Can cotton seed size mitigate preemergence herbicides injury?

Preemergence herbicides (PRE) have become integral for weed control in cotton (Gossypium hirsutum L.), especially with the prevalence of glyphosate-resistant Palmer amaranth (Amaranthus palmeri S. Wats.). However, PRE herbicides have the potential to injure cotton seedlings. Previous research has shown that a larger seed size can compensate for early season stresses which could mitigate potential PRE herbicide injury. In this study, we evaluated growth and yield of two cotton varieties with different seed sizes (large and small) in response to three PRE herbicides alone and in combination. Percent visual injury, biomass, plant heights, stand counts, lint yield, and fiber quality were obtained to make comparisons between seed sizes and PRE treatments. In both years, the large-seeded variety had a higher biomass at 3-leaf stage. However, both varieties had “grown out” of the herbicide injury at 42 days after planting and the early season vigor of the larger seed did not result in higher lint yield. The small-seeded variety had greater yield in both years of the study. This may be due to the genetics or yield potential of the small-seeded variety, or bolls containing smaller seeds typically have a greater number of seeds with more opportunity for lint production. Cotton treated with diuron had the most visual injury and decreased biomass. The results from this study will allow growers to make more informed decisions with regards to seed size, vigor, and PRE herbicide choices. If crop injury is likely, a larger seeded cotton variety may mitigate potential early season injury; however, seed size did not have an impact on final lint yield.