The Urgent Need to Address Nutrient Imbalance Problems in Iowa's High-Density Livestock Regions

The Iowa Departments of Agriculture and Natural Resources and Iowa State University initially developed the Iowa Nutrient Reduction Strategy (INRS) in 2012 to provide a framework for mitigating point and nonpoint-source nutrient pollution across the state. A primary goal of the INRS is reducing total nitrogen and total phosphorus loads to Iowa streams by 45%. A core aspect of the INRS approach to addressing nonpoint-source TN pollution is the implementation of multiple management practices that are categorized as: nitrogen management (e.g., timing, nitrogen application rate, cover crops), land use (perennial crops, extended rotations, grazed pastures), and edge-of-field (e.g., wetlands, bioreactors, buffers). The INRS reports various statewide scenario analyses, including an assessment of 15 nitrate-N reduction practices that ranks cover crops, wetlands, bioreactors, and perennial crops as providing the strongest reductions. Adoption of these practices remains low, largely because their economic benefits in terms of crop yield and farm revenue is neutral at best. The INRS scenario finds that various in-field nitrogen management practices, which can enhance farm profitability, offer little potential to reduce statewide stream nitrogen loading.