In order to investigate the release behavior closer to real conditions, soil release essays were carried out under aerobic conditions in plastic container containing 50 g of sandy soil (Table ) with 75% water saturation. The experiments were performed at 3, 7, 15 and 30 days, using a single pellet for each container, the pellet weight was standardized to 300 mg of P per kg of soil. After each release period the solid residues samples were removed from the soil and characterized by XRD; potassium and calcium were extracted from the soil by HCl (0.05 Mol/L) and KCl (1 Mol/L) methods, respectively; and phosphorus was extracted from soil using Mehlich 1 method .