A comparison of biosuper and superphosphate on a sandy soil in the monsoonal tropics of north Queensland

Biosuper, a biological fertilizer consisting of rock phosphate, elemental sulphur and an inoculum of sulphur-oxidising thiobacilli was compared with superphosphate as a source of phosphorus for Townsville stylo (Stylosanthes humilis) pastures on a deep sandy soil in Cape York Peninsula. The fertilizers were applied in the first year only, at rates varying between 24 and 84 kg of phosphorus ha-1. Harvests were made at the end of the first, second, and third growing seasons. Biosuper tended to be inferior to superphosphate in the first year with respect to dry matter and phosphorus yields, but over the three-year period the two fertilizers gave comparable results. At the higher rates of application, biosuper gave higher yields of sulphur ha-1, presumably because of its higher sulphur content and greater resistance to leaching then superphosphate. Under the conditions of the experiment (i.e. without maintenance dressings of phosphorus and sulphur) biosuper compared quite favourably with superphosphate and, for example, gave 3-year yields of 14,000 kg dry matter ha-1 at the lowest rate of application (24 kgP ha-1).