I would have to disagree on a few counts, Smallaxe. First, soils aren't "built-up" with cultivation. What does "built-up" even mean? This is usually a term used by people who don't know what they're talking about. If you're talking about encouraging OM accumulation, then tilling is the LAST thing you would want to do. Tilling destroys soil structure throughout the tillage depth. its oxygention of the soil in the plow depth is certainly helpful for plant growth, but it is also helpful for microbial activity, which reduces OM in the soil. A little discussed fact is that the largest ever atmospheric CO2 increase was not due to burning fossil fuels, but in fact came from plowing the great plains of North America, encouraging microbes to metabolize the OM that had accumulated under the prairie grasslands for thousands of years. Tilling WI soil does not produce a rich soil 8" deep -- that rich soil was already there. Tilling just destroyed its structure, decreased OM, and opened the soil to erosion. Soil is the most valuable resource on a farm. Why use practices that encourage its loss? Tillage also reverses C sequestration (see microbial activity above). No-till saves soil and sequesters C. Any farmer who values his crops and his land will run a no-till operation. But, just like lawn care, there are farmers who don't know what they're doing and plow everything in sight, use too much fert, chemicals they don't need, and do it in the least responsible way.