Phosphate requirement of paddy or upland were investigated by adsorption/desorption experiment under oxidized and reduced conditions in five red soils. Results showed that P adsorption capacity increased with the increase of added P concentration. Phosphate adsorption curves of soils fitted well with Langmuir equation. The range of the maximum capacities of P adsorption (Qm) ranged from 794.22 to 956.75 mg/kg under oxidized condition and from 867.31 to 1 195.62 mg/kg under reduced condition. The capacity of desorption P increased with the increase of the capacity of P adsorption, P desorption rate of soils was lower under reduced condition than that under oxidized condition. Phosphorus requirement was calculated from the Langumir equation on the basis of P concentration in soil solution at 0.2 mg/kg. Phosphorus requirement of soils increased after water logging.