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Preserving topsoil, the organic way

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Avoiding soil erosion is essential to maintain crop productivity, protect waterways and avoid or slow desertification. In the U.S. and around the world government-sponsored programs have made great progress in mitigating topsoil loss: U.S. soil conservation practices reduced topsoil loss from 3.1 billion tons to 1.9 billion tons between 1982 and 1997, for instance. But the majority of this mitigation has come at a cost. To avoid soil distrubance and the erosion that goes with it, conventional U.S. farmers have relied on herbicide-intensive no-till, polluting waterways and destroying soil microbial life in the process.

There is another way, and it turns out to be more climate-friendly to boot.

Using a combination of best management practices such as cover cropping, composting, conservation tillage, and organic fertilization farmers can reduce erosion, increase the amount of soil organic matter, conserve water, enhance fertility, and reduce incidence of disease. This, in turn, helps increase crop productivity and resistance to pests and drought—an increasingly important phenomenon in the face of climate change. Furthermore, these practices can actually help mitigate climate change. A 2009 University of California study concluded that these practices, when combined, will generate much greater greenhouse gas reductions than conservation tillage alone. The Environmental Working Group’s analysis of the UC study provides explicit recommendations for how the state should promote these practices in its implementation of the State's landmark climate change policy. Another California study estimates that implementing these practices in production agriculture can achieve a reduction of 17 million metric tons of carbon (in CO2 equivalents) per year or about 10 percent of California’s goal.

The Rodale Institute illustrates how organic no-till works. The innovative farmers they highlight plant cover crops then crush them with a rolling device so that the living-mulch mat acts as a barrier against weeds, conserves moisture, protects the soil, and—in the case of leguminous cover crops such as hairy vetch—also provides a source of nitrogen to the cash crop. Yields are good and the fields require far fewer operations—saving time and energy. And some folks at U.S. land-grant institutions agree, “from an organic matter and soil structure perspective, there is plenty of evidence that organic farming systems typically perform as well or better than conventional, herbicide-intensive systems with less soil disturbance.”

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