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2. Soil Fundamentals
How does water enter soil?
Water influences every aspect of soil—
physical, chemical, and biological—because
of its unique chemical properties. From the
initial stage of soil formation to transporting
soil nutrients after a rain event to providing
the habitat for soil microbial communities
and water for plant growth, water is essential
to understanding soils and soil health. Water
behaves in a unique way when interacting
with soil aggregates, which gives soil water
some special properties that are important to
consider when managing a ranch or farm.
One major property of water is that a lot
of compounds dissolve in it and so can be
transported through soil. For example, dry
inorganic fertilizer is not accessible to the
roots of plants until it dissolves in water and
moves down to the soil’s rooting zone.
Additionally most of the microscopic life in
soils is active in water films that form on soil
aggregates. All processing of organic matter
and other soil minerals and nutrients
depends on the presence of water. In semi-
arid New Mexico and Colorado, where rainfall
is seasonal and dry spells are intense, these
processes are also seasonal (for more on this,
see the chapter on biological characteristics,
page 51).
The source of irrigation water and how it gets
to a property can determine what minerals
come with it. If it flows in open dirt ditches,
it will pick up minerals on its way to your
property, and these could be concentrated
by evaporation. Groundwater, on the other
hand, can pick up minerals from the bedrock
surrounding it and can be quite rich in
sodium, calcium, iron, or sulfur. When these
mineral-rich waters are used to irrigate crops
or pasture, there may be impacts on soil
structure and plant health. This is why it
is important to evaluate irrigation waters as
part of soil testing (which will be covered in
the section on monitoring and evaluation,
page 80).
Photo: Miguel Santistevan
Water