Crop Nutrient Needs Potentially Supplied by Livestock Manure in Iowa, Illinois, and Indiana
分析美国中西部三个州各县的作物养分使用与牲畜粪便养分供应，评估粪便集中带来的环境风险，对关注农业面源污染和养分管理的学者有参考价值。
Midwestern agriculture is moving toward large, specialized production units where harvested crops are shipped off the farm and livestock are raised on purchased feed. Many people are concerned that increased manure concentration from specialized livestock units poses an unacceptable environmental risk. The unequal distribution of livestock production across counties in Iowa, Illinois, and Indiana suggests that a disaggregated analysis of crop nutrient use and manure nutrient supply is needed to estimate the risk of excess nutrient losses to the environment. The authors analyze nutrient use and supply at the county level.