Impact of Herbicide Combinations on Soil Microflora, Enzyme Activity, Nutrient Dynamics, and Weed Index in Dry Direct-Seeded Rice

Dry direct-seeded rice (DSR) is gaining prominence as a sustainable alternative to conventional transplanting due to labor shortages and water scarcity. However, weed infestation remains a critical challenge in this method, significantly reducing yields. This study evaluates the impact of various herbicide combinations on soil microflora, enzyme activity, nutrient uptake, and weed control in DSR. A field experiment was conducted at the Main Research Station, Hebbal, University of Agricultural Sciences, Bengaluru, India, using a randomized block design with twelve treatments, including chemical and mechanical weed management methods. The results showed that herbicide combinations such as bensulfuron-methyl + pretilachlor followed by bispyribac sodium or triafamone + ethoxysulfuron effectively controlled weeds with minimal impact on soil microbial activity and soil enzymatic functions. These treatments enhanced nutrient uptake by the crop while reducing nutrient loss through weeds, leading to higher grain and straw yields. Hand weeding at 20, 40, and 60 days after sowing recorded the highest grain (5.50 t ha⁻¹) and straw yield (7.22 t ha⁻¹), which was statistically on par with bensulfuron- methyl + pretilachlor followed by bispyribac sodium (5.39 and 7.16 t ha⁻¹) and bensulfuron- methyl + pretilachlor followed by triafamone + ethoxysulfuron (5.29 and 7.03 t ha⁻¹). The lowest yields (grain: 1.40 t ha⁻¹, straw: 2.32 t ha⁻¹) were recorded in the weedy check.