Mushroom farms have rows and rows of pasteurized, composted manure for growing the mushrooms.
The wheat straw is composted into the manure and the mushrooms are grown inside a building in a pile of the compost.
After the mushrooms are harvested, the compost still has lots of usable nutrients, it's just not good for growing mushrooms. So they haul the compost outside.
Then they sell it by the scoopful to hungry gardeners like me!
Now at home is the real work of shoveling the black gold into raised beds, pots, and the field garden spots (which are as yet untilled LOL). This stuff makes your garden grow like weeds!