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Cotton Irrigation Using Subsurface Drip: Growth, Cutout and Yield Depend on Amount of Water Applied

W.R. DeTar, S.J. Maas and J.R. McLaughlin


The main objective was to find the optimum level of water application to Acala Maxxa and Pima S-7 cottons, on sandy soil. The field test consisted of 6 different water application rates through a subsurface drip system on a 2-acre plot. Cutout occurred 4 days earlier for each 10% decrease in the full-canopy pan coefficient, for both Pima and Maxxa. The Maxxa was ready to defoliate 4.8 days earlier for each 10% decrease in the pan coefficient. The driest Maxxa treatment was ready to defoliate 37 days earlier than the wettest treatment. Plant height was found to be a linear function of the total depth of water applied from planting to July 7, with a 2.7" gain in height for every 1" of water applied. The concept of nodes-above-white-flower (NAWF) did not work well for determining the cutout date of the wetter treatments. A slight deficit irrigation treatment was found to produce optimum yields, which occurred at a full-canopy pan coefficient of 74% for Pima and 80% for Maxxa. Maximum yields for Maxxa occurred at a pan coefficient of 94%. The yield on Maxxa dropped off sharply with application rates higher than 105% of pan evaporation. By comparison, the Pima yields did not decrease at all with the wetter treatments; they remained essentially constant for application rates above 100% of pan evaporation. Using a slight deficit irrigation not only saves water, but because of the smaller plants, reduces PIX requirements, and defoliation is much easier. Because of the shorter season produced by deficit irrigation, a generation of whitefly development can be avoided.

Reprinted from Proceedings of the 1998 Beltwide Cotton Conferences pp. 417 - 421
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998