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

Previous studies have demonstrated higher corn (Zea mays L.) yield potential for prolific corn hybrids (more than one ear) compared to nonprolific hybrids (one ear). However, little is known about the relative contribution of the second ear to total yield at various N levels. This study compared yield responses to N rates of 56, 140, and 224 kg N ha - 1 of prolific Hybrids A (1202 x Mo 17) and B (I117 x B73) with responses of nonprolific Hybrid C (Pioneer 3320) at a uniform low plant population density. All three hybrids gave a positive yield response to N applications. The prolific hybrids increased both in apical ear weight and in subapical ear weight and number in response to N rate- Averaged over N rates, Hybrid A yielded 24% and Hybrid C 14% higher than Hybrid 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 the apical ears in the prolific hybrids. Total potential yield in response to N application appears to be highest in Hybrid A because of second ear formation. Factors contributing to yield increases from N applications in prolific Hybrid A included, in order of importance, an increase in the number of subapical ears, an increase in apical ear weight, and an increase in the subapical ear weight. Contrary to previous reports, apical and subapical ear weight increased simultaneously, with increasing N rates