Talking out of what I can see out of my window, hay and feed crops for cattle are sown in the same fields where animals are led to graze, with no added fertilizers besides the manure left behind that is tilled into the soil, in field rotation system.
The greenhouses and berry farms around here turn down the readily and locally available and cheap manures to instead consume huge amounts of synthetic fertilizers produced in far away factories that have to be trucked in.