Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2017
Publication Date: 10/15/2017
Citation: Burke, J.J., Ulloa, M. 2017. Stress responses of commercial cotton cultivars to reduced irrigation at flowering and maximization of yields under sub-optimal subsurface drip irrigation. Journal of Cotton Science. 21:290241.
Interpretive Summary: The gradual depletion of the Ogallala Aquifer in the Southern High Plains of Texas over the past fifty years has resulted in reduced well capacities for cotton irrigation. This study initially investigated cotton cultivar responses to reduced irrigation amounts from flowering to harvest; and then evaluated season long water deficits and the impact of the timing and amount of irrigation. Low levels of water-stress were observed among 19 commercial cultivars provided 5 mm of drip irrigation per day throughout the growing season. A broad range of water stress levels was observed when the plants received 2.5 mm of irrigation from flowering through maturity. Cultivars exhibiting a mild water-stress response when water was reduced at flowering also showed similar responses whether they were watered with 2.5 mm per day or 17.5 mm once a week from planting through maturity. Cultivars that exhibited a large response when water was reduced at flowering exhibited greater yields when watered once a week with 17.5 mm rather than 2.5 mm of irrigation daily. In summary, this study showed diversity in water-deficit stress responses among commercial cotton cultivars, and showed that altering the timing of drip irrigation can significantly enhance yields of water-deficit stress sensitive cultivars.
Technical Abstract: The gradual depletion of the Ogallala Aquifer in the Southern High Plains of Texas over the past fifty years has resulted in reduced well capacities for cotton irrigation. This study initially investigated cotton cultivar responses to reduced irrigation amounts from flowering to harvest; and then evaluated season long water deficits and the impact of the timing and amount of irrigation. In 2013, field-grown cotton was irrigated with 5 mm per day via subsurface drip until flowering. Half of the plants were maintained on 5 mm per day irrigation, while the other half received 2.5 mm per day. Stress responses were tracked using a chlorophyll fluorescence bioassay. With the exception of Phytogen 802, all of the cultivars studied showed relatively low stress levels as exemplified by efficiency of quantum yield values between 1.7 and 2.3 under the 5 mm per day irrigation regime. Genetic differences were observed within the efficiency of quantum yield values; however, all of the cultivars performed well under the high water regime. Reducing irrigation levels from 5 mm per day to 2.5 mm per day at flowering produced a range of stress levels (efficiency of quantum yield) from 0.28 to 0.54. Four of the commercial cultivars were grown in replicated plots receiving either 2.5 mm of irrigation per day or 17.5 mm of irrigation once a week. Plant responses to this limited irrigation were evaluated using a chlorophyll fluorescence stress bioassay previously reported by Burke. Varietal differences in plant stress were detected for the two irrigation strategies. Changes in plant size, boll production, and timing of cutout were observed. Two varieties exhibited no yield differences between the irrigation regimes, while two varieties showed yield decreases (25% and 20%) under the 2.5 mm daily irrigation regime.