Farm and county scale scenarios for sustainable agriculture in Western Iowa

This paper deals with ecosystem, social, and economic impacts of changes in land-use, crop rotations, and farm management in two counties in western Iowa. In this region, expansion of farm size, increase in the average age of farmers, and reductions in labor availability have been continuous processes, caused by agro-economic and social factors over the last several decades. The landscape of the Loess rolls in western Iowa includes fields with hill slopes ranging from 0 to beyond 14%. Many of the soils are highly erodible. A two-year rotation of corn-soybeans is currently the most common cropping system, and results in considerable soil loss from bare soils in winter and spring. On many farms livestock production has dramatically decreased or disappeared entirely over the last 25 years. Our project focuses on re-integration of crop and livestock production. Our main goal is to investigate the ecological impacts of replacing chemical fertilizers by animal manure and of including perennial crops and pastures in the cropping system. The I-FARM simulation model is being used to estimate the ecological effects of various crop and livestock production systems at the farm scale. When using local land-use data and the simulation model, we are able to predict effects of alternative cropping systems and livestock production at the county scale on soil loss, nutrient balances, and associated labor requirement. The paper will show some results of simulations in terms of crop diversity patterns, livestock to be raised in a closed system at the county level, fertilizer replaced by manure, farm labor required, erosion and nutrient control, and economic consequences. We also present some social trends.