Correction of manganese deficiency in barley crops on calcareous soils. 3. Application of elemental sulphur

Abstract

Infield experiments elemental sulphur (0 to 126 kg ha-1), incorporated in mixed and compound fertilizers with superphosphate (19 to 39 kg ha-1P) and manganous sulphate (0 to 16 kg ha-1Mn) was applied to calcareous soils of southern Yorke Peninsula, South Australia. The response of barley was measured in terms of grain yield, dry weight, and the manganese, phosphorus, and sulphur content of the shoots. Elemental sulphur (40 mg) alone or in compound fertilizers was incubated with 20 g surface soil for up to 52 weeks. The rate of oxidation of the sulphur and its effect on extractable manganese was measured. During 52 weeks' incubation, 20 to 50 per cent of the sulphur added to the soil was oxidized. The sulphur had little effect on the amounts of divalent and easily-reducible manganese extracted from the soil. Grain yields were increased by application of manganese and by increasing the amount of phosphorus applied from 19 to 39 kg ha-1. Elemental sulphur increased grain yield only at the low rate of phosphorus application. In one experiment a greater response to sulphur was obtained in the absence than in the presence of applied manganese. Sulphur applied with low amounts of phosphorus increased the uptake of manganese and phosphorus in the barley shoots sampled at stem extension in one experiment. In another experiment the effect on phosphorus content was not significant. Sulphur uptake was not affected. In no case did sulphur prevent the occurrence of manganese deficiency and its use to increase manganese availability and hence barley yields on these soils is not justified.