The third Gulf war is worrying the world’s farmers. A third of seaborne fertiliser exports come from the region; most have been stopped by Iran’s blockade. Urea, the most widely used of the lot, is around 70% dearer than before the war; ammonia, another nitrogen fertiliser, is 39% pricier (see chart). Madeleine Overgaard of Kpler, a data provider, reckons nearly 1.9m tonnes of plant nutrients are stuck on board 41 ships that cannot leave the Gulf—equal to 12% of all the fertiliser shipped out of the strait in 2024.