Urea, a key ingredient in agricultural fertilizer and diesel fuel, is skyrocketing in price due to disruptions in the global supply of this essential chemical. The dramatic rise in the cost of urea exports, which have in turn led to increased food and fuel prices, is exposing the vulnerabilities of an interconnected supply chain. The price of urea has risen over 70 percent this year, as urea futures have surged on high coal prices and concerns over low energy supplies. China and Russia, the world’s biggest producers of urea, have restricted exports to ensure supplies for domestic consumption, forcing countries to find alternative suppliers. China accounts for about a tenth of the world’s urea-based fertilizer exports and a third of exports of diammonium phosphate, another type of crop nutrient, according to the World Bank. South Korea and Australia, which import almost all of their urea from China, are facing critical shortages …