Soil/compost for raised bulb bed

[Alan_b]

I have constructed the framework of a raised bed for growing snowdrops and other spring bulbs and now I need something to fill it with - soil or compost.  I need about one cubic metre in volume, I don't have nearly enough of my own garden compost and I don't need a big hole somewhere else in the garden so I must buy something in.  Ideally I would like to use leaf mould but that isn't commercially available so I'm wondering about spent mushroom compost.  This has the advantage of being available in bulk for not too much money and would seem to both moisture-retentive and free-draining.  Does anyone have any thoughts or alternative suggestions?  I'm not an expert on composts so there could easily be fatal flaws in my idea.       

[ArnoldT]

Alan:

I can't quote a source but have heard that mushroom compost contains too much salt.

[Michael J Campbell]

Alan, I have some experience working with spent mushroom compost and I would advise you not to use it  under any circumstances. I have a conductivity reading somewhere and I will see if I can find it but I think it was almost 90%. I did manage to reduce it to about 3% for use as potting compost but it was a complicated process using micro-organisms.
The County Enterprise Board refused to grant aid the project so I did not proceed.

cheers.

[Ezeiza]

There are many disastrous experencies with spent mushroom compost accounted. The best use for it is some corner of the vegetable plot in which elements will thoroughly decompose (and rinse) it.

As for your bed, commercial potting soil with a large proportion (30 % or more) of coarse sand will suit most plants/bulbs. Decomposed leaves are of course very good, but ideally they should be shredded and done.

[Michael J Campbell]

Alan, here are the readings from the Leachate generated.

Ammonia before, 65 after 3.1
Nitrite  before, 11 after 0.35
Nitrate before, 14 after 14
Total phosphorus before, 12.5 after 5.7
Soluble reactive Phosphorus before, 9.2 after 3.8   

[ArnoldT]

Michael:

Thanks for the numbers.   Any theories as to the source of the salts. My guess would be added inorganic sources to push the mushroom growth.

[Michael J Campbell]

It has got to do with the ingredients of the compost to start with, straw and various types of manure, and then they add lots of Gypsum and heat up the lot.

[Pascal B]

Yes, they usually use a mix of horse manure and chicken manure. Gypsum is a form of calcium phosphate and the manure would explain the high values for the nitrogen compounds. It is sold here in NL as "champost". Dreadfull stuff, can't see why anyone would use it.

[David Nicholson]

Isn't mushroom compost usually very limey too? Don't think you'll go far wrong with some good quality bought in top soil, a couple of bags of composted bark and plenty of gritty sand.

[Maggi Young]

Some years ago (when Ian and I were working with a friend, David Atkinson, to make a new garden for Harold Esslemont when he moved house) we used a large quantitiy of spent mushroom compost to improve the very impoverished soil of the garden, after we removed dozens of huge conifers. This mshroom compost came from from a local  mushroom farm and tested out to be pretty much neutral. We incorporated huge amounts into the soli and it made a lovely planting medium and all the plants we moved into iut from Harold's old garden -  Dactylorhiza, Hemerocallis, Trillium and all manner of other herbaceous and bulbous subjects liked it very much.
I guess it depends on the mix you find available.  We had no problem with the stuff we sourced here.

[Michael J Campbell]

That is correct Maggi, it usually tests neutral and lime content is not a problem with the way they make the compost now,it used to be a problem many years ago. When mixed with good quantities of soil it is excellent stuff but no use for planting direct.

[Michael J Campbell]

Maggi, I was smiling to myself a while back when on another thread there was a discussion about Trichoderma, that is one of the scourges of mushroom growers,kills all the mycelia overnight,although I have to admit that I use it myself now.

[Maggi Young]

That's interesting Michael, I hadn't made that connection.

[Gerry Webster]

Some years ago (when Ian and I were working with a friend, David Atkinson, to make a new garden for Harold Esslemont when he moved house) we used a large quantitiy of spent mushroom compost to improve the very impoverished soil of the garden, after we removed dozens of huge conifers. This mshroom compost came from from a local  mushroom farm and tested out to be pretty much neutral. We incorporated huge amounts into the soli and it made a lovely planting medium and all the plants we moved into iut from Harold's old garden -  Dactylorhiza, Hemerocallis, Trillium and all manner of other herbaceous and bulbous subjects liked it very much.
I guess it depends on the mix you find available.  We had no problem with the stuff we sourced here.

My experience too. Several years ago in an  attempt to improve the heavy clay soil in my garden I dug in huge quantities of spent mushroom compost; it was available locally & very cheap. I had no problems, though I should perhaps point out that the stuff I used had been taken from big heaps left in a field, probably for some time.

[Maggi Young]

Mushroom compost we used was pretty much straight from the sheds....Harold and Agnes and all their friends were eating mushrooms for every meal for about three weeks!