Effect of Partial Acidulated on Phosphorus Kinetics Release from Phosphate Rock Compared to Conventional Phosphate Fertilizers in Gypsum Soils

A soil column experiment was conducted to study phosphorus release kinetics from gypsum soils provided by partially acidulated phosphate rock, to compare with conventional phosphate fertilizers and soil ability to release phosphorus over time Under a controlled environment. Two fertilizer sources were evaluated, the first was phosphate rock partially acidulated with sulfuric acid at concentrations of 30%, 40%, 50%, 60%, 70%, the second source was traditional phosphate fertilizers, namely single superphosphate(SSP) and triple superphosphate (TSP). Sulfuric acid concentrations were added and thoroughly mixed with gypsum soil. Plastic column was filled with acidulated soil. A funnel was placed under each column to collect leachate. Irrigation water was applied at a constant depth for a month. From each column, the leachates were collected with interval time of 24 hours, the Soluble phosphorus in the leachate was measured daily over a one month. Among all treatments, the level of partial acidulated 70% superior to all treatments in increasing the phosphorus solubility, where gave the highest reached 7.491 mg L-1after on month. Conversely, the Soluble phosphorus was 3.015, 3.184 mg L-1 after 30 days for traditional phosphate fertilizers, SSP and TSP respectively. When soluble phosphorus data were subjected to kinetic equations, the results showed that the best equation to describe the release of phosphorus was zero-order equation, where it gave the highest coefficient of determination (R2) and the lowest standard error (SEe). Moreover, the highest phosphorus release rate constant was observed in the partial acidulated treatment of 70% compared to the other treatments.