Greenhouse Measurement of Available Sulfur Using Radioactive sulfur

Abstract Available sulfur was determined in a greenhouse experiment with 30 surface soils from the Southeastern United States by growing cotton plants at six levels of applied sulfate‐sulfur, 0, 2, 4, 8, 16, and 32 ppm. The A value technique involving radiosulfur was used as an index of available sulfur. Sulfur A values varied from 9.8 ppm. to 42 ppm. A high degree of correlation was obtained between A values and the percent sulfur in the control plants. Growth responses from applied sulfate‐sulfur were also related to percent sulfur in the control plants and to A value sulfur in the soil. The total uptake of sulfur also was related closely to the total available sulfur in the soil ( A value plus fertilizer sulfur). A sixteen‐fold increase in the rate of sulfur addition increased the A value by approximately 20%.