Kinetics of Dissolution of Phosphate Rock, Partial Acidulated Phosphate Rock and Tri Super Phosphate in Calcareous Soil

A study was conducted to evaluate kinetics of phosphorus release from dissolution of phosphate rock (PR), partial acidulated phosphate rock (40%-PAPR) and tri super phosphate (TSP) in calcareous soil by using Batch equilibrium technique for five incubation times. The water soluble phosphorus was measured at end of each incubation times. Six kinetic equations were tested to know which one is the best in description of phosphorus release to soil. The results showed that were gradual increases in the released p from the dissociated 40%-PAPR and TSP. Liberation of p from phosphate rock was so weak with time. The accumulated amount of the released phosphorus at end of incubation time (720h.) was higher in TSP. The phosphorus release curves showed good liberation of phosphorus in PAPR and TSP. The Elovich equation was the best in explaining successfully phosphorus release and the rate of phosphorus release constant (kd) values were 4.38 h(-1) and 15.11 h(-1) in PAPR and TSP respectively.