Combination of modified biochar and polyurea microcapsules to co-encapsulate a fumigant via interface polymerization for controlled release and enhanced bioactivity.

Background Soil fumigants-the most effective agrochemicals for managing soil-borne diseases-have been extensively used. However, high volatility, moderate toxicity, and insufficient effective duration considerably limit their application. In the present study, a combination of modified biochar and polyurea microcapsules (MCs) via interface polymerization to co-encapsulate allyl isothiocyanate (AITC) was developed as a model fumigant for controlled release (AITC@BC-MCs). Results The physical characteristics of biochar modified by sand milling were significantly improved. In addition, chemical properties and morphological features of AITC@BC-MCs characterized by integrated methods revealed successful preparation of BC-MCs. Compared with monolayer MCs, BC-MCs could significantly delay AITC release due to the composite obstruction effect. Moreover, modified biochar endowed the cargo molecules with a pH-responsive release property. Additionally, this composite showed a longer persistent duration by prolonging AITC degradation half-life, which was 3.2-3.5 times that of the AITC technical concentrate under different soil conditions. Finally, the control efficacy of AITC@BC-MC against pathogens, including nematodes and fungi, as well as against weeds was significantly enhanced at the same dose, but it did not inhibit seed germination and growth after 10 days when fumigated soil was aerated. Conclusion Construction of a composite encapsulation system enhanced pesticide efficacy, reduced dose via controlled release, and delayed fumigant degradation in soil, indicating the great potential of this strategy for developing an effective and environmentally friendly fumigant formulation. This article is protected by copyright. All rights reserved.