A flow technique was applied to investigate the effect of organic acids with low-molecular-weight on phosphorus release from 3 soils:2 calcareous soils and 1 acidic soil (red earth).It was indicated that the release of soil phosphorus was significantly stimulated by organic acids for all of 3 soils tested.For calcareous soils, the ability of mobilizing soil phosphorus of organic acids followed the order:oxalic ≥ citric> malic>tartaric acid.As for red earth,the release of soil phosphorus was highly correlated with soil aluminum and iron extracted,and the mobilizing ability of organic acids for phosphorus followed the order:citric>oxalic>malic>tartaric acid.Regression analysis revealed,that parabolic diffusion equation was applicable to describe the release kinetics of soil phosphorus,as affected by organic acids (r>0.94). Both citric and oxalic acids increased the P diffusion coefficients significantly in all of 3 soils.However,remarkable increase of P diffusion coefficients by tartaric acid only occurred in acidic soil.