Topsoil and ErosionNeil Swanson & Olivia Miller

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USDA-defined range of tolerable soil loss

(Montgomery, 2007, Wilkinson, 2007)

Current farmland erosion: ~75 Gt/yr

Americans move ~30 tons/year/capita

(Hooke, 2000)

How long will it take to erode through our soil?

Using geological erosion <0.2mm/year and agricultural erosion >1 mm/year, it will take a few hundred to a few thousand years

T = S/(E-P)

S = initial thicknessE = soil erosion rateP = soil production rate

Limiting lifespan of an agricultural society according to Montgomery, (2007).

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Soil conservation

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USDA-defined range of tolerable soil loss

(Montgomery, 2007)

Organic vs. conventional farming

http://ngm.nationalgeographic.com/2008/09/soil/richardson-photography