Early Americans managed to grow plants without commercial fertilizer. All you have to do is have animals. I still remember when farmers used manure spreaders. Farmers can survive when the urbans starve.
I don’t know how it is where you are, but around here I see farmers using both manure and manufactured fertilizers. Although in some cases I think it might be mainly because the manure has to go somewhere.
I really hope my neighbors are braced for this. I grow using natural methods, but all the farms around me are conventional. Things are getting rough.