Soil Erosion: Why soil is disappearing from farms
Even if wind and water erosion were eliminated, modern agriculture is fundamentally a form of mining.<p>Farmers grow crops that remove nitrogen, phosphorous, potassium and a variety of other minerals from the soil. The crops are shipped to cities typically located on rivers or oceans. The crops are processed, eaten and the nitrogen, phosphorous, potassium and other minerals are flushed into the rivers and oceans.<p>The elements can be replaced as long as supplies of natural gas to fix atmospheric nitrogen and reserves of potash and phosphate rock last. But it is ultimately unsustainable.