Effects of organophosphate insecticides on soil dynamics and enzymatic activities in alluvial soil of West Bengal, India

The study investigated the impact of two organophosphate insecticides, monocrotophos, and profenofos, on microorganisms and enzymatic activities of soil. This was conducted in a laboratory using alluvial soil from Bidhan Chandra Krishi Viswavidyalaya, the experiment applied these insecticides at recommended rates (750 g and 1000 g a.i. ha -1 ) both individually and in combination over 60 days. Soil samples were collected from each pot after 0 (after 1 h), 20, 40, and 60 days of incubation from these treatments-T1:Control (No insecticide applied),T2: Monocrotophos (36% EC) applied @ 750 g a.i. ha -1 , T3: Profenofos (50% EC) applied @ 1000 g a.i. ha -1 , T4: Monocrotophos (36% EC) and profenofos (50% EC) applied @ 375 and 500 g a.i. ha -1 , respectively. Monocrotophos (11%) generally stimulated bacterial growth more than profenofos (7.3 %), with a significant increase in bacterial populations observed initially, though numbers declined by the study's end. Actinomycetes responded notably to the T4 (45.4 %), while fungal populations were highest in T2 (23.3%) followed by T4 (3.9 %) and T4 (0.6 %). Regarding enzyme activities, phosphatase and dehydrogenase activities were enhanced in treatment T4 showing the greatest effect. Urease activity peaked with monocrotophos at 40 days. The results indicate that the effects of organophosphate insecticides on soil microbial communities and enzymatic activities are complex and vary over time, with combined applications often having more pronounced effects. This research highlights the need for careful consideration of insecticide impacts on soil health in pest management strategies. This study faced several challenges in terms of environmental contron, microbial variability, and pesticide residue effects. It made significant contributions to our understanding of the coplex intractions between pesticides and soil microbial communities. These insights are essential for minimizing harm to soil health.