author(s)
R Sathya Priya, C Chinnusamy, P Murali Arthanari and P Janaki

abstract
An attempt was made in the present investigation to study the effect of new herbicide combination molecules like bispyribac sodium, metamifop, almix, clincher on rhizosphere soil microflora of direct seeded rice (DSR) at the research farm of Wetland Farm, Tamil Nadu Agricultural University, Coimbatore, India. The present study results showed that the herbicide treatments significantly inhibited the development of microbial populations in the soil and the degree of inhibition varied with the types of herbicide. Increasing trend of inhibition on growth of microbial populations was observed from the initial effect until 30 days after herbicide spray (DAHS). No inhibition was observed at 30 DAHS to harvest stage. A gradual raise was observed in the population of micro-organism like bacteria, fungi and actinomycetes with the application of herbicide combination in the rhizosphere soil of DSR. Among different herbicide treated plots, post emergence (POE) application of bispyribac sodium 4% SE + metamifop 10% SE at 70, 56 and 42 g a.i./ha + wetter at 100 ml/ha recorded maximum microbial populations and dehydrogenase activities. The study suggests that the herbicide application to soil cause transient impacts on microbial population growth, when applied at recommended field application rate.