Rice, Tillage, Zero tillage, Rhizobium, Azotobacter

A field study was conducted in an inceptisol with rainy season rice to evaluate the effect of different tillage systems vis-à-vis different weed control measures on the survival and growth of total bacteria, actinomycetes, fungi, Rhizobium and Azotobacter in rhizosphere soil. Four types of tillage system were evaluated viz. (i) conventional-conventional (ii) conventional-zero (iii) zero-conventional and (iv) zero-zero tillage systems. Among weed control measures comparative effect of hand weeding and recommended herbicidal application (butachlor as pre emergence and fenoxaprop ethyl + ethoxysulfuron as post emergence) were tested along with a weedy check. The results of the investigation revealed that maximum growth of different microorganisms was observed in conventional-conventional tillage system, whereas minimum was in zero-zero tillage system. Pre emergence herbicide suppressed the microbial population between 0 to 10 days after emergence of plant (DAE), whereas post emergence herbicide inhibited the microbial population for a period of 10 days between 20 to 30 DAE. In weedy check, the microbial population was found significantly higher over other weed management practices in most of the cases.