The required reading by Odum (for the Nov 30 lecture on agriculture) discussed the soil erosion that can occur from agriculture. In addition to problems of soil erosion, tilling is a major contributor to release of GHGs which, of course, lead to global warming. Many people now advocate no-till farming. I thought a lot of people in the class might be interested in learning more about no-till farming. Here are some good tidbits and sources of information:
Wikipedia says: "No-till has carbon sequestration potential through storage of soil organic matter in the soil of crop fields . Tilled by machinery, the soil layers invert, air mixes in, and soil microbial activity dramatically increases over baseline levels. The result is that soil organic matter is broken down much more rapidly, and carbon is lost from the soil into the atmosphere. This, in addition to the emissions from the farm equipment itself, increases carbon dioxide levels in the atmosphere. Cropland soils are ideal for use as a carbon sink, since it has been depleted of carbon in most areas. It is estimated that 78 billion metric tones of carbon that was trapped in the soil has been released because of tillage. Conventional farming practices that rely on tillage have removed carbon from the soil ecosystem by removing crop residues such as left over corn stalks, and through the addition of chemical fertilizers which have the above mentioned effects on soil microbes. By eliminating tillage, crop residues decompose where they lie, and growing winter cover crops field carbon loss can be slowed and eventually reversed."
Researchers at Ohio State have quantified where no-till farming occurs and the impact that has on carbon sequestration: "Lal and his colleagues estimate that no-till farming is practiced on only 5 percent of all the world's cultivated cropland. Farmers in the United States use no-till methods on 37 percent of the nation's cropland, which results in saving an estimated 60 million metric tons of soil CO2 annually."
With carbon trading on markets, farmers can get paid for no-till farming (which, because of various equipment required, is perhaps more expensive than regular farming). The WRI writes: "Environmental concerns have driven farmers around the world to switch to no-till farming. But, with the 2003 opening of North America's first voluntary carbon market, the Chicago Climate Exchange (CCX), farmers in Canada and the U.S. have a new incentive to switch—they get paid to do it. Under the terms of the CCX, no-till farming counts as a carbon offset. Contracts for these offsets are traded in a sort of carbon stock market, where they are purchased by corporations, governments, and other organizations. Though voluntary, the offsets are legally binding and subject to independent verification. The compensation farmers receive fluctuates, but one Wisconsin farmer estimates he annually earns an extra dollar or two per acre for a practice many farmers are already doing anyway."
And finally, to complement the possible income from no-till farming due to carbon offsets, rising energy prices (and other input prices) are making no-till farming look a bit more economically inviting. See this news article for one take on the emerging economics of no-till: http://www.pittsburghlive.com/x/pittsburghtrib/s_415344.html