Swine manure management plans in north-central Iowa: Nutrient loading and policy implications

Expansion of production in north central Iowa has occurred in dense cluster s of confined feeding operations (CAFOs) which poses questions about how ma nure nutrients are distributed on the landscape and whether manure manageme nt regulations are sufficient to protect water quality. Public record were wed to document the manure management practices of 10 CAFOs housing 59,700 finishing hogs in a 1,554 ha area of Hamilton County, Iowa. Together, the C AFOs generated an estimated 811,500 kg of nitrogen (N) each year, more than 70% of which volatilized into the atmosphere. CAFOs minimized the area req uired for applying manure by underestimating manure N content, projecting a bove average crop yields, and applying manure to soybeans. Some fields were claimed by more than one CAFO, and some field sizes were overestimated Man ure application based on crop demand for phosphorus would require 9,350 ha of cropland, compared to the 990 ha used by CAFOs. Several policy changes c ould alleviate the nutrient management problems inherent in CAFOs.