We have found it.

Not really infinite until the crop rotation glitch

If everyone gets away with the crafting glitch and goes too far with it, the waste generated severely affects the crop glitch on a global server level. And if nothing is done about the runaway crafting glitch, it can make the server unliveable
- That will only happen if a few chronically online players get together to use their resources to manipulate the playerbase. If that happens the game will die, but certain players just don't care about anything but themselves.
Pfft just live in truly fertile region bro. Or invent green revolution.

It's not that infinite without a way to refresh protein, such as mining ammonia, eventually you run out of soil resources and crash. It's got a hard limit, so to speak.

urine is a fantastic nitrogen fertilizer

bonemeal for phosphorus

wood-ash for potassium.

Probably not concentrated enough to work on an industrial scale, but probably on smaller communal farms.
- Yeah if you turn people who die into fertilizer and process all of their excrement you can probably sustain the fields they eat from. Can't argue with that.
And that's why we have been dumping our and our livestock's shit there for thousands of years.
- That alone is still not infinite. When you eat food you're taking the nutrients that you need out of it and excreting what is left. So even if all of your shit went directly to manure then you're still putting in less than you took out.
Legumes like lentils capture air nitrogen.
- Was wondering, do Orchids do this, too? They have "air roots" and basically subsist off zero substrate.
  
  According to this article
  
  Like other epiphyte orchids, the roots of Phalaenopsis roots are covered with a spongy epidural tissue called “velamen.” Just a few cells thick, velamen helps orchid roots absorb water and nitrogen from the air.
  
  It's probably my favorite plant. Hardy as hell despite a bad reputation for being picky. People don't realize they just go dormant until Spring.
- At between 20 to 300 lbs per acre, yes. Generally most legumes will need 60 lbs per acre, so most will be self sufficient in ideal weather.
  
  For 60 bushel per acre soybeans still require fertilizing with monoammonium and diammonium phosphates, as well as ammonium acetate, and to go beyond 70 bushels consistently supposedly does require supplemental nitrogen although this has yet to be recreated in studies.
  
  So, you still need to mine ammonia.
Bacteria take it out of the atmosphere slowly. It's a certain rate per land, and due to the coastline paradox we know that the area of land is infinite.