Band Spacing Effects of Dual‐Placed Nitrogen and Phosphorus Fertilizers on Corn

Band spacing of P fertilizer potentially affects many factors which influence fertilizer P efficiency. Band spacing affects soil‐P fertilizer contact, probability of root‐P fertilizer contact, the time that roots contact the P fertilizer, the distribution of P fertilizer in the band, and energy requirement during application. Four field experiments were conducted to evaluate the effect of band spacing of dual‐placed N and P fertilizers on corn (Zea mays L.) grain yield and P uptake. Four band spacings of 30, 45, 60 and 75 cm were applied with three P application rates in 1983 and 1984, and five rates in 1986. Two application depths of 7.5 and 15 cm were applied in 1983 and 1984. The N rates were 200 kg N ha−1 in 1983 and 1986, and 75 and 150 kg N ha−1 in 1984. Applied P was less effective and N more effective in terms of grain yield as band spacing increased indicating a different optimum band spacing for P than for N. This caused the net effect of band spacing of dual‐applied N and P fertilizers to be nearly neutral. Seven‐leaf stage and ear‐leaf P were not affected by applied P at the high N application rate, but at the low N rate P concentrations increased as P rate increased indicating the importance of adequate N for P uptake early in the growing season. The wide band spacing of 75 cm performed poorly in grain yield response to applied N at the high N rate compared to the low N rate probably because of loss of N during application. Band spacing of N and P fertilizers did not cause significant variation in corn growth. Plants growing directly over the dual‐placed band did not yield more or less than other plants regardless of band spacing.