Adjuvant-Enabled Halving of Florpyrauxifen-Benzyl Dose Maintains Paddy Weed Control and Enhances Soil Health and Rice Yield

Reducing herbicide input in paddy fields is essential for sustainable rice production and long-term soil health. Florpyrauxifen-benzyl effectively controls the dominant paddy weed barnyardgrass (Echinochloa crus-galli), yet excessive application poses environmental risks. Here, we investigated whether the compound adjuvant Sijiling, containing nonionic and anionic surfactants, could enable significant dose reduction in florpyrauxifen-benzyl while maintaining weed control efficacy and improving soil–plant system functions. Greenhouse dose–response assays and two-year field trials conducted in 2021 and 2022 demonstrated that the adjuvant permitted a 50% reduction in herbicide application without compromising control of barnyardgrass or other paddy weeds. Mechanistically, Sijiling disrupted the leaf cuticular wax barrier and amplified ethylene and ABA biosynthesis over two-fold. The reduced herbicide rate lowered residues in rice and soil, increased soil organic carbon and available potassium, and enhanced microbial diversity, particularly enriching beneficial Acidobacteria. Grain yield increased significantly under the reduced-input strategy, with Mantel analysis linking yield gains to improved soil available potassium and organic carbon. Our findings demonstrate that adjuvant-enabled herbicide dose reduction is an effective and sustainable weed management strategy for paddy rice, maintaining robust weed suppression while delivering measurable co-benefits for soil health and crop productivity, thereby supporting the sustainable intensification of rice-based cropping systems.