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3. Basic Soil Monitoring and Evaluation
Mollisols
The defining characteristic of a Mollisol is that
it has formed under grassland vegetation. The
soils often have a thick, organic-rich surface
horizon, and thus a dark O horizon. Because
of their high organic matter content, their
structures are good, with high aggregate
stability, and they show high productivity.
Mollisols are found in the western-most
extent of the Great Plains, in eastern New
Mexico and Colorado. In New Mexico the
largest patches are found between Almagordo
and Roswell and east of the Sangre de
Cristos in the north, and they are distributed
throughout Colorado. In some areas, where
mollisols were cultivated and tilled and then
subjected to extreme erosion by the storms
of the Dust Bowl in the 1930s, they are still
recovering.
Discussion – Soil Orders and Healthy Soil Principles
Let’s say you determined that you have an Aridisol on your ranch and that you have no water for
irrigation. How would you pursue the five healthy soil principles? Think about which physical,
chemical, and biological characteristics you could change and which you couldn’t. What would soil
health look like to you on a landscape where soil was mostly Aridisol?
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Alfisols
Alfisols form under forested vegetation.
In New Mexico and Colorado they are
found in mountainous areas similar to
those where Inceptisols are found, but Alfisols
cover larger areas. They have experienced
more weathering than any of the other soil
types we described, and therefore you would
expect to see more horizon development.
There is often a good amount of clay present
in Alfisols and like Mollisols they are very fertile
and good for cultivation. In the Southwest
they are generally found at higher elevations,
where cold and snow may pose a challenge to
agriculture.