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2.1 Physical Characteristics
Glossary
Aggregate Stability
the ability of soil aggregates to withstand
changing soil conditions.
Aggregate stability is a dynamic and important
soil property. It is affected by physical,
chemical, and biological processes.
Aggregate Stability
Aggregates
Sand, silt, and clay can be bound together
to form larger aggregates, which have many
benefits:
•
Promote water and air movement deep
into the soil profile
•
Effectively hold water against
evaporation
•
Provide sites for carbon sequestration
•
Provide sites for nutrient storage and
cycling
•
Provide sites of very high microbial
activity
Clays play the largest role in the physical-
chemical process of aggregate stabilization.
The interaction of clays with calcium, iron,
aluminum, and sodium can either increase or
decrease aggregation (see Salinity and Sodicity
page 50).
Biological processes and compounds increase
soil aggregation and stability. These include
the movement of soil organisms, organic
matter, and compounds produced by roots,
fungi, and microorganisms (bacteria and
archaea).
Aggregate stability has been shown to be
generally low across much of New Mexico
and Colorado rangelands, based on data
from the 2015 NRCS Rangeland Resource
Assessment. It is important to note that there
are a diversity of soil orders in New Mexico
and Colorado, and we would not expect these
diverse orders to show the same degree of
aggregate stability (for more on soil orders,
see “Where to Sample,” page 84).
Soil structure is affected by soil texture and
organic matter as well as by land use and
management practices.
Note that soil structure is different from soil
texture, which is generally not affected by
land use and practices.