Why does he have to account for livestock? That has nothing to do with the argument he's responding to.
Your other argument isn't especially persuasive, either. Statistically, is vitamin deficiency a serious public health problem in America? Whatever "protein, calcium, phosphorus, iron, riboflavin, and vitamin C" reduction there has been in corn over the last 50 years, it's extremely unlikely to have offset a factor of 8 increase in productivity.
[3> Why does he have to account for livestock? That has nothing to do with the argument he's responding to.
Actually it does. 90 million acres of corn were planted for livestock in 2018 [0] and we know that the nutritional density of corn has declined [1]. So the long term is we just keep yielding higher with lower nutritional value? The main reason we're after higher yields is livestock and mass produced "junk" food which provides what positive value? The sustainability problem aside, how does this benefit us globally and long term?
> Statistically, is vitamin deficiency a serious public health problem in America?
Is it a problem? Yes. [2] In America? Past studies [3] have shown this and I don't think it's a stretch to just look at the health epidemic here which is, generally, systemic from poor overall nutrition. [4]
Sure, the productivity factor is in our "favor", at least by the numbers. But it's very clear that there is negative impact that extends beyond just the yielded nutritional value. It flows down into additional consumption and requirements to fortify nutritionally sparse natural ingredients.
The claim being responded to was that there is no evidence that "growing with chemicals" has increased crop yields. Evidence was provided that crop yields have increased as the industry has switched to "growing with chemicals." The percentage of those yields ultimately going to livestock is unrelated.
Your other argument isn't especially persuasive, either. Statistically, is vitamin deficiency a serious public health problem in America? Whatever "protein, calcium, phosphorus, iron, riboflavin, and vitamin C" reduction there has been in corn over the last 50 years, it's extremely unlikely to have offset a factor of 8 increase in productivity.