Posted by Chris Hogg on March 3, 2010, 1:10 pm
On Tue, 2 Mar 2010 20:48:07 -0000, "Phil Gurr"
>> wrote:
>>
>>>Called into a DIY shop for some lime. They no longer stock it because a
>>>H&S issues, though I think that may be a good cop out. It occurred to me
>>>that builders merchants might be a cheap source. Is their lime ok for
>>>gardens, or does it need more refining?
>>
>>
>> Most 'lime' available in garden centres etc. these days is ground
>> limestone, i.e. calcium carbonate, whereas true lime is calcium oxide,
>> or if hydrated, calcium hydroxide. Calcium oxide rapidly converts to
>> calcium hydroxide when wetted, with the evolution of a lot of heat.
>> Calcium hydroxide slowly converts to calcium carbonate in the air as
>> it reacts with carbon dioxide. It's the mechanism by which lime mortar
>> sets. Much of the lime you spread on the ground will end up as calcium
>> carbonate. The only real difference between lime and ground limestone
>> from a horticultural point of view is that ground limestone is slower
>> to work.
>Much of the ground limestone available in garden centres contains a fair
>proportion of magnesium carbonate. Where the proportion is over 20% the
>product is often marketed as 'dolomite' lime. Magnesium carbonate is even
>less soluble in the soil, so very long lasting, but very beneficial to
>plants.
>Phil Gurr
>Northern Highlands of Scotland
From time to time I chuck a handful or two of the magnesium-containing
stuff into the pond to keep it from getting too acid and killing the
snails by dissolving their shells. AIUI dolomitic limestone gives a
slightly less alkaline pH than pure limestone. Certainly the pond pH
stabilises at around 7 when so treated.
--
Chris
Gardening in West Cornwall overlooking the sea.
Mild, but very exposed to salt gales
E-mail: christopher[dot]hogg[at]virgin[dot]net
Posted by Phil Gurr on March 3, 2010, 1:29 pm
> On Tue, 2 Mar 2010 20:48:07 -0000, "Phil Gurr"
>>
>>> wrote:
>>>
>>>>Called into a DIY shop for some lime. They no longer stock it because a
>>>>H&S issues, though I think that may be a good cop out. It occurred to me
>>>>that builders merchants might be a cheap source. Is their lime ok for
>>>>gardens, or does it need more refining?
>>>
>>>
>>> Most 'lime' available in garden centres etc. these days is ground
>>> limestone, i.e. calcium carbonate, whereas true lime is calcium oxide,
>>> or if hydrated, calcium hydroxide. Calcium oxide rapidly converts to
>>> calcium hydroxide when wetted, with the evolution of a lot of heat.
>>> Calcium hydroxide slowly converts to calcium carbonate in the air as
>>> it reacts with carbon dioxide. It's the mechanism by which lime mortar
>>> sets. Much of the lime you spread on the ground will end up as calcium
>>> carbonate. The only real difference between lime and ground limestone
>>> from a horticultural point of view is that ground limestone is slower
>>> to work.
>>
>>Much of the ground limestone available in garden centres contains a fair
>>proportion of magnesium carbonate. Where the proportion is over 20% the
>>product is often marketed as 'dolomite' lime. Magnesium carbonate is even
>>less soluble in the soil, so very long lasting, but very beneficial to
>>plants.
>>
>>Phil Gurr
>>Northern Highlands of Scotland
>>
> From time to time I chuck a handful or two of the magnesium-containing
> stuff into the pond to keep it from getting too acid and killing the
> snails by dissolving their shells. AIUI dolomitic limestone gives a
> slightly less alkaline pH than pure limestone. Certainly the pond pH
> stabilises at around 7 when so treated.
Magnesium carbonate is just as alkaline as calcium carbonate, but the
release is so slow that it is counteracted by natural acidity. This is
especially so in a pond where the water always tends toward acidity.
Phil
Northern Highlands of Scotland
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>>
>>>Called into a DIY shop for some lime. They no longer stock it because a
>>>H&S issues, though I think that may be a good cop out. It occurred to me
>>>that builders merchants might be a cheap source. Is their lime ok for
>>>gardens, or does it need more refining?
>>
>>
>> Most 'lime' available in garden centres etc. these days is ground
>> limestone, i.e. calcium carbonate, whereas true lime is calcium oxide,
>> or if hydrated, calcium hydroxide. Calcium oxide rapidly converts to
>> calcium hydroxide when wetted, with the evolution of a lot of heat.
>> Calcium hydroxide slowly converts to calcium carbonate in the air as
>> it reacts with carbon dioxide. It's the mechanism by which lime mortar
>> sets. Much of the lime you spread on the ground will end up as calcium
>> carbonate. The only real difference between lime and ground limestone
>> from a horticultural point of view is that ground limestone is slower
>> to work.
>Much of the ground limestone available in garden centres contains a fair
>proportion of magnesium carbonate. Where the proportion is over 20% the
>product is often marketed as 'dolomite' lime. Magnesium carbonate is even
>less soluble in the soil, so very long lasting, but very beneficial to
>plants.
>Phil Gurr
>Northern Highlands of Scotland