SULFUR, PHOSPHORUS, AND MOLYBDENUM INTERACTIONS ON THE CONCENTRATION AND UPTAKE OF MOLYBDENUM IN SOYBEAN PLANTS (Glycine max)

Abstract

At Haryana Agricultural University, we conducted greenhouse studies to observe the effect of applying sulfur, phosphorus, and molybdenum on the concentration and uptake of molybdenum in parts of soybean plant grown in a soil deficient in available sulfur (4.2 ppm) and phosphorus (4.2 ppm), but sufficient in available molybdenum (0.1 ppm). We applied sulfur as potassium sulfate at 0, 40, 80, and 120 ppm, phosphorus as monocalcium phosphate at 0, 40, and 80 ppm, and molybdenum as sodium molybdate at 0 and 1 ppm. The applied sulfur significantly depressed the concentration of molybdenum in leaves, pod husks, and grains, indicating an antagonistic relationship between molybdenum and sulfur, whereas phosphorus and molybdenum increased the concentration, indicating a synergistic relationship between molybdenum and phosphorus. The molybdenum concentration in the plant parts at maturity was in the order: grain > leaf > pod husk > stem. The application of 40 ppm sulfur significantly increased the total uptake of molybdenum in 45 and 110 days of sampling, which was governed by yield and concentration of molybdenum. The total molybdenum uptake in leaves, stems, pod husks, and grain at both stages of growth significantly increased with applications of 80 ppm phosphorus and 1 ppm molybdenum. The molybdenum concentration in leaves gave a significant correlation with molybdenum uptake at both stages: r = 0.835 at 45 days, and r = +0.717 at 110 days. Nevertheless, molybdenum did not influence the grain yield of soybean. More than 58 percent of the total molybdenum in plants was absorbed during the first 45 days of growth of the soybean plants. During the reproductive phase, however, more molybdenum was translocated to reproductive parts, and at maturity about two-thirds of the total molybdenum was contained in the grain and pod husks.