Abstract
BACKGROUND: Nutrient leaching threatens sustainable agriculture by depleting soil fertility and contaminating groundwater. Biochar offers a promising solution, but its effectiveness varies with feedstock, production, and application rates. Specifically, the potential of hazelnut husk biochar for nutrient retention and soil improvement has not been extensively studied, leaving a gap in understanding its practical applications and optimal usage in different soil types and crop systems. METHODS: This study investigated the influence of hazelnut husk biochar application on leachate properties, soil column characteristics, and nutrient dynamics over a 112-day period. The experiment employed a randomized split-plot design with four hazelnut husk biochar application rates (0%, 0.5%, 1%, and 2%) on sandy loam soil. Leaching events were conducted six times over 112 days of incubation period, simulating irrigation and fertilizer application for potato cultivation. Leachates were collected at each leaching event for analysis of pH, electrical conductivity (EC), and various nutrient contents. Following the experiment, soil samples were analyzed at three depths to assess nutrient content. RESULTS: The study revealed significant temporal dynamics in nutrient concentrations across different leaching events, emphasizing the impact of biochar on nutrient retention. Phosphorus (P) concentrations, for instance, decreased from 0.220 mg L(-1) to 0.176 mg L(-1) over four leaching events in the 2.0% biochar treatment. Similarly, potassium (K) concentrations declined from 6.44 mg L(-1) to 3.76 mg L(-1), indicating improved nutrient retention with biochar application. These findings contrast with the control (0% biochar), where nutrient leaching was more pronounced. While biochar had little effect on nitrate leaching, its inherent P content and adsorption characteristics influenced P leaching. Higher biochar application rates resulted in significant changes in soil properties and nutrient concentrations, particularly in the surface layer (0-10 cm), such as an increase in organic matter content from 0.84% in the control to 1.20% in the 2.0% biochar treatment, suggesting improved nutrient availability for plant uptake. CONCLUSION: These findings underscore the potential of hazelnut husk biochar as a sustainable soil management strategy for enhancing nutrient retention, reducing leaching, and improving soil fertility. However, the study also highlights the complexity of biochar-soil interactions and the need for further research to optimize biochar application practices for specific soil and crop systems.