Effects of fertilizer on concentrations of copper, molybdenum, and sulfur in subterrranean clover (Trifolium subterraneum)

Abstract

In pot experiments, subterranean clover (Trifolium subterraneum) was grown on four soils; two lateritic podzolic soils, a red-brown earth and a calcareous sand, to which various combinations of phosphorus (0 to 45 ppm as potassium dihydrogen orthophosphate), sulfur (0 to 45 ppm as calcium sulfate), copper (0 to 10 ppm as copper sulphate) and molybdenum (0 to 1 ppm as sodium molybdate) had been added. Applications of sulfur and copper had little effect on the dry weight of the clover tops on any soil, and none of the fertilizers affected dry weight on the calcareous sand. On the other soils, dry weight was increased by phosphorus, and by molybdenum when applied in combination with phosphorus. The copper treatment consistently increased the concentration of that element in the tops of the plants. On the lateritic podzolic soils and the red-brown earth, sulfur generally increased copper and sulfur concentrations but decreased that of molybdenum; phosphorus decreased copper and sulfur but increased the concentration of molybdenum. On the calcareous sand, application of sulfur had no effect on copper but decreased molybdenum and increased sulfur concentration; treatment with phosphorus decreased the concentration of copper but had no effect on sulfur or molybdenum in the plant tops. There were significant interactions between all treatments. These are discussed in relation to fertilizer practice and animal health.