Acidic compost

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Acidic compost
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wellington womble

Joined: 08 Nov 2004
Posts: 15051
Location: East Midlands

Posted: Sun Oct 18, 15 10:46 pm Post subject: Acidic compost
If I have a compost heap just for acidic kitchen waste (coffee grounds, tea bags, citrus etc) will it make acidic compost? Or is that too basic (no pun intended!)

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Sun Oct 18, 15 10:54 pm Post subject:
At a guess, I would think it would not break down as quickly as normal compost. Why would you want to?

Falstaff

Joined: 27 May 2009
Posts: 1014

Posted: Sun Oct 18, 15 11:27 pm Post subject:

All compost heaps end up acidic whether you use ammonium Nitrate or urine as an activator, or indeed you don't know any better and just let them go smelly and foul ! The generally accepted rule is that you alternate applications of activator with applications of lime. However Gardeners question time today recommended the use of wood ash on the compost heap as it apparently contains much lime !

Good old Flowerdew - you learn something new every day !

Tavascarow

Joined: 06 Aug 2006
Posts: 8407
Location: South Cornwall

Posted: Mon Oct 19, 15 6:27 am Post subject:

Composting goes through many stages & the earlier ones are acidic.
As Falstaff says if too acidic it will encourage anaerobic bacteria instead of aerobic & you will have putrid compost.
If left to mature completely & fully digested by earthworms regardless of the starting pH the resulting vermi-compost will be neutral to mildly alkaline.
There's something in the digestive enzymes of earth worms that neutralises.

Mistress Rose

Joined: 21 Jul 2011
Posts: 15587

Posted: Mon Oct 19, 15 7:32 am Post subject:
I wouldn't waste wood ash on a compost heap, and have never heard of it containing lime. It does contain potassium (potash) and dry wood ash can be used as a top dressing for tomatoes or other fruiting plants. Potassium hydroxide, which can be formed from wood ash, is alkaline, but very soluble and it will wash through the compost very fast.

Andrea

Joined: 02 May 2005
Posts: 2260
Location: Portugal

Posted: Mon Oct 19, 15 7:59 am Post subject:
Unless you've vast quantities of coffee grounds and orange peels, why do you compost them separately?

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Mon Oct 19, 15 8:34 am Post subject:

Andrea wrote:

Unless you've vast quantities of coffee grounds... why do you compost them separately?

If you do, I hear they are good for growing mushrooms on...

Treacodactyl
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 25795
Location: Jumping on the bandwagon of opportunism

Posted: Mon Oct 19, 15 8:42 am Post subject:

Mistress Rose wrote:

I wouldn't waste wood ash on a compost heap, and have never heard of it containing lime. It does contain potassium (potash) and dry wood ash can be used as a top dressing for tomatoes or other fruiting plants. Potassium hydroxide, which can be formed from wood ash, is alkaline, but very soluble and it will wash through the compost very fast.

Wood ash is alkaline though, so don't use it on lime hating / acidic loving plants such as blueberries. It can also be harsh so care is needed when top dressing.

I gather though that components of wood ash will react with nitrogen, tying up potash and nitrogen into less soluble minerals so it may be sensible to use it on some heaps.

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Mon Oct 19, 15 9:22 am Post subject:

Treacodactyl wrote:

I gather though that components of wood ash will react with nitrogen, tying up potash and nitrogen into less soluble minerals so it may be sensible to use it on some heaps.

If it reacts with nitrogen then that is probably great, because that would be making fertiliser out of the atmosphere, but I think that unlikely so perhaps you have it wrong?
You probably mean that it reacts with nitrates, but I am led to wonder what it is that is reacting and to form what...

dpack

Joined: 02 Jul 2005
Posts: 45477
Location: yes

Posted: Mon Oct 19, 15 9:59 am Post subject:

wood ash is better than lime imho
a bit of old tarp or plastic as a loose lid stops most leaching(if the heap drys out water it or use extra urine)

for stuff like coffee grounds ,wood chips etc etc mixing green and leafy in with the more solid stuff helps create a good general purpose compost.

the other thing to remember is that much like a fire a compost heap needs air so packing loosely adding a few twiggy branches etc helps speep things along and prevents smelly anaerobic bacteria being the prime decomposers.

Slim

Joined: 05 Mar 2006
Posts: 6540
Location: New England (In the US of A)

Posted: Mon Oct 19, 15 11:18 am Post subject:

Hairyloon wrote:

Treacodactyl wrote:

I gather though that components of wood ash will react with nitrogen, tying up potash and nitrogen into less soluble minerals so it may be sensible to use it on some heaps.

Maybe this is being confused with the reason you're better off liming a field in the fall, before you spread your spring fertilizer. The breakdown of lime in the soil can change ammonium into ammonia, which is volatile and can leave the soil environment.

Slim

Joined: 05 Mar 2006
Posts: 6540
Location: New England (In the US of A)

Posted: Mon Oct 19, 15 11:20 am Post subject:

Tavascarow wrote:

Composting goes through many stages & the earlier ones are acidic.
As Falstaff says if too acidic it will encourage anaerobic bacteria instead of aerobic & you will have putrid compost.

I can't imagine anaerobic bacteria ever gaining a competitive advantage over aerobic bacteria when there is an adequate supply of oxygen. Is this possibly a conflation of acidic type materials matting down and not staying as well aerated?

vegplot

Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd

Posted: Mon Oct 19, 15 11:29 am Post subject:

Falstaff wrote:

However Gardeners question time today recommended the use of wood ash on the compost heap as it apparently contains much lime !

Are you sure it was lime they were talking about? I heard the word lye.

tahir

Joined: 28 Oct 2004
Posts: 45426
Location: Essex

Posted: Mon Oct 19, 15 11:44 am Post subject:

vegplot wrote:

Are you sure it was lime they were talking about? I heard the word lye.

I think you're right, woodash contains potash

john of wessex

Joined: 18 Jun 2007
Posts: 2130

Posted: Mon Oct 19, 15 6:25 pm Post subject:
I just give mine a sprinkling of wood ash every time I have added a few inches of material, with a bit of B&Q Rockdust

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