This is a valid point. It's one of the concerns I have as a farmer. That you can inadvertently select for plant varieties and soil organisms that are less nitrogen efficient, because they are getting it provided to them.
But there also have always been inputs. They just changed over time. The Midwest traditionally had a much more varied cropping system, so their inputs were manure and a nitrogen fixing crop or crops.
So when one measures corn yield it would have to take that into account - those rotations were the input, and they had a cost and footprint associated as well. Also, if those rotations pushed your Corn Harvest to every other year then the total yield would be divided by two, making it even worse.
So while the systems have definitely changed, the larger part of the yield increase I would argue comes from synthetic fertilizer Plus simply genetic improvements in breeding varieties.
The effort that goes into plant breeding for staple crops around the world is massive, and it yields steady returns each decade.
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u/[deleted] 26d ago edited 2d ago
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