I absorbed a few things growing up in the corn belt and one of them was the idea of the Green Revolution of the 1970s. Factory farming combined with GMO crops resulted in a massive increase in the amount of food that could be grown per acre. The efficiency we saw in terms of raw food output was world changing. Acadamics had spent the previous decades arguing we were going to be unable to feed the world's population and we'd need population control mechanisms in place to save our species (sound familiar?)

Well, in addition to the GMO crops that were drought-resistant, pest-resistant, which grow bigger, faster, and more densely than ever before, you needed fertilizer to support their growth. We were way past medieval-era crop rotations and fallow fields technology. You need 3 key elements that simply can't be replaced fast enough naturally: nitrogen, phosphorus, and potassium. You won't get enough from livestock manure alone.

If you're planting a home garden, however, yes, use crop rotation. Use compost. Use fertilizer. You can do it entirely "organically" if that's your thing. But they don't scale to factory farms that run America's corn, wheat, and soybeans.