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[GWL]: Caliche

Nan,

I gardened in Albuquerque and Santa Fe for the first 25 years of my life as
a gardener.  I had to deal with all kinds of caliche--even made adobes with
it.

The classic 'caliche" is a light-colored, highly alkaline clay in which the
particles are cemented together with calcium carbonate.  It is formed in
shallow lenses--"pans"--(which over geologic time may develop into deep
layers) in low-lying areas where water repeatedly stands and eventually
evaporates, concentrating the minerals it contains into the soil left
behind.  This may occur either through natural processes (with runoff water
pooling after rains) or through repeated irrigation.  In the case of
irrigation, it is one of the major causes of desertification in important
agricultural areas (like California's Central Valley).  In New Mexico, it
may be the result of either cause, depending upon whether it occurs on the
mesas or in the river valleys (where irrigation has been practiced for
centuries).

There are varying definitions and consequences of caliche, depending upon
what your concerns with it are:

http://www.cahe.nmsu.edu/ces/yard/2001/081801.html

http://sis.agr.gc.ca/cansis/glossary/caliche.html

http://www.swanet.org/news.html


Here is how Agricultural Extension service agents in Arizona and New Mexico
recommend dealing with it:

http://ag.arizona.edu/pubs/garden/mg/soils/caliche.html

http://www.cahe.nmsu.edu/pubs/_a/a-127.html


Often these measures will work OK--at least for a while--depending upon the
alkali tolerance of the plants.  But this piecemeal approach is often just
stopgap.  A rose planted in such a hole soon will suffer from iron
deficiency if no other measures are taken.  The calicium ions will limit the
availability of iron to the plant, and it will turn  yellow and die.  Yearly
surface addition of soil sulphur, iron sulphate, magnesium sulphate (epsom
salts), and a thick organic mulch (which worms can gradually work down into
the soil) may maintain the plant in good health if continued indefinitely.
But if your entire garden consists of a thick layer of caliche, you are
fighting a losing battle.  In the long run, the best way to deal with
caliche is to break it up deeply enough to reach the underlying stratum to
ensure adequate drainage and convert it to good soil.

Digging unto caliche is very hard work, best accomplished with a mechanical
jackhammer or a backhoe.  Ideally, the caliche should be broken up with a
backhoe, thoroughly mixed with sand, soil sulphur, and ample organic matter,
and planted over with a legume cover crop like alfalfa, with this crop
turned under at the end of the season.  To avoid reformation of the caliche,
insure that any water applied to the soil either freely drains into a porous
subsoil (in New Mexico's river valleys, caliche often is underlain by a
stratum of sand) or can drain off on the surface.  It should be noted that
caliche soils may be rich in minerals that are necessary to plant growth and
that once their texture and drainage are corrected and biological processes
set in motion, they usually produce luxuriant growth in all but acid-loving
plants.

There are some variants of caliche.  In soils long subjected to irrigation,
the alluvium may be cemented with sodium nitrate, sodium chloride, or other
soluble salts.  in this case, you have a sodium-affected caliche, and and
these cases fall into several categories:

http://hermes.ecn.purdue.edu/cgi/convwqtest?ib-9.ut.ascii

Saline soils, in which the offending mineral is sodium chloride.  The high
sodium chloride content means plants become starved of water.  Leaching the
salt out of the soil with copious amounts of water that subsequently can be
drained away is the only way to substantially improve this condition.

Sodic, or sodium-affected soils (sometimes known as "black alkali" but not
always black), in which the sodium is accompanied with ions of calcium,
magnesium and sodium.  This is the instance where application of gypsum
(calcium sulphate) followed by leaching is appropriate.

http://ag.arizona.edu/OALS/IALC/soils/aridsoils/sodic.html

http://www.science.org.au/nova/035/035key.htm

http://www.science.org.au/nova/035/035box03.htm

Of course, throughout all this, an accurate soil test is an absolute
prerequisite.

>From prehistoric times, the various kinds of caliche have been employed as
building materials in New Mexico--either mined directly from the ground as
blocks like limestone or mixed with water and kneaded, then pressed into
forms to make sun-dried adobes.  After WWII, my parents bought the oldest
house in Albuquerque, which pre-dated the establishment of the church and
houses around the Old Town Plaza (1706) by about two decades.  Franciscan
friars had established a small mission in the center of fruit orchards that
they maintained for trading with the Indians.  The original one-room core of
our house was built--not of adobe, but of "terrones"--blocks sodium-affected
black clay cut from a nearby marsh, strengthened with the roots of water
plants left intact and mortared with the same alkaline mud.  After 250
years, the walls were as hard as poured concrete.  My parents had to hire a
paving contractor with a jackhammer to cut through in order to install a
two-way wall heater.  The walls held the heat in winter and were perfect
insulation against the sun in summer.  It was the most comfortable house I
ever lived in.

John MacGregor
jonivy@earthlink.net

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