Nigeria, April 28 -- Africa's next food crisis may not begin on the farm, but in a distant shipping lane. With the Iran war, international attention has focused on oil flows through the Strait of Hormuz and related shortages or price spikes in energy and fuel. Less visible is another vulnerability moving through the same corridor: the fertilisers underpinning global food production.

Fertiliser supply disruptions feed directly into food prices and agricultural output, and most African countries have high import volumes and are ill-positioned to absorb the shock. Domestic production in Africa is insufficient to meet the growing demand.

Production capacity exists in parts of North and West Africa, driven by massive phosphate deposits and n...