Assessment of the impact of agroforestry interventions on soil carbon sequestration and crop yield in smallholder farms.

Project Abstract

This study investigates the effects of agroforestry interventions on soil carbon sequestration and crop yield in smallholder farms across multiple agroecological zones, integrating quantitative field measurements, farmer participatory methods, and modeling to quantify environmental and economic benefits. A mixed-methods approach was employed, combining a controlled on-farm trial with farmer-managed plots to assess different agroforestry configurations, including scattered shade trees, alley cropping, and windbreak systems, over a two-year period. Soil samples were collected at 0–15 cm, 15–30 cm, and 30–60 cm depths to determine total organic carbon, soil inorganic carbon, bulk density, moisture retention, and humification indices, complemented by measurements of litterfall input, root biomass, and soil microbial activity using standardized soil respiration and enzyme assays. Crop yield data were gathered for maize, bean, and peanut intercrops, along with phenology records, casualty losses due to shading, competition, and pest pressures, and post-harvest quality assessments. Economic analysis included input-output budgeting, cost-benefit ratios, and risk-adjusted returns to capture the livelihood implications for smallholder farmers. Temporal trends indicate that agroforestry interventions enhanced soil organic carbon stocks by an average of 12–28% across sites, with the most pronounced gains in the 0–15 cm layer under alley cropping and in systems with leguminous nitrogen fixers. Soil moisture retention increased by 6–14% during dry spells, correlating with higher infiltration rates and reduced runoff. Crop yields exhibited system-dependent responses shade-tolerant crops benefited from moderated microclimates and improved soil structure, while some nutrient-demanding crops showed yield stabilization rather than peak yields, suggesting trade-offs between carbon sequestration and short-term production under dense canopy scenarios. The study reveals that integrating multipurpose tree species contributes to diversification of productivity and resilience to climatic variability, with co-benefits including enhanced biodiversity, reduced erosion, and improved soil health indicators such as higher cation exchange capacity and microbial biomass carbon. Multivariate regression and structural equation modeling were used to disentangle direct and indirect pathways linking agroforestry components to soil carbon dynamics and crop performance, revealing that tree density, species composition, and litter quality are critical mediators of outcomes. Policy implications highlight the need for farmer-centered extension services, access to credit for establishment costs, and incentive programs that reward carbon sequestration and ecosystem services. The findings provide actionable guidelines for optimizing agroforestry designs to balance carbon sequestration and food production, support climate-smart agriculture, and improve livelihoods in smallholder farming systems. Limitations include site-specific variability, limited long-term data, and potential edge effects in heterogeneous landscapes that warrant extended monitoring and scaling-up studies. Future research should explore long-term soil carbon stabilization mechanisms, broader crop portfolios, and integration with market-oriented value chains to maximize both ecological and economic benefits.

Project Overview

What This Project Is About

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This project looks at how planting trees or shrubs alongside crops (agroforestry) can change two important things on farms: the amount of carbon stored in the soil and the crop yields. It compares farms with agroforestry practices to farms without them to see if trees help soil hold more carbon and whether crops grow better or differently.

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The Problem It Addresses

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Many smallholder farms struggle with soil health and variable crop yields. There is a need to understand whether agroforestry can provide climate and production benefits in practical, everyday farming, especially in resource-limited settings. This project investigates whether integrating trees can improve soil carbon storage and crop productivity, which could support both farming livelihoods and environmental goals.

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Objectives of the Project

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1. Assess soil carbon levels in farms with and without agroforestry.
2. Measure crop yields under different agroforestry configurations.
3. Identify practical agroforestry practices that are easy for farmers to adopt.
4. Evaluate farmers’ perceptions and constraints related to agroforestry.

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What You Will Do Step by Step

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1. Review simple background literature on agroforestry and soil carbon.
2. Select study sites and establish a basic experimental or comparison framework.
3. Collect soil samples and record crop yields across seasons.
4. Analyze carbon content and yield data using straightforward comparisons.
5. Compare results between farms with and without trees and discuss practical implications.

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Expected Outcome

Expected outcomes include evidence on whether agroforestry increases soil carbon storage and how it affects crop yields. The project should provide simple, actionable recommendations for farmers considering agroforestry, along with a clear sense of potential trade-offs between carbon benefits and yields.