The effect of natural and artificial reduction on P extractability from soils used for rice production and the relation of these values to response to fertilizer P were investigated. Soil solution P increased from a mean of 3.8 mg P·kg−1 soil for naturally oxidized slurries of 28 soils to 19.8mg P·kg−1 when the soils were naturally reduced. The mean values were further increased to 40.8 and 45.3 mg·kg−1 when the soils were reduced with 0.1M Na2S2O4 and 0.2M Na2S2O4, respectively. These P-values compare with 18.2 mg kg−1 when the dry soils were extracted with Bray No. 1 extractant. When the yields of rice were correlated with solution and extracted P, the R2's for the quadratic relationships were 0.40**, 0.31*, 0.34**, 0.30*, and 0.55** for the naturally oxidized, the naturally reduced, 0.1M Na2S2O4, 0.2M Na2S2O4 and Bray No. 1, respectively. The Cate-Nelson calculation confirmed the superiority of the weak acid Bray extractant and the critical value of 8.6 mg P·kg−1 soil needed for satisfactory yields of rice.