I guess we'll have to switch to pure-meat based diet then. Native grass is the only thing that grows well and reliably on the majority of North American farmland without tillage or chemicals. And the best way to turn grass into calories is to run it through something with four stomachs first.

So if you want to raise cereals and vegetables, you have to choose: tillage or chemical use. The latter is much easier on the soil, even if it's not perfect.

You speak as if industrial farming is the only way to grow food, but of course that's false.[1] In fact after subtracting out government subsidies (including subsidies on chemical inputs) industrial farm fields are a net loss. TL;DR industrial ag is a way of funneling your tax dollars to chemical companies.

Chemical use can be eliminated (yes, even to grow cereals!) by cultivating healthy living soil. The easiest way is with green mulches/cover crops, which serve the same thermodynamic functions but using sunlight instead of fossil fuel.

* Legumes fix nitrogen. Yep, solar powered.

* Insect predators eat pests. They're part of the food chain, so they're solar powered.

* Deep rooted plants[2] bring up minerals (essentially micro-scale mining on site in response to mineral deficiencies) and make soil. Photosynthesis, natch.

You get the idea.

I don't really have to say that an erosive food system that compromises humanity's only closed-loop habitat is a bad value, do I?

[1] http://www.rand.org/pubs/occasional_papers/OP179.html

[2] e.g. Symphytum