Price of sulfur, a key but secondary fertilizer ingredient behind nitrogen and potassium, rises to $500 a ton from $50 a ton a year ago.

From The Wall Street Journal Online:

The use of food crops for biofuel at a time of fiscal and ecological petroleum worries isn't the only contentious nexus between surging food and oil prices. Fertilizer is also kicking up a big stink.

Demand for sulfur, long an ugly yellow waste product of petroleum refining, is surging as well, because it's needed to make sulfuric acid, which in turn is essential to the production of fertilizer, as the Times of London reports. The likes of Royal Dutch Shell, Chevron, Saudi Aramco and Abu Dhabi national oil producer Adnoc are expected to get windfall profits from the sulfur market, which has seen prices rise to $500 a ton from $50 a ton a year ago, the Times adds. And it isn't hard to see where the demand is coming from. In the U.S., fertilizer use has pushed prices for the plant nutrient up 65% in the past year -- faster than the 43% increase in farmers' fuel prices and a 30% increase in prices for seeds, as The Wall Street Journal points out. Sulfur is a key but secondary fertilizer ingredient, behind the nitrogen and potassium usually contributed through potash, and the phosphorus that comes in the form of phosphate. And the Journal reports farmers believe the small group of U.S., Canadian and Russian companies that dominate markets for potash and phosphate have too much market power. In some countries, these producers enjoy unusual protection from antitrust rules.

Whatever the cause, "those skyrocketing costs are making it harder for farmers to expand their harvests in response to the global food crisis that has sparked rioting, rationing and export controls in many countries," the Journal notes.