Sulfur is one of the nine major nutrients needed by crops. Being a structural component of amino acids, sulfur is essential for the formation of various plant proteins and enzymes. Additionally, sulfur is found to improve nitrogen use efficiency and improve root growth. Cotton crops need about 9 to 18 lbs. of sulfur per bale of cotton produced. In recent decades, sulfur deficiency has become common in many parts of the country. When sulfur is deficient in soil, cotton plants show yellowing of younger leaves. Remember that nitrogen deficiency produces similar yellowing symptoms, but they appear in older leaves. Soil tests show soil sulfur levels below 10 ppm or 20 lbs/acre indicate sulfur deficiency. Most of the cotton growing states recommend application of 10 to 20 lbs. of sulfur when soils are found to have low levels of it. Many sulfur-containing fertilizers are available in the market. As many producers use UAN as nitrogen fertilizer, use of UAN mixed with ATS (Ammonium thiosulfate) is a best option to apply sulfur. Use of UAN + ATS fertilizer that has 28% N and 5 % S is desirable for soils low in sulfur. Sulfur application at planting is strongly recommended to get the maximum benefit from its application.
