Fungi are an important component. Additionally, for every but of nutrients removed when the food leaves the ground or plant, the equivalent must be returned. Even with fungi, nutrients need added back into the soil.

We either have farmers who are providing food for others and there are inputs such as nitrogen, phosphorus, and others needed at a huge scale with easy application.

Or

70+% of the population are farmers again and we can grow things in more sustainable ways.

I farm on a small scale compared to modern grain farms but large compared to say a veg farm that sells at the farmers market.

If you are doing small scale agriculture, you still require inputs. Yes, fungi are important. It's not enough. If you are growing food, every thing you harvest contains nutrition. The nutrition in that came from the soil. You must put back what you took out!

I make my own fertilizers because I also commercial fish as a one person operation. I collect the fish waste of other fisherman in addition. I am able to get all the needed mircronutrients.

Biochar is also not enough, nor is a it a magic bullet. Studies show that sometimes it is detrimental to the soil, and it's not fully figured out when it will be a benefit or not, despite the near religious belief in it.

There are ways to farm sustainably.

There is more to it than fungi and biochar. Inputs are necessary no matter what type of farming you are doing.

Most of my farm is silvopasture. My pasture is native perennials. There are fruit and nut trees over. This provides shade and keeps the ground cooler, while also providing food. I get lamb and beef. But also honey locust beans, chestnuts, hazelnuts, and apples. I have non commercial levels but very ample homescale amounts of 20 other fruits. The fish fertilizers and crawfish fertilizers keep everything healthy.

People here making reductionist claims are not farmers. We have a very tight knit farmer community. Annually, we visit a different farm. Most of the farms are focused on vegetables. Last year, we went to the farm that has the best quality vegetables. They like all the other farms in the area are beyond organic. There were many questions about equipment, plant varieties and such. The thing that most farmers got stuck on at the tour what his inputs shed. How much does he use when, why, and how much? It's the key to his high quality vegetables. Others k ow they need more inputs, but he's cracked what he needs to add enough of everything needed while not adding too much also. You add too much and you can get mineral salts precipitating.

One can read about certain things and find what seem like a singularly important component of something such as growing food. The applied holistic science of actively growing food with care for the environment, shows it's more complicated.