I think there is a simple solution for making tillage sustainable: ley farming. Alfalfa with grasses will raise organic matter content (and on a deeper level) much more than any no-till, mulch system with annual plants can. Also giving us a lot of free nitrogen. So rotating tilled field with perennial grasses and legumes (ley) will help with regenerating soil after tilling. I experimented a lot with no-till, and it was a disaster, cover crops won't kill all the weeds and bringing a lot of mulch to the field was a big pain in the ass. Only tarp made the job, but I don't think using plastic is sustainable, not to mention it won't work on a bigger plot of land. And even if cover crops work, we are loosing something which could be a hay or pasture for animals, this same goes for planting any other plants for mulch, so then you need more space to grow this same amount of crops, which for me in highly populated area is big problem, not only economically but also in terms of sustainability. On the other hand, ley farming gives a big boost if it comes to soil fertility, gives us much more and better quality feed than typical meadow or pasture, and plants grown after plowing ley grow much better with much less pressure from weeds. So yes, constant tilling of land for many, many years is not good, but tilling once in few years won't harm too much but will make our work much easier.
