I.J. PARTRIDGE

Abstract

Biosuper pellets (mixtures of rock phosphate, and sulphur inoculated with sulphur-oxidising bacteria Thiobacillus) were made from three rock phosphates from the Pacific region and compared with single superphosphate in field experiments which lasted three years. Experiments were conducted on soils, known to be deficient in phosphorus and sulphur, on two hill sites in south western Viti Levu in Fiji, using two legumes, Siratro (Macroptilium atropurpureum) and stylo (Stylosanthes guianensis).
Only superphosphate gave a response within three months but it was outyielded by biosupers made from grade A and calcined grade C phosphates thereafter. Stylo responded more strongly to biosuper than Siratro but was similar with superphosphate. Over the three years, the accumulated yields of stylo from biosuper (grade A), biosuper (calcined grade C) and superphosphate were 52, 35 and 30% higher respectively than the unfertilised control.