A novel biodegradable gelatin capsule platform for input-efficient herbicide delivery in transplanted rice

Background Weed management in transplanted rice requires effective herbicide delivery while improving input-use efficiency and reducing reliance on conventional application practices. This study developed and evaluated a biodegradable gelatin capsule-based herbicide delivery system, subsequently protected through a design patent, as an alternative approach for herbicide application. Methods A two-phase study comprising preliminary screening and field validation was conducted using Pyrazosulfuron Ethyl, Butachlor, Bensulfuron methyl + Pretilachlor, and Triafamone + Ethoxysulfuron at different formulation rates. Selected capsule treatments were subsequently compared directly with corresponding conventional applications for weed suppression, crop growth, yield and economic performance. Temporal weed-control performance was quantified using the area under the weed control efficiency curve (AUWCEC) and area under the weed dry weight curve (AUWDWC), together with economic-threshold analysis. The response of culturable soil microbial populations to empty capsule placement was also assessed. Results Field performance varied with herbicide formulation and capsule rate, with the strongest response observed for Bensulfuron methyl + Pretilachlor. At the recommended 100% formulation rate, capsule delivery increased AUWCEC by 16.9% and reduced AUWDWC by 28.7% relative to the corresponding conventional application. The 100% capsule treatment maintained higher weed control efficiency than conventional spraying of the same herbicide combination at 15, 30 and 45 DAT (86.9, 68.7 and 68.3% vs. 81.3, 57.6 and 53.9%, respectively), and increased grain yield by 14.9% (5,463 vs. 4,755 kg ha −1 ). Although the 150% capsule treatment recorded numerically higher weed control efficiency (87.6%) and grain yield (5,710 kg ha −1 ), its yield was statistically comparable with the 100% treatment, which achieved the highest benefit:cost ratio (2.42). Overall, the 100% capsule treatment provided the most favorable balance of weed suppression, crop productivity and economic return. Empty-capsule placement was associated with increased culturable bacterial, fungal and actinomycete populations. Conclusion Optimized gelatin capsule-mediated herbicide delivery strengthened weed suppression and crop performance, with the 100% Bensulfuron methyl + Pretilachlor treatment providing effective control, comparable grain yield and the highest economic efficiency relative to conventional application. The findings demonstrate the potential of targeted biodegradable herbicide delivery for improving input-use efficiency and supporting sustainable rice production.