Cost-effectiveness and cost-benefit analysis of conservation management practices for sediment reduction in an Iowa agricultural watershed

Soil erosion from agricultural lands can be reduced by adoption of conservation management practices. The objectives of this study were to investigate the effectiveness and cost-benefit of conservation management practices on sediment reduction under a corn–soybean rotation. The experimental site was 6.4 ha (15.8 ac) and located within the Four Mile Creek watershed in eastern Iowa. Management practices consisted of tillage with a moldboard plow with a row cropped system of corn and soybeans. Annual sediment yield from this site was estimated using the Water Erosion Prediction Project (WEPP) model for three tillage systems (chisel plow, disk tillage, and no-tillage) as well as three conservation structures (grassed waterways, filter strips, and terraces). The WEPP model was validated using five-year (1976 to 1980) field-measured sediment yield and surface runoff data. Without supplemental conservation measures, predicted sediment yield was 22.5, 17.7, and 3.3 t ha–1 y–1 (10.0, 7.9, and 1.5 tn ac–1 yr–1) from chisel plow, disk tillage, and no-tillage, respectively. Supplemental conservation measures had the most impact on sediment yield reduction when used in conjunction with chisel plow management and the smallest impact with the no-tillage system. The value of lost soil resulting from soil erosion ranged between $10.9 and $137.3 ha–1 y–1 ($4.4 and $55.6 ac–1 yr–1) for the simulated scenarios in the study when a soil value of $6.1 t–1 ($5.5 tn–1) was considered. When factoring in the value of soil, no-tillage was the most efficient practice with the highest net benefit of $94.5 ha–1 y–1 ($38.2 ac–1 yr–1). This study indicated that the economic value of soil that is lost should be considered in the cost-benefit assessment of conservation practices in order to reflect the true value of the conservation practices in the long term.