SULFUR RESPONSES BY LEGUMES ON SOILS DERIVED FROM GRANODIORITE IN SOUTH-EAST QUEENSLAND

Established legumes on soils derived from granodiorite responded more strongly to sulphur than to phosphorus. These soils cover some 2400 km 2 of the better grazing lands of the coastal Burnett region. Wynn cass ia at one site (bicarbonate-extractable P 7 mg/kg; SO4-S 2 mg/kg) resp onded to phosphorus only when sulphur was applied; shrubby stylos at t he other site (soil P 5 mg/kg; SO4-S 4 mg/kg) responded only to sulphu r. Nitrogen concentration in leaf tips of cassia increased 30% (to 3.3 4% N) with P and S at 10 kg/ha, whereas that in stylo increased only 1 0% (to 2.45% N). As the previously recommended application (55 kg/ha/y r single superphosphate) for native pasture/legumes was economically m arginal, the use of sulphur-fortified super (45% S) at lower rates cou ld prove attractive.