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