Optimizing Plant Population and Nitrogen Rate for High-Oil Corn

Abstract

High-oil corn (Zea mays L.) has been grown because of the increased feed value and potential for price premiums. There are only limited data on how plant population and N rates affect grain yield, grain oil content, or grain protein content, and resulting net value per acre of high-oil corn. In a study conducted over three locations and three years, grain oil content decreased slightly and grain protein content increased as N rate increased from 80 to 200 lb/acre. Increasing the plant population from 25,000 to 40,000 plants/acre did not affect grain yield, grain oil content, or grain protein. Net crop value per acre - calculated using a base price of $3.50/bu, an oil premium of $0.08/bu at 6.5% grain oil plus $0.01 for each increase of 0.1 percentage point of oil up to 8% (maximum of $0.23/bu), and a protein premium of $0.04 for each percentage point increase from 8.5 to 10.5% (maximum of $0.08/bu) - was maximized at an N rate of 159 lb/acre, at which grain yield was 163 bu/acre. Increasing the protein premium by $0.01 per percentage point of protein between 8.5 and 10.5% protein adds about $1.67/acre to net value and increases the optimum N rate by about 0.3 lb/acre. Due to increasing seed costs and lack of yield response to increasing plant population, net value decreased as plant population increased. There was no interaction between N rate and plant population for any parameter measured. Managing high-oil corn for yield rather than for grain oil or grain protein content resulted in the highest net value per acre. Optimum plant population for high-oil corn was somewhat less, while the optimum N rate for high-oil corn was similar to that recommended for normal (yellow dent) corn grown in the same environment.