Soil Tilth: A Brand New Word To Me, That Means Everything.
The term soil tilth refers to the soil's general suitability to support plant growth or more specifically to support root growth.
Tilth is technically defined as "the physical condition of the soil as related to its ease of tillage, fitness as a seedbed, and impedance to
seedling emergence and root penetration."
A soil with good tilth has large pore spaces for adequate air infiltration and water movement. It also holds a reasonable supply of water and nutrients.
Soil tilth is a factor of soil texture, soil structure, and the interplay with organic content, and the living organisms that help make-up the soil ecosystem.
The "textbook" soil is composed of 45 percent mineral, 25 percent air, 25 percent water, and 5 percent organic matter.
Special attention to soil management is the primary key to gardening success.
80 percent of all plant problems begin with soil conditions.
Gardening can be a challenge. Sandy soils hold little water and nutrients, while some soils are rocky and shallow. Many soils are clayey and compact readily.
Compacted soils may have poor drainage, which restricts the movement of both water and oxygen, in the soil for roots. Plants only grow in soils with adequate
soil oxygen levels, so with poor drainage, root systems are typically shallow, reducing the plants tolerance to drought.
When ever gardening in any of the challenging-poor soils (sandy, clayey, rocky and shallow) the best practices answer is always the same, for managing soil
tilth improvement:
Routine applications of organic matter, as a soil amendment, fosters the activity of soil microorganisms and earthworms. As soil microorganisms decompose the organic matter, the
tiny soil particles bind together into larger clumps, increasing large pore space in clayey soils, and increasing aggregate size in sandy soils.
As soil microorganisms, insects and worms feed on organic matter (e.g. compost, manure) nutrients become available for plant use. Their activity also
significantly improves soil structure, reduces compaction and increases water and air movement.
Soil organisms do much of the work for gardeners of improving soil tilth and making nutrients available to plants. Encouraging their efforts is
central to building a healthy fertile soil supportive to optimum plant growth. They require an environment that is damp
but not soggy, is between 50 to 90 degrees F, and has organic matter as a food source for bacteria and fungi from soil amendments (compost, crop residues) or mulch.
This improvement takes place over a period of years. A single large application of organic matter does not do the trick. A gardener may start seeing
improvement in soil conditions in a couple of years. As the organic content increases, earthworms and soil microorganisms become more active, this over
time improves soil tilth.
On clayey soils, also take extra care to minimize soil compaction. Soil compaction is the primary factor limiting plant growth in urban soils. Soils generally
become compacted during home construction. Use organic mulches to help reduce soil compaction forces, that lower soil
oxygen levels needed by beneficial soil organism and roots.
Avoid unnecessary roto-tilling or cultivation, as it will destroy the delicate mycorrhizal web and the natural soil structure. Use mulches for weed control.
NOTE: Mulch refers to material placed on the soil surface. A mulch controls weeds, conserves water, moderates soil temperature and has a direct
impact on soil microorganism activity. A soil amendment refers to materials mixed into the soil.
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Soil Texture: Is your Soil Sandy? Clay? Loam? How Can you tell?
Soil Texture Procedure:
This test requires few tools, and is relatively fast. It will help you know if you have an extremely sandy soil, clayey soil, or something in between.
I have just moved, and after the winter ground thaws, I will be doing this test on my own soil. You need a container with fairly precise measurements.
I am going to use my 2 cup Pyrex kitchen measuring cup for measuring. But you also need a container, where you can shake your soil sample, mixed with water. I
am going to use a quart canning jar to do my shaking, and immediately pour the solution into the Pyrex measuring cup.
Obtain your soil sample by digging down 6 inches. Combine 3 such soil samples, as your soil may be different in different spots.
Fill a quart canning jar with 1/2 cup of your soil sample.
Dilute the sample by adding 1 & 1/2 cups of water.
Add either 1/2 teaspoon of salt, or 1/2 teaspoon of dishwashing detergent.
Cap the canning jar and shake for 2 minutes.
Immediately after 2 minutes of shaking, pour the contents of the quart canning jar into your 2 cup Pyrex measuring cup.
Allow the 2 cup Pyrex measuring cup to stand for exactly 30 seconds. Measure the height
in ounces (or ml) of the soil particles that have settled at this time. This is the sand portion. Record this value.
Allow the 2 cup Pyrex measuring cup to stand undisturbed for 30 minutes. Measure the height
in ounces (or ml) of the soil particles that have settled at this time and record that value.
Subtract the first (30 second) reading. This difference is the portion of soil that is silt.
Now let the 2 cup Pyrex measuring cup of soil stand for at least 24 hours. At the 24-hour
point, take another reading. Subtract the height at the 30 minute reading.
This difference is the clay portion of the soil. If the water is still very
cloudy, take another reading after it has completely cleared. Compare it to
the 24-hour reading. If the level has risen, subtract the 30-minute reading
from this value, and use this for the clay reading.
Now, put the three height readings in the form of percentages. For
example;
| Height in ounces after: |
Corresponds to fraction of: |
Example - total height in ounces: |
Difference in height, or portion: |
Portions expressed as percentage: |
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| 30 seconds |
sand |
4 oz |
4 oz |
4/8 = 36 % |
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| 30 minutes |
silt |
5 oz |
1 oz |
1/8 = 12.5 % |
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| 24+ hours |
clay |
8 oz |
3 oz |
3/8 = 37.5 % |
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total = 8 oz |
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Using the soil texture triangle below, find the spot on the diagram that corresponds to the fractions of sand, silt and clay in your soil test.
Write down the name of your soil texture. In the example, the soil texture as determined by the triangle for a soil with 50% sand, 12.5% silt and 37.5% clay is a
Sandy Clay Soil. You can now use this soil texture classification when estimating water, and fertility requirements of your soil, as well as choosing
the best ammendment for your soil.
A sandy soil is one with large particles that drains quickly but holds nutrients poorly.
A clay soil is composed of extremely small particles, with a large capacity for holding water and dissolved plant nutrients. Un amended clay soil is
sticky, heavy, and hard to breathe. It tends to expand when wet and crack apart when dry.
A silt soil is one with medium-size mineral particles, larger than clay and smaller than sand. Silt adds little to the characteristics of a soil.
The term loam refers to a soil with a combination of sand, silt, and clay sized particles.
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Soil texture triangle, showing the 12 major textural classes, and particle size scales.
In the public domain: "U. S. Department of Agriculture."
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The following is a derivative version (by virtue of changing and/or adding content) of the article:
Soil: From Wikipedia, the free encyclopedia
The links contained within the context of the derivative text, have been maintained for our education, pointing back into
Wikipedia, the free encyclopedia
This article is licensed under the GNU Free Documentation License.
It uses material from the Wikipedia article "Soil: From Wikipedia, the free encyclopedia"
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Soil texture refers to sand, silt and clay composition in combination with
gravel and larger-material content. Sand and silt are the product of physical weathering while clay is the product of chemical weathering. Clay
content is particularly influential on soil behavior due to a high retention capacity for nutrients and water. Due to superior aggregation, clay soils resist wind
and water erosion better than silty and sandy soils. In medium-textured soils, clay can tend to move downward through the soil profile to accumulate as
illuvium in the subsoil. The lighter-textured, surface soils are more responsive to management
inputs, but also more vulnerable to erosion and contamination.
Texture influences many physical aspects of soil behavior.
Available water capacity increases with silt and, more importantly, clay content. Nutrient-retention capacity tends to follow the same relationship. Plant growth,
and many uses which rely on soil, tends to favor medium-textured soils, such as loam and sandy loam. A balance in air and water-handling characteristics within
medium-textured soils are largely responsible for this.
Picture caption: A homeowner tests soil to apply only the nutrients needed. Farmers practice the same testing procedure.
End of derivative version of the Wikipedia article "Soil: From Wikipedia, the free encyclopedia"
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The following is a derivative version (by virtue of changing and/or adding content) of the article:
Porosity: From Wikipedia, the free encyclopedia
The links contained within the context of the derivative text, have been maintained for our education, pointing back into
Wikipedia, the free encyclopedia
This article is licensed under the GNU Free Documentation License.
It uses material from the Wikipedia article "Porosity: From Wikipedia, the free encyclopedia"
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Porosity of soil
Porosity of surface soil typically decreases as particle size increases. This is due to soil aggregate formation in finer textured surface soils when
subject to soil biological processes. Aggregation involves particulate adhesion and higher
resistance to
compaction. Typical bulk density of sandy soil is between 1.5 and 1.7 g/cm3. This calculates to a porosity between 0.43 and 0.36. Typical bulk
density of clay soil is between 1.1 and 1.3 g/cm3. This calculates to a porosity between 0.58 and 0.51. This seems counterintuitive because
clay soils are termed heavy, implying lower porosity. Heavy apparently refers to a gravitational moisture content effect in combination
with terminology that harkens back to the relative force required to pull a tillage implement
through the clayey soil at field moisture content as compared to sand.
Simplified
Think of soil pore space this way; water coats the solid particles and fills the smaller pore spaces. Air fills the larger pore spaces.
To help understand pore space, visualize a bottle of marbles and a bottle of table sugar. The pore space between marbles is large compared to
the pore space between the sugar grains. The relative percent of clay size particles versus the percent of medium to coarse sand size particles
influence the pore space of a soil.
Porosity of subsurface soil is lower than in surface soil due to compaction by gravity. Porosity of 0.20 is considered normal for unsorted gravel size
material at depths below the biomantle. Porosity in finer material below the
aggregating influence
of pedogenesis can be expected to approximate this value.
Simplified for the Gardener
Organic matter also plays a key role in creating large pore space. The quantities of large and small pore spaces directly
impact plant growth. On clayey soils, a lack of large pore spaces
restricts water and air movement thus limiting root growth and the activity of beneficial soil organisms. On sandy soils, the
lack of small pore space limits the soil's ability to hold water and nutrients.
Water movement is directly related to pore space. In the small pore space
of clayey soils, water slowly moves in all directions by capillary action. The
lack of large pore space leads to drainage problems and low soil oxygen levels.
On sandy soils, with the large pore space, water readily drains downwards by
gravitational pull. Excessive irrigation or precipitation can leach water-soluble
nutrients, like nitrogen, out of the root zone and into ground water.
End of derivative version of the Wikipedia article "Porosity: From Wikipedia, the free encyclopedia"
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The following is a derivative version (by virtue of changing and/or adding content) of the article:
"Soil: From Wikipedia, the free encyclopedia"
This article is licensed under the GNU Free Documentation License.
It uses material from the Wikipedia article "Soil: From Wikipedia, the free encyclopedia"
Some of the links contained within the context of the derivative text, have been maintained for our education, pointing back into
Wikipedia, the free encyclopedia Otherwise, they link to text below.
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Soil Structure is the arrangement of soil particles into aggregates. These may
have various shapes, sizes and degrees of development or expression. Soil structure influences aeration, water movement, erosion resistance, and
root penetration. Observing structure gives clues to texture, chemical and mineralogical conditions,
organic content, biological activity, and past use, or abuse.
Surface soil structure is the primary component of tilth. Where soil mineral particles are both separated and bridged by organic-matter-breakdown products
and soil-biota exudates, it makes the soil easy to work. Cultivation, earthworms., frost action and
rodents mix the soil. This activity decreases the size of the peds to form a granular (or crumb) structure. This structure allows for good porosity
and easy movement of air and water. The combination of ease in tillage, good moisture and
air-handling capabilities, good structure for planting and germination are definitive of good tilth.
End of derivative version of the Wikipedia article "Soil: From Wikipedia, the free encyclopedia"
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Soil Structure
Soil structure refers to units composed of primary particles. The cohesion
within these units is greater than the adhesion among units. As a consequence,
under stress, the soil mass tends to rupture along predetermined planes or
zones. These planes or zones, in turn, form the boundary. The term
"structural unit" is used for any repetitive soil body that is commonly bounded
by planes or zones of weakness that are not an apparent consequence of
compositional differences. A structural unit that is the consequence of soil
development is called a ped. The surfaces of peds persist through cycles of
wetting and drying in place. Commonly, the surface of the ped and its interior
differ as to composition or organization, or both, because of soil development.
Earthy clods and fragments stand in contrast to peds, for which soil forming
processes exert weak or no control on the boundaries. Some clods, adjacent to
the surface of the body, exhibit some rearrangement of primary particles to a
denser configuration through mechanical means. A
size sufficient to affect tilth adversely must be considered.
Some soils lack structure and are referred to as structureless. In
structureless layers or horizons, no units are observable in place or after the
soil has been gently disturbed, such as by tapping a spade containing a slice of
soil against a hard surface or dropping a large fragment on the ground. When
structureless soils are ruptured, soil fragments, single grains, or both result.
Structureless soil material may be either single grain or massive. Soil material
of single grains lacks structure. In addition, it is loose. On rupture, more
than 50 percent of the mass consists of discrete mineral particles.
Some soils have simple structure, each unit being an entity without component
smaller units. Others have compound structure, in which large units are composed
of smaller units separated by persistent planes of weakness.
In soils that have structure, the shape, size, and grade (distinctness) of
the units are described. Field terminology for soil structure consists of
separate sets of terms designating each of the three properties, which by
combination form the names for structure.
Shape.—Several basic shapes of structural units are recognized in soils.
Supplemental statements about the variations in shape of individual peds are
needed in detailed descriptions of some soils. The following terms describe the
basic shapes and related arrangements:
platy: The units are flat and platelike. They are generally oriented
horizontally. A special form, lenticular platy structure, is recognized for plates that are thickest in the
middle and thin toward the edges.
prismatic: The individual units are bounded by flat to rounded vertical
faces. Units are distinctly longer vertically, and the faces are typically casts
or molds of adjoining units. Vertices are angular or subrounded; the tops of the
prisms are somewhat indistinct and normally flat.
columnar: The units are similar to prisms and are bounded by flat or slightly
rounded vertical faces. The tops of columns, in contrast to those of prisms, are
very distinct and normally rounded.
blocky: The units are blocklike or polyhedral. They are bounded by flat or
slightly rounded surfaces that are casts of the faces of surrounding peds.
Typically, blocky structural units are nearly equidimensional but grade to
prisms and to plates. The structure is described as angular blocky if the faces
intersect at relatively sharp angles; as subangular blocky if the faces are a
mixture of rounded and plane faces and the corners are mostly rounded.
granular: The units are approximately spherical or polyhedral and are bounded
by curved or very irregular faces that are not casts of adjoining peds.
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This article incorporates text from http://soils.usda.gov/technical/manual/contents/chapter3g.html#60,
a public domain work of the United States Government, United States Department of Agriculture (USDA).
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