Pre- and post-emergence herbicidal impact on nodulation of soybean crop and soil biological indicators

A field trial to investigate the effect of pre- and post-emergence herbicides on soil biological indicators in soybean was conducted at AICRP-Weed Management farm, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola during Kharif 2021. The experiment was laid out in a randomized block design with three replications and twelve treatments. Wheat straw applied as mulching 5 t/ha on the soil recorded significantly higher dehydrogenase activity, CO₂ evolution, soil microbial biomass carbon, microbial count (bacteria, fungi and actinomycetes) and maximum root nodulation. Among chemical weed control, higher soil microbial biomass carbon was recorded in diclosulam 84% WDG 0.026 kg/ha as pre-emergence whereas in post-emergence herbicides, it was higher with quizalofop-ethyl 10% EC + chlorimuron-ethyl 25% WP 0.037+0.009 + 0.2% surfactant. Results revealed that mulching may have very good effect facilitating the degradation of herbicides also not only maintaining but increasing the microbial biomass carbon. Higher dehydrogenase activity was observed in mulching with wheat straw 5 t/ha and farmer’s practice at flowering stage due to higher substrate availability. In herbicidal application treatments, suppression of dehydrogenase activity was observed, which might be due to the lethal action of herbicides on soil microorganisms.