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Abstract
Laboratory experiments were conducted to evaluate the effect of phospho-compost applied at different rates through using kinetic approach on the P release. Different kinetic models were tested to select the best one(s) describe data; however, modified Freundlich, parabolic Diffusion and Hoerl equations gave the highest ones. The rate constants of used models indicated that rate of P release from PR to compost influenced by rate of PR applied to compost, meanwhile phosphate desorption from phospho-compost system consistently influenced by several factors such as pH of the media and residence time. Fractionation of phosphorus in soil treated with phospho-compost and phosphate rock acidified at different rates of citric and oxalic acids were conducted in order to evaluate the phospho-compost for using it as phosphate fertilizer. Results indicated that application of compost treated with 15%PR (T2), increased the extractable phosphorus fraction extracted with H2O (WS) as compared with the other treatments. The acidification of PR by citric acid at different rates of 2 and 4 % applied to sandy soil gradually increased the WS fraction as compared with control (PR). The extractable fraction of P by sodium bicarbonate varied significantly for the investigated treatments and time of incubation. Data revealed that the extractable fractions of phosphorus by EDTA were varied according to treatment applied and/or incubation time.
In field experiment application of phospho-compost at different rates of phosphate rock at (10, 15 and 20%) increased the weight of 100 seeds. Result showed that compost treated with 15% phosphate rock increase the yield production by about 20% as compared with 10% PR. Increasing rate of phosphate rock (20%) increased the yield production by 67% as compared with compost+10%PR.