Bringing CSA practices to scale: assessing their contributions to narrow nutrient and yield gaps

Photo: Vanessa Meadu
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Project description

In a business as usual scenario for sub-Saharan Africa, both expansion of cropland area and intensification of crop management, are anticipated to increase food production to keep up with the growing population’s food needs and preferences. This will come with substantial increases in greenhouse gas (GHG) emissions from agriculture. Both avoidance of expansion and the widespread adoption of climate-smart agricultural practices can mitigate GHG emissions.

The Crop Nutrient Gap project aims to substantially increase the productivity of maize-legume smallholder farming systems in Ethiopia, Kenya and Tanzania without substantially increasing GHG emission intensity, nitrogen pollution or other negative externalities by employing the “4R nutrient stewardship approach.” The 4R approach means applying nutrients using the right source, at the right rate, at the right time and in the right place.

To address the current gap in meeting crops’ nutrient requirements, the project identifies and assesses climate-smart fertilizer management options and agronomic practices (4R nutrient management options) to develop site- and crop-specific fertilizer best management practices for legumes and cereals. The project assesses and tests promising best management practices. Trade-offs of 4R nutrient will be analysed between food production, economic costs and profits, and GHG emissions.

The alternative scenarios of intensification, fertilizer use and greenhouse gas emissions at (sub-)national level and promising nutrient management practices at local level listed above will be disseminated and outscaled to stakeholders from the public sector (fertilizer industry), NGOs or social enterprises and public institutions, including extension agencies. The approach – and specific practices – will be shared widely with other countries when applicable, an important interest of the private sector.


Outputs after one year:

The project conducted an initial stakeholder consultation, resulting in collection of essential data for quantifying legume yield gaps, defining nutrient gaps and packages, selecting suitable trial sites and setting up joint trials. A generic protocol for calculating nutrient gaps was drafted. To outscale best management practices efficiently so-called Technology Extrapolation Domains (TEDs) were defined based on biophysical (climate and soil) and socio-economic criteria (population and livestock density, market distance).


The project is led by Wageningen University & Research (WUR), in collaboration with:

Further information

For more information, please visit the direct project website at or contact project leader Martin Van Ittersum (WUR) at (