Green Double-Cross-Linked Composite Hydrogel Beads for Controlled Release of Diuron and Sustainable Weed Control

Green and environmentally friendly controlled-release formulations represent an effective approach to achieving efficient pesticide utilization, thus minimizing environmental pollution. In this study, hydrophobic diuron was loaded onto organically modified montmorillonite (O-MMT). The obtained diuron-loaded O-MMT was encapsulated within a double-cross-linked network structure formed through hydrogen bonding between sodium alginate (SA) and corn starch (CS), as well as calcium ion cross-linking with SA, to create Diuron@O-MMT@SA/CS composite hydrogel beads. The hydrogel beads exhibit multiple responsive controlled slow-release properties in response to pH, temperature, and α-amylase, displaying the release ratio of 86.79% in 144 h at pH = 8, and the cumulative release rate reached a maximum of 95% at a temperature of 45 °C. Moreover, compared to commercial diuron (Diuron SC), Diuron@O-MMT@SA/CS demonstrated effective control of barnyard grass at a lower concentration of 250 mg/L. Additionally, at 21 days postapplication, the fresh weight control effect of Diuron@O-MMT@SA/CS (93.69%) is better than that of Diuron SC (89.27%) at a concentration of 2000 mg/L, demonstrating that Diuron@O-MMT@SA/CS has a prolonged effective duration with excellent herbicidal efficacy against barnyard grass. The results of soil column leaching experiments revealed that the application of the hydrogel beads with slow-release characteristics can effectively mitigate pesticide pollution of soil and groundwater. Furthermore, toxicity tests on corn plants explored the outstanding biocompatibility of hydrogel beads. This study offers a potential avenue for the development of controlled-release systems for pesticides that are both efficient in reducing pesticide application and environmentally friendly.