I.J. PARTRIDGE¹ and J.W. WRIGHT²

¹Department of Primary Industries, Toowoomba, and
²Bundaberg, Queensland, Australia

Abstract

Established legumes on soils derived from granodiorite responded more strongly to sulphur than to phosphorus. These soils cover some 2400 km² of the better grazing lands of the coastal Burnett region. Wynn cassia at one site (bicarbonate-extractable P 7 mg/kg; S0₄-S 2 mg/kg) responded to phosphorus only when sulphur was applied; shrubby stylos at the other site (soil P S mg/kg; S0₄-S 4 mg/kg) responded only to sulphur. Nitrogen concentration in leaf tips of cassia increased 30% (to 3.34% N) with P and S at 10 kg/ha, whereas that in stylo increased only 10% (to 2.45% N).
As the previously recommended application (55 kg/ha/yr single superphosphate) for native pasture/legumes was economically marginal, the use of sulphur-fortified super (45% S) at lower rates could prove attractive.