Sulfur Applications for No-Tillage Cotton and Comparison of Soil Sulfur Testing Methods

Symptoms of sulfur (S) deficiencies have been increasingly observed in Tennessee cotton during recent years. Field cotton trials were conducted at over 10 different locations across Tennessee during 2014-2016. Five S application rates of 0, 10, 20, 30, and 40 lb S/acre were tested at each location in a randomized complete block design with four replicates. Soil available S level, leaf S concentration, lint yield, and fiber quality were determined on a plot basis. The effects of S application rate on leaf S concentration were frequently significant at early bloom, but less significant at late bloom. Leaf S concentration generally increased as S application rate went up. The effects of S application on lint yield were significant at some locations. Application of 10 lb/acre of S was adequate for cotton production and increased lint yield by 11 to 14% relative to zero S on the S responsive locations. Effects of S application rate were sometimes significant on soil residual S after cotton harvest. Leaf S concentration at early bloom frequently had a significant regression with S application rate. Lint yield significantly regressed with S rate at several locations. There was a significant regression between post-harvest ammonium acetate extracted soil S and S application rate at some locations. The correlation between the two soil S exacting methods: Mehlich 3 extracted soil S and ammonium acetate extracted soil S varied with locations. In conclusion, more attention is needed to S management for cotton under no-tillage in the mid-South.