SULFUR, PHOSPHORUS, AND MOLYBDENUM INTERACTIONS IN RELATION TO GROWTH, UPTAKE, AND UTILIZATION OF SULFUR IN SOYBEAN

Abstract

The effect of sulfur, phosphorus, and molybdenum on the growth, uptake (milligrams/ pot) and utilization (percentage in plant of added sulfur) of sulfur was studied in the greenhouse on a light-textured soil deficient in sulfur and phosphorus, at Haryana Agricultural University, Hissar, India. The sulfur was applied at 0, 40, 80, and 120 parts per million; the phosphorus was applied at 0, 40, and 80 ppm, and molybdenum was applied at 0 and 1 ppm. The addition of sulfur to soil up to 80 ppm increased growth and grain yield of soybean; higher applications (120 ppm) significantly decreased the yield. The response to phosphorus was also observed up to 80 ppm, and the highest grain yield was obtained with the application of 80 ppm sulfur and 80 ppm phosphorus. There was no response in grain yield to molybdenum. The uptake of total and fertilizer sulfur by soybean plants increased significantly with increases in added sulfur and phosphorus to the soil. Total and fertilizer sulfur concentration (ppm) and uptake (mg/pot) indicated a strong synergistic relationship between phosphorus and sulfur in plants. The addition of molybdenum in the absence of phosphorus decreased the concentration and uptake of sulfur, showing an antagonistic relationship with sulfur. When phosphorus was applied, however, the antagonistic effect of molybdenum was overcome. The percentage utilization of sulfur decreased from 6.9 to 3.9 at 45 days and from 14.1 to 7.5 at 110 days with the 40− and 120-ppm sulfur levels, respectively. The application of phosphorus helped in the utilization of added and native soil sulfur, but molybdenum appeared to depress sulfur utilization. At maturity, grain and leaves had the highest amount of sulfur, and stems had the lowest. Fruiting parts, i.e., pod husks and grain, contained between 47 and 54 percent of fertilizer sulfur.