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3. Basic Soil Monitoring and Evaluation
Entisols
Entisols have formed very recently in geologic
time and are the most common soil type in
the world. If you have these types of soil on
your ranch or farm you should not expect to
see much soil profile development, possibly
only one or two horizons. These soils can
form in a river valley that has experienced
recent sediment deposition from a flood, or
they could form on rocky slopes or moving
sand. Entisols recently formed on river
sediment can be very fertile, in contrast to
those formed on rocky slopes or shifting
sands, which are usually not very fertile. River
valley Entisols are significant areas of food
production world wide.
In New Mexico and Colorado, Entisols
are present because the parent material
is young as well as the limited time exposed
to the soil forming factors. Entisols form
primarily on higher sloping areas where
soil particles erode and move out before
developing sufficiently for another soil order.
You may also encounter them along flood
plains of the Rio Grande or other larger rivers,
for example, where sediments have been
deposited very recently. Entisols generally
occur in patches around both states, with
highest concentration in northwestern New
Mexico and the western and eastern plains of
Colorado (not in the Rockies).
Inceptisols
These soils are one next step further along
the weathering process from Entisols. You can
expect to see a bit more profile development,
but still very far from the hypothetical profile
shown on page 12.
In New Mexico and Colorado, Inceptisols
are concentrated in mountainous regions,
such as ranges of the Gila, Sangre de Cristo,
Jemez, San Juan, and Rocky mountains. You
would likely not encounter them in cropland,
but might well find them on a ranch or leased
grazing land in a national forest.
Aridisols
Aridisols are soils that form in arid climates.
The natural vegetation found on these soils
is scattered, which means that the influence
of organic matter deposited by plants is also
scattered. Some areas have none; some
have a lot, for example, immediately under
a bunch of grama grass or creosote shrub.
The soil horizon closest to the surface is
characteristically light in color (don’t expect an
O horizon here). These soils generally have a
high pH, and caliche layers are common. Also,
they contain a lot of salts, simply because
there has not been sufficient moisture during
soil development to wash salts away. For this
reason, salinity and sodicity are often an issue.
Aridisols are the most common soil order
in New Mexico. In Colorado, they are
distributed sparsely throughout the state, with
the largest patches in the east. As we know,
both New Mexico and Colorado can be very
windy, and precipitation is often intense. When
sparse vegetation is removed from aridisols
(due to overgrazing or compaction, etc.), soil
loss can become a very serious issue.