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Crop Water Status Control With Temperature-Time Threshold Irrigation

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  032136,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.14012) @2003
Authors:   Donald F. Wanjura, Dan R. Upchurch, James R. Mahan
Keywords:   Irrigation scheduling, Water stress, Canopy temperature

Center pivot and subsurface drip irrigation systems can accurately apply variable quantities of irrigation. A robust irrigation timing protocol that can function in variable environments is needed to maximize crop use of available water. Canopy temperature (TC) has been successfully used to time irrigation applications for well-watered crop growing conditions. The cumulative daily time that TC exceeds a crop specific temperature threshold, designated as stress time (ST), is used to indicate the need for irrigation. The ST value that generates the irrigation signal is the time threshold (TT). Manipulation of the TT value changes irrigation frequency and seasonal irrigation quantity. This paper describes a procedure for estimating the relationship between TT for cotton and quantity of water input. Data were analyzed from multiple studies that included a common control TT of 330 min/day above a canopy temperature threshold of 28 C as the irrigation signal criteria for well-watered cotton. Daily ST averaged over the irrigation season was correlated with cotton yield and water input. A procedure for identifying control TT to establish different crop water status levels is described. Average TT values were 408, 468, and 528 min./day, which corresponded with control TT values of 330, 390, and 450 min/day. These control TT should result in different water application amounts during the growing season and produce different cotton yields.

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