Effect of harvest method and feed value on the economic optimum nitrogen rate for corn

Consideration of the harvest method and protein content of corn grain and forage may be important variables for estimating Economic Optimum Nitrogen (N) (EON) rates for corn. Corn grain yield, forage yield, grain protein and forage protein data from twenty five N response experiments conducted in Pennsylvania were analyzed to determine the effect of harvest method and a price adjustment based on grain and forage protein content on the EON rate. The value of the protein in this study was assumed to be that of substituting soybean meal in the ration for growing beef cattle or dairy cattle. There was no difference in the EON for corn harvested for grain compared to corn harvested for forage when the protein content was not considered. When price adjustments were made for the protein content of the grain and forage, the EON rates increased 10 kg/ha for grain and 22 kg/ha for forage. With the protein price adjustments, the EON was 14 kg/ha higher for forage than grain. These results support the recommendation for higher N rates for corn harvested for forage, where the protein value of the forage is considered, compared to corn harvested for grain. In situations where the amino acid composition of the grain is important, such as for poultry or swine, or where urea or anhydrous ammonia can be substituted in the ration for protein, it is.