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

Photo: Vanessa Meadu

Project description

The Crop Nutrient Gap project aims to substantially increase the cereal food production in sub-Saharan Africa (SSA) by focusing on the potential of crop nutrient management with minimum greenhouse gas emissions and soil nutrient mining. The project assessed the increase in cereal demand until the year 2050 based on population growth and dietary change for ten SSA countries (Burkina Faso, Ghana, Mali, Niger, Nigeria, Ethiopia, Kenya, Tanzania, Uganda, Zambia). Using crop growth models, we evaluated whether SSA can be self-sufficient for cereals (maize, millet, rice, sorghum and wheat) in 2050 by intensifying crop production on existing cereal area. Next, within the project estimations were done on minimum required nutrient inputs (NPK) to prevent soil nutrient mining. For each country different scenarios of intensification and/or cropland expansion were explored, and greenhouse gas (GHG) emissions from fertilizers and land use change were calculated.

Intensification requires large increases in nutrient inputs and will therefore result in extra GHG emissions. Yet, it can bring much lower GHG emissions than cropland (cereal) expansion, but this depends on agronomic nitrogen use efficiency achieved. Thus, both avoidance of expansion and the widespread adoption of climate-smart agricultural practices leading to high nutrient use efficiency can mitigate GHG emissions.

The project therefore also assesses different options to increase rates of nitrogen use efficiencies and economic feasibilities in Ethiopia and Tanzania by investigating and testing climate-smart nutrient management options employing the “4R nutrient stewardship approach” (i.e., applying nutrients using the right source, at the right rate, at the right time and in the right place). It includes testing the combination of mineral and recycled organic sources of nutrients in on-farm and on-station trials as well as using data-mining and model-based analysis (the use of liming and the role of legumes in nutrient management).

Expected outcomes

  • Enabling evidence-based decision making on GHG mitigation at international, regional and local levels
  • Revised targets and INDCs for agricultural mitigation

Gender and youth

Gender is not a major focal point of the project, but we will certainly account for gender-specific aspects of nutrient management in the three countries.

More information

For more information, please contact project leader Martin Van Ittersum, WUR  (

Project Activities

1.1 Estimation of yield gaps of key legume crops in project countries
1.2 Development of a generic protocol to calculate and prioritize nutrient gaps
1.3 Mapping of nutrient gaps for different percentages of yield gap closure for project countries
1.4 Assessing GHG emissions of different intensification scenarios in project countries
1.5 Expanding nutrient gaps for other cereals

2.1 - Method development to identify nutrient management options at field-cropping system level using 4Rs
2.2 - Detailed and comprehensive assessment of nutrient management options at the field-cropping system level

3.1 - Running prototype of bio-economic farm model (NUTMATCH) for trade-off analysis at farm level of productivity (physical, economic), NUE and GHG emissions.
3.2 - Trade-off analysis at farm level to identify low emissions options
3.3 - First set of piloting experiments (on-farm and/or on-station) of promising nutrient management options
3.4 - Second set of piloting experiments (on-farm and/or on-station) of promising nutrient management options

4.1 Defining Technology Extrapolation Domains (TEDs) with climate, soil water and farming system dimensions
4.2 Testing of TEDs for Ethiopia, Kenya and Tanzania
4.3 Scaling out local work at field and farm level to the regional and national level

5.1 Project governance and external engagement
5.2 Communication and (end) user engagement

This project addresses the challenge of scaling climate smart nutrient management among African smallholder farmers by addressing the institutional factors and conditions relating to CSA knowledge service delivery (the CCAFS overall research question). It aims to understand and improve the 'scaling readiness' of climate smart, nutrient management decision support tools (DST) in different institutional environments: Ethiopia and Tanzania. 'Scaling readiness' is seen as the product of: (a) the fit between the DSTs (and its constituent climate smart nutrient management advices) and their envisaged users who operate at different scales, and; (b) the necessary (institutional) conditions which enable scaling by these different actors (i.e. extension, NGOs, agro-dealers). By working directly with different users operating at different scales, we examine the user logics that can inform the design of better decision support tools and the enabling (institutional) environments, which together shape the effective scaling of climate smart nutrient management advice.

Project Deliverables