Use Spent Mushroom Compost To Make New Compost

by Laurie Scott
(Victoria, Australia)

Do NOT use spent mushroom compost directly on your garden rather, use mushroom compost to make better compost, by using it for composting. I am a small commercial composter and this is how I use it.

It is mentioned on your spent mushroom compost page that there is no microbial life in mushroom compost, RUBBISH! It is full of life. What grew the mushies in the first place?. My recommended ratio is one part spent mushroom compost to two parts overall of other compost material. Have some gypsum on hand for cation exchange(metabolism) and this will help with any saline problems.

Good luck everyone.

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Dec 30, 2011
Rubbish, eh?
by: Compost Junkie Dave

Thanks so much for your comments Laurie. I'd like to hear more from you, can you contact me directly using our contact us form?

I have edited some of the content on our spent mushroom compost page to match your comments about the microbial life in mushroom compost. You're right, not ALL microbial life is destroyed during pasteurization. But a lot of it is. This is a cache 22 from a fertility stand-point. On one hand, these microbes contain nutrients that we want available to our plants. When the mushroom compost is sterilized, it indirectly releases these nutrients into the surrounding organic matter (exploding microbe bodies release nutrients contained within). On the other hand, we're significantly knocking back the microbe population in the compost.

However, if we follow this one step further, something really cool happens. After pasteurization, we may have lower microbe numbers, but we also have higher nutrient levels. Guess what that means? The microbes that are present can proliferate again using all of these readily-available nutrients released by their deceased family members. Therefore, by the time you have the spent mushroom compost delivered to your house/farm, there is a very high likelihood that the microbe populations have rebounded.

This would be a great time to own a microscope. Then we could analyze the before and after life within the mushroom compost.

In conclusion, I need to thank you for pointing this out. I will make the necessary changes to my original post. This is why I love you guys, and this is why we're a tribe! I don't have all of the answers, so it's nice when someone like Laurie stands up and says, "Wait a minute? He's a LIAR!!!" haha

Thanks again Laurie.

By the way, please follow the advice in the article as well as Laurie's recommendation...RE-compost your spent mushroom compost prior to adding it to your gardens/lawns. As for the cation exchange and saline issues, you can use gypsum or our rock dust.

Jan 07, 2012
Microbial Life in Compost
by: Ron

I believe there is a lot of microbial life in compost. When I obtained my last load, I put my hand a few centimeters into the pile and it was so hot I had to pull my hand out. It is the microbial activity that creates this heat.

Jan 09, 2012
by: Compost Junkie Dave

Right on Ron! Those little microbes are the powerhouses of the entire composting process. Without them the whole process would fall apart. It's not a whole lot different than our own digestive tract...if we take care of our intestinal microbes (flora), they'll take care of us. And the same goes for compost...if we learn to take care of our compost microorganisms, they'll produce a wonderful end-product.

Nonetheless, we were originally discussing the microbial life in spent mushroom compost.

What does everyone else think? Is it a good idea to re-compost your spent mushroom compost or would you rather get it and spread it?

We would love to hear more from you.

Jan 12, 2012
mushroom compost
by: kate the flower farmer

I use a lot of spent mushroom compost in the raised beds I make in high tunnels ( greenhouses without heat). To save time and money I add mushroom compost and straw to the bottom of my 6 inch raised planting beds and then fill the beds with 4 inches of planting bed mix. The flower plugs are planted in the top two inches of soil. As the plants grow the compost and straw is breaking down and feeding the plants. Yearly soil analysis has shown me that I have lots of organic matter and plenty of fertility for 3 to 4 years without adding any more soil to my beds. A bi- weekly feeding of compost tea through drip irrigation lines are all I need to keep everything healthy and growing well.

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