A sustained‐release fludioxonil/Metalaxyl‐M delivery system for root‐zone protection against soybean root rot

Abstract BACKGROUND Soybean root rot occurs throughout soybean growth, yet traditional fungicide formulations may provide insufficient persistence for full‐cycle control. The contrasting soil behavior of fludioxonil and metalaxyl‐M further limits their coordinated release, retention, and persistence. RESULTS To improve control efficacy against soybean root rot, we developed SA/CS@Flu@CA/Met@ATP by integrating fludioxonil‐loaded calcium carbonate with metalaxyl‐M and attapulgite through adsorption‐assisted granulation, followed by encapsulation within an alginate/chitosan hydrogel shell. The formulation regulated the soil mobility of the two active ingredients differently, promoting limited redistribution of fludioxonil within the soil column without substantial leaching loss, while enhancing the upper‐soil retention of metalaxyl‐M and slowing its subsequent depletion. In a field evaluation, SA/CS@Flu@CA/Met@ATP showed calculated control efficacies of 89.7–94.9% at 60 days. Earthworm exposure and amplicon sequencing indicated no significant treatment‐related reduction in earthworm survival or relative body weight and no broad restructuring of bacterial or fungal communities. CONCLUSION Material‐level coordination of fungicide release, retention, and stability supported the potential of the formulation for soybean root‐rot management while maintaining crop compatibility and preliminary soil biological compatibility under the tested conditions. © 2026 Society of Chemical Industry.