Comparison of enzyme activity with depth under tea plantations and forested sites in south India

The soil profile of Western ghats are often many meters deep. Since majority of enzyme studies deal only about the surface soils, very little is known about the nature of the soil and soil enzymes inhabiting in the deeper regions. It was our objective to determine the vertical distribution of various enzymes over the latosols under tea cultivation as well as the nearby forested soils. Soil samples collected from eight different depths of tea cultivated area and from a nearby virgin forest were analysed for activities of various enzymes like acid phosphatase, alkaline phosphatase, aryl sulfatase, urease and protease. In general, the enzyme activities declined with depth. While the phosphorus availability was considerably higher up to a depth of 125 cm, exchangeable K and soil organic matter (OM) content decreased drastically below a depth of 25 cm. No obvious variation was seen in the pH measured in both forested and cultivated soils. At any given depth, the acid phosphatase activity was significantly higher than alkaline phosphatase activity in both the soils. The soils under tea cultivation were richer in urease activity than what was estimated in forested soils. The protease activity was almost nil below 50 cm of soil depth. At any particular depth the urease activity observed in the soils under tea plantations was higher than that of forested soils. Surprisingly, the acid phosphatase activity did not show significant correlation with soil available phosphorus. The activities of all enzymes estimated in tea soils have shown positive correlation with soil OM content and so also with forested soils.