Nitrogen Budgets and Economic Efficiency: A Case Study of Southeastern Minnesota

Public agencies are likely to enact policies aimed at reducing agricultural contributions of nitrates to groundwater. These policies are likely to be aimed at N application rates and methods. Current application methods and rates relative to crop needs would be a primary determinant of how farmers respond to particular policies and the costs of those responses. A budget model is used to estimate both aggregate and farm level N needs, sources, and deficiencies or excesses. The model is applied to the six‐county karst area of southeastern Minnesota (SE MN), because of its intensive crop and livestock production and demonstrated susceptibility to groundwater contamination. The model also is estimated for Fillmore County, within the six county area, and four individual farms in Fillmore County. The four individual farms include a mixed dairy and crop operation, two livestock‐crop operations, and a continuous‐corn farm. Secondary data and direct interviews were the primary data sources in the aggregate and farm level applications, respectively. Nitrogen sources exceeded crop needs in Fillmore County and SE MN by ≥ 50 lb/corn acre. Individual farm estimates indicate highly variable N applications across farms. The continuous‐corn farm exhibited a close balance between crop needs and N applications, the non‐dairy livestock operators had excesses of 20 to 60 lb/acre, and the dairy operator's sources exceeded crop needs by about 130 lb. Due to the indicated concentration of “excess” N applications on farms with livestock, policies aimed at reducing N applications and otherwise improving N management should consider manure and legume sources, as well as commercial fertilizer.