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Early Season Irrigation Influence on Soil Temperature and Cotton Yield

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


A two-year cotton field study investigated the effect of initiation time of irrigation for a high frequency irrigation scheduling method on soil temperature, plant growth, and final yield using bare soil and polyethylene film covered beds to expand the range of soil temperatures. An Early Irrigation (EI) treatment started automated irrigation when seedlings had 3 to 4 main stem nodes. The other treatment, Delayed Irrigation (DI), treatment was delayed until squaring began (7 to 9 main stem nodes). The period when only the EI treatment was irrigating was designated as the early irrigation period (EIP) and following this was the late irrigation (LIP) when both the EI and DI treatments were irrigated. Clear, white, and black polyethylene film was installed in the plots immediately before the EI treatment started and was removed after first bloom. Soil temperature was measured in the center of the bed with thermocouples placed at 50, 100, 200, and 500 mm below the surface. Soil temperatures in bare soil were consistently higher at all depths in the DI treatment than the EI treatment during the EIP of both years. This was caused by cooling from evaporation since the soil surface moisture of the EI treatment was higher than the DI treatment. Soil temperatures under clear polyethylene were higher than under the white and black film. In the EI treatment average soil temperatures under polyethylene films were greater than those in bare soil (1 °C to 5 °C during the EIP and 4 °C during the LIP). Plants were tallest in the EI treatment for bare soil and the polyethylene films for all measurement dates during the early and late irrigation periods. At first bloom in both years plants growing in the polyethylene film were taller than in bare soil in both irrigation treatments. In 1993 and 1994 average yield produced with polyethylene film were similar in both irrigation treatments. Lint yields in bare soil were the same in both irrigation treatments in 1993 but in 1994 the EI treatment produced higher yield than the DI treatment.

Reprinted from Proceedings of the 1996 Beltwide Cotton Conferences pp. 517 - 522
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998