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.
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.
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.
If you look at a regenerative certification program like [1] you’ll see that you’re allowed to apply synthetic fertilizer but it has to be no more than the rate removed by harvested crops. This means, hopefully, that you aren’t losing much to erosion, runoff, or volatization, and that good soil structure is keeping them available.
[1] https://s3.amazonaws.com/media.regenified.com/wp-content/upl...
Most small-scale regenerative ag farms are bringing in a lot of outside material to add those minerals back in.
My farmland hasn't been farmed for 50 years. If I clear an area and put a veggie bed in, I get 1 year of great yield, 1 year of "okay" yield, and then it becomes impossible to grow anything due to nutrient deficiencies.
Remember all those post WWII photos showing how fertilizing with phosphorous resulted in incredible crop yields?
Guess what element China (which has some of the world's largest reserves) has quit exporting?
I think selenium would run out long before phosphorus.
The crust contains selenium at 0.05-0.09 ppm, but most plants require around 0.1-1 ppm. It's also one of the hardest nutrients to remediate because you can't just dump a bunch of selenium on the surface when 5-10 ppm starts to become toxic to lots of other organisms.
Selenium, along with taurine, is one of the supplements which genuinely drove my physicians vehemently crazy, so I doubled up, and ensured that they were the focal point of my daily regimen.
Psychiatrist's parting shot was, "they're all bio-active!"
Micronutrients are no fad, because guess what, they used to come in our fruits, vegetables, and meats.
Selenium is commonly recommended by doctors in New Zealand.
Selenium is one chemical element that, like nickel and cobalt, has been needed by all living beings already some billions of years ago, but nowadays there are many living beings which have lost their dependency of selenium, which has been a beneficial trait for them, due to the scarcity of selenium.
The terrestrial plants, because of their environment which frequently lacks many minerals, have lost their dependencies of several chemical elements, e.g. of cobalt, of sodium, for most of them also of nickel, which is optional even in those which can use it, and apparently also of selenium.
If you have seen any source which says that it has been discovered that some plant needs selenium, please indicate it.
As I have said, many plants happen to contain selenium only because they are not selective enough in their sulfur intake, not because they need selenium for anything, unlike the animals, which would die without selenium.
One issue with phosphate ore is contamination with undesirable elements, like cadmium and also uranium and its decay products, like radium. The waste stream from sulfuric acid treatment of the ores is radon-emitting gypsum.
Sulfuric acid itself may become limiting once we're off fossil fuels, since almost all of it is currently produced by oxidation of sulfur extracted in the desulfurization of oil and gas.
Composting the food waste, and use composting toilets to create a "circular economy".
That is apparently how it was done in the old days...
See also, Paul Wheaton criticism of The Humanure Handbook ("No, do fear your poop! Fear it!!"). Timecode link, but I recommend the whole video. https://www.youtube.com/watch?v=6vZPTPIHO8w&t=4980s
It's about unknown unknowns, right? But we could map out where those may be.
I guess chemical toxicity, drugs with long half-lives that affect soil organisms, and antibiotics that promote resistance.
(yeah yeah they are all chemicals.)
For the chemical toxicity, it's chemicals that are harmful to plants but allowed for human consumption, or chemicals in sufficient quantity to disrupt soil balance. Doesn't seem like a real concern?
With metabolic disruption to soil organisms, yes, there may be real danger there. That smells like previous environmental mistakes.
Antibiotics, yeah, some danger. Livestock is exposed, and resistance-conferring genes might jump directly to human pathogens.
It's worth studying. There are requirements for both sewage processing and fertilising soil, so the value of a solution would be high.
Like many things, poop doesn't easily scale....