Efficiency of Phosphatases in Mobilization of Native Phosphorus Fractions Under Different Vegetation

Abstract

The efficiency of acid and alkaline phosphatase toward hydrolysis of different P fractions was studied underfallow, rhizosphere and non-rhizosphere soils of crops, trees and grasses from Aridisol, and forest rhizosphere and non-rhizosphere soils of Inceptisol. Native P of soil was fractioned into four different pools: water-soluble inorganic phosphorus(Pi) and organic phosphorus (Po), NaHCO3(0.5 M)-extractable Pi and Po, NaOH (0.1 M)-extractable Pi and Po, HCl(1.0 M)-extractable Pi and Po and residual P after digestion to H2O2:H2SO4(1:4). The decrease in different Po fractionsdue to the action of both acid and alkaline phosphatase showed 41.3–86.7 % of water-soluble fraction, 50–84.1 % ofNaHCO3fraction, 14.6–25.9 % of NaOH fraction and 8.0–19.2 % of HC1 fraction was hydrolyzed under differentvegetation. The rate of organic phosphorus hydrolysis by acid and alkaline phosphatase was initially rapid followed by agradual declining rate, which was constant after 8 h onwards for acid phosphatase and after 9 h onward till 24 h foralkaline phosphatase. At initial stage (\4 h), the rate of hydrolysis by acid phosphatase was almost doubled than alkalinephosphatase. The result indicates that acid phosphatase was 8.8–13.8 % more efficient as compared to the alkalinephosphatase toward hydrolysis of different soil P fractions, while the residual P fractions were hydrolyzed 17.3 % more byalkaline phosphatase than acid phosphatase. Among the different P fractions, the residual P was most resistant and watersoluble and NaHCO3-P was most susceptible to phosphatase enzymes