Role of Sulfur in Cotton Production

Sulfur is present in both inorganic and organic forms and around 90-95% of soil-S is in the organic fraction. Soil sulfate is used by plants and soil organisms, or adsorbed on to soil particles. Sulfates are readily leached from soils especially those with a sandy texture.

Elemental sulfur in the soil is converted to sulfate by bacteria. All soils contain low levels of at least some of these bacteria species, which rapidly increase in number when elemental sulfur is added. Sulfur should be applied ‘little and often’ because of sulfur’s propensity for leaching.

Application

The standard S recommendation is 10 lb/A, applied either pre-plant or at sidedress with Nitrogen. S fertilization is important where higher rates of N are used due to increased plant biomass, thus allowing the N:S ratio to stay optimum. As sulfur leaches readily in sandy soils, sulfur fertilization is most important on sandy, low organic matter Coastal Plain soils. Sulfur deficiencies commonly appear even with an adequate soil program when heavy leaching has occurred due to heavy precipitation. Foliar S applications can alleviate mid-season deficiencies and should be applied at 14 day intervals up until first bloom.