There seems to be insufficient discussion of soil erosion, here or anywhere. Organic deals, among other things, with soil composition, but the more existential question of some soil or none is seldom addressed. The way I see it is that soil erosion from bare field by wind or water can easily remove 5 tons or more per acre each year, whereas the rate of soil formation -- be it ever so varied -- is no more than half a to per acre . It would take a long time to remove soil totally from agricultural fields, but consider this: agriculture is about 10,000 years old, and can we last another 10,000 years with present practice? Of course one can't say "Would never happen", because it has happened to many ancient civilizations and some marginal areas in present times. Regards, Peter.