Organic P fractions in a calcareous soil.. .

Organic amendments are an excellent source of phosphorus (P) for plant production in sustainable agriculture. This paper describes the short term (100 days) effects of sewage sludge (SS), cow manure (CM) and poultry manure (PM) on the soil organic P (OP) fractions and their availability to wheat in a calcareous soil of Kerman Province . The experiment was arranged on a completely random design consisting of control (with no P fertilizer) and two levels (2 and 4%) of SS, CM and PM in four replications. Organic amendments markedly (pCM>PM. A significant correlation were observed between labile organic P with soil available P (r=0.92**), P uptake by wheat (r=0.92**) as well as between MLOP and shoot dry weight (r=0.96**), showing that labile and moderately labile organic P fractions have more contributors to available P than the others. These results suggest that adding of organic amendments can increase P availability and plant growth due to increase in soil OP fractions especially labile and moderately labile organic P fractions.