Grain Sorghum Yield Response to Nonuniform Stand Reductions
Nonuniform stand reductions caused by poor emergence, insect damage, or other factors, occur frequently in grain sorghum [Sorghum bicolor (L.) Moench] fields. This research was conducted to determine the effect of within-row skip patterns on grain yield and yield component compensation, particularly for hybrids differing in tillering ability. Dryland field studies were conducted at Manhattan (Reading silt loam, fine-silty, mixed, mesic Typic Argiudoll) and St. John (Naron fine sandy loam, fine-loamy, mixed, thermic Udic Argiustoll), KS, during 1988 and 1989. Two medium-maturity hybrids, DeKalb DK-46 and Pioneer 8500, were selected based on low and high tillering ability. Plots were three rows, with the middle row containing a within-row skip pattern. Results were analyzed separately by skip row, adjacent row, and average for the three rows. Skip lengths within a 7.6-m row were 0.9 m, 0.9 m repeated three times, and 2.7 m within the skip row, and the 0.9 m ✕ 3 pattern in all three rows. Yield of the skip row was reduced by every configuration bordered by control stand adjacent rows. Yield compensation from adjacent rows and within the skip row compensated for reduced stands, except for a 2.7−m skip resulting in 5.1% yield reduction, 64% uniformly spaced stand in all three rows with 6.9% yield reduction, and three 0.9 m within-row skips in all three rows with 10.9% yield reduction. Compensation was primarily in number of heads per plant and seeds per head. Difference in hybrid tillering response did not influence grain yield. Thus, yield reduction is likely only where skips result in severe plant spacing nonuniformity.
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