The effect of pre-drought mepiquat chloride management on cotton sensitivity to drought during peak water demands.

Drought can substantially limit yield in cotton, and water loss in any crop is closely associated with plant growth, but studies addressing the effects of growth management on drought sensitivity are limited in cotton. We tested the hypothesis that aggressive plant growth management would decrease cotton sensitivity to drought during flowering and boll development. Cotton was grown at a field site near Tifton, GA during the 2021 and 2022 growing seasons. Treatments included mepiquat chloride (MC) strategies (aggressive and untreated) and two water availability treatments (well-watered and drought-stressed). At approximately 2 weeks after first flower, water was withheld from the drought-stressed treatment for a three-week period, and well-watered plots were kept irrigated using a regionally accepted water balance approach. Measurements throughout the season included heights, nodes, length of the fourth internode below the plant terminal, nodes above white flower (NAWF), and soil moisture. End-of-season measurements included lint yield, fiber quality, and yield component assessments. MC treatment significantly affected plant height, mainstem node number, 4th internode length, and cutout date. Soil moisture was significantly reduced during the drought stress period. Aggressive MC treated plots showed less drought-induced yield reduction than untreated in response to drought, but did not reach the same lint yield, boll density, or uniformity as well-watered, untreated plots. Aggressive MC treatment produced greater seed surface area, seed number boll-1, and boll mass. Aggressive MC management may prevent drought-induced yield reductions but penalize yield under well-watered conditions. Among the potential components driving yield, boll number per unit land area was the most important contributor. Our findings highlight the potential for aggressive MC management to mitigate drought risk, but future efforts should evaluate this possibility in a broader range of cultivars adapted for production in the southeastern United States and with the inclusion of a moderate MC treatment. • Aggressive mepiquat chloride treatment can mitigate drought risk but also penalize yield in a well-watered environment. • Aggressive mepiquat chloride treatment produced greater seed surface area, seed number boll-1, and boll mass. • Boll density was primarily associated with lint yield. • Only fiber uniformity and strength were impacted by aggressive mepiquat chloride treatment. [ABSTRACT FROM AUTHOR]