Improving Nitrogen Fertilizer Management for Overhead Sprinkler-Irrigated Cotton in the Western US

Land and canal infrastructure means that level-basin surface irrigation in raised beds is the predominant irrigation system for cotton production in central Arizona.  High yields (i.e. statewide averages 1500 lb lint ac^-1) are achieved with typical 36 inch or more inches of in-season surface irrigation. However, up to 20 % of applied surface irrigation water can deep percolate below 5 feet.  Nitrogen fertilizer recovery is a low 15 to 30 % in the surface irrigation systems.  Overhead sprinkler irrigation would likely achieve the same high lint yields of surface irrigation with less water, and with greater N recovery efficiency.  We tested different N fertilizer management approaches in a linear-move sprinkler system in with DP 1044 in Maricopa, AZ in 2014.  Nitrogen treatments included a pre-plant nitrate-N soil profile (3-ft) test-based approach, an NDVI-based treatment, and soil test N management with Agrotain Plus.  Nitrogen fertilizer as urea ammonium nitrate was sprayed/dribbled in an 18-inch wide band in the bottom of each furrow just prior to an irrigation. Nitrogen recovery at first open boll and final lint and seed yields will be reported.