U.S. farmers planted about 90 million acres of corn last year, aiming to profit from high prices driven by high demand for corn for ethanol production. That was a 15 percent increase from 2006, and the largest acreage of corn planted since 1944, according to the National Agricultural Statistics Service.

Almost every acre of corn is treated with an average of 136 pounds of nitrogen per year, statistics from The Fertilizer Institute’s Web site show. That adds up to more than 12 billion pounds of nitrogen applied just to corn. The amounts of phosphate and potash applied to corn are also relatively high, at an average of 60 pounds and 85 pounds per acre, respectively.

Area planted to wheat increased to 60 million acres last year, the NASS reported. Eighty-six percent of the acreage was treated with nitrogen at an average rate of 68 pounds per acre.

Plantings of sorghum, canola, and barley also increased. However, plantings of soybeans were down significantly. Soybeans are treated with a relatively low rate of nitrogen (21 pounds per acre) but a high rate of potash (89 pounds per acre).