Preplant irrigations on the Southern High Plains represent an increasingly larger portion of the total irrigation water pumped and can be extremely inefficient, particularly with traditional application systems. One possible method of reducing preplant evaporation losses and increasing water use efficiency is the use of subsurface drip irrigation (SDI). A field experiment was established to compare two preplant irrigation scenarios at two irrigation capacities with water delivered by spray, LEPA, and SDI systems.

High rainfall from March through June of 1999 resulted in few significant differences in lint yield and water use efficiencies (WUE) due to limited versus full preplant irrigation scenarios. However, abnormally low rainfall in July and August of 2000 resulted in limited preplant treatments having significantly lower yields (792 vs. 864 lb lint/acre) and WUE (46 vs. 54 lb lint/acre-in.) than comparable full preplant treatments. In both 1999 and 2000, less than 15% of the annual precipitation occurred during the critical cotton development months of July and August. This occurrence highlighted differences in irrigation delivery systems under limited irrigation capacity conditions. SDI treatments resulted in increased lint yields of 42 and 45% over spray and 25 and 22% over LEPA and increased WUE by 40 and 44% over spray and 20 and 18% over LEPA in 1999 and 2000, respectively. Cotton loan prices were significantly affected by irrigation system and preplant scenario treatments in 1999, and by irrigation capacity treatments in 2000.