At 08:43 AM 12/24/03 -0500, Nina Shishkoff wrote:
Basically, it is important to water all plants from the top because as
the water moves down through the soil it will push out the old air and
draw in fresh air.

Bill, I bow to you in most situations, but this sounds bogus to me. Water
will displace air whether you add it from the top or bottom, and when it
drains, air will come back.

Nina. I bow to Bill. Really. Watch at the next MidAtlantic Conference.

Folks

It's not a REALLY big deal, unless you live in a hard water area, BUT there
most certainly is a difference:

When you soak a plant (dunk it), it sits in the same volume of water
without any active circulation. The soil gets saturated. When you lift it
out, it drains. There has been a flush with only the volume of drain water,
regardless of the size of the container used for soaking. If you don't let
water go above the rim of the pot, but rather let it get to the top by
capillary action, there is effectiviely NO flushing action of the top
layers of soil. Each watering will add a little more salt deposit as the
water is evaporated or absorbed by the plant

When you water from above, the reverse is true. The top layers of soil are
continually bathed in fresh water with a less than saturated amount of
dissolved salt. This tends to dissolve any salt left behind by the
evaporation of the previous watering. Additionally, as the soil becomes
saturated, it drains, and additional watering will flush the soil with many
times the volume of the pot depending on how long you water. If you are in
a hard water area, watering overhead by a mist irrigation spray or other system
attached to a timer allows you to flush virtually all of the dissolved salt
that is practically possible.

The same is true of air flow through the soil mixture, although I doubt
this is as important as the salt flushing action of water flow. If you dunk
your plant, the water drains out the bottom and pulls in a fresh charge of
air behind it. One change of air, but probably adequate. If you water from
above much more air will be pulled through the soil mixture, unless you
water with a firehose and have some way of not blasting out the soil. Hey,
glued on rocks!


Brent in Northern California
Evergreen Gardenworks USDA Zone 8 Sunset Zone 14

http://www.EvergreenGardenworks.com

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