898. Challenges in African Agriculture
―Contribution of Soil Microorganisms and the Potential of Neglected and Underutilized Plant Species―

1. Challenges for African food systems in a global context

Agriculture in Africa faces many challenges that must be addressed to improve production and human nutrition. The greatest challenge is making food products enough to feed the ever-growing population expected to triple by 2100. While the food required to provide the world population in 2050 will be 1.63 times that of 2007, in sub-Saharan Africa (SSA) and South Asia, it will be 2.32 times. Currently, Africa relies heavily on agricultural imports to feed its population. A key example is the primary reliance on Russia and Ukraine wheat. The recent conflict between Russia and Ukraine has shown how vulnerable countries that rely on food import could be.

Key historical events of the world food system directly or indirectly impacted Africa's food system. These events include the establishment of the fertilizer industry since 1840, the "Green Revolution" since the mid-20th century, the acceleration of globalization in the 2000s, the Russian-Ukrainian conflict of 2022, and very recently the declaration of the UN Secretary General in 2023 that "the world is now at a global boiling point." To eradicate hunger through increased production, the "Green Revolution" itself focused on a few strategic staple crops such as corn, rice, and wheat, and the use of large amounts of fertilizer with little regard for environmental concerns. As a result, global grain yields improved significantly, and the increase in food production outpaced the rate of population growth.

The Green Revolution was unevenly applied across the world. It was applicable in the Americas, characterized by large-scale/homogeneous conditions, with the selection of improved genetic resources and the realization of economy of scale through large-scale monocultures. It was also applicable in Asia, where highly fertilizer-responsive genetic resources, such as rice, are cultivated in homogenized agricultural conditions. However, it has been challenging to apply the Green Revolution to the African context, characterized by small scale and heterogeneous settings, complex agricultural conditions due to weathered and heterogeneous soils, and the inter/intra-regional diversity of the management system. Still, the genetic diversity unique to tropical/subtropical regions of Africa has positive implications for providing healthy foods but also has a vast potential of "neglected and underutilized plant species'' crucial for human nutrition.

2. Climate change and its impacts in Africa

The heavy use of chemicals to eradicate hunger is causing some elements, such as nitrogen, to cross planetary boundaries, posing a threat to Earth's health. The food production systems, which include the use of chemicals and deforestation in search of arable lands that continues in some areas, are significant contributors to greenhouse gases (GHGs). Although Africa is not considered to contribute to GHG emissions, it suffers from impacts such as global warnings (boils), flooding, and recurrent droughts. Unfortunately, grain yields are said to decrease by approximately 5% for every 1-degree Celsius increase in temperature, which is significant in Africa. Therefore, climate change is expected to reduce wheat yields in Africa by 15% by the mid-century. The most affected region is the Sahel region, which stretches from eastern to southern countries. Southern African countries such as Mozambique, Zimbabwe, and South Africa will likely be much affected. Therefore, countermeasures must be taken to limit the effect of climate change, including accelerating the breeding of new, adapted varieties, introducing smart agriculture, and promoting the use of NUS, which are considered more resilient to climate change.

3. Soil fertility issues in Africa and the potential of soil microorganisms

Above all, it is difficult to maintain crop production on infertile soils. Therefore, it is essential to overview the African soil fertility challenges in the current context of rising fertilizer prices and introduce the potential contribution of soil microorganisms in improving crop production. African soils are globally poor in key elements such as phosphorus and nitrogen. The high phosphorus retention in the weathered soils in the central parts of Africa up to Madagascar limits the utilization efficiency of applied phosphorus. In southern countries and the Sahel region and above, phosphorus retention is low, but soils are deficient in phosphorus. The difference in soil phosphorus status across the African regions implies applying a different phosphorus management system. One of these strategies is manufacturing fertilizer using locally existing materials. In the SATREPS project with Burkina Faso, the International Agricultural Research Institute introduced phosphate rock-rhizosphere soil-compost as a fertilizer that significantly revitalizes the soil and improves its biological health while increasing crop yields. The rhizosphere soil is a habitat for beneficial microorganisms containing phosphorus solubilizers that promote the solubilization of phosphorus in phosphate rock during composting. Mature compost not only contains more available phosphorus but also more phosphorus-solubilizing microorganisms that can accelerate phosphorus cycling when applied to fields. This compost can compete with chemical fertilizers in crop production and is more environmentally friendly. 

To rely less on nitrogen fertilizers, soil nitrogen limitation may be overcome by cultivating leguminous crops, which generate nitrogen through symbiosis with nitrogen-fixing bacteria that fix atmospheric nitrogen. When leguminous cover crops are used, they also enhance carbon sequestration and reduce soil erosion due to the soil coverage. However, the population increase and the search for new arable lands do not favour the extensive adoption of non-edible leguminous cover crops nowadays. As an alternative, it is possible to isolate and purify high nitrogen-fixing bacteria and use them as biofertilizers. In a study conducted in Cameroon, we isolated bacteria from Pueraria phaseoloides root nodules and identified strains (Bradyrhizobium yuanmingense) with a high nitrogen fixation potential. Field inoculations using the strain significantly increased the amount of nitrogen in plants and crop growth. The fixed nitrogen can be beneficial to associated and subsequent crops.

Arbuscular mycorrhizal fungi (AMF) are another important group of microorganisms that enhance plant phosphorus uptake. They infect the roots of plants, extend their hyphae to deeper soil horizons, extract phosphorus, and transport it to the plants. Therefore, AMF-inoculated plants grow better than non-inoculated plants. Colletotrichum tofieldiae (Ct) is also a fungus identified to increase plant phosphorus uptake in low-phosphorus soils.

4. Potential of NUS for improving nutrition in Africa

In Africa, the use of only a few crops that are sensitive to climate change has contributed to low crop production with associated nutritional deficiencies (21% in 2020, World Vision). There is a need to promote context-smart agricultural technologies that can function under climate change, are compatible with markets, and provide sufficient nutrients for human health. One of the strategies is to promote NUS. Although NUS is used in food, medicine, trade, and cultural practices, it has never been widely commercialized or studied as part of mainstream agriculture. The NUS may be part of the crops used by humans throughout history or the globally identified but not widely used plant species. There are approximately 45,000 plant species in Africa, 5000 of which are in use, indicating the presence of many NUS.

Furthermore, many species are so neglected that their characteristics may be lost. With low water requirements and tolerance to poor soils, promoting NUS contributes to reducing the environmental footprint and improving the health of the planet and humans. Developments in biotechnology have the potential to accelerate G (Gene) x E (Environment) research, like the breeding of diverse genetic resources to meet heterogeneous needs under diverse edaphoclimatic and socio-economic conditions. Smart or digital agriculture can facilitate M (Management) x E (Environment) research or detailed optimization of agricultural practices. In Africa, NUS crosses a variety of plant groups, from legumes like Bambara beans to grains like teff and fonio, to roots and tubers, to trees, and more. In this way, NUS has the potential to contribute to improving nutrition and promoting health in Africa.

References

877. Seminar on “Neglected and Underutilized Plant Species: Their Contribution and Potential for Sustainable Food Systems in Sub-Saharan Africa”
https://www.jircas.go.jp/en/program/proc/blog/20231013

714. Achieving both food production and improving soil fertility through the power of soil microorganisms
https://www.jircas.go.jp/en/program/proc/blog/20230209

Press Release: Development of Organic Fertilizer Production Technology Using Low-Grade Phosphate Rock - Yield increase effect comparable to chemical fertilizer due to the action of soil microorganisms https://www.jircas.go.jp/en/release/2022/press202212

Project on establishment of the model for fertilizing cultivation promotion using Burkina Faso phosphate rock. https://www.jircas.go.jp/en/satreps-burkinafaso
 

Contributors: Sarr Papa Salou (Crop, Livestock and Environment Division), IIYAMA Miyuki (Information Program), and NAKASHIMA Kazuo (Food Program)