U.S. soil erosion not as severe as thought

Planting cotton in ultra-narrow rows in rye residue protects is one of the soil conservation efforts that appears to be working

Fertile topsoil is not flowing down the Mississippi River into the Gulf of Mexico as fast as thought, according to research published in the Aug. 20 issue of the journal Science.

Stanley Trimble from the University of California, Los Angeles, said that his study challenges other research that concludes aggressive farming practices are causing erosion to become as serious as it was during the dust bowl six decades ago.

In 1995, David Pimentel of Cornell University in Ithaca, N.Y., reported in Science that the world had lost nearly one third of its arable land over the past 40 years due to unsustainable farming practices.

Trimble gathered 140 years worth of information about sediment buildup and erosion from the Coon Creek River and its tributaries in Wisconsin farm country. He concluded that soil erosion overall in this watershed has been steadily decreasing, to six percent of what it was during the 1930s.

During the dust bowl of the 1930s, poor land management practices contributed to soil erosion

That means, he said, that soil conservation efforts appear to be working. Since the 1980s, more farmers have been trying new techniques, for example, tilling the soil as little as possible, or fitting crops to the contours of the land.

To reach his conclusion, Trimble reasoned that if soil were really eroding from the croplands around Coon Creek River, then it should show up in various spots throughout the watershed as well. He found that the buildup of sediment in the watershed had been progressively slowing down.

"We found that much of the sediment in Coon Creek doesn't move very far, and that it moves in very complex ways," said Trimble.

He believes that watersheds are more intricate than scientists have imagined and that existing models of erosion need to be re-evaluated.

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