Abstract

                                The pre-emergence herbicide, Nitrofen at 1.5 lit. a.i./ha imposed an initial depres- sion of the general microbial activity which after 55 days steadily increased. The rhizosphere soil of ragi crop revealed more number of #zotobacter following the herbi- cide treatment than were found in non-rhizosphere and control soils. The rhizosphere soil at all stages of crop growths harboured more number of microorganisms tolerant to 500 ppm of the herbicide than the other soil samples. Bioassay of the herbicide treated soil using mustard seedling revealed that the toxicity of Nitrofen was lost within 50-65 days after application.

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