Water retained by various soil ingredients

Peter Taggart petersirises@gmail.com
Wed, 24 Oct 2012 14:05:17 PDT
Apologies for sending a blank reply.

I agree that a proportion of fine particles in soil mixes is very
desirable. How much fine material depends partly on the watering practices
and also on what is being grown. I add clay or loam to grit for most of my
potting composts.

frames or plunge beds containing containing 'cinders' are part of
traditional horticulture in the UK though rarely found now, since cinder
production is not common now  in domestic circumstances. It was often
obtained from coal fired furnaces.
Peter (UK)

On Wed, Oct 24, 2012 at 9:52 PM, Peter Taggart <petersirises@gmail.com>wrote:

> On Wed, Oct 24, 2012 at 9:50 PM, Hannon <othonna@gmail.com> wrote:
>> Since it is a natural product, what is sold as the same item (pumice) can
>> vary from very clean and sharp-edged particles to soft-edged rounded
>> particles with more dust-like fines included. I agree with Jane that the
>> fines are helpful to the roots, in part by coating them and protecting
>> them
>> with a 'powder coating', especially when plants are dormant. Fines in
>> general, especially organic ones, help with cation exchange (places where
>> nutrients can be stored in the soil).
>> Scoria sounds like what is also known as cinder. This is volcanic material
>> that is crushed in huge quantities to make cinder blocks and this seems to
>> be its nearly exclusive use. A fine grade of cinder (black or red) with
>> pieces 1-2mm is very clean and sharp and one of the best materials I have
>> found to start seedlings of cacti, bulbs, etc. Again, with horticultural
>> demand so low it is no wonder it is difficult to find a source for it.

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