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Making
the Most of Mountain Soil
by
Susan Fernalld, Master Gardener
High
altitude soils vary so greatly that it is hopeless to generalize
about the physical properties and nutrition in them. The soil of
a mountain ridge top may be rocky, shallow, and alkaline, but the
valleys below that ridge may be loamy, deep and acidic. Mountain
gardeners will find their soil sufficient to grow area native plants,
while non-native plants don’t thrive. Gardeners who wish to
use non-native plants are advised to get a soil test and then gradually
make soil improvements based on the test results. Over time, amendments
mixed into soil and mulches applied on top of the soil create a
soil ecosystem that promotes deeply-rooted plants capable of surviving
our temperature extremes and drying winds.
Soil Amending
Soil amendments improve the physical properties of soils by:
• increasing
aeration
• increasing water infiltration and drainage
• increasing nutrient-holding capacity of soil
Because Colorado
soils are naturally low in organic matter, organic soil amendments
such as compost are a good choice. Microorganisms in compost increase
soil tilth and make nutrients available to the plants. If soil has
less than 3% to 5% organic matter, lay 1-1/4 inches of organic matter
on top of the soil and cultivate in thoroughly. Repeat every year.
More than that in a year may add too much salt to the soil.
Mulching
Organic mulches provide plant protection and improve soil by:
• improving
aeration and water-holding capacity of the soil
• suppressing garden weeds
• conserving water by reducing evaporation
• protecting shallow-rooted plants from freezing and
frost heaves
• reducing soil erosion
• breaking down slowly without depleting soil nitrogen
• preventing soil compaction
Wood chips,
readily available in the mountains where many home-owners these
days are thinning trees for forest health and fire mitigation, make
ideal mulch around plants or as a surface material for paths. Apply
a two- to four-inch layer of wood chips on top of the soil at any
time of the year, and apply more mulch each year to renew the proper
depth. Pull back six inches from the base of trees and shrubs, three
inches from flowers.
Consult your Colorado State University Cooperative Extension office
or commercial laboratories about soil tests to determine what kind
of soil you have and recommended amendments and fertilizers. CSU
Cooperative Extension has several fact sheets available with more
details on understanding soil problems and choosing amendments and
mulches.
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