Why Fertilizer and Soil Health Must Go Hand in Hand

A recently released peer-reviewed paper presents a conceptual framework for understanding the relationship between mineral fertilizer use, crop productivity, and soil health in sub-Saharan Africa.

The npj Sustainable Agriculture paper, titled “Fertilizer and Soil Health for Sustained Crop Production in sub-Saharan Africa: Theory and Conceptual Framework,” brings together scientists from leading agricultural research institutions, including APNI’s Director of Research and Development, Dr. Shamie Zingore.

“The article addresses a central question for African agriculture on how can fertilizer be used to increase food production while restoring and sustaining soil health? Mineral fertilizers are indispensable for reversing decades of nutrient depletion in African soils, but they must be used as part of an integrated approach that combines mineral and organic nutrient sources with good agronomic practices.” – Dr. Shamie Zingore

Addressing Africa’s soil fertility challenge

Agricultural production in sub-Saharan Africa (SSA) must increase substantially to meet the food and nutrition needs of a growing population. If this increase is achieved mainly by expanding cropland, it could place further pressure on forests, biodiversity, and other natural ecosystems. Sustainable intensification, producing more from existing farmland, is therefore increasingly important.

However, the productive capacity of much of the region’s agricultural land has been weakened by decades of soil nutrient mining. Nutrients removed when crops are harvested have not been adequately replenished through fertilizers, manure, crop residues, or other nutrient sources.

This has created a negative cycle: nutrient-poor soils produce low crop yields and limited biomass, leaving farmers with fewer crop residues to return to the soil. With less organic material and soil cover, the soil’s physical, chemical, and biological condition deteriorates further, reducing its capacity to sustain future production. The paper argues that increasing and improving nutrient inputs is essential to break this cycle.

Understanding soil health

The authors define soil health as the soil’s continued capacity to support the production of food, feed, and fiber while also delivering essential ecosystem services.

Healthy agricultural soils must perform several interconnected functions. They must store and supply nutrients, regulate water movement, support root growth and soil organisms, maintain their physical structure, buffer pollutants, and contribute to environmental and human health. The paper identifies five particularly relevant indicators of soil health from an agronomic perspective:

1. soil organic matter;
2. available phosphorus;
3. exchangeable potassium;
4. soil acidity or pH;
5. soil bulk density.

These indicators influence nutrient availability, root development, water storage, aeration, and the ability of crops to respond to fertilizer. The authors nevertheless caution against applying universal soil-health thresholds across all farming environments. Soil texture, mineralogy, climate, cropping system, and management history all influence what can be considered an appropriate or attainable level for a particular indicator.

Fertilizer and soil health are closely connected

The paper challenges the assumption that mineral fertilizer and soil health are opposing objectives. Appropriately managed fertilizer can improve soil fertility directly by replenishing essential nutrients. It can also improve soil health indirectly by increasing crop yields and biomass production. Higher biomass production may generate more roots and crop residues, which can contribute organic matter and protect the soil from erosion when retained or recycled.

At the same time, fertilizer does not automatically improve every aspect of soil health. Its effects depend on how it is selected and managed. For example, the long-term use of some ammonium-based fertilizers can increase soil acidity. This is an important concern in SSA, where many highly weathered soils have limited capacity to buffer changes in pH. Soil acidity can reduce nutrient availability and eventually cause aluminium or manganese toxicity, restricting root growth and crop productivity.

Similarly, fertilizer-induced yield increases will not necessarily increase soil organic carbon when crop residues are removed from fields for livestock feed, fuel, or other purposes. The paper therefore emphasizes balanced nutrient application, soil acidity management, residue recycling, and continued monitoring of soil conditions.

Why mineral and organic inputs must be combined

Organic resources such as manure, compost, and crop residues play a critical role in soil health. They can improve soil structure, water retention, nutrient storage, biological activity, and soil organic carbon. Yet the quantities of organic resources typically available to smallholder farmers are rarely sufficient to meet the full nutrient requirements of productive crops.

Mineral fertilizers provide nutrients in more concentrated and immediately available forms, enabling crops to respond quickly. However, their effectiveness can remain limited when poor soil structure, acidity, low organic matter, drought, weeds, pests, or other constraints are not addressed.

For this reason, the authors advocate integrated soil fertility management (ISFM), which combines:

1. mineral fertilizers;
2. locally available organic resources;
3. improved crop varieties;
4. appropriate nutrient sources, rates, timing, and placement;
5. good crop and soil management;
6. amendments such as lime where required;
7. adaptation to local farming and socioeconomic conditions.

The complementary use of organic and mineral nutrient sources can improve fertilizer-use efficiency, restore the responsiveness of degraded soils, increase crop productivity, and support long-term soil fertility.

Moving beyond blanket recommendations

The paper also highlights the considerable diversity of African farming environments. Soil type, rainfall, crop requirements, farm resources, market access, and farmer objectives can vary considerably, even between neighbouring fields.

As a result, the authors call for a move away from generalized fertilizer recommendations toward more locally adapted and field-specific guidance. Advances in soil data, digital agriculture, modelling, and artificial intelligence provide new opportunities to develop and deliver recommendations at scale. These technologies could help tailor advice to the nutrient needs and soil conditions of an individual field. However, technical recommendations alone are not enough.

Making soil health economically viable for farmers

Farmers’ decisions are shaped not only by what is agronomically possible, but by what is economically worthwhile and financially accessible. High fertilizer prices, uncertain crop prices, erratic rainfall, limited credit, insecure land tenure, and weak market access can discourage investment, even when fertilizer use could technically increase yields.

The paper distinguishes between the agronomic yield gap, the difference between current and technically attainable yields, and the economic yield gap which reflects the yield level that maximizes farmer profit. Closing the full agronomic yield gap may not be financially rational for farmers when input costs are high and production risks are substantial. Profitability, risk management, and access to markets must therefore be considered when designing fertilizer and soil-health interventions. Women farmers may face additional constraints, including unequal access to land, labor, extension services, inputs, credit, and markets. Addressing these structural barriers is essential to achieving inclusive adoption of soil-health technologies.

Creating an enabling environment

Restoring degraded soils is a long-term process, while the benefits may not be immediately visible to farmers. Those facing short-term financial and food-security pressures may understandably prioritize practices that provide faster returns. The authors therefore call for supportive policies and institutions, including:

1. effective agricultural extension;
2. improved access to finance and markets;
3. digitally enabled decision-support tools;
4. bundled input, advisory, and credit services;
5. targeted incentives;
6. smart fertilizer subsidies linked to soil-health outcomes.

Rather than focusing only on reducing fertilizer prices, public programs should encourage balanced nutrition, organic matter management, appropriate agronomic practices, and the long-term restoration of soil function.

An integrated pathway to productive and healthy soils

The study’s central message is that crop productivity and soil health should not be pursued separately. Sub-Saharan Africa will need greater and more efficient use of mineral fertilizer to replace nutrients removed through crop production and raise yields on existing farmland. At the same time, fertilizer must be integrated with organic resources, soil amendments, improved varieties, and locally appropriate agronomic practices.

By combining these elements with enabling policies, market incentives, and accessible advisory services, African farming systems can move toward higher productivity while rebuilding the soil resources on which future food production depends.

Acknowledgment
This summary was extracted from the article published by Bernard Vanlauwe, Tilahun Amede, Prem Bindraban, Rémi Cardinael, Antoine Couëdel, Marc Corbeels, Achim Dobermann, Oluwole A. Fatunbi, Gatien Falconnier, Ken E. Giller, Rebbie Harawa, Mercy Kamau, Roel Merckx, Johan Six, Zachary Stewart, Martin van Ittersum, and Shamie Zingore. 2026. Fertilizer and soil health for sustained crop production in sub-Saharan Africa: Theory and conceptual framework npj Sustain. Agric. 4, 56 (2026). https://doi.org/10.1038/s44264-026-00161-w

Contributor: Sara Lamsilli, Project Communication Manager