Determination of an Optimal Cropping System for Erosive Soil
1990
Smith, Elwin G. | Hallam, Arne
Economic models are often used to evaluate the long-term effect of soil erosion on economic returns and cropping patterns. Such models implicitly make assumptions about technology, soil characteristics, the effects of cropping patterns on erosion and soil productivity, the resources available to the producer, and producer preferences. The sensitivity of model results to common assumptions has not been systematically investigated. This paper analyzes the effects of assumptions regarding productivity inputs of soil erosion, the producer's stock of tilling equipment, technological improvement, time preferences, and integrated field modelling on model results. Optimal cropping and tillage practices for a representative farm in northeast Iowa were determined using two common methods of estimating the productivity impacts of soil erosion. Both realized productivity impacts and optimal suggested cropping practices were substantially different between the two methods. Minimum tillage was the most cost-effective means of conserving soil. Optimal cropping and tillage practices included crop rotations with alfalfa hay and terracing, when measurement methods implying high erosion productivity impacts were used, while corn-soybean rotations were optimal when methods implying lower impacts were utilized. The effect of the producer's initial stock of tillage machines on tillage practice was minimal for the erosive fields but major for the nonerosive fields. Yield increasing technology was soil conserving, but, with projected yields of crops that have a high erosion potential increasing faster than crops that have a low erosion potential, there was an economic incentive to grow crops with a high erosion potential in the future.
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