However, the quantity of crops produced was more than twice that of 1948. In both years, the crops were produced with approximately the same overall quantity of measured inputs such as labor, capital, fertilizer, and pesticides, resulting in much higher production per unit input in 1997. Recreation is an important use of cropland in some areas, but no comprehensive data exist on the acreage used for recreation or farm income from recreation. Information on recreational uses of cropland will likely remain incomplete in the near future. Soil quality is affected by multiple factors.
Soil erosion affects cropland productivity and water quality.
Cropland with highly erosion-prone conditions declined by more than 28 million acres, from 30 percent of US croplands to 24 percent, between 1982 and 1992, while the amount of cropland with low susceptibility to erosion increased by 31 million acres. Erosion is not measured directly, and additional work is required to reach agreement on a preferred measure for reporting on erosion. Most states had high levels in fewer than 25 percent of soil samples. Irrigated acreage has risen by 25 percent since 1969, accompanied by a 25 percent drop in water used per acre. Concentrations of most forms of nitrogen and phosphorous considered to be water pollutants are generally higher in agricultural streams and ground water than streams and groundwater in residential or forest areas.