Source: Practice Brief Climate-smart-agriculture: Integrated Soil Fertility Management
Healthy and productive soils are essential for food and nutrition security. However, soils may also contain chemicals or pathogens that can negatively impact human health. Poor soils also result in low yields and low household income.
In an IFPRI research seminar on May 8, 2019 Patrick Mutuo, a Courtesy Associate Professor at the Department of Soil and Water Sciences, University of Florida and a Visiting Scientist at the International Institute of Tropical Agriculture (IITA) presented on the status, challenges and future prospects for soil fertility management in sub-Saharan Africa.
Mutuo began his talk by citing FAO statistics, which show while average cereal yield productivity in Africa south of the Sahara increased from 1 t/ha in 2005 to 1.6 t/ha in 2014, the region continues to have much lower cereal yields than other continents. In China, cereal yields increased from 5 to 6.5 t/ha and in South America and Asia yields increased from 3 to 4.5 t/ha during the same time period.
Integrated soil fertility management (ISFM) aims to address this yield gap by combining good agronomic practices with better management of inorganic and organic fertilizers, seeds and other organic inputs, that are tailored for different cropping systems, soils, and socioeconomic profiles (Vanlauwe et al, 2010). Looking closer at the yield gap, Mutuo argued that the potential yield is constrained by several factors: (1) lack of technology, (2) lack of resources, and (3) decisions that draw resources from farming.
Mutuo then described recent research on the impact on soil fertility of agronomic practices that make up ISFM. Fertilizer use was seen as a basic prerequisite to economic development and Mutuo highlighted, that the use of fertilizers in Malawi has increased over the last decade. This increase is mainly related to the Malawi government Farm Input Subsidy Program (FISP), which was introduced in 2005/2006. A study by Nziguheba et al in 2010 across five African countries, implementing the Millennium Villages Project, showed that mineral fertilizers increased yields by almost 2 t/ha. Apart from mineral fertilizers, the incorporation of legumes can also boost nitrogen content in soils. Legumes act as organic nitrogen factories can capture 80–150 kg of nitrogen per hectare. They also recycle potassium and add organic carbon to soils. Legume yields can be further increased by inoculating seeds with bacteria and applying additional phosphorous to the soil. Mutuo then reported on recent trials with biochar in Kenya, which shows that biochar input of 10 t/ha in combination with Nitrogen-Phosphorous (NP) fertilizer can triple maize productivity over three years.
Adoption of good agronomic practices, using good varieties, managing fertilizer well and combining it with organic inputs will improve yields significantly. Farmers’ attitudes towards farming play a major role on the adoption of agronomic practices. Traditional farmers are much less likely to adopt a new technology than those farmers who actively seek information and network with others. A 2017 study by Nkonya et al. in Kenya, Rwanda, and Zambia noted the low uptake of ISFM in all three countries. While ISFM can substantially increase farmers’ profits over time, most studies find low adoption rates: farmers use mineral fertilizer, improved seeds, and organic inputs rather than engaging in comprehensive ISFM.
It takes time to sustainably intensify yields. Many agronomic practices, such as crop rotation and intercropping, take time to improve soil health, and yields will remain low until a fully healthy soil is achieved. ISFM can provide a faster pathway to improved soil health and increased yields. Mutuo further explained that soil testing is crucial to understand nutrient constraints, liming requirements, and the need to add organic matter and lime (where needed).
Mutuo concluded his presentation with his diagnosis of how to close the yield gap in Africa. Sub-Saharan Africa can move from 1 to 3 t/ha by increasing access to improved seeds and fertilizers. But going from 3 to 5 t/ha will require interventions across the entire agricultural value chain; involving changes to production, post-harvest handling, and markets. To close the yield gap in Africa, inputs and finance have to be available at scale and linked to improved production (agronomy), better processing and storage (technology), and enabling institutions (policy).
Further reading
Nziguheba et al., 2010. The African Green Revolution: Results from the Millennium Villages Project. Advances in Agronomy 109, 75–115.
Kihara et al., 2011. Effects of Tillage and Crop Residue Application on Soybean Nitrogen Fixation in a Tropical Ferralsol. Agriculture 1(1): 22–37.
Franke et al., 2016. Poor farmers – poor yields: socio-economic, soil fertility and crop management indicators affecting climbing bean productivity in northern Rwanda. Experimental Agriculture 1:1–21.
Nkonya et al., 2017. Mapping Adoption of ISFM Practices Study - The Case of Kenya, Rwanda & Zambia. https://doi.org/10.7910/DVN/1Y6C4J
Vanlauwe et al., 2010. Integrated soil fertility management - Operational definition and consequences for implementation and dissemination. Outlook on Agriculture 39(1):17–24.
Click here to download the presentation. (PDF 3 MB)
