Soil Management
 Where
it all begins
The soil is the home of the root. Matching the plant to
the soil, creating a hospitable home, is the first essential
step in successful and beautiful landscapes and gardens. soils
may look dead, but healthy soil is alive with literally millions
of micro-organisms that support plant life.
Soil chart from the planet ag booth (pdf)
In the forest or native plains, soil is kept healthy by nature’s
own processes of plant growth, death, and decay. In managed
landscapes, we consider dead plant material unsightly, so
we have to substitute management strategies to keep soil healthy.
Success tip: Dead soil can’t support live plants.
Soil Primer
Healthy soil
Components of Soil
Organic Matter
Remains of plants and animals. Living area with millions
of microscopic critters that keep the soil alive and vital.
Heat burns up organic matter in Texas soils.
Water and Air
Carbon dioxide in the soil combines with water to form
a solution that can be used by plants for food. Air provides
space for water and roots to move.
Plant Nutrients (food)
20 elements needed for growth
The fertility of soil is its ability to hold and release
nutrients in adequate amounts and suitable proportions.
Adequate amounts of water and air are needed, as well as
a proper balance of the 20 elements
What determines the amount of
organic matter in soil?
- Long term management
- Kinds of plants that have been grown there
- Temperature
- Drainage
Success Tip: Compost enhances each of the components of
soil making a living, hospitable environment for the plants.
Physical Properties of Soil
Agro/Hort
100 Intro to Plant Science - Soil
Color
Light clear, bright color: low organic matter content,
coarse texture
Dark: high organic content
Red and brown: free movement of air and water, good
aeration
Yellow, mixed or drab: poor drainage, too much water,
too little air
Texture
Sand: coarse, rough, fast draining
Silt: fine, floury, smooth
Clay: finest particles, smooth when dry, sticky when wet
Loam: moderate amounts of all three - best for plants
Structure
Good soil structure is promoted by (1) adequate supply
of organic matter (2) working the soil only when moisture
conditions are right. Plants can actually change the soil
structure. So can earthworms as they tunnel through the
subsoil.
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Over the Top
Illustration: Texas Geologic Regions with Plant Material
Illustration
Success Tip: Knowing the types of soil native to an area
helps identify the plants that will be easiest to grow there.
What lies beneath?
Soil Depth
The Effective depth is the point to which a plant’s
roots can grow before they hit something that stops them.
Plants have different depth needs depending on the type and
size of plant. Deeper topsoil holds more water and needs less
frequent irrigation.
Very shallow - 10”
Shallow - 10-20”
Moderately deep - 20-36”
Deep - 36-60”
Very deep - 60” plus
Soil not only changes across the surface, it changes below
the surface as well. What we call topsoil is only the beginning:
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01 Horizon of undecomposed (01) and decomposed (02) organic matter. It is absent in cultivated soil and many other types. |
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A Mineral surface soil which has accumulated decomposed organic matter and is usually darker in color than lower layers. It is also the layer of downward movement of organic matter, clay, iron and aluminum. |
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B Mineral subsoil which accumulates clay, iron, aluminum and organic matter from the layer above. Texture is usually finer than the layer above. Structure is often more distinct than in the A horizon. |
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C Mineral horizon of weathered parent material or other substratum for unconsolidated material. May or may not be like that in which the solum (A plus B horizons) formed. |
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R Underlying consolidated bedrock. Absent under many soils except at great depth. |
Success Tip: The deeper the organic matter layer, the
less water required for successful landscaping.
Soil Testing
Test the soil every 3-4 years or when establishing a new
landscape
Get a soil testing kit from your local nursery or your Texas
Cooperative Extension Office
Use clean sampling equipment, not brass, bronze, or galvanized
tools
Mix samples in a clean, plastic bucket.
Sample location.
Each sample should represent only one soil type or area—for
example, a lawn, vegetable garden or perennial landscaped
area
Take least six to eight sub samples and combine them to
make one sample.
If one area of the yard seems healthy and another has bare
or yellow areas, sample healthy and unhealthy areas separately.
Sample Depth
Lawns - 4” excluding any turf thatch.
Vegetable and flower gardens - 4-6”
Shrubbery4-6 inches at base of plant
Success Tip: Match the plant to the soil or amend the
soil to match the plant.
Soil Testing FAQ
What is a Soil Test?
A soil test is a series of chemical procedures that determine
the presence and availability of the major plant nutrients
in the soil.
Why test soil?
All plants need some 15 different nutrients to live. Most
of these are found in the soil or come from the air. In the
artificial environment of the urban landscape, soils will
rarely provide optimum amounts of these nutrients so we add
fertilizers. A soil test tells the condition of the soil so
that a proper fertilization process can be developed. Adding
more of any nutrient than a landscape can use costs extra
money, may contribute to disease problems, and is environmentally
undesirable. A soil test is the only way to ensure that you
are adding only needed nutrients in quantities that don’t
adversely affect environmental quality.
When should soil be tested?
The best time is during the winter. The next best time is
any time of year. A test should not be conducted within two
weeks of applying any fertilizer.
How do you do a soil test?
Simple step
by step instructions are available online Aggie Horticulture.
Your local TNLA member nursery professional can assist in
soil testing. Find a nursery in your area by using the TNLA
Products and Services Finder.
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