Effects of the Timing of Water Deficits on Cotton Water Economy, Growth, and Yield

Aims: This study was conducted to evaluate the effects of water deficits applied at different phenological periods on whole-plant responses of cotton grown under rain-sheltered conditions.

Study Design: A complete randomized design with four replications.

Place and Duration of Study: The study was conducted at the Drought Tolerance Laboratory at the Texas A&M AgriLife Research and Extension Center near Corpus Christi during the 2014 and 2015 cotton growing seasons.

Methodology: Individual plants of the commercial cultivar Phytogen 375 were grown in 13.5-L pots. Daily irrigation of individual pots was controlled with electronic timers and daily whole-plant transpiration was calculated lysimetrically from 10’-interval pot weights measured with electronic load cells. Plant measurements included height, leaf area, total dry biomass and seed-cotton production.

Results: With only few exceptions, the water deficit treatments had significant impact on plant’s production of biomass, leaf area, and seed-cotton, as well as whole-plant transpiration and transpiration per unit leaf area. The responses to these plant variables showed to be different between years as the environmental conditions were more stressful in 2014 than in 2015. Water deficits applied during first bloom (FB) to mid-bloom (MB) had the largest impact on plant growth, plant transpiration, and yield in both years; decreased dry biomass 32% in 2014 but had no effect in 2015, decreased seed-cotton 57% in 2014 and 23% in 2015, completely inhibited plant leaf area growth in both years, decreased cumulative whole-plant transpiration 46% in 2014 and 41% in 2015, decreased transpiration per unit leaf area 41% in 2014 and 37% in 2015.

Conclusion: Seed-cotton production per plant was most affected by water deficits during FB to MB stage (decreased 57% in 2014 and 23% in 2015), less affected during MB to open boll (decreased 49% in 2014 and 0% in 2015), and least affected during match head square to FB (0% in 2014 and 17% in 2015).