Effect of different levels and sizes of walnut seed residues on phosphorus availability and alkaline phosphatase activity in calcareous soil

A laboratory experiment has been carried out in the College of Science-University of Salahaddin to study the effect of different levels (0,5,10 and 15%) and sizes(250 and 1000 mu m) of walnut seeds residues and (160mg.kg(-1)) phosphorus fertilization on the concentration of phosphorus availability and alkaline phosphatase activity in calcareous soil during 15 and 30 days period of incubation, the experimental design in factorial complet randomize design (C.R.D) with three replications. The results indicated that the application of different levels of walnut seed residues decreases the concentration of phosphorus availability and alkaline phosphatase activity, however the results revealed that combination between levels and sizes of sieved walnut seed residues and phosphorus fertilizer significantly (p <= 0.05) affected the alkaline phosphatase activity and the concentration of available phosphorus, the highest values (29.633 mu gPNPg(-1).hr(-1)and 6.442mg.kg(-1)) have been recorded in treatments combination received 1000 mu m, 15% walnut seed residues and phosphorus fertilizer, respectively.