Relationship of N Deposition to Grain Yield and N Response of Three Maize Hybrids1

Abstract

Three maize (Zea mays L.) hybrids were evaluated for their grain yield under different levels of spring‐applied anhydrous ammonia fertilizer. The N content in the vegetative tissues and grain was analyzed at the midsilk stage and at 60 days after pollination. Of the three hybrids tested, B14 ✕ Oh43 (intermediate type) responded to moderate levels of N fertility, B73 ✕ Mol7 (high‐fertility type) had a great response to additional N, and Pioneer 3732 (low‐fertility type) performed well under low levels of N fertilizer but reached maximum yield with only 67 kg N/ha. There are at least three factors affecting grain yield which distinguish the high‐fertility from low‐fertility type hybrids. These include 1) ability to absorb additional N fertilizer after the midsilk stage, 2) rate and duration of grain fill, and 3) rate of zein synthesis (kernel N sink) affected by N fertilizer. When the kernel genotpye of Pioneer 3732 was modified by pollinating with pollen from B73 ✕ Mol7, the developing F1 kernels not only had grain protein concentration higher than Pioneer 3732 F2 kernels but had dry matter accumulation kinetics complementary to Pioneer 3732 and B73 ✕ Mol7. This complementation resulted in larger kernels than those obtained with selfed kernels of either hybrid. This result indicates the kernel sink is more important than the vegetative source in affecting kernel weight and grain yield.