Fertilisation des sols en Afrique : entre organique et minéral, un jeu d’équilibriste

Current events continue to be marked by the sharp rise in the price of mineral fertilizers on global markets. This is impacting the production costs of basic agricultural food products in many regions of the world. Furthermore, the climate emergency has led to a rediscovery of the benefits of soil organic matter content and highlighted the contribution of certain synthetic fertilizers to GHG emissions. It is therefore time to seek the best options for agriculture and the climate, particularly in Africa.

This topic was discussed on October 2, 2023 during a round table organized by the FARM Foundation, in partnership with Inter-Réseaux Développement rural and the Cité du développement durable which made it possible to take a quick look at most of these questions^[1].

Is the global context in the fertilizer market a new constraint for Africa or an opportunity for agroecological intensification?

Global prices for synthetic fertilizers (N) and minerals (P, K) reached record highs at the end of 2022. Since the beginning of 2023, they have returned to less extravagant levels but remain high. Against a backdrop of growing global demand, this sharp rise was driven by the post-Covid-19 pandemic recovery. The peak reached in spring 2022 was triggered by the war between Russia and Ukraine, which sent the grain and oilseed markets, as well as fertilizers, into a tailspin.

Thus, Africa appeared to be doubly dependent, in fertilizers and in agricultural commodities necessary for its food (cereals and oilseeds). Even if these two dependencies must be put into perspective[2], they justify the reactions of African governments (diplomatic commitment to a Black Sea maritime corridor, tariff reductions, and fertilizer subsidies). The strategic question of the place of fertilizers in agricultural systems is back at the heart of continental discussions on agricultural development. Thus, from November 5 to 7 in Nairobi, an African Union summit was held dedicated to "Fertilizers and Soil Health"[3] whose agenda addressed the economic and structural issues for the continent.

Globally, per hectare of arable land^[4], the level of fertilizer consumption is very variable. It is falling in the countries that are the biggest consumers. Thus, in France, after a maximum of 350 kg/ha in 1990, it fell to 153 kg in 2021. In China, after a world record of 474 kg/ha in 2015, it fell to 374 kg in 2021. We are very far from these levels in Africa (3% of global consumption), with 75 kg/ha north of the Sahara, as well as south of the Sahara with 23 kg/ha.

However, the most recent recommendations from agricultural research in West Africa are in the order of 100 kg/ha^[5]This gap between uses and recommendations has long been a concern for those involved in agricultural development. There are many reasons why fertilizers have historically been underused, on average, on the African continent. In "forest" regions, low population densities allowed fertility to be restored through long fallow periods, and the use of mineral fertilizers was limited until very recently. In areas where rainfall is unpredictable and without water control, there is a high risk of not obtaining a sufficient yield to cover the cost of fertilizers, hence low use.

Conversely, the use of fertilizers is closer to the recommendations in sectors where contractualization with downstream parties makes it possible to overcome the failures of financial services to farmers, the failures of markets (products, inputs) and agricultural advice, or in irrigated areas.

But, overall, the modest use of mineral fertilizers results in low yields. Of course, there are other explanatory factors, whether technical (irrigation, genetics, phytosanitary, consulting, R&D) or political (taxation, land). These low yields result in the expansion of cultivated areas to the detriment of areas of ecological interest and in fine an erosion of Africa's agricultural trade balance, whose domestic demand for agricultural products is increasing, driven by demographics, urbanization and rising living standards. Thus, both governments and professional stakeholders in the agricultural sector have good reasons to support a reasonable increase in the use of fertilizers in Africa.

However, at the international level, for several years, scientists have been changing their recommendations for soil fertility. The importance of organic fertilization has been rediscovered. For three reasons. First, it concerns the effectiveness of mineral fertilizers (best used in rich soils) and resilience to climatic hazards (humus retains moisture better). Second, preserving or increasing soil organic matter is an inexpensive way to store carbon and could be paid for as an ecosystem service. Finally, locally, excess mineral fertilizers are harmful to the environment and health (climate, water, air).

It is therefore no longer relevant to oppose "modern" (pro synthetic fertilizers and minerals) and "post-modern" (pro organic fertility through photosynthesis which fixes atmospheric carbon and nitrogen). The right combination of the two sources of fertility, depending on the soils and climates, is essential. This is a key dimension of a agroecological transition preserving production capacities which is now well documented by numerous agricultural research projects on all continents[6], and which are relayed at the political level. In this regard, we can cite the FAO global partnership for soils established at the end of 2012[7], And the international initiative "4 per 1000"^[8] carried in 2015 by France during the COP 15 Climate.

When it comes to organic fertility, Africa has some very good cards in hand, but the rules of the game are changing...

Organic fertility renewal practices are very diverse and, above all, very perennial on the African continent, in all agrarian systems. From agro-forestry wetlands where the power of photosynthesis allows for strong and rapid biomass production, to Sahelian zones, where knowledge of water conservation in soils goes hand in hand with measured fertilization, using powders[9] livestock parks or wooded parks Faidherbia albida[10]. Generally speaking, the techniques are well known to farmers : intercropping, particularly legumes, agroforestry, permanent plant cover, shallow tillage, even zero tillage, all forms of livestock-agriculture integration, etc.

However, these organic solutions are not so easy to implement. Photosynthesis converts atmospheric carbon and nitrogen into fertilizers, but these resources are neither completely free nor completely open to the public.

Organic fertilization requires a lot of work (service crops, residue collection, transport, grinding, handling of manure or compost, spreading). It therefore has a cost that agricultural markets must pay.

Also, organic matter is not accessible to everyoneMaintaining organic fertility requires long-term management on farms and transfers of fertility from common areas to farms. In particular, "institutions" are needed that can regulate the sharing of access to pastoral commons, agricultural conquests of savannahs and forests, and common grazing on crop residues. Therefore, public land, pastoral and forestry policies are decisive for organic fertility. However, in many regions, historical intercommunity agreements between farmers and transhumant herders or pastoralists are being disrupted by demographics, the expansion of cultivated areas, and the growth of livestock owned by farms. These farms increasingly intend to reserve for themselves the fodder resources, residues from their fields, and rangelands of their land. Thus, the transfer of organic matter from common areas via the droppings of transhumant herds to farms is more difficult.

In general, the organic fertilization of farms by animal droppings must be understood as a transfer of organic matter, and therefore of fertility, between the spaces (natural or cultivated) which produced the animal feed and the cultivated spaces where the manure is spread. These transfers must also be analyzed in light of the loss inflicted on the soils which produced them.[11]. It should be considered that good organic fertilization is only produced very locally. Ideally in the plot, on the farm or in its immediate vicinity. This requires great precision in the technical itineraries, necessarily specific to each agro-system. As soon as it is requested (and has the means), research is now able to propose the appropriate coupling organic solutions (increase organic carbon in soils, capture nitrogen) with precision mineral fertilization (in its composition, dosage, application, etc.).

For mineral fertilizers, the price increase has triggered political initiatives, both short term (aid to farmers) and long term (knowledge, production, formulation and distribution).

As the FARM Observatory on public support for agriculture shows that the very low support that African farmers receive compared to farmers in other regions of the world is largely allocated to input subsidies, of which fertilizers represent a majority share. This old and simple method of supporting sectors has always been debated, due to its cost. Historically, this fertilizer subsidy often benefited only farmers who participated in integrated sectors that allow the pre-financing of inputs (cotton for example). Now, some countries offer "vouchers" (purchase vouchers) accessible to all farmers.

Criticisms regarding the budgetary cost of input subsidies are largely unfounded. The budgetary cost of an aid method without administrative costs is offset by tax revenues from export sectors. Moreover, in contractual sectors such as cotton, farmers do not hesitate to optimize fertilizer use, to which they are entitled by their reference sown areas across all their crops. Moreover, some companies can allocate, and therefore pre-finance, volumes of fertilizer greater than the needs of the contracted crops alone. Furthermore, group orders at the level of a sector, or even a country, make it possible to negotiate prices internationally.

So, in the present situation, The budgetary effort of certain countries to reduce the impact of the increase in mineral fertilizers via fertilizer subsidies appears to be quite legitimate.

Nonetheless, this method has its drawbacks. The porous nature of borders means that the most generous country subsidizes farmers in its less generous neighbor. This raises a difficult issue for regional cooperation. Furthermore, when fertilizers are distributed by state services, this does not allow for the structuring of distribution networks adapted to the very wide diversity of agricultural systems. In this regard, the deployment of "vouchers" for "mixtures" that comply with specific fertilization guidelines for soils and crops should be welcomed.

Moreover, Africa's autonomy in mineral fertilizers is a matter of continental industrial policy. With the notable exception of the world leader, the Office Chérifien des Phosphates (OCP).[12], long-standing commitment to industrial and technical partnerships in several countries on the continent, investments are insufficient. Not all phosphate, lime, or potash deposits are exploited. Urea production in oil-producing countries is exported to other continents. Solar energy, which is so abundant, is not yet used to manufacture urea... There are few mixing and formulation plants. And organic fertilizer production units from agro-industrial residues are still too rare.

So we can only wish with others[13], that in view of the continental and global issues at stake in the transformation of agriculture in Africa, countries should equip themselves with national “soil fertility and health” strategies ambitious and comprehensive. The scope of these policies is broad, from organic to mineral, crossing their agricultural and industrial policies, regulatory incentives and financial aid for investments in skills as well as in sectors.

We must also hope that these dimensions are much more supported by international Climate Finance mechanisms so that African states can invest in their soils by fixing carbon there.[14], for themselves and for the Planet!

[1] This event was hosted by Olia Tayeb Cherif (FARM). It brought together Salif Ayefoumi Olou Adara (ROPPA), Hubert Cochet (AgroParisTech), Julie Stoll (Fair Trade France), Paul Luu (4 per 1000), Matthieu Le Grix (AFD) and Marc Chapon (AVSF Benin).

[2] As the FARM Foundation recalled in a recent publication devoted to the impact of the war in Ukraine, the dependence on agricultural products from the Black Sea concerns the Mediterranean countries more than the countries south of the Sahara, and in these countries, the big cities more than the countryside.

[3] https://au.int/en/announcements/20231011/africa-fertilizer-and-soil-health-afsh-summit-call-side-event

[4] https://donnees.banquemondiale.org/indicateur/AG.CON.FERT.ZS?contextual=aggregate&locations=ZG-CN-FR-BR-ZQ

[5] http://www.coraf.org/wp-content/uploads/2023/11/Livre-paquet-intrant-agricole-coraf.pdf.

[6] See for example: https://www.cirad.fr/dans-le-monde/nos-directions-regionales/afrique-de-l-ouest-foret-et-savane-humide/actualites-afrique-de-l-ouest-foret-et-savane-humide/plantes-de-couvertures-au-benin

[7] https://www.fao.org/global-soil-partnership/fr/

[8] https://4p1000.org/

[9] Powdered manure is the manure from livestock pens in the Sudano-Sahelian region, mainly composed of feces mixed with the soil by trampling livestock. This soil is used as fertilizer.

[10] A tree species characteristic of Sahelian ecosystems, providing numerous agricultural services. See for example “Faidherbia albida”, the refuge tree of Sahelian agriculture (lemonde.fr)

[11] The extreme example, less important in Africa than in Europe, is the intercontinental transfer of fertility from intertropical agricultural zones subject to deforestation via manure from animals fed on imported feed (corn, soybeans).

[12] See for example, in 2023, in Rwanda: https://afriquemagazine.com/ocp-africa-rfc-l-usaid-et-cnfalancent-un-vaste-programme-de-soutien-aux-agriculteurs-rwandais

[13] https://theconversation.com/reconcilier-engrais-mineraux-et-agroecologie-une-piste-pour-nourrir-les-populations-dafrique-de-louest-214183

[14] https://theconversation.com/pieger-le-carbone-dans-le-sol-ce-que-peut-lagriculture-216768