Evaluation of banana peel and watermelon rind composite extracts as a green Nano-Fertilizer.

Abstract

Rising demand for sustainable agriculture and expanding interest in alternatives to conventional fertilizers, which contribute to soil degradation, nutrient leaching, and environmental pollution, have stimulated research into eco-friendly nano-fertilizers. As a result, this study investigated the green synthesis method for producing nano-fertilizer using banana peel extract (BPE) and watermelon rind extract (WRE), with Aloe vera gel extract (ALvE) functioning as both a reducing and stabilizing agent. The objectives entailed synthesizing and characterizing composite nano fertilizer derived from agricultural waste and assessing its agronomic performance on Solanum lycopersicum L. (tomato) and Capsicum annuum L. (bell pepper) crops under greenhouse conditions. A completely randomized factorial design (2 ×10 × 4 ) was used to evaluate crop type, composite formulation (BPE:WRE ratio of 50:50, 75:25 and 25:75 with Aloe vera gel extract concentrations of 5,10,15 mL, including appropriate control treatments), and application dose during the 2024 growing season. Physicochemical characterization was performed using Ultraviolet-visible (UV-Vis) spectroscopy, Transmission Electron Microscope (TEM), Scanning Electron Microscopy – Energy Dispersive Spectroscopy (SEM-EDS), and colorimetric phytochemical screening, followed by an evaluation of their impact on plant development and soil parameters. The results confirmed the successful formation of noncovalent composite nanoparticles rich in oxygen-containing phytochemicals (flavonoids, phenols, tannins, saponins) and essential nutrients (potassium (K), magnesium (Mg), calcium (Ca)). Lower ALvE content (5 mL) produced well-dispersed nanoparticles, whereas higher ALvE levels (10 mL) caused polymer bridging and particle agglomeration (>500 nm). Consequently, crop type, composite formulation, dose, and their interactions significantly influenced plant growth and soil parameters, with tomato crops generally outperforming bell peppers across most evaluated growth parameters. In particular, 5 mL of ALvE composites at reduced application doses improved seed emergence percentage and plant height, whereas higher doses had the opposite effects. Leaf traits, stem diameter, flowering and biomass traits varied depending on crop type and composite formulation. Soil pH and electrical conductivity declined after application of the nano-fertilizer, indicating nutrient uptake and rhizosphere modification. This study demonstrates that effective nano fertilizers capable of improving agronomic performance can be produced from agricultural waste without inorganic salt precursors, highlighting a promising avenue for sustainable agricultural practices.