In article , Rodger Whitlock
writes
On 19 Nov 2002 20:36:25 GMT, (DaveDay34) wrote:

it? Osmosis will operate until all the soil is truly saturated.

Osmosis doesn't operate until all the soil is saturated.

You are both confusing osmosis with capillarity.

It's capillary attraction that causes a pot standing in 1/2" of
water to become waterlogged, not osmosis.

To expand on that - osmosis is what happens when you have something -
for argument's sake, say salt - dissolved in water (or other liquid). If
you dump some salt in water, it diffuses across the whole lot so that
the strength of the solution is the uniform - you don't get a strong
salt solution where you dumped the salt and pure water elsewhere.

But if there is a barrier dividing the water into two, and this barrier
is such that water can get through but salt can't, the tendency is still
to try to even out the strength of the solution across the barrier, but
the only way this can happen is for water to go through the barrier from
the dilute side to the concentrated side. This is osmosis.

Capilliary action is the tendency for water to seep from wet area to dry
area - which can happen upwards if the route for seepage is small - eg
it's between the particles of soil.



--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/garden/