Multifunctional biopolymer hydrogel encapsulating Bacillus consortium and micronutrients for sustainable control of Sclerotium rolfsii and improved soil water retention

Stem rot caused by the soil-borne pathogen Sclerotium rolfsii significantly reduces crop productivity, particularly under warm and humid conditions; this study aimed to develop and evaluate a multifunctional biodegradable hydrogel-based bioformulation for improved microbial delivery, pathogen suppression, and soil moisture conservation. Bacillus strains ( Bacillus velezensis , Bacillus sp., and Bacillus safensis ) were evaluated for antagonistic activity and encapsulated in a carrageenan–sodium carboxymethyl cellulose (Na-CMC) hydrogel matrix cross-linked with citric acid and supplemented with zinc (Zn) and manganese (Mn), followed by assessment of physicochemical properties, biodegradability, water retention, microbial viability, antifungal activity, and seed germination. All three Bacillus spp. showed strong antifungal activity with inhibition rates of 70–97%; the optimized hydrogel exhibited high swelling capacity (1105%), porosity (~ 90%), and pH-responsive behavior; soil application reduced water loss by 13.6%, achieved ~ 80% biodegradation within 14 days, and maintained > 75% bacterial viability over 35 days with sustained antifungal activity. The developed hydrogel-based bioformulation enhanced microbial survival, supported sustained bacterial release, suppressed S. rolfsii , and improved soil moisture retention, highlighting its potential as a sustainable microbial delivery system for crop protection.