UPTAKE OF SULFUR BY 4 COTTON CULTIVARS GROWN UNDER FIELD CONDITIONS

There has never been an intensive study of the sulfur (S) nutrition of cotton (Gossypium hirsutum L.) when grown under field conditions. Fie ld studies were conducted on two non-irrigated soils to evaluate the S -uptake characteristics of four selected cotton cultivars that are rep resentative of those produced in the Southern United States. Four cult ivars with diverse genetic backgrounds, Deltapine 90, Coker 315, Payma ster 145, and Stoneville 825 were grown on a Norfolk fine sandy loam ( fine loamy, siliceous, thermic, Typic Kandiudults) and a Decatur silt loam (clayey, kaolinitic, thermic, Rhodic Paleudults). Whole plants we re collected at two-week intervals over the growing season starting at 15 days after planting. The plants were partitioned into leaves, stem s, burs, seed, and lint, and analyzed (except for lint) for S. Total S uptake when averaged over both soils and all four cultivars was 20.4 (+/-9.4) kg/ha [or 2.7 (+/-0.7) kg S per 100 kg lint produced]. Sulfur uptake on the Norfolk soil (15.6 (+/-8.5) kg/ha) was lower compared t o the Decatur soil [25.1 (+/-7.9) kg/ha]. There were no cultivar diffe rences in total S uptake on the Norfolk soil, but total S uptake on th e Decatur soil was affected by the interaction between sampling date a nd cultivar. The concentration of S and S uptake by some plant parts w ere affected by the interaction between sampling date and cultivar, ho wever, cultivar differences were not consistent among soils or over th e growing season. Maximum daily accumulation of S occurred during the final two week sampling period at the end of the growing season (cumul ative heat unit 1193-1444) during which an average of 29.5% of the tot al S was accumulated.