Crop residues can be a potential source for available phosphorus (P) in South Australian soils. The objective of this study was to compare the effects of crop residues and an inorganic P source on soil P pools and P availability in an incubation experiment. The soil was a Red Chromosol under a long-term wheat-pasture-fallow rotation. Crop residues (4 Mg ha^-1) of pea (Pisum sativum L.), canola (Brassica rapa L.) and wheat straw (Triticum aestivum L.), or triple super phosphate (TSP) as an inorganic P source were added. The soils were kept at 60% field capacity and at 25ºC temperature. Resin extractable P, microbial P, carbon (C) and nitrogen, and biological activity (respiration) were determined during 12 weeks of incubation period and were related to residue characteristics such as soluble C and P contents, and C:P ratio .