of the cover crops. The strong yield increase

seen in the corn that does not receive fertilizer associated with the proceeding red clover

85

cover crop does not carry through the entire rotation, while the cost of a cover crop was
present in three of the four years of the rotation. However, there are beneﬁts from cover
crops that were not captured in this economic analysis. Long term beneﬁts in yield may

only show up if the experiment is run for many years. The current analysis does not give
credit for the ecosystem services rendered by the cover crops nor does it account for the

additional forages provided by the cover crops that may be available for grazing or haying. r.
A late fall haying of the red clover cover crop may also occasionally be possible when

weather conditions permit.

 

The compost rates used in this trial were inadequate to supply the N needs of corn without
a signiﬁcant preceding leguminous cover crop such as the wheat-red clover combination.
The dairy compost used was unable to supply the eariy season N needs of the winter
wheat crop. Possibly, a substitution of dairy manure for the compost would be able to
meet these N needs. Another approach would be to evaluate more wheat varieties for

their ability to produce high yields under lower soil N conditions.

The ranking of treatments was fairly robust with only minor re-rankings occurring when
crop prices were increased one standard deviation from their mean value or selected input
expenses were doubled. The continuous corn produced under conventional management
was sensitive to the price of pesticides relative to the other treatments. The rotations that
were produced in the treatments receiving compost were sensitive to the price of compost

relative to the other treatments.

86

This intermediate-term economic analysis does not factor in the differences in value of
ecosystem services provided by the various management systems. The long-term
biological beneﬁts of crop rotation, use of compost, and cover cropping may not be
apparent in the short-term price structures that are typically examined for economic
analysis. Some of the long-term biological beneﬁts associated with rotation, compost and
cover crops seen in this trial include an increase in soil organic matter (0-25 cm), and
increases in both the total soil N pool and the mineralizable soil N pool. Changes in the
nematode community structure that favor non-plant parasitic nematodes have also been

seen in the treatments with compost and cover crops.

On a coarse textured soil where winter leaching complicates N management, a three year
corn-soybean-wheaﬁred clover rotation might be preferable to the corn-corn-soybean-
wheat +red clover rotation actually used. The frost-seeded red clover retains enough N
through the winter to usually meet the N needs of the following corn crop under these
rain-fed conditions. The residual N following soybeans is adequate to meet the fall
demands of the winter wheat crop, but supplemental N ill the spring is necessary for high

wheat yields.

87

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91

 

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Table 3

 

Cont.
Com

Table

Table 3: Generalized Table of operations by crop and management

8qu App. Field Rot. Add. Post App. Bale Clip
Felt Comp Disk Cultiv. Hoe Cultiv. N Herb. Cover Straw Straw

 

Cont. lCover O 1 1 1
Corn None 0 1
Cover IC 1
None IC 1
Cover IF 1

None iF 1

None C 1

1

1

‘A
geld-I‘d

 

 

 

15! Cover 0
Corn None 0
Cover IC
None IC
Cover 1F 1
None IF 1
None C 1

d—L-b-l

J
.3

 

 

 

2nd Cover 0
Com None 0
Cover IC
None IC
Cover IF 1
None IF
None C 1

NNNN

d
J
d-ﬁ—Id-A
d

 

 

 

Soys Cover 0
None 0
Cover 10
None lC
Cover lF
None IF
None C

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.a

Aunt-Add

 

 

Wheat Cover 0
None 0
Cover lC
None IC
Cover IF 1
None IF 1 1
None C 1 1

All Treatments were chisel plowed, planted, and combined

1 1

d‘dd‘dd ddddd‘d ‘dddddd ddddddd ddddd“

ddddddd
d‘A-b‘dd

 

 

Table 4: Average crop prices

 

 

 

 

 

Conventional Organic
Corn $2.20 $3.75
Soybean $5.50 $8.00
Wheat $2.85 $5.00

 

93

 

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