GardenBanter.co.uk - View Single Post - Lime-garden,ground or hydrated?

chris French · 26-01-2009, 11:16 PM posted to uk.rec.gardening

In message
,
writes
On Jan 26, 12:12*pm, michael wrote:
I am aware that one should not put lime onto a plot at the same time
as manure,but what is a reasonable interval-3 weeks,3 months?
Also,what is the most cost effective type of lime to use.I am aware
that hydrated lime is expensive,and lowers the pH more,but is it worth
twice the price? At our allotment trading hut,25 kg of hydrated lime
is £7.10,whereas garden lime or ground lime is £3.90.
Cheers,Michael

Hi Michael,

Put very simply, ground limestone is used for "sweetening the soil"
and hydrated lime (hot lime) is used for sterilising the soil. Ground
limestone is always the cheaper product but not because it's inferior,
its just quarried differently.

I've never heard of hydrated lime being used to sterilise soil, nor of
it being called hot lime. I think you are mixing up your limes.

I have heard of hot lime (probably because it's not nice stuff to get on
your skin) being used to refer to Calcium Oxide or Quicklime, (which is
what was made in lime kilns by heating Chalk or limestone).
Incidentally, this was used to produce light for stage lighting, hence
the term 'limelight'. I imagine if you put this in soil it would have a
sterilising effect.

You can make hydrated lime or slaked lime by adding the quicklime to
water - which can get very hot in the process. This produces Calcium
hydroxide. This can be applied to soil, and will increase the PH, but
has a greater effect, and it's easier to over do it. It also can be sued
to improve the structure of clay soils as it flocculates the soil
particles (basically causing the clay particles to clump together)

Unless the PH is especially low (test the soil pH first, don't just
chuck it on regardless) then I'd probably go with the calcium carbonate.
There might not be any need at all though, we don't regularly lime
--
Chris French