Soil biological indicators such as microbial population and enzyme activities are highly sensitive to chemical weed control and serve as early signals of soil health. Integrated weed management (IWM) with low-dose, high-efficiency herbicides is considered to be environmentally acceptable; however, its impact on soil biological functioning is poorly understood. In the present study, the influence of IWM, comprising pre- and post-emergence herbicides, wheel hoe weeding and hand weeding on soil microbial population and enzymatic activities was evaluated for 2 seasons in grain cowpea. Results indicated that all herbicide applications significantly reduced bacterial, fungal and actinomycete populations temporarily up to 15 days after spraying (DASP), but this reduction was more intense under chlorimuron-ethyl and haloxyfop-R-methyl treatments. Microbial count gradually increased over time as herbicide concentrations declined in the soil, reaching the initial levels by 30 DASP. Dehydrogenase, β-glucosidase and acid phosphatase activities decreased shortly after the application of the herbicides but returned to pre-application levels by 30 DASP, indicating soil resilience and microbial adaptation. However, hand weeding and untreated weedy plots showed higher microbial and enzymatic activities due to increased organic inputs and reduced chemical stress. Among the herbicides evaluated, diclosulam and pretilachlor were identified as the least disruptive to soil biological health. The results indicated that although herbicides may temporarily suppress soil biological activity, the soil system shows strong potential for recovery under integrated weed management practices.
Kalyani et al. (Thu,) studied this question.
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