Supplemental Sulfur for Kentucky Wheat Production.

The need for sulfur in Kentucky wheat production is often questioned. Reported yield responses to sulfur in Kentucky have been limited, but are more common in surrounding states. Ammonium thiosulfate (ATS) is a 12-0-0-26S product that is compatible with the liquid urea-ammonium nitrate (UAN) commonly used in wheat production. In addition to supplying N and S, ATS is reported to be a weak urease and nitrification inhibitor. A study was initiated to determine the influence of ATS as a S source, but mixed with UAN. To separate any S response from any N loss inhibition response, another loss inhibitor containing both NBPT and DCD was used and compared with UAN alone and UAN plus ATS. The fertilizer N and S management at the four locations, with soils (well drained Paleudalfs and moderately well drained Fraglossudalfs) commonly used for wheat production, consisted of a split spring application of N with a total of 11 kg S ha^-1 as ATS. At three locations, the treatments were imposed at Feekes 2, and at Feekes 5 in the remaining site. Soil samples (0 to 10 cm and 0 to 30 cm) were collected prior to treatment addition. Tissue samples (flag leaves) were collected at Feekes 10.5, and grain was harvested for yield. Sites varied in soil S levels, ranging from 10 to 12 ppm Mehlich III extractable S at 0 to 10 cm and 7 to 16 ppm extractable S over the 0 to 30 cm depth increment. Yields, tissue S and N, and the tissue N/S ratio were different between sites, but not within sites among treatments. No benefit was observed either to ATS or the N inhibitor, above that of the untreated UAN, but all products were acceptable for winter wheat production in western Kentucky. Economics of the fertilizer source should be considered in developing a fertilizer management program.