Adaptive Nitrogen Management for Corn, Sorghum, and Wheat in the Coastal Plain of North Carolina.

Determining nitrogen (N) rates in the south is very difficult because the economic optimum nitrogen rate (EONR) varies by crop, yield, soil, climate, and other multiple factors and there is no soil test that has been shown efficacy. Nitrogen rates have been established for each soil/crop combination; however, often these rates are disregarded. We know that farmers learn best through self-experimentation or farmer-to-farmer programs. Thus, our current adaptive N management project works directly with farmers who apply fertilizer N to corn, sorghum, and wheat. The objective of this on-going research is to help farmers optimize commercial N inputs through multiple rate strip trials on corn, sorghum, and wheat. A total of 20 producers in the Coastal Plain of North Carolina participated in the project and 54 trials (over 100 acres spanning 5 counties) were conducted during 2013 and 2014. Treatments were three N rates (the growers’ typical N rate and + 25% of this N rate).  Each N rate was replicated 4 times and applied at the appropriate time for each crop (V6 stage for corn, GSII for sorghum, and growth stage 30 for wheat). Grower N rates ranged from 111 to 211 kg ha^-1 for corn, and 85 to 148 kg ha^-1 for sorghum, and 74 to 162 kg ha^-1 for wheat. Yield data was collected spatially using calibrated yield mapping equipment.  Results show there was significant yield variability within fields and between fields; the recommended N rate was either appropriate or slightly greater than the farmers needed. The yield response to N at different treatments will be assessed to determine an overall site-specific EONR for each participating producer and this information will be presented.