Effect of combined application of systemic herbicides on microbial activities in north bengal alluvial soil

An experiment was conducted under laboratory conditions to investigate the effect of combined application of three systemic herbicides, viz., fenoxaprop, pendimethalin and paraquat at 50 g, 1.0 kg and 1.0 kg a.i. ha(-1), respectively, on the changes of microbial biomass C, N and P in relation to transformations and availability of some plant nutrients in an alluvial soil (Typic Orchraqualf) of West Bengal, India. Application of the herbicides, in general, significantly increased microbial biomass C, N and P, resulting in greater availability of C, N and P in soil. The microbial biomass C was highly induced (28.4 %) when fenoxaprop was applied with pendimethalin, while fenoxaprop along with paraquat exerted maximum stimulation towards microbial biomass N (19.9 %) and biomass P (16.2 %). Application of fenoxaprop along with pendimethalin retained the highest amount of organic C (17.4 %), exchangeable NH4(+) (29 %) and available P (19.6 %), while fenoxaprop with paraquat augmented total N and soluble NO3(-) by 21.4 % and 25.2 %, respectively in soil.