YIELD CONTRIBUTION OF APICAL AND SUBAPICAL EARS IN PROLIFIC AND NONPROLIFIC CORN

Previous studies have demonstrated higher corn (Zea mays L.) yield pot ential for prolific corn hybrids (more than one ear) compared to nonpr olific hybrids (one ear). However, little is known about the relative contribution of the second ear to total yield at various N levels. Thi s study compared yield responses to N rates of 56, 140, and 224 kg N h a - 1 of prolific Hybrids A (1202 x Mo 17) and B (I117 x B73) with res ponses of nonprolific Hybrid C (Pioneer 3320) at a uniform low plant p opulation density. All three hybrids gave a positive yield response to N applications. The prolific hybrids increased both in apical ear wei ght and in subapical ear weight and number in response to N rate- Aver aged over N rates, Hybrid A yielded 24% and Hybrid C 14% higher than H ybrid B in 1987. In 1988, they yielded 13 and 10% higher than Hybrid B . Yield of single ears of nonprolific hybrid was higher than that of t he apical ears in the prolific hybrids. Total potential yield in respo nse to N application appears to be highest in Hybrid A because of seco nd ear formation. Factors contributing to yield increases from N appli cations in prolific Hybrid A included, in order of importance, an incr ease in the number of subapical ears, an increase in apical ear weight , and an increase in the subapical ear weight. Contrary to previous re ports, apical and subapical ear weight increased simultaneously, with increasing N rates