Biogenic Co2O3/ZnO Nanocomposites for Sustainable Agriculture: Mechanistic Insights into Black Chickpea (Cicer arietinum) Seed Germination and Seedling Growth

Abstract

Sustainable nanotechnology offers an environmentally responsible approach to improving crop establishment. This study synthesised Co₂O₃/ZnO nanocomposites using Citrus limon leaf extract and evaluated their effects on the germination and early seedling growth of black chickpea (Cicer arietinum). The nanocomposites were characterised using X-ray diffraction, Fourier-transform infrared spectroscopy, UV–visible spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Seed-germination experiments were conducted under controlled laboratory conditions using nanocomposite amounts of 0, 1, 2, and 3 mg. The 3 mg treatment produced the highest response, with 18 of 20 seeds germinating, equivalent to 90% germination. This treatment also produced the highest reported seedling vigor index and the greatest root and shoot growth within the tested range. During the 20-day assessment, seedlings treated with 3 mg reached root and shoot lengths of 11.3 and 6.2 cm, respectively, compared with 8.2 and 3.5 cm in the control. The characterisation findings supported the formation of the Co₂O₃/ZnO nanocomposite, while the germination experiment demonstrated concentration-dependent improvements in early seedling performance within the tested range. These findings indicate that lemon-leaf-mediated Co₂O₃/ZnO nanocomposites merit further evaluation as nanopriming materials. Greenhouse and field investigations are required to assess their longer-term agronomic performance, optimum application levels, and environmental safety.