Study on the forms of organic and inorganic phosphorus(P) and their usefulness under available P depletion conditions through pot experiment.The results showed: amount of P absorbed by soybean supplied with nitrogen-fixation(N2-N) was larger 58.0% than urea supplication,but use efficiency was lower 3.3%.Inorganic P composing is O-P > Al-P > Fe-P > Ca10-P > Ca8-P > Ca2-P,organic P is MLOP>HROP>MROP>LOP,irrespective of nitrogen source supplication.For inorganic P,the main potential pool is Al-P and O-P for soybean supplied with N2-N,while supplication with urea is O-P.MLOP and MROP mineralization were promoted by soybean with N2-N,which contents decreased by 29.48 mg/kg and 14.16 mg/kg compared to no-plant CK treatment.In urea supplication treatment,MROP and HROP mineralization were higher than others,decreased by 12.47 mg/kg and 3.68 mg/kg,separately.These suggested that P absorbed by soybean with N2-N is larger than that with urea.