There are no substitutes for micronutrients which are indispensable for plant growth and the human diet; nevertheless low concentrations of these elements in African soils are looming and a cause for concern. In this PBL study, we determined the potential size of the demand for some key elements and investigated whether countries in Africa are ready to cope with that demand.
We combined novel data on soil micronutrient densities with agricultural development scenarios for Africa, and estimated the likely volumes of micronutrients required to sustain a pathway of agricultural intensification. Because of uncertainties in the relationships between nutrient availability, plant uptake and growth, we constructed a range for each element.
Understanding supply risks and vulnerability
Inspection of these ranges, expressed as a fraction of annual supply from global mining, suggests relatively modest demand for most elements. However, to fully appreciate whether these volumes are high or low, other variables also need to be factored in. Therefore, for each element, we assessed the supply risk, and, for each element and each country, the vulnerability to supply restrictions. Although the supply risks for manganese and zinc are sizeable, vulnerability varies considerably between countries, due to differences in national supply from mining, foreign currency reserves and the relative importance of the agricultural sector.
Getting the right nutrient at the right place
Supply from external sources thus becomes essential when seeking sustainable agricultural intensification. However, this also creates competition between farmers and industries over much sought-after elements such as boron and manganese.
The study identifies and discusses three main focus areas for policymakers:
- Competing non-agricultural and agricultural demands should be kept as low as possible; for instance by stimulating substitution, recycling and minimising losses.
- Fertiliser product innovation could be fostered through field trials and data collection, via public and private research and development.
- To bring impact to scale, farmgate fertiliser prices need to decrease, while, in some cases, mandatory application of lacking nutrients could be effective.