Changes in the Phosphorus Availability as Influenced by the Electro-chemical Properties of Acidic Soils under Submerged Conditions

The electro-chemical changes in flooded soils largely control the beneficial and detrimental effects thereof on rice production and these changes, particularly those in pH and Eh, influence the available P status in the soil. A pot experiment was conducted by raising rice in an acid soil under flooded condition, with recommended doses of N and K application and application of P as various sources, either singly or in combination. The changes in pH, Eh and available P content of the soil under crop were progressively monitored. The pH of the soil increased towards neutral range and drop in the Eh was evident in all the treatments upon submergence resulting in the increase in available P₂O₅ content of the soil at different intervals of crop growth. Although no significant difference in Eh values of different treatments was noticed, there was a significant difference in the available P₂O₅ content of soil treated with compacted fertilizers containing MAP and MAP+S over other treatments. While the electro-chemical properties of flooded soils are well known, the transformation of compacted fertilizers in such environments is new.