Cotton Response to Irrigation Timing and Use of Enhanced Efficiency Nitrogen Fertilizer and Biosolids

In a three year field trial at the Judd Hill Foundation in NE Arkansas, we evaluated cotton response to four N fertilizer treatments,100 lb N applied as either: 1) urea, 2) enhanced efficiency N (trade name ESN),  3) urea + 300 lb/A biosolids (trade name Top Choice) or 4) unfertilized check  (0 N) grown using three furrow irrigation regimens: 1) Late Start (weekly irrigation started at first flowers, 2) Early Start (irrigation started at early squaring) and 3) Rainfed (no irrigation). We documented plant response to water and nutrients including pace of nodal development, square and boll retention using weekly in-season plant monitoring with the COTMAN system. Fertilized cotton yielded similar amounts regardless of urea formulation or addition of biosolids; plants in the unfertilized check produced the lowest yields. In the hot, dry summers of 2010 through 2012, fertilized cotton receiving irrigation produced significantly higher lint yields than rainfed. An early start time for irrigation produced highest yields. If irrigation start time was delayed, fertilized plants developed fewer main stem fruiting branches by first flowers, shed more small bolls in the first two weeks of flowering, reached physiological cutout (NAWF=5) later, and produced 16% lower lint yields compared to cotton grown with early start irrigation.