Cotton Irrigation Management Using Linear-Move Sprinklers in the Southwestern USA

Cotton produced in the arid regions of the Southwestern USA has been predominately irrigated using surface irrigation systems, which typically apply large volumes of water at each irrigation to meet cotton water requirements.  With the cost of irrigation water ever increasing, more cotton growers in the region are investing in moving sprinkler irrigation systems. To assist cotton growers in the region with the transition from surface irrigation management, cotton irrigation studies were initiated in 2014 with a linear-move sprinkler irrigation (LMSI) system in central Arizona. The project objectives are to develop irrigation management and scheduling technologies for cotton under LMSI. The 2014 study was conducted from May through Nov. at the Maricopa Agricultural Center (MAC), in Arizona, on a 6.9-ha site. The ditch-fed system lateral was ≈ 370 m and it included six spans plus an overhang. Nozzles along the lateral were spaced every 1.02 m. Cotton was planted on May 1 on 180-m long beds, spaced every 1.02 m. Treatments imposed in late May included several ETc estimation models that were used to determine irrigation for full ETc replacement plus a stress treatment that received 70% of full irrigation. All treatments, except the stress treatment were based on 45% soil water depletion of the root zone obtained from the soil water balance for each treatment. Results on irrigation water use, measured soil water contents and cotton yields, and irrigation treatment comparisons will be reported.