Effect of Delayed Nitrogen Availability on Cotton Yield in Varying Soils and Across a Range of Irrigation Regimes

Water and nitrogen are the two greatest limiting factors for cotton production. Irrigated cotton acreage in West Tennessee has grown steadily for several years. With supplemental irrigation, questions arise about how nutrients, especially nitrogen, will behave with respect to availability or possible losses. These questions are confounded even more because of the range of potential soil types that can be encountered within a field. Studies in Jackson, TN have shown distinct and different responses to irrigation amounts and timing on different soil types. Soils varied largely in water holding capacity and ranged from deep silt loams to shallow silt loams over sand to soils that are quite sandy throughout. Lower water holding capacity soils often require more water earlier to achieve optimal yields, which could create environments susceptible to leaching of nitrogen. With this in mind, we investigated the effect of delayed nitrogen availability via the use of a polymer-coated urea fertilizer. Our objective was to evaluate the effect of a timed-release nitrogen fertilizer on cotton yield and nitrogen use efficiency across a range of soils and irrigation regimes. Environmentally Smart Nitrogen (ESN) was used as a way to delay nitrogen release to the crop. ESN and ammonium nitrate were broadcast after planting and were each examined over the previously established range of soils and over a range of irrigation regimes. Leaf samples and cottonseed samples were taken to monitor nitrogen uptake. Results from a wet 2013 revealed higher yields from ammonium nitrate in the heaviest-irrigated low water holding capacity soils. Delayed nitrogen availability achieved similar yields when irrigation was delayed or at lower rates.