Nitrogen, phosphate, and potash 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 into the air, leaching into ground water, emission
from soil to air, or runoff into surface water. These losses can be
reduced by the adoption of best management practices that match
nutrient supply for crop needs, minimize nutrient losses, and
enhance plants' capability to uptake nutrients. For corn, the share
of planted acres with excess nitrogen applied (above 25 percent of
the crop's needs) declined from 59 percent in 1996 to 47 percent in
2010, while the share of acres with excess phosphate declined from
43 percent in 1996 to 31 percent in 2010. Other crops also exhibit
either declining or unchanged shares of planted acres with excess
use of nitrogen or phosphate. This chart can be found in the ERS
report, Agricultural Resources and Environmental
Indicators, 2012 Edition, EIB-98, August 2012.