Seed encapsulation with pelleting formulations to enhance germination and enable precision drone-assisted planting of direct seeded rice

Direct-seeded rice (DSR) systems often face challenges such as poor germination, uneven crop establishment, and inefficient input use. To overcome these limitations, this study developed a biodegradable seed encapsulation system designed to create a favorable microenvironment for seedling emergence and early growth, with potential application in drone-based precision seeding. The encapsulation formulations combined different pelleting materials (clay, bentonite, clay + bentonite, and mycorrhiza), natural adhesives (gum arabic, starch, and sucrose), and two levels of calcium peroxide (0% and 10%) as an oxygen releasing agent. Capsules of three standard longitudinal dimensions i.e., 23.3 mm, 21.7 mm, and 19.4 mm were evaluated under laboratory and field conditions. Laboratory germination experiments conducted in puddled soil at 37°C revealed that formulations M2A2S2T2 (bentonite + sucrose, size 1 (19.4 mm) capsule with CaO₂) and M4A1S2T2 (mycorrhiza + gum arabic, size 1 (19.4 mm) capsule with CaO₂) achieved the highest germination rate of 88%. Field validation further demonstrated a 17% improvement in germination compared to conventional DSR, along with significantly enhanced root and shoot length in encapsulated seeds containing 10% CaO₂, indicating improved oxygen diffusion and reduced hypoxic stress. Aerodynamic analysis showed that encapsulated seeds exhibited a terminal velocity of about 6.9 m/s compared to 3.18 m/s for bare seeds and lower mean horizontal deviation when released from 1.5 m height. These findings demonstrate that biodegradable encapsulation enhances seed germination, and descent stability, highlighting its potential for drone-enabled precision planting to improve establishment and sustainability in DSR systems.