[jonewer]

One of the old boys on the site advised me to put chimney soot (from the sweepings) into the soil as a fertiliser/compost type thing.

Just wanted to check here first - I know wood ash is good for the soil but also that coal ash is toxic. Would the chimney soot be safe from mixed coal/wood fires?

[mumofstig]

My garden soil is black from years of people adding soot and ash to it.
Well weathered soot makes a good soil conditioner, and darkened soil warms up more quickly in spring, but it tends to make the soil more acidic
I don't think it's bad for the soil,  but there are plenty of better things you could be adding

[Yorkie]

It depends what you've been burning.  I think the smokeless fuel briquettes have chemicals in them which you wouldn't want to put on your garden ...

[8doubles]

But if the EU have not tested , approved and taxed your chimney soot it will probably be illegal to use it on edible crops !

[mumofstig]

But if the EU have not tested , approved and taxed your chimney soot it will probably be illegal to use it on edible crops !

 

but it's going on the soil, not on the crops 

[JayG]

As Mum has said, well-weathered soot is almost entirely just carbon particles, which is pretty resistant to nature's attempts to attack and rot it down, and the colour can help soils to warm up quicker.

Fresh soot will also contain various organic and inorganic chemicals deposited by the smoke - some will be sulphur and nitrogen-based acidic compounds, some will be complex organic molecules, of which some are likely to be carcinogenic.

Personally I'd avoid fresh soot because of those "unknown quantities" but then again there is probably a whole generation of soot-users out there who swear by it and are living proof that it never did them any harm! 

(Plenty of info to read if you Gurgle "chimney soot carcinogen")

[jonewer]

Thanks all. How do you weather soot?

[mumofstig]

just leave it in a corner for the wind and rain to work on for a few months

[jonewer]

OK, I'm going to have my chimney swept and may ask the sweep if he has any spare soot for me. He'll probably think I've been punishing the brandy! 

[ilan]

No As my father in law was a  sweep he was always being asked for soot best is from wood fires tho as coal soot is very acid 

[mumofstig]

and that's why you weather it first 

[Growster...]

My book says that soot has about the same nitrogen content as bone meal (5%), and as said here, is a good top dressing and darkens the soil to retain heat.

There are a few trace elements as well, which apparently may benefit roses and chrysanths, but this is applied by soaking a bag of the stuff in water for a couple of weeks.

I also tried it on peas, and they perked up a bit, although I wouldn't be able to prove that!

[New shoot]

I've used quite a bit of chimney soot on the heavier sections of clay on my plot. I do only burn wood and I weather the soot by leaving it in a heap for a few months as Mum says.  Over winter is best as it gets lots of rain on it.

If you have heavy soil it works wonders on opening it up  Not sure how much nutrient content it has after being left to weather but its worth using for me just for the soil conditioning properties.  I usually spread it and dig it in with compost in the spring  

[8doubles]

I've used quite a bit of chimney soot on the heavier sections of clay on my plot. I do only burn wood and I weather the soot by leaving it in a heap for a few months as Mum says.  Over winter is best as it gets lots of rain on it.

If you have heavy soil it works wonders on opening it up  Not sure how much nutrient content it has after being left to weather but its worth using for me just for the soil conditioning properties.  I usually spread it and dig it in with compost in the spring  

The burning * questions which must be asked is where do you weather the soot, does the concentrated run off from the weathering soot heap damage the surrounding soil (hopefully not near any watercourses) and if no damage is evident why bother ?

*

[mumofstig]

AFAIK It doesn't damage the soil, but it could damage foliage if used fresh, in the same way fresh manure can be too acidic.