Effects of Tillage and N Fertilizer on Cotton Growth, Yield, and Fiber Quality.

Increasing restrictions on ammonium nitrate have spurred interest in alternative sources of N fertilizer, including urea-ammonium sulfate (UAS). However, UAS has not been widely tested, particularly in row crop agriculture. A cotton (Gossypium hirsutum L.) field study was conducted in Central Alabama from 2009 to 2011 on a Coastal Plain soil (Marvyn loamy sand; fine-loamy, kaolinitic, thermic Typic Kanhapludult) comparing UAS to two common granular fertilizers [urea, ammonia sulfate (AS)] under both conservation and conventional tillage systems. The overall objective was to determine the influence of UAS on cotton growth parameters, yield, and fiber quality. Cotton was fertilized with 101 kg N ha^-1 urea, AS, or UAS 5 to 6 wk after planting each year. Plant growth characteristics were evaluated 3 to 4 wk before defoliation, and cotton yield and fiber quality were determined on the machine-harvested lint. Tillage had little influence on plant growth, while UAS and/or AS tended to produce the largest aboveground, root, and total biomass, as well as the largest number of bolls and lint yield in 2009 and 2011 compared with urea. Both tillage and fertilizer source had minimal influence on cotton fiber quality. Results suggest that UAS could be a suitable N fertilizer for cotton producers. However, more research is needed to determine the long-term influence of UAS on soil acidity and N loss compared to AS and urea, as well as the economics of these N sources in cotton production systems.