Impact of new herbicide molecule bispyribac sodium+metamifop on soil health under direct seeded rice lowland condition

Soil microflora and soil enzymes are considered to be the biological indicators of soil health. Hence, an experiment was conducted in the farmer's field to study the impact of bispyribac sodium+metamifop 14% SE (a combination of broad spectrum herbicide bispyribac sodium 9.5% and a grass effective herbicide metamifop 3.8%) on soil microflora and enzyme activity in soil during kharif 2014. The experiment was conducted in randomized block design with seven treatments viz., bispyribac sodium+metamifop 14% SE applied at 60, 70, 80 and 90 g a. i./ha, bispyribac sodium 10% SC applied alone at 25 g a. i./ha, hand'weeding twice on 20 and 40 days after sowing (DAS) and weedy check. The study results revealed that, on 15 days after herbicide application, an increase in the population of bacteria and fungi arid decline in the population of actinomycetes was observed. But on 45 days after herbicide application, an increase in population of bacteria, fungi and actinomycetes was observed. In general, herbicides had no negative impact on total microbial population. An increase in dehydrogenase activity was observed in all herbicide treated plots on 15 days after herbicide application. The same trend was observed on 45 days after herbicide application. With regard to phosphatase activity irrespective of treatments decline in activity was observed on 15 days after herbicide application. On 15 and 45 days after herbicide application, bispyribac sodium applied at 70, 80 and 90 g a. i./ha was on par with weedy check. Similar to phosphatase, a decline in urease activity was observed on 15 days after herbicide application. At 15 and 45 days after herbicide application bispyribac sodium applied at 70, 80 and 90 g a. i./ha recorded higher urease activity than weedy check. From the results, it can be concluded that bispyribac sodium+ metamifop has no adverse impact on soil microflora and enzyme activity in the soil, implying that it is an ecofriendly herbicide.