Evaluating the Effectiveness of Biochar Amendments on Soil Nutrient Retention in Agricultural Fields

Thesis Abstract

In the face of escalating concerns over soil degradation and the need for sustainable agricultural practices, this study investigates the effectiveness of biochar amendments in enhancing soil nutrient retention on agricultural fields. Soil nutrient loss due to leaching, erosion, and microbial activity remains a critical obstacle to sustainable crop production, necessitating innovative amendments capable of improving nutrient dynamics while maintaining ecological balance. The primary aim of this research is to evaluate the impact of biochar on soil nutrient retention, focusing specifically on nitrogen, phosphorus, and potassium dynamics, and to identify optimal application rates under field conditions. The study also seeks to analyze the influence of biochar properties derived from different feedstocks on nutrient retention efficacy, thereby providing practical guidelines for biochar use in diverse agricultural contexts. The research adopts a randomized complete block design experimental framework across three commercial farms in the temperate region, each measuring approximately 10 hectares. A total of 120 plots, divided into four treatment groups with 30 replicates each, will be established. Treatment groups include control (no biochar), low-rate biochar application (2 tons per hectare), medium-rate (4 tons per hectare), and high-rate (6 tons per hectare). The biochar used will be produced from agricultural residues such as maize stalks and rice husks via pyrolysis at 500°C, characterized by proximate and ultimate analysis to determine yield, pH, surface area, and mineral content using techniques such as scanning electron microscopy (SEM) and X-ray fluorescence (XRF). Soil samples will be collected at depths of 0–15 cm and 15–30 cm at quarterly intervals over two growing seasons. Data collection involves chemical analysis of soil samples for nutrient concentrations utilizing inductively coupled plasma mass spectrometry (ICP-MS) for elemental quantification. Additionally, soil microbial biomass will be quantified through phospholipid fatty acid (PLFA) analysis. Crop yield data will be gathered at harvest to link nutrient retention with productivity metrics. Statistical analysis will employ Analysis of Variance (ANOVA) to identify significant differences between treatment groups, followed by multiple regression analysis to examine relationships among biochar properties, soil nutrients, and crop yields. A conceptual framework based on the nutrient cycling theory will underpin the analysis, exploring how biochar influences microbial activity and nutrient dynamics. It is anticipated that the findings will demonstrate that biochar amendments significantly improve nitrogen and phosphorus retention in soils, with optimal efficacy observed at medium and high application rates. The study expects to reveal that biochar derived from maize stalks exhibits greater nutrient retention owing to its higher surface area and mineral ash content compared to rice husk biochar. These insights will contribute to establishing a quantitative relationship between biochar properties and soil nutrient dynamics, filling a notable gap in empirical data concerning field-scale applications. The contribution to knowledge from this research lies in providing empirically validated guidelines for biochar application tailored to specific feedstocks and soil conditions, thereby facilitating more sustainable nutrient management practices in agriculture. The main conclusion underscores that biochar is a cost-effective and environmentally sustainable amendment for enhancing nutrient retention, with application rates optimized to maximize crop yield benefits without risking nutrient runoff. Based on the findings, it is recommended that farmers adopt medium-rate biochar amendments, particularly from maize residues, for improved soil fertility. Further research should consider long-term impacts over multiple cropping cycles and explore biochar effects under different climatic conditions to generalize applicability. This study aims to substantively advance current understanding of biochar’s role in soil nutrient management, offering practical and scientifically grounded strategies for sustainable agriculture.