Dry Matter Accumulation in Maize in Response to Defoliation

Prior investigations have reported the effect of leaf removal at various stages of development on yield of corn (Zea mays L.), but none have studied the pattern of grain dry matter accumulation. Therefore, this study was conducted to evaluate the effect of leaf loss on dry matter accumulation patterns of corn grain and grain yields. Defoliation was begun 10 days after 50% silking and continued at 10-day intervals for the next 40 days. Leaf removal treatments consisted of removing 1) no leaves (control), 2) all leaves below the ear, 3) all leaves above the ear, and 4) all leaves. Dry matter accumulation was monitored by sampling ears at 5-day intervals from 50% silking to black layer formation. Regardless of severity, defoliation within 30 days after silking significantly reduced total accumulated dry matter. Complete defoliation was more detrimental (6.4 to 82% yield loss) than partial defoliation (1.5 to 32.7% yield loss). These losses varied with time (after 50% silking) of treatment application. The effect of removing all leaves above the ear was not significantly different from that obtained by removing all leaves below the ear. Yield component affected most by leaf loss, for the overall treatment period, was kernel weight (12.7 to 53% decrease). However, number of kernels was greatly reduced (62.3%) when all leaves were removed 10 days after silking. Complete leaf removal thereafter and partial leaf removal affected number of kernels considerably less (approximate decline, 20%). This study showed that severe leaf loss at the onset of silking and until at least 10 days after 50% silking decreased grain yields because of fewer kernels. However, yield decreases associated with less severe leaf loss or loss 20 days or more after 50% silking were largely related to a decline in kernel weight. In addition to providing a better understanding of patterns of dry matter accumulation, these data may be useful to individuals required to estimate grain yield after a significant loss, to natural causes, in plant leaf area.