ScienceDaily (July 24, 2007) — Organic farming can build up soil organic matter better than conventional no-till farming can, according to a long-term study by Agricultural Research Service (ARS) scientists.

Researchers made this discovery during a nine-year study at the Henry A. Wallace Beltsville Agricultural Research Center (BARC), Beltsville, Md. BARC is operated by ARS, the U.S. Department of Agriculture's chief scientific research agency.

Plant physiologist John Teasdale, with the ARS Sustainable Agricultural Systems Laboratory in Beltsville, was surprised to find that organic farming was a better soil builder than no-till. No-till has always been thought to be the best soil builder because it eliminates plowing and minimizes even light tillage to avoid damaging organic matter and exposing the soil to erosion.

Organic farming, despite its emphasis on building organic matter, was thought to actually endanger soil because it relies on tillage and cultivation—instead of herbicides—to kill weeds.

But Teasdale's study showed that organic farming's addition of organic matter in manure and cover crops more than offset losses from tillage.

From 1994 to 2002, Teasdale compared light-tillage organic corn, soybean and wheat with the same crops grown with no-till plus pesticides and synthetic fertilizers.

In a follow-up three-year study, Teasdale grew corn with no-till practices on all plots to see which ones had the most-productive soils. He found that the organic plots had more carbon and nitrogen and yielded 18 percent more corn than the other plots did.

John Teasdale records data on weeds growing in a ripening organic wheat field next to a recently cultivated plot of organic corn. (Credit: Charles Phillips)

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