Comparison of precision and conventional irrigation management of cotton and impact of soil texture

Soil textural variability diminishes the effectiveness of conventional irrigation management. Variable rate irrigation (VRI) can address soil variability; however, users need guidance to prepare prescriptions for optimal water application. A study was conducted at Portageville, MO, USA, in 2016 and 2017 with the objective to compare yield and irrigation water use efficiency among three water-management treatments for cotton: rainfed, irrigated based on the USDA-ARS Irrigation Scheduling Supervisory Control And Data Acquisition (ISSCADA) system, and irrigated based on a water balance method. Sand content in the top 533 mm soil layer was estimated from apparent electrical conductivity (ECa). Yield values measured near an ECa observation were averaged to create a data set containing sand content and associated yield. Although the trend was for the rainfed treatment to have the lowest yield in both years, the yield differences among all treatments were not significant when sand content was not considered. A strong effect of sand content on cotton yield was observed in both seasons, although the slopes differed among the water management treatments in 2016. The ISSCADA system tended to have a higher irrigation water use efficiency in both seasons, but the difference was not significant in 2016 when total irrigation applications were low. The study is continuing at Portageville and other locations and the ISSCADA system is constantly being improved to better meet the needs of agricultural producers.