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Defoliation Effects on Grain Fill, Stalk Rot, and Lodging of Grain Sorghum

Dep. of Agronomy, Univ. of Nebraska, Lincoln, NE 68583-0817.

^* Corresponding author.

Yield response to defoliation in grain sorghum [Sorghum bicolor (L.) Moench] can be influenced by time and intensity of leaf removal. Limited information is available for defoliation x environment interactions and the defoliation response of yield-related traits, stalk rot, and basal stalk lodging. This study was conducted to examine the effect of time and extent of defoliation on hybrid grain sorghum in three eastern Nebraska environments in relation to yield components, duration and rate of grain filling, nonsenescence period, stalk rot, and lodging. Four levels of defoliation (0, SO, 95, and 100%) were applied to plants at 10 d preanthesis, anthesis, 10 d post anthesis, and 20 d post anthesis. Defoliation significantly decreased yield components, grain-fill duration, grain-fill rate, and the nonsenescence period, while increasing the occurrence of stalk rot. The most pronounced effects on all traits occurred when plants were defoliated prior to or during anthesis. Significant defoliation level x time interactions and environment x defoliation treatment interactions were observed for all traits. Variance component estimates indicated that environmental interaction comprised 18 to 25% of total variation for the yield components, 5% for stalk rot, and 50% for lodging. Use of defoliation in a limited number of environments may not prove effective in evaluating tolerance to lodging. Small environmental interactions for the stalk rot response suggest that observations from only a few environments are necessary for its evaluation.

Received for publication September 5, 1989.