A COMPARISON OF LOW INPUT GRAIN SYSTEMS ON WICST (1995-2002)

Janet L. Hedtcke [1] , Joshua L. Posner [1], and Jon O. Baldock [2]

INTRODUCTION

Marginal profits, increasing pest pressure, and concern for pollution hazard have resulted in increased interest in including small grains in corn-soybean rotations and using less inputs.  Data from the WICST trials show environmental advantages of using a chemical free three-phase system but yields were often lower than in the high input systems.  Researchers have found that expanded rotations plus low input levels can be quite competitive with shorter rotations and high chemical inputs  (Singer, 1998; Singer and Cox, 1998 and Clark et al., 1999).  We decided to test a ‘ChemLite’ approach adding reduced inputs to the 3-phase cash grain rotation and compare it to the three phase organic system (CS3), and the no-till corn soybean system (CS2).  The ChemLite system would aim for half rates of N on cereals and half rates of post-emergent herbicide on row crops (when necessary). 

MATERIALS & METHODS

The Wisconsin Integrated Cropping Systems Trial (WICST) is a long-term trial that was initiated in 1989 to compare production, economic, and environmental impacts of six cropping systems common to the upper Midwest.  Further description of the background details, design and conduct of the main WISCT cropping systems can be found in Posner et al. (1995).

In 1995, a satellite trial was initiated at the Arlington site on a Plano silt loam soil (fine-silty, mixed, mesic, Typic Argiudoll) to compare a reduced-chemical system of corn-soybean-wheat/red clover (hereafter referred to as ChemLite) to the No-till corn-soybean system and the chemical free corn-soybean-wheat/ red clover system (hereafter referred to as ChemFree) of the core WICST trial. 

Inputs.  A list of inputs and rates for the ChemLite system are shown in Table 1. Generally, three inputs were added to ChemLite: starter fertilizer on the corn, N fertilizer on the corn and occasionally the wheat, and post-emergence herbicides on the corn and soybeans. ChemLite received half-rates of N fertilizer on the corn phase which averaged 80 lb N/a.  Rotary hoeing, cultivation and post-emergence herbicide was applied in 15” bands over the row or broadcast on the whole field at half rates during the corn and soybean phases, depending on the equipment set available at the time.  Herbicides were applied as deemed necessary, and in some years, no herbicides were applied.  The No-till corn-soybean received inputs according to Best Management Practices (i.e. 120 lb N/a on corn, pre- and post-emergent herbicides in both phases).

 The experiment was set up with two replicates adjacent to the main WICST experiment, which was a randomized complete block.  All plots were 0.70 acres and field-sized equipment was used.  Each phase of the rotation existed each year during the 8-yr trial to encompass different environments.  All effects in the model are fixed except year, which is random.  To compare corn and soybean phases, 95% confidence intervals were calculated for the two systems in WICST (ChemFree and No-till corn-soy) across the 8 years and 4 replicates and across the 8 years and 2 replicates in ChemLite.  Wheat grain and straw yields were compared between ChemLite and ChemFree using an independent t-test statistic.  Preliminary tests showed variances to be homogeneous between the core WICST plots and the ChemLite experiment for all the dependent variables.

The Crop Rotations Options Program (CROP) software (Baldock et al., 1998) was used to determine net returns (to labor, capital, and management) each year and for testing scenarios on price premiums.  A 1000-acre farm was used in CROP and yearly input prices, yields, and commodity prices were entered for each system.  Harvest-time commodity price (October price without storage option) was used across systems without any governmental price supports. 

Table 1. Inputs for the ChemLite system.

† The rates shown are the amount per total acre. From 1995-1998, the applications were made in a 15-inch band on 30-inch rows, thus the rate in the band itself was twice that shown. In 2001 and 2002, herbicides was broadcast across the 30-inch row at half rate.

RESULTS & DISCUSSION

Agronomic Performance and Risk.  Corn yields were similar for ChemLite and the No-till corn-soy systems and both were statistically higher than ChemFree at p<0.05 (Fig. 1).  However, there was no significant difference between systems for soybean yield (Fig. 2).  Wheat yields were also not different between ChemLite and ChemFree averaging 58.2 bu/a of grain and 1.03 tons DM/a of straw.  There was no year by system interaction for any crop yield so the 8-year mean is reported. 

Yield variability and the associated risk are important factors apart from mean yields.  There was more variability in ChemFree corn and soybean yields than the other two systems (Table 2). There was a 2-fold difference in corn yield variability between ChemLite and ChemFree systems (53 vs. 114 bu/a, respectively).  However, soybean yields were less variable between ChemLite and ChemFree systems (29 vs. 32 bu/a, respectively).  In wet years (i.e. 1996, 2000), mechanical tillage is less effective on weed control, which can reduce yields significantly.  Forty-five percent of the 18-bu/acre of corn advantage for the ChemLite system vs. ChemFree system occurred in 1996, which was a cool, wet spring.   These conditions should not be regarded as rare because similar conditions with similarly low ChemFree corn yields occurred in 1992, 1993 and 2000 in the WICST core trial. 

Economic Analysis.  The 8-yr. average net return was highest for No-till corn-soy ($51/a/yr) and lowest for ChemFree ($30/a/yr) with ChemLite very similar to No-till corn-soy at $49/a/yr.   Net returns on all three systems have declined over the trial period mostly due to decreasing commodity prices.  Corn, soybean and wheat prices decreased by 38, 26 and 45%, respectively, from 1995-2001.  Excellent yields and somewhat better commodity prices in 2002 have brought net returns ‘out of the red’ for that year (Fig. 3). 

Premiums can improve the economics of the low input systems.  Although the gap between organic premiums and conventional is narrowing, organic grains are still enjoying more than 100% premium according to local elevators surveyed in 2001 (Peavy, Delong, QTI, pers. com., 2001). Results from the  CROP program, using the 8-yr average commodity prices, indicate that with a modest organic premium of only 9% was needed for ChemFree to equal the No-till corn-soybean net returns [3] .  Similarly, only a 1% ‘stewardship’ premium would bring ChemLite to same net returns as the No-till standard.  One can imagine that in the future, the 2002 Conservation Security Act will reward lower input cropping systems.

Environmental Impact.  Soil test phosphorus was significantly higher (p<0.05) in ChemLite and the No-till corn-soybean system than ChemFree (Fig. 4).  Both these systems received starter fertilizer (about 10 lbs P/a) to increase nutrient uptake in cold wet springs.  Even without starter fertilizer, STP was still quite high for ChemFree after 12 years of farming organically.  This underscores the excessively high P levels in the plots at the start of the trial, a condition similar in most dairy farm fields.  The year by system interaction was not significant.

Soil nitrates, measured after crop harvest, were significantly lower (28%) in the 3-crop systems compared to the 2-crop system (Fig 5; p<0.0022).  This can be explained by lower N inputs in the expanded rotation due to N credit from green manure.  In addition, the winter wheat phase “traps” some of the fall nitrates in the soil profile.

There were obvious differences in soil erosion potential between No-till and the low input systems (Fig. 6). Soil loss was well under ‘T’ for the No-till system at 1.2 tons/ac/yr.  However, ChemFree had the highest soil erosion hazard, followed by ChemLite, due to annual tillage and repeated cultivations.  On average, ChemFree had one more rotary hoeing and one additional cultivation than ChemLite.

CONCLUSION

In terms of production, profitability and environmental impact, the ChemLite system performed as well as or better than the standard corn-soy rotation.  Managed organically, ChemFree is too short a rotation to effectively control weeds.  Even so, only a small premium (9%) is needed for ChemFree net returns to equal the standard 2-crop system.  Reducing inputs and increasing crop diversity appears to be the best approach to meeting the twin goals of reduced environmental impact and maintaining profitability.

LITERATURE CITATIONS

Baldock, J.O., D. Fisher, J. L. Posner.  1998.  Crop Rotations Options Program.  Software University of WI, Madison, WI

Clark, S., K. Klonsky, P. Livingston, and S. Temple.  1999.  Crop-yield and economic comparisons of organic, low-input, and conventional farming systems in California’s Sacramento Valley.  American Journal of Alternative Agriculture.  14(3):109-121.

Posner, J.L., M.D. Casler, and J.O. Baldock.  1995.  The Wisconsin Integrated Cropping Systems Trial: Combining agro ecology with production agriculture.  American Journal of Alternative Agriculture.  10(3): 98-107.

Singer, J.W., and W.J Cox.  1998a.  Economics of different crop rotations in New York.  J. Prod. Agric.  11(4):447-451.

Singer, J.W., and W.J Cox.  1998b.  Agronomics of corn production under different crop rotations in New York.  J. Prod. Agric.  11(4):462-468.

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