The Relative Influences of Moisture and Nitrogen Fertilizer on Sorghum Development for Grain and Forage Production under Double Cropping

Three high yielding and three low yielding grain sorghum hybrids were grown for grain yield and total dry weight in late planted simulated double-crop after barley or wheat harvest with two levels of irrigation (dry and wet) and two levels of nitrogen fertilizer (0 and 100 lbs/acre). The experiment was conducted on the University of Arizona Marana Agricultural Center. Nitrogen fertilizer and the interaction between nitrogen fertilizer and water irrigation had no significant effect on the grain yield of sorghum hybrids. Additional nitrogen fertilizer applied under dry conditions reduced both grain and total dry matter production, and when applied under wet conditions produced gains in grain or dry matter production of only 1% to 4% for the high and low yielding groups. Additional irrigation water produced 61% to 77% additional grain under low and high fertilizer levels for high and low yielding sorghum groups. Additional irrigation water produced 8% to 38% more plant dry matter under low and high fertilizer levels