Design and evaluation of biochar amendments for soil fertility enhancement

Thesis Abstract

Soil degradation and declining crop productivity pose significant challenges to sustainable agriculture, particularly in regions where chemical fertilizers induce environmental concerns and long-term soil fertility decline. This study aims to design and evaluate biochar amendments as sustainable soil fertility enhancers by examining their physicochemical properties, agronomic efficacy, and potential environmental impacts. The specific objectives are to optimize biochar production parameters for maximum nutrient retention, assess the influence of different biochar types on soil physical and chemical properties, evaluate crop yield responses to biochar-amended soils, and analyze the economic feasibility and environmental sustainability of biochar applications in agricultural systems. The research employs a mixed-methods approach comprising laboratory, greenhouse, and field experiments. The laboratory phase involves producing biochar from three feedstocks—woodchips, rice husks, and poultry manure—using slow pyrolysis at varying temperatures (400°C, 500°C, and 600°C). Characterization of biochar includes proximate analysis, scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and nutrient content assessment. In the greenhouse phase, biochar samples are incorporated into local sandy loam soils at rates of 5%, 10%, and 15% (by weight). A randomized complete block design (RCBD) with three replicates is employed, involving maize as the test crop. Soil parameters (pH, cation exchange capacity, organic carbon, bulk density) are measured before and after amendment using standard soil analysis techniques, while plant growth metrics and grain yield are recorded at harvest. Field trials are conducted in a representative agricultural site over two planting seasons to validate greenhouse findings, with treatments including control (no biochar) and biochar-amended soils at optimal rates identified from greenhouse experiments. Data collected encompass soil chemical and physical parameters, crop yield components, and nutrient uptake, analyzed via ANOVA and regression analysis to determine treatment effects and relationships. Cost-benefit analysis and life cycle assessment are integrated to evaluate economic and environmental sustainability. It is anticipated that specific biochar types, particularly those produced at 500°C from rice husk, will significantly improve soil pH, cation exchange capacity, and nutrient availability, leading to increased crop biomass and grain yield. The study expects to establish optimal biochar application rates and production conditions tailored for local soils, with evidence of enhanced soil health and crop productivity. Findings are projected to demonstrate that biochar amendments are economically viable and environmentally sustainable alternatives to conventional fertilizers, contributing to reduced chemical input reliance while promoting soil carbon sequestration. This research contributes novel insights into the design parameters influencing biochar effectiveness, enhancing understanding of biochar-soil-plant interactions within the framework of the Technological-Structural Model of soil amendment efficacy. It also advances practical knowledge by providing empirically-based guidelines for farmers and policymakers on optimizing biochar production and application for sustainable agriculture. The study concludes with specific recommendations for integrating biochar into soil management practices, emphasizing the need for standardized production protocols and further long-term field evaluations to assess cumulative effects on soil health and climate resilience.