I'm looking into getting a load of mushroom compost from a nearby mushroom farm and am curious about other people's experience with this compost on their vegetable and fruit gardens. There was an article I read about being careful using the stuff due to some excess salts which could harm germination and young seedlings and other salt-sensitive plants. Any wisdom would be great!

Thanks,
sky

Be careful not to conflate salts with just one particular salt, NaCl.

http://extension.oregonstate.edu/news/story.php?S_No=28&storyType=gard e

spicedham: yep, that's the article I came across.

I'm new here and did a search but didn't find the information I was looking for. Maybe I should try a different area of the forum?

Thanks!

The stuff from the mushroom plants is more properly called Spent Mushroom Substrate (SMS). Search on that term and you will become well educated. The farm may call it anything they want but it is still not composted sufficiently to be considered mature compost.

It is very good for heaping potatoes but I would not use it in a potting mix. I once put a whole truckload in an empty compost bin until the potatoes were ready for it. It was packed in very tightly in order to get it all in. In 5 days time water was dripping off the underside of the lid and the temperature was up to 120F. That is NOT mature compost.

Now your farm may compost this material past this point until it is black crumbly stuff. But I suspect not.

Yes, called "compost", but as delivered, very hot, and I purchased from a middleman who had it stockpiled on his farm. (He's a part time trucker). I have assumed this was spent compost, which the somewhat local houses give away, whereas they do not give away feedstocks. Basically my cost is the trucking fee.

Had lots of wood, twig & branch parts. Also trash; plastic bottles, caps, twine etc. Didn't like that.

I incorporated some at around 5%, used some as mulch and started a new pile with the rest.

No trouble with seedlings or transplants. I'd heard about the salts issue; my intent was to maintain OM at the 5% level since I couldn't make my own compost that year.

mushroom compost from the farm is almost our stock in trade when we make our raised beds, use it around fruit trees as well, can't answer about germinating seeds in it but there ae oterh ways seeds can be germinated util the mushy decomposes completely.

we plant seedling directly into it, just keep in mind it is still decomposing so will get hot at times, we don't mulch until the heat has lessened. any salt has never manifested into an issue.

anyhow check our garden presentation.

len

if used in the raised bed culture your soil has nothing much to do with what you will end up with, which is a raised bed of premium growing medium.

see our presentations.

len

1) I killed a Japanese maple (prefers acidic/neutral soil) when I put a bag of mushroom compost mixed with soil in the planting hole. My soil is alkaline clay, pH of 7.7, tested professionally by EarthCo.

2) Mushroom compost is very alkaline, due to the lime used. My neighbor also stunted her roses with mushroom compost. When I planted a new rose this summer, I forgot my decade-old mistake with the Japanese maple, and put mushroom compost in the planting hole. The leaves turned yellowish with brown fertilizer burnt. I had to dig the rose up, and replaced the soil.

The West coast is usually alkaline - I would not use Spent Mushroom Substrate unless you are 100% sure that your soil is very acidic.

Reported pH of mushroom compost varies: The bagged one has been reported at 9, others from nurseries are reported at much lower values. Bagged soils have lime added to deodorize and suppress mold from growing inside the bags - which raise the pH to high values. From what people report on pH of bagged soils: it's either really acidic stinky cow manure at pH of 4, or really high pH for mushroom compost or top soil.

I tested the neighbor's new top soil with super-green grass: it's a 50% blend with mushroom compost from a nursery - the pH in red cabbage indicator is less alkaline than mine (tested at 7.7 by professionally by EarthCo.) Anything with lime in it doesn't change its pH even when it's composted. I tested horse manure at various stages: fresh, 6 months composted, and fully composted at 1 year - they all have pH of above 8, due to the lime that stables use to deodorize the stalls. If mushroom compost has lime added, the pH will be high - Colorado State University Extension gives dire verdict: free lime soil cannot grow acid-loving plants.

Here's the reason why bagged soils are either too alkaline or too acidic. MiracleGro potting soil pH is between 6 to 6.5 - some bagged cow manure are reported at 4. Bagged mushroom compost is reported at 9 pH.

Contrasting Soil pH Effects on Fungal and Bacterial Growth

Department of Microbial Ecology, Lund University, Ecology Building, SE-223 62 Lund, Sweden & Soil Science Department, Rothamsted Research, Harpenden, Hertfordshire ALS 2JQ, United Kingdom

ABSTRACT
The influence of pH on the two principal decomposer groups in soil, fungi and bacteria, was investigated along a continuous soil pH gradient at Hoosfield acid strip at Rothamsted Research in the United Kingdom. This experimental location provides a uniform pH gradient, ranging from pH 8.3 to 4.0, within 180 m in a silty loam soil. .. The growth-based measurements revealed a fivefold decrease in bacterial growth and a fivefold increase in fungal growth with lower pH. .. Below pH 4.5 there was universal inhibition of all microbial variables.

Of course, alkalinity can have a negative effect on those plants as well but I would expect more yellowing and stunting rather than burning and dying. At least in the short term.

In addition to salinity, I would put a lot of my eggs in the same basket as Novascapes. I had the same thoughts concerning potential drainage issues. If the roots rot secondary to anaerobic conditions, and/or pathogens that are favored by high soil moisture, that can interrupt the plants' ability to take up water and nutrients as well, causing drought-like and nutrient deficiency symptoms.

I have two healthy 12-years old Japanese Maple trees that were planted in native soil amended with peat moss. They are big trees with zero leaf burn. The 3rd one planted in native soil mixed with BAGGED mushroom compost had leaves brown at the margin - looks more like high salt. Then it died.

The 4th Japanese maple is planted in 10 bags of Scott's premium top soil with no amendments. Leaves also are brownish at the edges, zero new growth in 7 months. It's stunt, barely alive. pH test in red cabbage juice showed Scott's soil to be more alkaline than my native soil tested at 7.7 by EarthCo. I ran the pH test the 3rd time with the soil around this tree. It's so dense, like mud and doesn't dissolve as easily as my native soil, or MiracleGro potting soil.

I don't know what's in Scott's premium top soil - it's pitch-black, not light brown/yellow clay like my native soil, nor my neighbor's soil from the nursery. After working with bagged soils, I am stained black like coming out of a chimney, I have to alcohol my skin to get the black stain out - is it woodash, reportedly high in salt ???