Irrigation Scheduling with Temperature Thresholds

D.F. Wanjura, D.R. Upchurch, and J.R. Mahan


 
ABSTRACT

Irrigation of cotton was scheduled using a minimum 3-day irrigation cycle which was modified by temperature-thresholds (TT). The TT ranged from 2.5 to 7.0 hours of time that cotton canopy temperatures exceeded a threshold temperature of 28°C beginning on the second day after the last irrigation event. Irrigation cycles between the period Doy 159 and Doy 243 were 5.5, 4.6, 4.2, and 3.7 days, respectively, for treatments 7.0 TT, 5.5 TT, 4.0 TT, and 2.5 TT. Average canopy temperatures for the TT treatments were 29.7, 29.0, 28.5, and 28.5°C in the daytime when air temperature exceeded 28°C and total radiation exceeded 500 w/m2 during the period Doy 198 and Doy 243. During the period Doy 159 - 243 total irrigations of 26.7, 30.5, 34.4, and 41.3 cm were applied to treatments 7.0 TT, 5.5 TT, 4.0 TT, and 2.5 TT, respectively. Average canopy temperature and irrigation application varied among TT treatments but yield was not significantly affected. The lack of yield response to different amounts of irrigation was caused by a combination of stresses caused by Verticillium wilt, a severe infestation of Aphids, and 26.6 cm of rainfall during July to September. The range of TT treatments did result in differences in irrigation scheduling and average canopy temperature.



Reprinted from 1992 Proceedings Beltwide Cotton Conferences pp. 499 - 501
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998