Development and evaluation of biochar-amended soils to enhance carbon sequestration and crop yield in the Semi-Arid Tropics: A field and lab-based assessment

Project Abstract

Biochar amendments offer a promising pathway to simultaneously improve soil health, sequester carbon, and boost crop productivity in semi-arid tropical environments characterized by erratic rainfall, low organic matter content, and high vulnerability to erosion. This study integrates field trials and controlled laboratory experiments to evaluate the agronomic and environmental performance of locally sourced, pine-wood and agricultural-residue biochars applied at multiple rates (0, 5, 10, and 20 t ha-1) over two consecutive cropping seasons in an agronomically important legume-cereal rotation. The primary objectives are to quantify impacts on soil physical properties (bulk density, infiltration rate, soil aggregation), chemical properties (pH, cation exchange capacity, available phosphorus, nitrate and ammonium dynamics, micronutrient status), and biological indicators (microbial biomass, enzyme activities, and soil respiration), and to link these soil-mediated changes to crop yield, water-use efficiency, and nitrogen-use efficiency under variable rainfall regimes approximated by rainout shelters and irrigation supplements. In the field component, a randomized complete block design with split plots examines biochar type (pyrolyzed pine-wood vs. crop-residue), application rate, and cropping sequence under maize and cowpea cultivation. Measurements include soil moisture retention, aggregate stability, infiltration rates, nutrient mineralization patterns, and trace gas emissions (N2O, CO2) to evaluate climate footprint implications. Parallel lab-based incubations explore biochar’s sorption-desorption dynamics, phosphorus fixation, and interactions with added organic amendments and mineral fertilizers under controlled moisture and temperature regimes. The study also investigates the persistence and aging effects of biochar in tropical soils through sequential sampling over the experimental period and physicochemical characterization (surface area, porosity, functional groups, and mineral associations). Analytical approaches combine traditional agronomic metrics (grain and biomass yield, harvest index, phenology) with stable isotope tracing to partition soil-derived carbon and nitrogen fluxes, enabling a mechanistic understanding of nutrient use efficiency improvements. Economic analyses assess production costs, farm-gate prices, and a simple cost-benefit framework to determine the economic viability of biochar adoption at each rate. Life cycle assessment complements the environmental evaluation by estimating global warming potential and net soil carbon sequestration over the study period. Expected outcomes include quantifiable gains in soil water retention and nutrient availability, enhanced microbial activity, increased crop yields, and improved nitrogen-use efficiency with moderate biochar rates, alongside diminishing returns or potential immobilization at higher rates. The research aims to provide actionable guidelines for farmers operating in semi-arid tropics, informing policy on sustainable soil management practices, climate-smart agriculture, and carbon credit mechanisms. The integrated field-lab approach ensures robust, scalable insights into biochar’s role in transforming degraded tropical soils into productive, resilient agro-ecosystems while contributing to regional carbon sequestration targets.

Project Overview

What This Project Is About

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A plain-language look at using biochar in soils to boost soil health, store carbon, and improve crop yields in dry to semi-arid areas. Biochar is a charcoal-like material added to soil to improve nutrients and water holding capacity. The project compares soils with and without biochar under field and lab conditions to see how it affects plant growth, soil carbon, and fertility.

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The Problem It Addresses

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Soils in semi-arid regions often lose fertility and store little carbon, limiting crop yields and contributing to climate change. There is a need for affordable, practical soil amendments that improve water retention, nutrient availability, and carbon sequestration without harming the environment.

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Objectives of the Project

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1. Assess how biochar changes soil properties relevant to plant growth.
2. Measure effects on crop yield and quality under realistic field conditions.
3. Evaluate short- and medium-term carbon storage in biochar-amended soils.
4. Identify practical application rates and methods for farmers.

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What You Will Do Step by Step

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1. Review existing studies on biochar and semi-arid soils.
2. Collect soil samples and grow crops with different biochar treatments in field plots.
3. Conduct lab tests on soil texture, nutrients, moisture, and microbial activity.
4. Monitor crop growth, yield, and health throughout the season.
5. Analyze data to compare treatments and assess carbon changes.
6. Interpret results to propose practical guidelines for farmers.

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Expected Outcome

The project should show whether biochar improves soil properties, increases yields, and adds measurable carbon to the soil, along with recommended application rates for semi-arid farming systems.