Abstract

Environmental alterations leads to fluctuations in the soil microbial population and soil enzyme activities, as different weather parameters affect microbial biota and their activities in rhizospheric soil of crop. An agroclimatic study was carried out to study the effect of environmental alterations on soil microbial population and enzyme activities in rhizospheric soil of rice and wheat crop. Rice and wheat crop were grown under field conditions and under temperature gradient tunnel which was maintained at 4-5°C higher temperature than open field temperature. Soil samples were taken from rhizospheric soil of rice and wheat. Microbial population was enumerated by serial dilution spread plating technique. Statistically significant higher microbial population of total bacteria, nitrogen fixers and P-solubilizers was found in rhizospheric soil samples taken from temperature gradient tunnel as compared to soil samples taken from rice and wheat grown under field conditions. Fungal population was found to be statistically, significantly higher in soil samples taken from field conditions in case of rice but, higher in soil samples taken from temperature gradient tunnel in case of wheat crop. Activities of alkaline phosphatase and dehydrogenase were assessed by using para nitro phenl phosphate (PNPP) and tri phenyl tetrazolium chloride (TTC) as substrates, respectively. Enzymes activities were found to be significantly higher in rhizospheric soil samples taken from temperature gradient tunnel. Microbial population and enzyme activities were found over a broad range of temperature but, maximum microbial and enzyme activity was found only at and near optimum conditions.

Key words: Environmental alterations, microbial activities, rice, temperature gradient tunnel, wheat.