Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: January 11, 1996
Publication Date: N/A
Interpretive Summary: The effect of initiation time of crop irrigation on optimizing yield and water use efficiency is not considered by irrigation scheduling methods that control water application during the growing season. Irrigating early can minimize water stress but soil temperature is lowered which slows crop growth. Two beginning times for early season irrigation of cotton were compared where soil was covered with polyethylene film or left bare using high frequency drip irrigation. Irrigating early when cotton seedlings had three main stem nodes (EIP) was compared with delaying irrigation until there were seven main stem nodes (LIP). Irrigation reduced soil temperature more in bare soil than under polyethylene film. Soil temperatures under polyethylene film were 2.8 degrees C greater during the EIP and 4.3 degrees C greater during the LIP than in bare soil. Lint yields for cotton grown under polyethylene film was the same for both starting times of early irrigation. Since plant height was increased by early irrigation but yield response was inconsistent suggests that plant height at first bloom is not a good indicator of final yield and early irrigation reduces the efficiency of irrigation water use.
Technical Abstract: A two-year cotton field study investigated the effect of initiation time of irrigation for high frequency irrigation on soil temperature, plant growth, and final yield using bare soil and polyethylene film covered beds. Early Irrigation (EI) started automated irrigation when seedlings had three main stem nodes and Delayed Irrigation (DI), was delayed until there were 7 main stem nodes. The period when only the EI was irrigating was designated 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 multiple depths. Soil temperatures in bare soil were higher at all depths in the DI than in the EI during the EIP. Soil temperatures under clear polyethylene were higher than under the white and black film. In EI average soil temperatures under polyethylene films were greater than those in bare soil (1 degree C to 5 degrees C during the EIP and 4 degrees C during the LIP). Plants were tallest in the EI for bare soil and the polyethylene films. At first bloom plants growing in the polyethylene film were taller than in bare soil. Average yield produced with polyethylene film was similar in both irrigation treatments. Lint yields in bare soil were in 1994 when EI produced higher yield than DI.