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Comment by Retric | Hacker News Reader

Most of the matter in food comes from water H2O or Air CO2 + N2. Nitrogen fixing bacteria are literally getting that nitrogen from the air not the soil even if they live in the soil. https://en.wikipedia.org/wiki/Nitrogen_fixation

Modern agriculture uses fertilizer for extra nitrogen (N), phosphorus (P), and potassium (K).

Plants also need a few trace minerals from soil but it’s a tiny fraction of their mass Iron, Calcium, etc and can also be added back: https://en.wikipedia.org/wiki/Rock_flour

PS: There’s some really destructive agricultural like sod that’s literally shipping soil, but the premium pays to replace the soil.

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Every unit of a crop has a specific amount of minerals forever taken away. Nitrogen comes from the air and to isn't an issue. but where are you going to get those tons of phospeous from? Farmers now have to add sulfur because while not much is needed some is taken away and needed - they used to get that from acid rain but we cleaned up that source (overall a good thing but one unexpected issue)

i don't know how much iron crops need compared to what is in most soils. I know farmes are adding sulfar and other mineral.

> Nitrogen comes from the air and to isn't an issue

I thought it was a huge issue because natural nitrogen fixation was slow and unreliable, and that's why Haber-Bosch was such a big deal.

By not an issue I mean we have plenty and it is 'easy' to replace. Of course fixing is slow and so we need to add a lot but supplies won't run out.

You sure? I vaguely remember that the Green Revolution was roughly a 10x in yield. That sounds pretty significant. What's the yield difference using modern techniques?

Nitrogen fertilizer alone is a long way from 10x yield. The initial program got 3x yields over 20 years from a host of changes (pesticides, farm equipment, new hybrids etc), but at the core it was really a mix of education and loans not just some novel techniques.

https://en.wikipedia.org/wiki/Green_Revolution

Yes it is. And not only does fertilizer take significant amounts of power, it also uses hydrogen as a reagent which is sourced from fossil fuels. But despite that, it is still "cheap" because the alternative is using twice as much land, and smaller farmers who are most interested in regenerative farming don't have the capital to double their land usage which is a problem. They are getting beat out by larger scale corporate farms that aren't worried about the state of the land 30 years down the road.

Unless you are doing nuclear physics, those elements will persist. Let's say you are growing grain for cattle. The manure gets spread on the fields. Closed loop.

Mostly it isn't though as we ship the crops elsewhere where cattle grow but corn dose not (technically it grows but not wel)

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