Paddy soils developed from red earth [pH 5.2-5.9, organic matter 1-3.1% and total phosphorus (P) 0.022-0.044%] were used in present experiment. Field experiments applied phosphatic fertilizer were carried out in Jinhua and Quxian area of Zhejiang province. Contents of soil available phosphorus were determined by four conventional egtractants, i.e. 0.511M NaHCO₃ (Olsen),0.025 N HCl+0.03N NH₄F (Bray),0.05 N HCl+0.025 N H₂SO₄ (Nelson) and 0.3 N NaOH+0.5 N Na₂C₂O₄ (Al-Abbas).