Terry C. Kelly, Yao-chi Lu and John Teasdale

Agriculture, Ecosystems and Environment 60:17-28. 1996

This article contributes to the growing body of knowledge about the economic and environmental impact of alternative cropping systems. The authors cite several key studies conducted over the past several years that have made such assessments (Jones et al., 1991; Kim and Mapp, 1993; Faeth, 1993; Faeth et al., 1991; Hughes et al., 1995; Teague et al., 1995). These studies evaluated a variety of cropping systems in diverse locations worldwide, but they all used the Erosion Productivity Impact Calculator (EPIC) to generate their information. EPIC is a comprehensive cropping systems model designed to analyze alternative cropping systems and their environmental and economic sustainability. The research reported here used EPIC to: 1) evaluate the long-term impacts of different cropping systems on net return, soil erosion and environmental quality; and 2) analyze the tradeoffs among net returns, soil erosion and other components of environmental quality.

Materials and Methods

The seven rotations examined in this study are ones that are currently being evaluated as part of the Sustainable Agriculture Project at the USDA’s Beltsville Agricultural Research Center. This project began recently and field data will not be available for several more years. By using EPIC the authors hope to develop some preliminary information that can be compared to actual results and that can perhaps be applied across a wide range of conditions.

The seven rotations evaluated are summarized as follows:

1. Conventional 2-year rotation. Corn (May-October)—Winter Wheat (October-July)—Soybean (July-November), conventional tillage and herbicides used.
2. No-till conventional 2-year rotation (#1 above), herbicides used.
3. Cover crop rotation with fertilizer. Corn (planted into hairy vetch cover crop)—Winter Wheat (grown as cover crop and mown May 12)—Soybean planted into mown wheat (harvested in October)—Hairy Vetch (no-till planted), fertilizer and herbicides used.
4. Cover crop rotation (#3 above) with no added fertilizer.
5. Manure rotation. Corn—Winter Wheat—Forage Legume (red clover overseeded in wheat). No synthetic fertilizers or pesticides used. Manure applied twice in two years (23.76 MT/ha applied in May prior to corn, 11.2 MT/ha applied in October prior to planting wheat).
6. Same rotation as #5, but with manure applications cut in half.
7. Same rotation as #5, but with manure applications reduced to one-fourth.

Using EPIC to simulate conditions over a 30-year period, the authors were able to estimate for each rotation:

• Yield and income;
• Environmental hazard index based on potential contamination from nitrogen, phosphorus, and pesticides;
• Tradeoffs between income and environmental hazards related to nitrogen, phosphorus and herbicides.

Results

The model predicted that the no-till rotation would provide the greatest net returns, followed by the conventional rotation. Net returns for the two cover crop rotations were lower because the wheat grown in those rotations would be sold for hay and not grain. When considering environmental impacts, the model predicted that the no-till rotation would have the lowest nitrogen loss, and the cover crop rotations would perform best in terms of erosion and phosphorus loss. Because herbicides are necessary to control weeds in no-till, the pesticide hazard index for this rotation was high, suggesting a tradeoff between pesticide hazard and other environmental considerations. Similarly, there were tradeoffs between erosion and environmental hazard for manure and no-till rotations. The results also showed that farmers may be able to make gains on one objective without sacrificing significantly on another. In the cover crop rotation, for example, the analysis showed that fertilizer could be reduced without significant loss in income, but with substantial reduction in environmental contamination.

The environmental hazard index (a weighted average of the three individual indices for nitrogen, phosphorus, and pesticides) was developed to help decision-makers deal with some of the difficulties in examining various alternatives. An analysis of the tradeoff between environmental hazard (as defined by the environmental hazard index) and income showed that any one of three rotations might be preferred, depending on the individual’s (or society’s) primary concerns: no-till, manure at medium application rates, and cover crop without fertilizer. Individuals concerned mainly with economic gains would be inclined toward the no-till rotation, while those strongly concerned about reducing environmental hazard might choose the cover crop–no fertilizer rotation.

(Editor’s note: These conclusions provide some useful information about the transition to more environmentally sound production systems. It will be important to follow this experiment to see if the predicted results are borne out in the actual field experiments.)

References

Faeth, P., R. Repetto, K. Kroll, Q. Dai and G. Helmers. 1991. Paying the Farm Bill: U.S. Agricultural Policy and the Transition to Sustainable Agriculture. World Resources Institute, Washington, DC.

Faeth, P. (Editor.). 1993. Agricultural Policy and Sustainability: Case Studies from India, Chile, the Philippines and the United States. World Resources Institute, Washington, DC.

Hughes, D., W. Butcher, A. Jaradat and W. Penaranda. 1995. Economic analysis of the long-term consequences of farming practices in the barley cropping area of Jordan. Agricultural Systems 47(1):39-58.

Jones, C.A., P.T. Dyke, J.R. Williams, J.R. Kinery, V.W. Benson and R.H. Griggs. 1991. EPIC: an operational model for evaluation of agricultural sustainability. Agricultural Systems 35:341-350.

Kim, S. and H.P. Mapp. 1993. A farmlevel economic analysis of agricultural pollution control. Paper presented at the AAEA Annual Meetings, Orlando, FL, August 1-4.

Teague, M.L., D.J. Bernardo and H.P. Mapp. 1995. Farm-level economic analysis incorporating stochastic environmental risk assessment. American Journal of Agricultural Economics 77(1):8-19.

For more information: Yao-chi Lu, Systems Research Lab, USDA-ARS, Bldg. 007, Room 8, BARC-West, Beltsville, MD 20705.

(DEC.547) Contributed by David Chaney