Background: Soil microbial diversity is indispensable to maintain functional diversity and enzyme-mediated critical soil processes that detoxify soil from environmental pollutants, like pesticides. Use of pesticides can have potential implications for nutrient cycling in soil. Repeated pesticide use may permanently impair soil health decreasing its productive capacity. Thus the present study was carried out to assess the effect of different concentrations of the fungicide Mancozeb on the activities of alkaline phosphatase, protease, urease, amidase and asparaginase in silt loam soils of orchards of Kashmir Himalaya, India.
Questions: 1.What is impact of Mancozeb on activity of various soil enzymes?
2. How does it affect activity of soil microorganisms?
3. Does the impact vary at different application rates?
Methods: Alkaline phosphatase (Tabatbi and Bremner, 1969; Eivazi and Tabatabai, 1977), Protease (Lad and Butler, 1972; Rangaswami et al., 1994), Urease (Tabatabai and Bremner, 1972), Amidase (Frankenber and Tabatabai, 1980ab) Asparaginase (Frankenber and Tabatabai, 1991) and Dehydrogeanse (Casida et al., 1964)
In comparison to untreated control, application ten times the recommended concentration (N10) of pesticide increased soil phosphates activity by about 41 % after 14 days of incubation. However, after 28 days of incubation, activity declined by about 30 % under different application treatments. Pesticide induced stimulation of protease activity was recorded up to 21 days of incubation and thereafter a 17 % decrease in the activity was observed in comparison to untreated control. Though all the pesticide application treatments had an inhibitory effect on urease activity, the N100 treatment had more consistent inhibitory effect. Amidase activity was stimulated up to 21 days of incubation irrespective of the concentration of pesticide used. Asparaginase activity, however, was reduced from 12 % to 72 % in comparison to control for most of the incubation period. Microbial activity, evaluated through measurement of dehydrogenase activity, was stimulated in response to different concentrations of the pesticide. Soils are capable of tolerating moderate levels of stress. Soil enzyme activity is the net result of complex process of synthesis, persistence, stabilization and catalytic behaviour of enzymes therefore response to an applied disturbance is a complex event. Overall, Mancozeb had significant effect on the activity of soil enzymes which may have potential implications for the nutrient cycling and plant productivity.