LAND RESOURCES: From The American Journal of Clinical Nutrition More than 99.2% of US food is produced on land, while < 0.8% comes from oceans and other aquatic ecosystems. The continued use and productivity of the land is a growing concern because of the rapid rate of soil erosion and degradation throughout the United States and the world. Each year about 90% of US cropland loses soil at a rate 13 times above the sustainable rate of 1 ton/ha/y (28). Also, US pastures and rangelands are losing soil at an average of 6 tons/ha/y. About 60% of United States pastureland is being overgrazed and is subject to accelerated erosion. The concern about high rates of soil erosion in the United States and the world is evident when it is understood that it takes approximately 500 y to replace 25 mm (1 in) of lost soil (28). Clearly, a farmer cannot wait for the replacement of 25 mm of soil. Commercial fertilizers can replace some nutrient loss resulting from soil erosion, but this requires large inputs of fossil energy.
Posted on: Mon, 09 Sep 2013 16:31:17 +0000
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