Effects of Irrigation Timing on Water Economy, Growth, and Yield of Water Stressed Cotton

Abstract

Aims: Objectives were to evaluate the effects of timed irrigations on plant biomass and seed-cotton production, plant leaf area, whole-plant transpiration, and transpiration per unit leaf area. Study Design: A complete randomized design with four replications. Place and Duration of Study: Study was conducted in the Drought Tolerance Laboratory at the Texas A&M AgriLife Research and Extension Center near Corpus Christi, TX during the 2014 and 2015 growing seasons. Methodology: One plant per pot of the cultivar Phytogen 375 was grown in the greenhouse; pots were irrigated during nighttime with 0.5 L of a modified Hoagland’s nutrient solution to prevent pot weight changes affecting the calculations of hourly daytime transpiration. A computerized system developed to convert whole-plant transpiration from changes in pot weight included an algorithm to remove nighttime weight data “noise” related to pot weight data collection when excess water drainage occurs, that otherwise would affect hourly and daily whole-plant transpiration calculations.  Results: The full irrigation treatments applied during different phenological stages had significant impact on production of biomass, leaf area, and seed-cotton, as well as whole-plant transpiration and transpiration per unit leaf area. Seed-cotton production per plant increased 49% in 2015 when irrigation was applied during MH-FB and FB-MB, but not when applied late during MB-OB. These effects could not be confirmed in 2014, although not significant numerical differences due to experimental data variation were pointing to comparable effects. Conclusion: The slope of the linear regression of seed-cotton on cumulative whole-plant transpiration (CWPT), which represents the overall impact of irrigation on plant seed-cotton production regardless of their timing, showed that seed-cotton per plant increased 1.063 and 0.554 g per L of CWPT increase in 2014 and 2015, respectively. This difference illustrates the effect of environmental conditions affecting the overall response of plant seed-cotton production to irrigation.