N2Africa – Putting nitrogen fixation to work for smallholder farmers in Africa


N2Africa is a large scale, development to research project focused on increasing inputs from biological nitrogen fixation (BNF) by grain and fodder legumes among smallholders in sub-Saharan Africa. Net soil nitrogen accrual from the incorporation of grain legume residue in Africa can be as much as 140 kg N ha-1depending on the legume type and variety. This N tends to be released quickly when legume residues are incorporated into the soil and can contribute to substantial improvements in yield of subsequent crops. Grain legumes are also a key source of nitrogen-rich edible seeds, providing a wide variety of high-protein products and constituting the major source of dietary protein in the diets of the poor in most parts of sub-Saharan Africa. Legumes such as groundnut and soybean are also major sources of edible oil and other industrial by-products. In addition, residues of grain legumes as well as herbaceous and fodder tree legumes provide an excellent source of high quality feed to livestock especially during dry seasons when animal feeds are in short supply. 

Successful BNF by legumes in the field depends on the interaction: (GL×GR)×E×M

(Legume genotype × Rhizobium strain) × Environment × Management 

where environment encompasses climate (temperature, rainfall, day length etc to encompass length of growing season) and soils (acidity, aluminum toxicity, limiting nutrients etc). Management includes aspects of agronomic management (use of mineral fertilizers, sowing dates, plant density, weeding). Incidence of diseases and pests are also a function of (GL× GR) × E × M. Thus establishment of effective BNF depends on optimizing all of these components together. Legumes are often women’s crops, grown for home consumption and they are thus often grown in poorer soils with little application of manure. They are also allocated less attention in terms of labor for crop management. This means that E and M often override the potential of the legume/rhizobium symbiosis for BNF. Understanding these interactions, how these are affected by constraints at a farm or farming system level and what this means for the ability of different farmers to adopt legume technologies are key in the research activities of this project.

Various research topics can be addressed through a thesis within the framework of N2Africa: 

-       Research on legume varieties, inputs, intercropping, crop rotations, and non-responsive soils with the objective of understanding the variability in responses of legumes to inputs and rotational effects of legumes at a field level

-       Characterisation of farming systems and studies of adoption processes with the aim to identify socio-ecological niches for legume technologies among different types of farmers

-       Farm simulation modeling to assess current farming systems and explore scenarios with an increased adoption of legume technologies impacting households’ food self sufficiency and ability to generate cash income


N2Africa is led by Wageningen University together with CIAT-TSBF,IITAand has many partners in the Democratic Republic of Congo, Ghana, Kenya, Malawi, Mozambique, Nigeria, Rwanda and Zimbabwe. Currently, new partnerships are established in Ethiopia, Uganda, Tanzania. 


Several courses are relevant such as Analysing Sustainability of Farming Systems, Crop Ecology, Systems Analysis & Simulation, and QUALUS. 

Location and Period

Wageningen and various African countries. Projects can start any time


Ken Giller                                           0317 – 48 58 18                      ken.giller@wur.nl

Joost van Heerwaarden                      0317 – 48 69 40                      joost.vanheerwaarden@wur.nl