D Devadharshini, P Srinivasan, S Vijayakumar
The development of eco-friendly nanofertilizers offers a sustainable strategy to improve crop productivity. In this study, the marine macroalga Codium decorticatum was employed as a green reducing and stabilizing agent for the biosynthesis of magnesium oxide nanoparticles (MgO NPs), and their agronomic potential was evaluated in Vigna radiata and Vigna mungo. The synthesized MgO NPs were characterized by UV-visible spectroscopy, FT-IR, XRD, FE-SEM, and EDX, confirming the formation of crystalline, phase-pure nanoparticles. XRD analysis revealed a cubic crystalline structure with an average crystallite size of 28 nm, while FE-SEM showed spherical to irregular nanoparticles with an average size of 38 nm. Seed priming and foliar application of MgO NPs (5-160 mg L-1) demonstrated a concentration-dependent response. The optimum concentration of 20 mg L-1 significantly enhanced seed germination (87% in V. radiata and 84% in V. mungo), chlorophyll content, biomass, and yield. At this concentration, V. radiata produced 40 pods plant-1 (40 g), whereas V. mungo produced 38 pods plant-1 (38 g). In contrast, concentrations ≥80 mg L-1 reduced growth and yield, indicating phytotoxicity. These findings demonstrate that C. decorticatum-mediated MgO NPs represent an effective and sustainable nanofertilizer for improving legume productivity while reducing reliance on conventional agrochemical inputs.