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 reso...