Nutrient Management for High Yield Corn

The University of Georgia N-P-K fertilizer recommendations for irrigated corn start with a base yield goal of 150 bu/a.  Mehlich 1 extraction is used to get the starting point for P & K and then for every 10 bu/a more yield goal an additional 12-6-10 (lb/a N-P2O5-K2O) is added to the base fertilizer recommendation.  For N, this turns out to be 1.2 lb N/bu yield goal. Since this recommendation was developed many years ago and has not been tested in recent years, a 5-year study field study was conducted to verify this recommendation.  Irrigated corn was fertilized with increasing rates of N-P-K for 150, 200, 250 and 300 bu/a yield goal levels.  When fertilized for 150 bu/a that yield was always achieved. The 200 bu/a yield goal was achieved  3 out of 5  years, the 250 yield goal 2 out of  5 years and 300 bu/a was never quite met.  Economics or ROI on fertilizer for this study will also be discussed as well as issues such as low Mg and dilution of nutrients in tissue samples depending on plant population.