PARIS/SINGAPORE, April 28 -- Farmers around the world are facing the second surge in fertiliser prices in four years due to the Iran war. But with grain prices too low to cushion the blow from the deeper supply crunch this time around, many are rethinking planting plans, putting global food production at risk. The Middle East is a leading fertiliser production hub, and much of the global fertiliser trade typically passes through the Strait of Hormuz, which has seen traffic brought to a standstill by the conflict. Supplies of urea - a nitrogen-based fertiliser - from the world's largest production facility in Qatar have been halted, and flows of sulphur and ammonia, common inputs for a range of fertilisers, have also been curbed. With a resolution of the conflict proving elusive, analysts, traders, fertiliser producers and agronomists are looking back at the last supply crisis, Russia's 2022 invasion of Ukraine, worried that this time things could get even worse. "Back in 2022, a lot of the fertiliser was ultimately flowing through," said Shawn Arita of the Agricultural Risk Policy Center at North Dakota State University. "It's a much steeper supply crunch that we're seeing now." As fertiliser prices have jumped since the onset of the war in late February, urea has seen the sharpest price spike, reflecting the loss of the roughly one-third of globally traded volumes typically exported from the Gulf. Some are paying. India, the world's largest rice producer and second-biggest wheat grower, has booked record volumes of urea in a single import tender, paying nearly twice as much as it did just two months ago. But such price levels are beyond the reach of many, analysts say. In 2022, high global grain prices helped farmers offset the steep increase in input costs caused by the Ukraine war. But ample harvests of grains and oilseeds in recent years have restrained crop prices....