Responses of three early maturing corn hybrids to nitrogen fertilizer

Little information is available on the responses to N fertilizer of adapted, short-season corn (Zea mays L.) hybrids differing in grain N concentration. The influence of three rates of N fertilizer on grain and stover yields, N accumulation, and partitioning of N between stover and grain of three 95- to 100-d relative maturity hybrids AgriPro (AP) 175, Pioneer (P) 3906 and P3737, was studied in two irrigated experiments at Oakes, ND, in 1989 and 1990. The soil was a Maddock sandy loam (sandy, mixed Udorthentic Haploborolls) low in available N. Marked yield responses to N fertilizer were obtained, but the N fertilizer X cultivar interactions were not significant for 11 yield and N characteristics. Hybrid AP175 averaged over N fertilizer rates yielded 9 and 7 bu/acre more than P3906 in 1989 and 1990, respectively. There were no significant differences in grain yields between AP175 and P3737. Grain N concentration of P3906 at maturity in 1989 was 14 and 9% greater than that of AP175 and P3737, respectively. The corresponding increases in 1990 were 15 and 7%, respectively, Differences in grain N concentration due to hybrid did not result entirely from dilution effects. For instance, AP175, the highest grain-yielding hybrid, accumulated 8 lb/acre less grain N in both years than did P3906, the lowest yielding hybrid. The N use efficiency (NUE) (lb grain/lb N in above-ground plant parts) was relatively constant for individual hybrids, and averaged over N rates ranged from 68 in both years for AP175 to 61 and 60, respectively, for P3906 in 1989 and 1990. Grain of P3906 in both years was a more concentrated N source than grain of P3737, and especially of AP175, grown under similar conditions.