NITROGEN BIOREMEDIATION BY ARBUSCULAR MYCORRHIZAL FUNGI AND BIOCHAR FOR OPTIMUM REDUCTION IN ENVIRONMENTAL POLLUTION AND SUSTAINABLE PRODUCTION OF GARDEN EGG (Solanum aethiopicum L.)

Abstract

Nitrogen (N) loss in agricultural systems is a significant environmental problem, contributing to greenhouse gas emissions and water pollution. This study examined the potential of Arbuscular Mycorrhizal Fungi (AMF) and Biochar as sustainable solutions to mitigate Nitrogen losses and enhance soil health in garden egg (Solanum aethiopicum L.) production. The research addressed the combined effects of these amendments on Nitrogen Bioremediation, Nutrient Use Efficiency (NUE), soil properties, and crop productivity, with a focus on nutrient-poor soils in Ghana. The objectives were to (1) assess reduction in leachate volume and model nitrate leaching with AMF and Biochar; (2) evaluate Nitrogen Uptake Efficiency (NUpE) and NUE in garden egg; (3) investigate the impact of AMF and Biochar on soil properties, including pH, organic carbon content, and cation exchange capacity (CEC); and (4) analyze the effects of these treatments on crop productivity across two seasons. A 2 x 2 x 3 factorial study in a Randomized Complete Block Design (RCBD) was used, involving two AMF levels (0, 8 kg/ha), and two Biochar levels (0, 10 tons/ha) and three Nitrogen levels (0, 150, 200 kg ha-1). The study was conducted at the West African Centre for Water, Irrigation, and Sustainable Agriculture (WACWISA), University for Development Studies, Ghana. Nitrate leaching was modeled using an exponential Probability Density Function-based Model, and soil properties, plant growth, and yield were measured with standard methods. The study showed that when Nitrogen was applied at similar rates, the addition of AMF and Biochar significantly reduced nitrate levels in the leachate and decreased the total leachate volume (P < 0.05). At the optimal Nitrogen rate of 200 kg N ha⁻¹, the absence of AMF and Biochar resulted in nitrate concentrations and leachate losses from the root zone being 16.77 and 4.99 times higher, respectively, compared to when both were present. The model predicted that, at 200 kg N ha⁻¹, nitrate loss from the root zone would be 60.04% without AMF and Biochar, versus only 4.92% when they were applied. Additionally, regression analysis identified a moderate to strong negative correlation between cumulative field capacity (FC) and Nitrogen leaching (NL), as predicted by the Exponential Probability Density Function-based Model, with a multiple R value of 0.6948. The model's moderate fit (R² = 0.4828) explained roughly 48% of the variability in nitrate leaching. The negative coefficient for cumulative FC (-0.0244) supported the idea that improved soil water retention effectively reduces nitrate leaching. These findings emphasize the crucial role of soil moisture management in minimizing Nitrogen loss. Results revealed that AMF and Biochar combined significantly reduced leachate volume and Nitrogen leaching, particularly at higher Nitrogen levels (200 kg/ha). The synergistic application of AMF and Biochar also improved NUpE and NUE, with the highest efficiency achieved with AMF and Biochar at 200 kg N/ha. Biochar enhanced soil pH, organic carbon, and CEC, while AMF increased root biomass and colonization. These changes led to higher plant height, fresh fruit yield, and chlorophyll content. The study concluded that integrating AMF and Biochar in Nitrogen-fertilized soils effectively improved Nitrogen bioremediation, soil health, and garden egg yield. It is recommended that farmers adopt these practices to optimize Nitrogen use and minimize environmental impacts. Further research should explore the long-term effects, economic feasibility, and underlying mechanisms of AMF and Biochar applications across agro-ecosystems. Crop-specific studies can determine their broader applicability in sustainable agriculture.