I don't know the specifics of Iowa, but European soil can only keep up with the rising yields thanks to the dung of a rising headcount of livestock that is fed with imported feed that is at least in part from slash-and-burn farming or from depopulating the oceans. If those animals consume more than the local yields could supply, the farming is still unsustainable despite local soils not depleting.

I'm not saying that there are no improvements (three certainly are), but that they might be much smaller than we think.