Top Soil Depletion

Top Soil Depletion

Top Soil Depletion

Top Soil Depletion

Topsoil depletion occurs when the nutrient-rich organic topsoil, which takes hundreds to thousands of years to build up under natural conditions, is eroded or depleted of its original organic material. Historically, many past civilizations’ collapses can be attributed to the depletion of the topsoil. Since the beginning of agricultural production in the Great Plains of North America in the 1880s, about one-half of its topsoil has disappeared.

Depletion may occur through a variety of other effects, including overtillage (which damages soil structure), underuse of nutrient inputs which leads to mining of the soil nutrient bank, and salinization of soil.

According to Alan Durning of the WorldWatch Institute, it costs about 35 pounds of eroded topsoil to produce one pound of feedlot steak. To replenish the lost soil, however, is not easy. Scientists believe it takes between 200 and 1,000 years to create
one inch of topsoil under natural conditions. It is estimated that the direct and indirect costs of soil erosion in the U.S. alone exceed $44 billion a year.1
Michael Karr, Ph.D. is an ARCPACS Certified Professional Soil Scientist. He wrote a brilliant paper entitled, MINERAL NUTRIENT DEPLETION IN US FARMS AND RANGE SOILS.
He dispels many myths including one that suggest that plants get all of the nutrients they need from the soil and therefore we get all of the nutrients we need by eating those plants. He says, “Plant absorption of mineral nutrients is dependent upon not only the presence of the necessary mineral nutrients in the appropriate amounts but also the existence of favorable conditions to facilitate absorption.”
See especially in the US we produce crops that are then exported or used in a way where the nutrients will never return to the ground from which they came. Karr says, “The practice of removing part or all of the crops grown from the soil accelerates the loss of nutrients from the soil. The cycling of nutrients from plant uptake and release is interrupted by crop removal. This loss, if not corrected by fertilization, must be made up by nutrient release from primary soil minerals and from soil organic matter.”

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