Six alkaline-calcareous and two acid soils were treated with saturated solution of monocalcium phosphate {Ca(H2PO4)2].H2O], (2.1 pH, 9.92% P, 5.76% Ca) for five minutes. Solutions were extracted and analysed immediately. Phosphorus, Fe and Al contents of the extracts decreased and pH increased with increasing CaCO3 content of the soils. Soils retained 39.3 to 84.2 per cent of added P within five minutes. Remaining part of the extracts were incubatedfor eight weeks at 25±i°C temperature. By X-ray analysis of the precipitates, brushite (CaHPO4,2H2O), potassium taranakite (K3H6Al4PO4)8.18H2O), metakingite (Al3(OH)3(PO4)2.4H2O), parahopeite (Zn3(PO4)2,4H2O), andstrengite (FePO4,2H2O) orthorthombic were the reaction products identified in the extracts of alkaline-calcareous soils, while in acid soils, the reaction products were bushite (CaHPO4,2H2O), potassium taranakite (K3H6Al5(PO4)8,18H2O) and metakingite (Al3(OH)3(PO4)24H2O).
Monocalcium phosphate, reaction products, alkaline-ealcareous and acid soils
