Economic-environmental tradeoffs among alternative crop rotations

Simulated long-term impacts of different cropping systems are evaluated and analyzed in terms of the tradeoffs among net returns and different components of environmental quality. The cropping systems are modeled after the BARC Sustainable Agriculture Demonstration Farm. EPIC was used to obtain crop yields, soil erosion, and the environmental fate of nitrogen, phosphorous, and herbicides in response to weather and management practices over a simulated 30 year period. This procedure provides a way to estimate the environmental impact of cropping rotations, and to analyze the tradeoffs between competing objectives, whether they are farm income, erosion control, or the reduction of multiple hazards. The results indicate that the no-till rotation provides the greatest net returns, followed by the conventional rotation, The net returns on the two cover crop rotations are lowest. In terms of environmental impacts, no-till rotation dominates all other rotations with lowest nitrogen loss, and the covercrop rotations perform best in terms of erosion and phosphorous loss. However because herbicides are necessary to control weeds in no-till, the pesticide hazard index is very high, suggesting a tradeoff between pesticide hazard and other environmental considerations. To provide decision makers with better information, an environmental hazard index was constructed to analyze the tradeoffs between potential chemical contamination and net returns, Depending on preference structure, any one of three rotations could be preferred: no-till; manure at medium application rates; and cover crop without fertilizer.