Here are a couple of views:
Turning soil over stirs oxygen into it and, while ploughing successfully combats weeds, the oxygen causes rotting of crop residues and other organic matter in the soil, resulting in the release of carbon dioxide into the air. One calculation has it that the world's farm soils have lost about 100 billion tons of carbon over the centuries of farming, most of that loss occurring within the past 100 years. But Rattan Lal, professor of soil science at Ohio State University, believes that much of that carbon could be recaptured within the next half-century through simple improvements in farming methods such as reducing ploughing. Ploughing is "the equivalent of setting a match to soil organic matter", says Don Reicovsky of the US government's Soil Conservation Research Laboratory in Minnesota. He calculates that the soils of the US corn-belt prairies "have lost between 30 and 50 per cent of the carbon they held when they were first cultivated". If farmers reduced their ploughing, the process could be reversed. The US Department of Energy estimates that three-quarters of the carbon lost from US soils could be returned within 50 years through changes in farming methods and other land-use improvements such as little or no ploughing; preventing soil erosion; ceasing to cultivate poor, marginal land; restoring degraded soils with manure and composts; and planting trees. (For further reading see the downloadable publication Sustainable Soil Management – Soil System Guide on the Alternative Technology Transfer to Rural Areas website, www.attra.org).
http://www.self-willed-land.org.uk/arti ... plough.htm
I can't say I agree with all the views of Allan Yeomans (below) but this bears looking at.
Soil humus is composed of 58%carbon. So increasing the natural fertility of soil can
only occur by extracting carbon dioxide from the air. To illustrate, the destruction of
the soil fertility of the Great Plains in the US dumped as much carbon dioxide into the
atmosphere as came from every car Americans ever built. So we reverse the process.
We buy organic produce. Because, to make money out of organic produce a farmer has
to increase the fertility of his soil. Switch today. It’s healthier and free of chemicals.
Additional, most agricultural chemicals destroy soil fertility so agricultural chemicals
must cease being a tax-deductible item. We must also cease subsidizing any type of
chemically based agriculture.
http://www.yeomansplow.com.au/priority-one.htm