Availability Indices of Phosphorus in Paddy Soils

Abstract

Using soils used for rice production throughout Thailand, a study was made to compare available phosphorus estimates and rice plant phosphorus uptake, using air dried and submerged incubated soil, for the different phosphorus extration techniques. The results indicated that the soil should be incubated under submerged conditions for three weeks before extraction. All available phosphorus estimates based on the use of different extracting solutions (Bray Ii (0.03N NH4F + 0.1N HCI), Losen Edta (0.5m NaHCO3pH 8.5) and Olsen EDTA (0.5M NaHCO3 + 0.02M EDTA) showed highly significant correlations with phosphorus uptake by the rice plant. However, the most significant relationship was obtained using the Olsen EDTA technique.