Changes in microbiological characteristics of rice soil by post-emergence herbicides

A field study was conducted in an Inceptisol with summer season rice to evaluate the degradability of different post-emergence herbicides applied alone or in combinations in terms of microbiological characteristics of rhizosphere soil. Five different herbicides (bispyribac-sodium, metamifop, chlorimurone-ethyl, metsulfuron-methyl and cyhalofop-butyl) were applied as an individual or in combination at post-emergence stage (15 DAS). A wetting agent (agrisol) was also used with some herbicides to increase the effectivity of applied herbicides. Application of different herbicides had inhibitory effect on microbial population and their activities in soil after application, but their effects were not pronounced and the soil properties were restored. Although herbicides applied at different rates but their degradability was almost equal and they took only 30 days or less period for complete degradation except cyhalofop-butyl and bispyribac-sodium + metamifop, which ware applied 80 g and 140 g/ha, respectively and found completely degraded before harvest.