Choked off shipping in the Strait of Hormuz isn't just grinding oil tankers to a halt. The Iran war is creating a one-two punch for the world's fertilizer supply, blocking both the export and one of its critical ingredients from leaving the Persian Gulf. It remains to be seen whether the temporary ceasefire reached on Tuesday will significantly ease that blockage. Nearly half of the world's traded urea, the most widely used nitrogen-based fertilizer, comes from the Gulf. As does one-fifth of the world's liquified natural gas (LNG). A quick chemistry refresher: the century-old Haber-Bosch process combines nitrogen from the air with hydrogen (that's where the LNG comes in) to make ammonia, which you need to produce nitrogen fertilizers. "This is literally a step removed from the worst-case scenario," Josh Linville, who tracks global fertilizer markets for the commodities firm StoneX, told DW. Fertilizer and LNG plants from Qatar to Bangladesh have already begun shutting down .…