Cotton Irrigation Scheduling: Which Approach is the Best Fit for Georgia?

Cotton (Gossypium hirsutum) is one of the most difficult crops to manage irrigation effectively due to the crop’s perennial physiology. In recent years, many new technologies have been developed to help improve irrigation management. The main objective of this study was to evaluate various irrigation management tools and to assist farmers in determining which method is best for their operation. Other objectives included monitoring soil moisture and determining the optimal irrigation application point of each method by logging total rainfall and irrigation distribution throughout the growing season. A three-year study was conducted at the University of Georgia (UGA) Stripling Irrigation Research Park near Camilla, GA where cotton was grown on loamy sand soil. A lateral movement, overhead sprinkler system equipped with a variable rate system allowed plots to be irrigated independently based on treatment. Irrigation treatments included 20- and 45-kPa weighted average soil water tension (SWT) measurements made using three Watermark SWT sensors placed in two of the three replicates. The UGA SmartIrrigation Cotton app (SI app), UGA Checkbook method, and a rainfed check were included in the trial. Each irrigation method was evaluated based on crop yield, irrigation water-use efficiency, and profitability. The analysis revealed significant variations in several metrics between treatments and validates the 45-kPa SWT threshold and SI app are top-performing advanced irrigation scheduling tools and showed the importance of advanced irrigation scheduling and the strengths and weaknesses of each method.