Subscribe Now to the Digital Almanac Monthly Magazine!
Reporting
Assuming it is of desirableAssuming it is of desirable quality (possessing the proper odor, moisture content, organic and ash matter, pH, and other characteristics), 1 to 2 inches of mushroom soil tilled 4 to 6 inches into the existing soil, can supply nutrients for a year, possibly longer. We hope this helps.

2015 Special Edition Garden GuideCooking Fresh with The Old Farmer's AlmanacThe Almanac Monthly Digital MagazineWhat the heck is a Garden Hod?