Nitrogen and other nutrients are essential in the production of crops used for food, feed, fiber, and biofuel. Applied annually, most of these nutrients are absorbed by the crops, but when applied in excess, they can be lost to the environment through volatilization, leaching, or runoff, contributing to air and water quality impairment. For corn, the share of planted acres with excess nitrogen applied (over 125 percent of the crop’s needs) declined from 59 percent in 1996 to 47 percent in 2010. Cotton also exhibited declining shares of planted acres with excess use of nitrogen, while winter wheat exhibited a slight decrease in share since 2004 after increasing earlier in the decade. Yield growth is a major factor improving nutrient use efficiency in corn in recent years. Higher yields result in more nutrients being absorbed by the crop, thus reducing nutrient losses. Yields (and efficiency) have benefited from increased crop rotation (corn planted after soybeans), soil testing for nitrogen, use of genetically engineered seeds to reduce pest damage, seeding rates, and adoption of precision technology (such as yield monitors and soil maps). This chart comes from the Crop & Livestock Practices topic page on the ERS website, updated December 2012.