Case Study: Developing Field-Scale Nitrogen Budgets for Wastewater Irrigation.

Food-processing facilities must obtain an operating permit to allow beneficial crop irrigation using the treated process wastewater generated by the facility.  It is becoming common for regulators to require a nutrient management plan, including a nitrogen (N) budget, as a condition of that operating permit. A case study from a large-scale (> 500 ha) facility in Texas exhibiting the development, and validation of N budgets for land application of food-processing wastewater is presented. Annual micro-site nitrogen budgets were calculated from 1992 to 2009 using readily available analytical data and management records. Budgets were validated with annual profile soil sampling.  Budget validation was challenged by limited or incomplete data, personnel changes, different operational objectives, crop and irrigation management, data quality, weather effects, time and budget constraints, and other factors. Compiling area-weighted field-scale and project-wide N budgets improved the ability to evaluate long-term progress of nitrogen management strategies.