johnny skeptical - 1/13/2019 16:06 It depends hinfarm, once we quit tilling soybean stubble in the fall( used to plow soy stubble here) things started to turn, but the high yield hybrids of the last 20 years or so really put the afterburners on. We have a unique situation where we farm a field that was in a cos rotation, and had the corn stalks burned off several rotations in a row before we started farming it. After 15 years we finally have got it to the point where it yields with the rest of our stuff. Don't know what this means exactly but I think it is interesting. if you take a field that had a corn/soybean rotation with burning and plowing for a number of years, and stopped the burning and eliminated soybeans (moved to continuous corn) but kept plowing, that would probably result in a net SOM increase after a couple decades. But only because it was so seriously mined out before the change. Broadleaf crops such as soybeans only sequester a small fraction of the C that grass crops such as corn sequester. Not only that, but corn roots deeper. So there's a lot more C going into the soil with cont corn vs corn/soy. If tillage is held constant, after a couple decades there will be more SOM in the continuous corn. Within any given rotation, the less tillage the greater the SOM. Adding cover crops or eliminating fallow periods (anytime something isn't growing) will dramatically increase SOM. Indeed, NT with cover crops or very intensive cropping (and with lots of grass species) seems about the only way to significantly move the needle on getting SOM closer to what it was in its native, pre-cropland condition. | 
Another why tillage has little to do with building OM
