Transformation of Phosphates Varying in Citrate and Water Solubility in a Calcareous Soil after Incubation with Cattle Dung

Six phosphatic fertilizers containing different proportions of citrate soluble and water soluble phosphorus were applied to a calcareous soil at the rate of 0, 25, 50 and 100 ppm P with and without pre-incubation with cattle dung. Initially, water soluble P was transformed into saloid-P, Al-P and Fe-P which changed into Ca-P with time. Incubation of fertilizers with dung prior to their application in soil retained higher amount of saloid-P and available P for longer period. Per cent recovery of saloid-P, Al-P and Fe-P increased with water solubility of the fertilizer. In dung treated and untreated soil 19.35 and 7.45 ppm, respectively of organic P was mineralized during 12 weeks. Individually, only Fe-P contributed significantly to available P in the soil not incubated with dung followed by Al-P and saloid-P. The contribution of Ca-P was negligible. In dung treated soil, saloid-P contributed significantly followed by Al-P, Fe-P and Ca-P in decreasing order.