Carboxymethyl chitosan hydrogel particles for Pretilachlor delivery: ensuring sustained release and environmental safety in rice weed control

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Abstract
BACKGROUND: Pretilachlor (PR), a pre‐emergence herbicide crucial for rice weed management, is prone to rapid degradation and poses significant environmental risks, necessitating frequent applications. This study aims to develop an environmentally friendly carboxymethyl chitosan (CMCS)/Cu 2+ hydrogel delivery system that provides controlled release, enhances application efficacy, and mitigates ecological impacts while utilizing biowaste‐derived materials. RESULTS: CMCS hydrogel particles crosslinked via Cu 2+ coordination achieved a PR loading capacity (LC) of 13.70 ± 0.32%. The system displayed pH‐responsive behavior with maximum swelling (429%) at pH 8, enabling sustained PR release (51.2% over 80 h) and rapid biodegradation (83.9% mass loss within 7 days). At an agronomically relevant dosage of 500 g a.i. (active ingredient) ha −1 , the hydrogel formulation provided effective Echinochloa crus‐galli control comparable to commercial standards while eliminating rice phytotoxicity. Ecotoxicity assessments revealed significantly reduced environmental risks, with LC 50 values of 0.60 mg L −1 for Danio rerio (1.7‐fold safer than emulsifiable concentrate (EC)) and >1600 mg kg −1 for Eisenia fetida . CONCLUSION: This study demonstrates the feasibility of utilizing CMCS/Cu 2+ hydrogel particles as a controlled‐release delivery system for PR in rice cultivation. The developed formulation provides sustained herbicide release aligned with early weed growth stages, reduced non‐target toxicity, and enhanced biodegradability compared to conventional formulations. While further field validation is needed, this approach offers a promising foundation for developing more environmentally compatible pesticide delivery systems that could potentially reduce application frequency and environmental loading in rice production. © 2026 Society of Chemical Industry.

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