Fluid Nitrogen/Sulfur Formulations to Mitigate Sulfur Deficiencies and Maximize Cotton Yields in the Upper Southeast Coastal Plain

Six trials were conducted over two years to evaluate the use of differing fluid formulations of nitrogen (N)/sulfur (S) containing fertilizers in upland cotton. The objectives of the study were to evaluate the response of upland cotton to side-dress N sources with varying N/S ratios to ascertain if higher proportions of S are needed to maximize lint yields and nutrient status. The N/S sources were granular urea and ammonium sulfate and fluid source with the analyses 32-0-0, 24-0-0-3S, 24-0-0-6S, and 24-0-0-9S. Granular versus fluid N/S source were evaluated at 100 lb N per acre and across S application rates of 0, 10, 20 and 30 lb S per acre. Fluid N/S sources were compared in a factorial arrangement with three N rates 60, 100, and 140 lb N per acre. All sites were responsive to N and S rates when petiole and leaf nutrient concentrations were measured during the first week of bloom. Fluid N/S sources that were injected produced higher petiole N concentrations than broadcast urea/ammonium sulfate. Sulfur responses depended on soil type, residual S soil concentrations, and environment yield potential. Sulfur rates above 30 lb S per acre produced cotton that was “rank” and hard to defoliate. If sites were S responsive high N application rates cutout normally due to S deficiencies.