An optimization model for zero-excess phosphorus management

Livestock production in the 21st century is moving in the direction of higher animal densities. Accompanying livestock expansion is the challenge of manure handling and utilization. A model for zero-excess phosphorus (ZEP) management has been developed for a dairy-crop operation that is based on multicriteria optimization. ZEP management practices are identified by simultaneously minimizing excess manure phosphorus, feed cost, and cropland requirement. System components include commercial fertilizer application, feed crop production, P storage in the soil profile, surface runoff, procurement of feed supplements, ration formulation, dairy herd structure and dynamics, manure handling, manure storage, and manure spreading. Manure is recycled as a fertilizer nutrient source in crop production. ZEP management practices include a cropping system, nutrient applications, and animal rations which are characterized by low feed cost and maximum use of land resources.