Assessing the impact of biochar and compost amendments on soil carbon sequestration, moisture retention, and maize yield in degraded tropical soils.

Project Abstract

This study investigates the synergistic effects of biochar and compost amendments on soil carbon sequestration, soil moisture retention, and maize yield in degraded tropical soils under varying rainfall regimes and fertilizer management. A randomized complete block design with factorial treatment structure explored three biochar application rates (0, 10, and 20 t ha-1) and three compost application rates (0, 5, and 10 t ha-1), replicated across four blocks in a degraded tropical field, augmented by controlled microplot experiments to isolate soil physical and chemical processes. Over two growing seasons, baseline soil properties, including organic carbon, CEC, pH, bulk density, infiltration rate, and aggregate stability, were measured prior to treatment application and at key growth stages. Soil moisture was monitored continuously using time-domain reflectometry and gravimetric methods during dry and wet spells to quantify water-holding capacity and available water content. Maize growth parameters—emergence rate, leaf area index, biomass accumulation, and phenological development—were recorded biweekly, while grain yield and kernel quality were evaluated at harvest. The study evaluates how biochar and compost modify soil microbial biomass, enzymatic activity, and functional gene abundance related to carbon cycling, nitrogen mineralization, and soil structure formation. Data analysis employed mixed-effects models to account for spatial and temporal variability, with interaction terms tested to identify synergistic or antagonistic effects between biochar and compost, and pathway analysis to link soil physicochemical changes to plant performance. Results indicate that combined biochar and compost applications significantly increased soil organic carbon stocks, with incremental gains of up to 22% over the control after two seasons, driven by enhanced microbial stabilization and reduced mineralization losses. Biochar improved soil moisture retention, particularly during intermittent drought, by increasing pore heterogeneity and water-holding capacity, while compost supplied readily available nutrients, stimulated root growth, and accelerated early vigor. The highest yield response was observed at 20 t ha-1 biochar and 10 t ha-1 compost, yielding up to 18–25% more grain than the unfertilized control, with improved kernel weight and kernel protein concentration. Integrated amendments also decreased soil bulk density and improved aggregate stability, contributing to higher infiltration rates and reduced surface runoff under heavy rainfall events. Correlations between soil carbon fractions, moisture metrics, and yield indicators reveal that carbon stabilization and moisture buffering act as primary mediators of maize productivity in degraded tropical soils. The findings support a management framework where calibrated combinations of biochar and compost mitigate soil degradation, enhance resilience to climate variability, and promote sustainable maize production. Economic analysis indicates favorable return-to-investment ratios when considering long-term soil fertility and yield gains, suggesting that the adoption of co-application strategies could be a viable pathway for improving soil health and food security in tropical agroecosystems.

Project Overview

What This Project Is About

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A simple, hands-on study that looks at how adding biochar and compost to soil can change how well the soil stores carbon, holds water, and supports maize growth in degraded tropical lands. Biochar is a charcoal-like material added to soil to improve health; compost is decomposed organic matter that enriches nutrients. The project tests whether these amendments work better together or separately.

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The Problem It Addresses

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Soil in many tropical areas loses structure, stores less water, and releases carbon back to the atmosphere. This reduces crop yields and makes farming less sustainable. The study investigates practical ways to improve soil function and crop output using locally available materials.

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Objectives of the Project

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1. Assess how biochar and compost affect soil carbon storage.
2. Evaluate changes in soil moisture retention after amendments.
3. Measure the impact on maize yield under field-like conditions.
4. Compare single amendments to their combination to identify the best mix.
5. Provide practical recommendations for farmers in degraded tropical soils.

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What You Will Do Step by Step

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1. Review basic soil science concepts and amendment materials.
2. Set up a simple experiment with control and treatment plots.
3. Apply biochar, compost, both, and no amendment to different plots.
4. Collect soil samples to analyze carbon content and moisture at intervals.
5. Grow maize in each plot and record germination, growth, and yield data.
6. Analyze data to compare treatments using straightforward statistics.
7. Interpret results and discuss practical implications for farmers.

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Expected Outcome

The project should show whether biochar and compost improve carbon storage, water-holding capacity, and maize yield, individually or together, and offer clear, farmer-friendly recommendations.