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 under fallow, rhizosphere and non-rhizosphere soils of crops, trees and grasses from Aridisol, and forest rhizosphere and nonrhizosphere 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 fractions due to the action of both acid and alkaline phosphatase showed 41.3–86.7 % of water-soluble fraction, 50–84.1 % of NaHCO3 fraction, 14.6–25.9 % of NaOH fraction and 8.0–19.2 % of HC1 fraction was hydrolyzed under different vegetation. The rate of organic phosphorus hydrolysis by acid and alkaline phosphatase was initially rapid followed by a gradual declining rate, which was constant after 8 h onwards for acid phosphatase and after 9 h onward till 24 h for alkaline phosphatase. At initial stage (\4 h), the rate of hydrolysis by acid phosphatase was almost doubled than alkaline phosphatase. The result indicates that acid phosphatase was 8.8–13.8 % more efficient as compared to the alkaline phosphatase toward hydrolysis of different soil P fractions, while the residual P fractions were hydrolyzed 17.3 % more by alkaline phosphatase than acid phosphatase. Among the different P fractions, the residual P was most resistant and water soluble and NaHCO3-P was most susceptible to phosphatase enzymes.