i was not aware of this. Could you elaborate? do you have a source for fungus fixing Nitrogen from the atmosphere?
I thought fungus got most of it’s nutrients from decomposing organic material.
big picture if i oversimplify. you have things that “cycle” nutrients and make it more (bio) available. Like for example the mexican sunflower, and fungus
And you have things that fix (import) nutrients.
Like legumes. Legumes literally take N from the air, and fix it in the soil.
importing compost, wood chips or any organic material, is actually fertilizing. Usually slow release though.
Phosphorus has verry low soil mobility, and thus erodes verry slowly with rain. And thus you usualy only need to fertilize a little P, to account for the exported P thats in the things your harvest.
Kalium also has low soil mobility. higher than P though. So the same goes for that. You fertilize to compensate for export mainly, and a little to compensate for it raining away to groundwater.
Nitrogen however is very soil mobile. And thus easily rains away. So this means you fertilize enough N to compensate for the N your exporting (harvested and exported material) and you have to fertilize to compensate for the N raining to groundwater.
This is why N fixers are so awesome.
In most orchards due to the deep rooting nature, P and K are cycled really efficiently. And thus if enough is present you only have to account for export due to harvest.
N however is a different story, if you don’t fertilize, it will drop rapidly.
(mulch compost ect is also fertilization. since the organic material contains the NPK’s although in a “slow release” form.)
you see this to when a lot of animal manure has been used. The P and K tend to build up in the soil, and will be plenty years of not decades later. The N however can be deficient.