ارزیابی فعالیت آنزیم فسفاتاز قلیایی و قابلیت استفاده شکل‌های مختلف فسفر برای گیاه لوبیا (Phaseolus vulgaris) در تعدادی از خاک‏های آهکی تیمار شده با لجن فاضلاب شهری

To evaluate the relationship of various P fractions and alkaline phosphatase activity with bean indices growing in 10 calcareous soils, amended with municipal sewage sludge from Chaharmahal-Va-Bakhtiari province, a greenhouse research was carried out. Soil samples were incubated for one month with sludge at a rate equivalent to 1% (w/w). Then, the P fractions, including P adsorbed by Fe and Al oxides (]NaOH+CB]-P), occluded P (CBD-P) and P absorbed by Ca (HCl-P), were determined by Olsen and Summers' sequential fractionation procedure. Furthermore, total P, organic P and residual P were determined. Also, alkaline phosphatase activity was measured. A pot experiment in a completely randomized design with three replications in the ten soils was done to evaluate the bean plant indices. The results showed that the amount of P fractions decreased in the following order: HCl-P>residual-P>]NaOH+CB]-P > OP>CBD-P. The results also indicated that alkaline phosphatase activity was significantly correlated with CBD-P fraction, organic P and total P. In addition, significant correlations were found between ([NaOH+CB]-P) and HCl-P and plant shoots. In general, the results of this research showed that P fractionation method appears to be a powerful tool to identify the P status and availability in the soils amended with sewage sludge.