Planting in mushroom compost

[clancaster23]

I may have made a mistake. Last year the wife planted some tomatoes in small metal bins just using bagged topsoil. Went pretty well so she decided that this year we wanted to go bigger and plant a few different things so I built a 9'x3' raised bed that's about two feet high. In the bottom I have mostly the soil that was in the metal containers that we planted the tomatoes in last year along with some grass clippings and stuff like that. That took up about 6" of space in the box. I wanted to do it better than just topsoil so I had about two tons of mushroom compost delivered today. I shoveled it into the box to the top and have a little bit left. Then get to reading about what I can plant in it and that's where I see I'm pretty sure I'm not supposed to plant anything in pure compost. Oops. Now I'm not sure what to do. I do not want to take it all out again and I don't have anywhere to put it anyway and no one to take it. Can I somehow plant in this without taking it out? Please help!

 

[Chuck]

I wouldn't take a chance. Most mushroom compost is pretty high in nitrogen and in salt. It might kill seedlings. Why not build 3 or 4 more beds and dilute the compost with soil. After all, your wife wanted a bigger garden.

 

[clancaster23]

I'd consider that but I don't have many places I can put another bed and the majority of the property is on a hillside so it makes it difficult to put multiple things up. I'll have to think about it. What should the compost to soil ratio be? Can I get away with a 50/50 mix?

 

[redback]

Mushroom compost has a good reputation in Australia. It is acidic and maybe be high in salt, but it does break down quickly and is okay for mature plants particularly the acidic loving ones which include tomatoes.

Spread agricultural lime and then water the bed down heavily and allow it to subside. Then trench the rows, add a sprinkle of lime and plant seedlings with extra potting mix along the trenches and in the planting holes.

Alternately a green manure crop of lucerne (alfalfa) tolerates acid and salt and can be planted, grown to six inches high and then turned into the soil. This will modify the soil sufficiently to plant your tomatoes, zucchini and corn later in the season.

I may be wrong, but I have grown into mushroom compost/soil mixture before and had good results. I would go for the lime, watering and adding soil to the planting hole method. Perhaps just plant six seedlings to check first.

 

[Meadowlark]

Mushroom compost...wouldn't touch that stuff with a ten-foot pole.

However, you have it and now what? If you have some good topsoil, mix that in. I would plant cover crops in it, then turn them under green into the compost mix. Probably will need to do that at least a couple of times before it is good to go.

 

[clancaster23]

I planned on planting actual already growing plants, not actually from seed or very small newly sprouted plants. Not sure that makes a difference in planting in this. I think I'm going to try redbacks suggestion. I'll do some tomatoes in the compost and also a couple in the soil pockets. Any other plants I'll do the soil pocket as well. Appreciate all the suggestions. Maybe bey next year it'll break down enough that I can actually do it right.

 

[Chuck]

I'd consider that but I don't have many places I can put another bed and the majority of the property is on a hillside so it makes it difficult to put multiple things up. I'll have to think about it. What should the compost to soil ratio be? Can I get away with a 50/50 mix?

I just looked it up on Google and it said 4 parts soil to 1 part mushroom compost

 

[Chuck]

I'd consider that but I don't have many places I can put another bed and the majority of the property is on a hillside so it makes it difficult to put multiple things up. I'll have to think about it. What should the compost to soil ratio be? Can I get away with a 50/50 mix?

I just looked it up on Google and it said 4 parts soil to 1 part mushroom compost

 

[DiggersJo]

Tomatoes are like weeds, personally I would risk it if the plants are strong to start with. Perhaps adding a little perlite and something like john innes base fertilizer or the equivalent over there. Obviously feed as you would normally.

 

[Oliver Buckle]

Mushroom compost...wouldn't touch that stuff with a ten-foot pole.

The lady next door told me one of the previous tenants years ago had a huge pile of mushroom compost delivered, when I dig I can see where it has been used, and it is a lovely bit of soil there. In the short term it might not be ideal in it's raw state, but in the long term it seems to be really good for the soil, I think 'Wouldn't touch it with a barge pole ' is a bit strong, it's going to be mainly animal manure and straw, with maybe a bit of gypsum or such, nothing too awful.

 

[Meadowlark]

... I think 'Wouldn't touch it with a barge pole ' is a bit strong, it's going to be mainly animal manure and straw, with maybe a bit of gypsum or such, nothing too awful.

Actually, wouldn't touch it isn't strong enough.

First of all, it is spent material, nutrients used up for the most part.

Secondly, it is very high in salt.

Thirdly, you have absolutely no idea what is in that stuff. They may have herbicide residue from the hay. My one experience with it the compost contained medical wastes, syringes, and used condoms. Yuck!!

No, "wouldn't touch it" is definitely not strong enough. "Nothing too awful" how do you know?

 

[Oliver Buckle]

Actually, wouldn't touch it isn't strong enough.

First of all, it is spent material, nutrients used up for the most part.

Secondly, it is very high in salt.

Thirdly, you have absolutely no idea what is in that stuff. They may have herbicide residue from the hay. My one experience with it the compost contained medical wastes, syringes, and used condoms. Yuck!!

No, "wouldn't touch it" is definitely not strong enough. "Nothing too awful" how do you know?

I suppose practices vary, and food production regulation and enforcement. I have seen quite a bit of mushroom compost, both from my own use and others and never seen anything untoward. It is straw they use here rather than hay. There are quite a few 'leisure' horse owners around here who pay to have manure taken away, so the mushroom growers collect at both ends of the operation, it really wouldn't be worth it to risk queering things with a zealous food inspector. I am also puzzled by the salt, where does that come from?

 

[Meadowlark]

A study by Uzun et al (linked below) found that spent mushroom compost contains high levels of salt. Uzun advised leaving mushroom compost to mature two years before use.

https://www.researchgate.net/publication/228703372_Use_of_spent_mushroom_compost_in_sustainable_fruit_production

There is a basic principle here that I believe is critical to those who home grow their own veggies for consumption. Nothing goes into the garden soil unless I know for certain it is safe and free of harmful chemicals. I live by that principal...and it works for me.

 

[DiggersJo]

Does this impact the mushrooms?

 

[Oliver Buckle]

A study by Uzun et al (linked below) found that spent mushroom compost contains high levels of salt. Uzun advised leaving mushroom compost to mature two years before use.

https://www.researchgate.net/publication/228703372_Use_of_spent_mushroom_compost_in_sustainable_fruit_production

There is a basic principle here that I believe is critical to those who home grow their own veggies for consumption. Nothing goes into the garden soil unless I know for certain it is safe and free of harmful chemicals. I live by that principal...and it works for me.

Of the ingredients in that article only poultry manure could contain salt, so I Googled it, and it does, quite high levels. Then I Googled horse manure and it has low levels, lower even than cattle.
I am talking about horse based mushroom compost, and it looks as though it is a completely different kettle of fish from the poultry based one they are talking about. I was puzzled, I have seen some excellent results with what is produced locally.