From scraps to sprouts: Boosting Vigna radiata growth with kitchen waste-synthesized iron nanoparticles

The metal nanoparticles (MNPs) are tremendously being used as growth-promoting agents in agricultural crops. One such MNP is iron nanoparticle (FeNP) as iron is an essential growth element for plants. In the current study, a unique method is employed to recycle kitchen waste (KW) and employ it in the synthesis of FeNPs. Further, the growth-promoting activity of these particles was assessed on Vigna radiata (Mung bean). The FeNPs were prepared using KW extract containing crucial phytocompounds as identified using GC-MS analysis. The synthesized KW-FeNPs were ellipsoidal/spherical in shape (150–185 nm) and had -6.14 mV Z-potential. Nano-priming of the seeds at varying concentrations of FeNPs (50–150 ppm) was done before germination of the seeds along with spraying of FeNPs throughout the growth period of the plantlets. In vitro and in vivo growth parameters were evaluated after the 10th and 21st day respectively. The seedlings sprayed with 150 ppm KW-FeNPs showed a highly significant increase in SL (21.63 ± 2.66 cm), RL (7.21 ± 2.11), and seedling length (28.85 ± 2.41) when compared to the control. The lower values of the S/R ratio (3.40–4.49) and increased number of lateral roots were seen in seedlings treated with Kw-FeNPs. A significant (13.02 ± 0.12 mg/g of leaves) and highly significant (17.01 ± 0.82 mg/g of leaves) increase in chlorophyll content was observed in 100 and 150 ppm KW-FeNPs treated plantlets respectively. The synthesized NPs were able to stimulate seedling and plantlet growth even at lower concentrations. A dose-dependent increase in all the plant growth parameters was observed till 150 ppm KW-FeNPs treatment without any visible sign of oxidative stress. The present research work has successfully utilized kitchen waste in the synthesis of a metal-based nanofertilizer for sustainable agricultural practice.