Bob, Campbell Soup used to have a mushroom farm in our area. I heard that they used to sell the "mushroom soil" to individuals, but then decided it was too much trouble, and got a contract with someone to take it all, However, employees could still take it at no cost, and I had a neighbor whose daughter-in-law worked there. So I think it was 3 times that he and I went over there, each of us with a pickup pulling a 16' trailer and they loaded all they could pile on both trucks and trailers, and of course we tilled it into our vegetable gardens. Unfortunately, they closed down that place a few years ago, but it's good stuff for your garden. They told me it was 3 ingredients; chopped straw (wheat or oat), turkey manure, and I forgot what the 3rd one was. /forums/images/graemlins/frown.gif They said it was only used one time; i.e., one crop of mushrooms, then discarded. As for price, I have no idea because I never paid for any.
