DEPARTMENT FOR SCIENCE, INNOVATION AND TECHNOLOGY

A Soft Matter Physics approach to tuning soil acidity in sub-Saharan Africa

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Description

Context Soil acidification is an urgent and escalating barrier to agricultural productivity in sub?Saharan Africa (SSA). Climate change amplifies nutrient leaching (Ca²?, Mg²?, K?) and the accumulation of toxic ions (H?, Al³?), which degrade soil structure, reduce water retention, and inhibit root growth. Over 35 % of SSA?s cropland (>350 million hectares) is acid-affected (pH < 5.5), especially in East, Central, and Southern Africa. The economic burden is estimated at US $68 billion annually, equivalent to a ~3% reduction in the region?s agricultural GDP. While conventional solutions such as liming (e.g. calcite or dolomite) are widely used to raise pH to optimal ranges (6.5?7.5), their real-world efficacy is constrained by uncontrolled delivery?heavy rainfall or drought can wash away, over-dissolve, or limit uptake of amendments. In response, embedding dolomite microparticles within a porous, organic polymer matrix offers a route to regulated delivery, simultaneously restoring soil organic matter (SOM). This introduces a rich but unexplored soft matter physics problem. Key themes include: Moisture retention: leveraging polymer physics to link network structure, tortuosity, and water holding Ion transport & reaction: using reaction-diffusion and fluid dynamics to capture ion release, swelling, and internal reactions Soil coupling: applying granular physics and capillarity to model fluid flow, particle rearrangements, and ion transport interactions Challenge Addressed The central challenge is to control the spatial and temporal release of liming ions under realistic soil and weather conditions?minimising loss, overliming, and inefficient uptake. Current approaches rely on trial-and-error, and there is a lack of mechanistic, multi-scale understanding that spans from molecular diffusion within polymers to macro-scale interactions in heterogeneous soils. This gap constrains the development of robust, scalable, low-cost acidification remedies in SSA. Aims & Objectives We propose a physics-driven design and evaluation of composite particles (CPs): dolomite microparticles (DLP) encapsulated in a bio-polymeric matrix (BPM) derived from agrowaste. These materials are affordable, biocompatible, and locally available across Africa. Properly engineered CPs can (i) enhance crop yields by maintaining soil pH, retain moisture and nutrient balance over time; (ii) reduce waste and over liming risks; and (iii) increase soil resilience. The research is structured into 4 Work Packages, with the following objectives: · WP1: Create CPs, characterise and model ions transport and water retention as a function of composition and environment. · WP2: Quantify effects of CPs on model soil as a function of environmental conditions and density of CPs. · WP3: Investigate CP release on a range of real soil samples representative of SSA. · WP4: Build an active network enabling the testing, manufacture and deployment of CPs in SSA. Three PDRAs based in DeKUT (Kenya), Embu (Kenya), and Stellenbosch (South Africa) will carry out experimental, characterization, and modelling tasks, supervised by an international UK-Africa team. The PDRAs will spend 3-6 months in the UK for research, training and cross?team integration. Stakeholder co-design begins with a workshop in Kenya to align technical goals with user needs. Potential Applications & Benefits There are two primary beneficiaries in this project: 1. The project helps build a pan-African physics?soil network, strengthening capacity in soft matter approaches to soil challenges. 2. Smallholder farmers across acid-impacted regions in SSA, and potentially other tropical and subtropical regions with acidified soils. Integration with stakeholders such as AGRA, ACTS and local agricultural agencies fosters pathways for scale-up, manufacture, and adoption.

Objectives

Context Soil acidification is an urgent and escalating barrier to agricultural productivity in sub?Saharan Africa (SSA). Climate change amplifies nutrient leaching (Ca²?, Mg²?, K?) and the accumulation of toxic ions (H?, Al³?), which degrade soil structure, reduce water retention, and inhibit root growth. Over 35 % of SSA?s cropland (>350 million hectares) is acid-affected (pH < 5.5), especially in East, Central, and Southern Africa. The economic burden is estimated at US $68 billion annually, equivalent to a ~3% reduction in the region?s agricultural GDP. While conventional solutions such as liming (e.g. calcite or dolomite) are widely used to raise pH to optimal ranges (6.5?7.5), their real-world efficacy is constrained by uncontrolled delivery?heavy rainfall or drought can wash away, over-dissolve, or limit uptake of amendments. In response, embedding dolomite microparticles within a porous, organic polymer matrix offers a route to regulated delivery, simultaneously restoring soil organic matter (SOM). This introduces a rich but unexplored soft matter physics problem. Key themes include: Moisture retention: leveraging polymer physics to link network structure, tortuosity, and water holding Ion transport & reaction: using reaction-diffusion and fluid dynamics to capture ion release, swelling, and internal reactions Soil coupling: applying granular physics and capillarity to model fluid flow, particle rearrangements, and ion transport interactions Challenge Addressed The central challenge is to control the spatial and temporal release of liming ions under realistic soil and weather conditions?minimising loss, overliming, and inefficient uptake. Current approaches rely on trial-and-error, and there is a lack of mechanistic, multi-scale understanding that spans from molecular diffusion within polymers to macro-scale interactions in heterogeneous soils. This gap constrains the development of robust, scalable, low-cost acidification remedies in SSA. Aims & Objectives We propose a physics-driven design and evaluation of composite particles (CPs): dolomite microparticles (DLP) encapsulated in a bio-polymeric matrix (BPM) derived from agrowaste. These materials are affordable, biocompatible, and locally available across Africa. Properly engineered CPs can (i) enhance crop yields by maintaining soil pH, retain moisture and nutrient balance over time; (ii) reduce waste and over liming risks; and (iii) increase soil resilience. The research is structured into 4 Work Packages, with the following objectives: · WP1: Create CPs, characterise and model ions transport and water retention as a function of composition and environment. · WP2: Quantify effects of CPs on model soil as a function of environmental conditions and density of CPs. · WP3: Investigate CP release on a range of real soil samples representative of SSA. · WP4: Build an active network enabling the testing, manufacture and deployment of CPs in SSA. Three PDRAs based in DeKUT (Kenya), Embu (Kenya), and Stellenbosch (South Africa) will carry out experimental, characterization, and modelling tasks, supervised by an international UK-Africa team. The PDRAs will spend 3-6 months in the UK for research, training and cross?team integration. Stakeholder co-design begins with a workshop in Kenya to align technical goals with user needs. Potential Applications & Benefits There are two primary beneficiaries in this project: 1. The project helps build a pan-African physics?soil network, strengthening capacity in soft matter approaches to soil challenges. 2. Smallholder farmers across acid-impacted regions in SSA, and potentially other tropical and subtropical regions with acidified soils. Integration with stakeholders such as AGRA, ACTS and local agricultural agencies fosters pathways for scale-up, manufacture, and adoption.

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Location

The country, countries or regions that benefit from this Programme.

South of Sahara, regional