In an earlier article, we wrote that it will be difficult for Sub-Saharan Africa (SSA) to feed its own population by around 2050 without expanding arable land. This is true even with an accelerated increase in production per hectare, as the population is also still growing rapidly. To prevent famines, there are two additional options: further expansion of arable land and a sharp increase in food imports. Both options have major drawbacks.

First the good news. Agricultural production is growing faster on average in Africa than on other continents.

The bad news is that production per hectare, the productivity, is actually growing slower than elsewhere. In fact, almost half of the growth still comes from expanding arable land: from 196 to 223 million hectares in the period of 2006-2020 alone.

This comes at the expense of forests and savannahs, and in turn, biodiversity and climate, as clearing of land is accompanied by high emissions of CO2. Moreover, serious conflicts keep arising between arable and livestock farmers who are used to utilizing savannahs as natural pastures for their livestock.

Economically, this is not a desirable development either, because prosperity does not increase through expansion of agricultural land, but through increases in productivity (production per hectare and per worker).

One of the reasons for the average slow growth in productivity is that the natural production potential per hectare (i.e. the potential at the combination of soil and climate) of large parts of Africa is lower than that of soils in other continents (excluding Australia). Moreover, many soils are impoverished because for a long time more nutrients have been drained rather than supplied. This applies even to the naturally fertile soils in the East African highlands. But fortunately, potential production is still much higher than current levels. Therefore, substantial productivity growth is still possible.

Increasing productivity
How can farmers increase productivity? Mainly by taking better care of soil health and fertility through the application of soil amendments (especially organic matter and lime) and fertiliser. This usually has to include both, because without fertilisers there is rarely enough organic matter, while using only fertiliser eventually leads to soil degradation and is often associated with soil and water pollution. SSA must be able to avoid mistakes made earlier and elsewhere when intensifying its agricultural production. Europe and China are burdening their environments with too much fertiliser. In Africa, the green revolution in the 1960s and 1970s failed for several reasons, including the unilateral use of fertilisers.

Carefully combining fertilisers and organic matter is sometimes referred to as 'integrated soil fertility management'. It is a potentially powerful strategy because on soils rich in organic matter, nitrogen fertiliser can generate grain yields twice as high as on soils poor in it. In addition, what is not widely known is that even in arid areas, nutrient availability is often more limiting than water availability. In the Sahel, for example, water only becomes more limiting than nutrients at less than 300 mm of rainfall.

Organic matter
Where can that organic matter come from? Mainly from crop residues and roots, compost or animal manure. At the natural production potential (i.e. without artificial fertilisers) of fields and pastures, the availability of crop residues is nowhere near sufficient for agriculture that can feed today's population. Fertiliser can help remove that limitation; pastures become more productive and crop yields increase. So there is more manure, and as crop yields increase, there are also more crop residues. However, care must then be taken to ensure that the above-ground increased yield does not come at the expense of root growth, as this would actually be at the expense of organic matter accumulation.

There are three options for utilising crop residues. The farmer can
  • plow them under directly.
  • They also have the option to compost first. If this option is taken, nutrients, especially nitrogen, are lost.
  • The final option is for the farmer to first feed the crop residues to the cattle and then use the extra manure.
Even with that diversion, nutrients are lost, but the crop residues add to food in the form of milk and/or meat.

In areas with livestock, mixtures of grasses and legumes can be grown. Leguminous plants bind nitrogen, which is usually the most limiting nutrient for grass. For legumes, phosphate is often limiting. Consequently, phosphate fertiliser can also indirectly increase nitrogen availability.

As an aside, partly because of the drawbacks of mere fertiliser, the African Union broadened its initially too narrow focus on Fertilisers in the Abudja Declaration (2006) to Fertilisers and Soil Health. Under that title, the second Plan of Action for Increasing Agricultural Productivity is now being prepared and will be presented for endorsement at a summit of African heads of government next year. See also: H. Breman, 2023, Africa's fertilizer and soil health action plan: An African Green Revolution. Fertilizer Focus, 40-1: 36-41.

Maize sown under integrated soil fertility management (left) and simultaneously sown unfertilised maize (right) (East DR Congo), Henk Breman

Where can fertiliser come from? Only part of it is produced in Africa itself; phosphate fertilisers mainly in Morocco and nitrogen fertilisers in Nigeria. However, the world market is still a very important source and determines the price. As mentioned, fertiliser has continued to become more expensive for African farmers in recent years than it already was. First due to an export freeze by China, then by Covid, then due to logistical problems in the economic recovery, and more recently even further due to the Ukraine war. This pinches, because although fertiliser use in SSA increased from an average of 8 to 22 kg/ha over the period of 2006-2020, this was still far below the global average of 146 kg/ha and also below the African Union's provisional target of 50 kg/ha (Abudja, 2006). By 2020, only 7 countries in SSA had reached that target. Ultimately, there is still much to be gained, provided that soil improvement is also given adequate attention. Even more can be gained if quality seeds are used.

Agricultural inputs shop in Uganda sells fertiliser alongside organic inputs, Henk Breman

Three propositions
Three propositions follow from the above:
  1. In most SSA countries, agriculture can increase its productivity faster and much further;
  2. As productivity improves, less food needs to be imported. In addition, the need to expand the agricultural area diminishes and thus more forests and savannahs can be spared, which is also beneficial for biodiversity and climate)*;
  3. Increasing productivity requires, above all, integrated soil fertility management through soil improvement and increased use of fertilisers. Often, oth are often needed.

The key here is to avoid the mistakes that Europe and China, as well as Africa itself, have made before.

Governments can effectively encourage this development. How? We will address that question in a subsequent article.

* It is true that the production of fertilisers entails energy consumption and thus CO2 emissions, but these are much less than the emissions that would occur without fertilisers by clearing forests and savannahs. Moreover, integrated soil fertility management also sequesters carbon in soil organic matter.

Africa and intensification
This article is the first in a series of four on what Africa can do to improve its food security and development and how the Netherlands and the European Union may support that, by Henk Breman and Wouter van der Weijden.

Breman is an agrobiologist with long-term research experience in several African countries. Van der Weijden is an environmental biologist and director of the Dutch Stichting Centrum voor Landbouw en Milieu (Centre for Agriculture and Environment Foundation). They claim that sustainable agricultural intensification can be beneficial for food security, development, nature and climate. This is not in line with the much-heard pleas for organic farming in Africa and only half in line with the pleas for agroecological and regenerative agriculture.

In a previous article, they wrote that the war in Ukraine will have a negative impact on food security in Africa for several more years, even if the war would be over soon. The cause: besides food, fertilisers have also become much more expensive. Farmers who use fertilisers will be forced to reduce their use or even stop using them. Yet, there are also farmers who use just as much or even more fertiliser because they expect food prices to continue to rise.

In their four-part series, Breman and Van der Weijden address five questions:
  • How can agriculture in SSA increase its productivity faster?
  • What policies are needed to achieve this?
  • What are the prospects for food security and economic development?
  • Which other sectors can contribute to development?
  • How can the EU and the Netherlands support agricultural development?

Intensification is a loaded term. To avoid misunderstandings: Breman and Van der Weijden mean sustainable intensification, i.e. not agriculture with maximum use of inputs, but agriculture with higher production thanks to the most efficient use of fertilisers and soil amendments, improved seeds and plant protection products. This also requires application of organic matter, which can often only become sufficiently available if fertilisers are also used, providing more crop residues and roots and/or manure. Where possible, ecological and biological crop protection is always preferable to chemistry, say the authors.

The authors thank Prof Ken Giller, Dr Niek Koning and Prof Leo van Wissen for their comments on draft versions of this article.