claude sweet sweetent at HOME.COM
Thu Jun 14 18:18:09 CEST 2001

> Jim wrote regarding adding sand:
> >....I would emphasize the the word "COARSE"!! Two years ago what was
> >delivered to me wasn't very coarse and I made the mistake of going
> >ahead and using it inconstructing several of my "layer cakes".
> >They've been death on arisaemas!
> Another name used for sand when it is mixed with clay:   cement.
> Nina Lambert, Ithaca, New York, USA

Adding ONLY sand (any size of of particle - fine or coarse) should not
be added to soils described as clay. The result will indeed be cement
like, especially at low moisture levels.

Fine particles of sand will actually repel water if added as a layer
rather than incorporated into the soil.

Composted organic materials should be added to a clay soil to improve
its texture and drainage. Uncomposted organic materials will reduce in
mass over several seasons and in the process of decomposition will be a
nitrogen sink. Inert materials like perlite remain unchanged in size
unless physically crushed. The larger particle sizes allow pockets of
"empty" space that allows oxygen and water to penetrate the soil -
producing a mixture of both producing healthy growth.

Incorporating organic materials into a sandy soil provides the necessary
moisture retention to produce healthy growth without excessive water
draining through the root zone and being wasted.

The mixture of combinations of organic materials (peat moss, redwood
compost, rice hulls, etc.) and inert materials (sand, perlite,
vermiculite, etc.) are commonly known as artificial planting mixes. Such
mixes are generally used for small containers (<15 gallons). The expense
of the materials usually preclude their use in larger containers.

In a permant planting where the plants will not be disturbed - growers
should be concerned with the interface between soils that are amended
and natural soils.

Drainage tiles should be installed in heavy soils that collect water
during wet seasons unless you are planning a bog garden. Digging a large
hole and putting stones in the bottom does not provide any more drainage
than putting stones in a bucket.

Raised beds created from adding 30 to 60% amendments into the top 8 - 12
inches is an affordable method to achieve drainage and provide an ideal
medium for bulbs and annuals.

My perspective has evolved since graduating 40+ years ago with a degree
in horticulture from an eastern school and moving to the west coast.
University research has changed advice for planting trees with
amendments and been modified as the production in nurseries changed from
a ball & burlap plants to a container/box plants. Circumstances vary
widely from the arid western states to heavy rainfall areas in other
parts of the country. In areas were freezing and thawing occur,
modifications to soils may also require heavy mulching once cold weather

Claude Sweet
San Diego, CA
USA zone 10

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