Liming with calcium oxide (quicklime)

I have been a lurker on these forums for a while now and many others, this is my first thread :).
With regards to liming many people use slaked lime (Calcium carbonate) however when anyone seems to ask the question can I use quicklime everyone gets rather iffy and nervous around the substance. I come from a family of traditional building restoration stonemasons so we make a lot of lime mortar and render.
The problem many people have with using quicklime is the fact that it is a caustic substance that when it comes into contact with water it produces a highly exothermic reaction (gets hot) However quicklime is not as bad as people would have you believe, yes it can sting if you breathe in loads but the issues of it's use are much overplayed amongst gardeners.
The key with using quicklime is not to slake it in a bucket and then apply this lime gum to the land.- may seem simple but people actually do this. what I do is I fill a bucket with it and get my trowel and throw it around the soil and rake it in. After this I give it a quick soak with a watering can. However the reaction in the soil is very slow and relatively harmless because of the length of time it takes to react and the fact that it is underground. After you apply the lime in autumn and rake you wait for the winter frosts and rains to do their work, by mid february the calcium oxide is now calcium carbonate (garden lime) what should be done now is forking the lime in.
It is not the problem of quicklime and it being a dangerous substance, it is the problem of lack of understanding and stupid fears that if you are careful you can avoid.
for those who do not understand how garden lime and quicklime differ here is a quick version of the lime cycle.
Limestone (Calcium carbonate) CaCO3 apply a great heat and the carbon and 2 oxygen become CO2 and float off. Quicklime (Calcium oxide) CaO Add water and mix about this becomes slaked lime which the reacts with the carbon dioxide in the air. when the CO2 is added back to the CaO it becomes CaCO3 and thus is Limestone again or to you and I, Garden Lime.
I hope this has helped and informed you in the use of liming with quicklime.
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aaronleadley

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aaronleadley wrote:

Then you should know that slaked lime is calcium hydroxide not calcium carbonate, the latter is usually called garden lime or agricultural lime.

And have it spit in your face when you mix it if you are not careful

Agreed you don't want to do that.

On the contrary the reaction between quicklime and water is still extremely fast, as soon as the water touches it will be gone. Spreading it on the soil before you wet it will stop the heat accumulating because it is dispersed it will not make any difference to the speed of the reaction. Even if you don't wet it quicklime will react with soil moisture quite quickly.

I doubt that it will convert that quickly. In any case if you want calcium carbonate why not add calcium carbonate?

A few of points that you haven't mentioned:
- Slaked lime (calcium hydroxide Ca(OH)2 ) takes a long time to react with dissolved carbon dioxide and convert to calcium carbonate. If it is not exposed to air and water or to water that is exposed to air it won't happen at all. In the meantime it may do harm.
- There are some reasons why you would not apply quicklime or slaked lime to your garden. Although not very soluble in water it is still much more soluble than garden lime and it produces a much more alkaline solution than garden lime. The result of these factors is that it is going to raise the pH of your soil much quicker.
This has two risks, it is easier to over-do it and make your soil too alkaline and altering the pH a lot quickly will decimate the microbes in the soil. Microbes usually only grow well in a limited pH range, if you change the pH you will change the set of bugs that can live there. This needs to be done slowly so that the ecology of your soil stays healthy. Soil is a living community not a pile of chemicals. You should be kind to your soil not shock it with harsh substances.
- Garden lime is readily available, safe, cheap and effective. Why would you want to play with quicklime no matter how careful you might be? There is no benefit to it.
David
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On 2/4/2011 1:15 PM, aaronleadley wrote:

Slaked lime is calcium hydroxide vs quick lime which is calcium oxide.
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