Solubility of Added Phosphates in a Phosphate Saturated Soil

When a soil is allowed to react with phosphate solution for five days, the adsorption is gradual. But on prolonged contact, the adsorption reaches a steady value at higher concentration. As the soil tends towards saturation with soluble phosphorus, the availability is increased. When to the soil initially treated with soluble phosphate to its optimum phosphate fixing capacity, further phosphatic fertilizers are added, there appears to be no risk of fixation and hence availability of added phosphorus is not likely to be affected. The different forms of phosphates applied in native and phosphate saturated soils follow the following trend of availabilities: calcium phosphate > potassium phosphate > aluminium phosphate > ferric phosphate.