Improving Nitrogen Fertilizer Management for Surface-Irrigated Cotton in Arizona

In central Arizona the common regional practice of N fertigation was compared to knifed N injections in surface-irrigated cotton (i.e., level furrow irrigation).  We also compared ammonium sulfate with urea ammonium nitrate as an N fertilizer source for fertigation.  Additionally, we compared reflectance-based nitrogen fertilizer management with soil test-based management.  Canopy reflectance-based vegetative indices correlated well with in-season biomass and plant N.  Lint yields and N use efficiencies were similar among the N managment strategies.