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

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Abstract
Greenhouse studies were conducted to observe the effect of applying S, P and Mo on the concentration and uptake of Mo in parts of soybean plant grown in a soil deficient in available S (4.2 ppm) and P (4.2 ppm), but sufficient in available Mo (0.1 ppm). S was applied as potassium sulfate at 0, 40, 80 and 120 ppm, P as monocalcium phosphate at 0, 40 and 80 ppm, and Mo as sodium molybdate at 0 and 1 ppm. The applied S significantly depressed the concentration of Mo in leaves, pod husks and grains, indicating an antagonistic relationship between Mo and S, whereas P and Mo increased the concentration, indicating a synergistic relationship between Mo and P. The Mo concentration in the plant parts at maturity was in the order: grain > leaf > pod husk > stem. The application of 40 ppm S significantly increased the total uptake of Mo in 45 and 110 days of sampling, which was governed by yield and concentration of Mo. The total Mo uptake in leaves, stems, pod husks and grain at both stages of growth significantly increased with applications of 80 ppm P and 1 ppm Mo. The Mo concentration in leaves gave a significant correlation with Mo uptake at both stages: r = +0.835 at 45 days, and r = +0.717 at 110 days. Nevertheless, Mo did not influence the grain yield of soybean. More than 58% of the total Mo in plants was absorbed during the first 45 days of growth of the soybean plants. During the reproductive phase, more Mo was translocated to reproductive parts, and at maturity about 2/3 of the total Mo was contained in the grain and pod husks.
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