what is soil?
It is a
composite of inorganic minerals, organic humus, living organisms, moisture, and air.
Soils are the product of interactions between abiotic and biotic processes and take
thousands of years to form.
The study of soils is called?
what are factors that form soil?

1. The type of parent(source) material
2. The climate under which the soil components have existed since accumulation
3. The plant and animal life in and on the soil
4. The relief of the land
5. The length of time the other factors have interacted

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the factors are inderdependent of each other

what is the process of the formation of soil?
Soil formation begins with the
degradation of the parent material. The parent material is unconsolidated, chemically
weathered mineral, rock, or organic matter. Precipitation, temperature, humidity, and
wind are the climatic forces that act on the parent material to form soil. The relief of the
land greatly influences how wind and water act upon parent material components as
well as the types of plants and animals that inhabit the area. Animals, insects, bacteria,
fungi, and other plants furnish organic matter. Differences in the amount of organic
matter, nutrients, structure, and porosity of soil are caused by plant and animal actions.
Time is an important factor in soil formation.
o horizon
The O horizon is dominated
by organic material. It contains fresh
and decaying plant matter from leaves,
needles, twigs, moss, lichens, and other
organic accumulations.
A Horizon
The A horizon is formed at
the surface or below the O horizon. It is
an accumulation of organic matter and
minerals. It is generally darker than the
lower horizons because of the decaying
organic matter. This horizon is where
most plant root activity occurs. It may
be referred to as the surface layer in a
soil survey.
E Horizon
The main feature of the E
horizon is the loss of silicate clay, iron,
or aluminum, or some combination of
these, leaving a concentration of sand
and silt-sized particles.
B Horizon
The B horizon lies directly
below an A, E, or O horizon. It is
referred to as the subsoil. It is usually lighter colored, denser, and lower in organic matter than upper horizons. As the
recipient of material from upper and lower soil layers, the B horizon is often called the
“zone of accumulation.” As rain and irrigation waters percolate downward, they wash
(leach) soil components through the A horizon and into the B horizon. The process by
which these materials are moved downward by water is called leaching. For this reason,
the A horizon is called the “zone of leaching.” Some minerals are drawn upward from
lower soil layers by high evaporation rates and plant absorption.
C Horizon
Still deeper is the C horizon or the substratum. This layer may consist of less
clay or other less-weathered sediments than the layers above. Partially disintegrated
parent material and mineral particles are in this horizon.
R Horizon.
The very lowest horizon, the R horizon, is bedrock. It can be within a few
inches of the surface or many feet below.
what is soil texture?

the percentages of sand, silt, and clay in a sample of soil. Soil texture refers only to
mineral particles smaller than 2 millimeters (mm). Each grouping of particle sizes is
called a soil separate. Hence, sand, silt, and clay are soil separates

Very coarse sand 2.00–1.00 mm
Coarse sand 1.00–0.50 mm
Medium sand 0.50–0.25 mm
Fine sand 0.25–0.10 mm
Very fine sand 0.10–0.05 mm
Coarse silt 0.05–0.005 mm
Fine silt 0.005–0.002 mm
Clay less than 0.002 mm

The process by which soil separates are obtained is called?
mechanical analysis. All
mineral soils are made up of a mixture of soil separates. Textural class names of soils
are based on the proportion of these separates. There are 12 major textural class names:
sand, loamy sand, sandy loam, sandy clay loam, sandy clay, clay, clay loam, loam, silt
loam, silty clay loam, silty clay, and silt.
remember how to use textural triangle
soil color

hue is written in letters like yr= yellow red

the value goes from 0 to 10, ten being white 0 being black

The notation for chroma
consists of numbers beginning with 0 for neutral grays and increasing at equal intervals
to a maximum of about 20.

Thus the notation for a
yellowish-red colored soil of hue 5YR, value 5, and chroma 6 is yellowish-red (5YR

Porosity refers to the amount and size of spaces between soil or rock particles.
Porosity determines the amount of water that a soil can hold.Sands and gravels have
high porosity. Clays are very porous

Permeability refers to the rate of water and air movement through soil or
bedrock, if present. It is an indication of downward movement of water when the soil is
saturated. This may be considered internal drainage.Permeability is measured in the number of inches per hour (in/hr) that water moves
downward through a saturated soil.

Very slow less than 0.06 in/hr
Slow 0.06–0.20 in/hr
Moderately slow 0.20–0.6 in/hr
Moderate 0.6–2.0 in/hr
Moderately rapid 2.0–6.0 in/hr
Rapid 6.0–20 in/hr
Very rapid more than 20 in/hr

what is soil compaction?

Soil pores are destroyed by
tillage, intense agricultural operations, or heavy vehicle and foot traffic. This
destruction is known as soil compaction.

The largest pores (macropores) are the most
vulnerable to compaction.

macropores and micropores

The macropores are essential to the movement of gases and

The small pores (micropores) are important in holding and retaining water in the soil.

The loss of these pores lowers the permeability of the soil, thereby restricting
percolation and increasing runoff, erosion, and flooding.

what does drainage patterns refer to?
Drainage classes refer to the periods of saturation or partial saturation during soil
formation, as opposed to altered drainage.
Excessively drained
Water is removed from the soil very rapidly. Excessively drained
soils are commonly very coarse-textured, rocky, or shallow. Some are steep. All are free
of mottling related to wetness.
Somewhat excessively drained
Water is removed from the soil rapidly. Many
somewhat excessively drained soils are sandy and rapidly pervious. Some are shallow.
Some are so steep that much of the water they receive is lost to runoff. All are free of the
mottling related to wetness.
Water is removed from the soil readily, but not rapidly. It is available to
plants throughout most of the growing season, and wetness does not inhibit growth of
roots for significant periods during the growing seasons. Well-drained soils are
commonly medium textured. They are mainly free of mottling.
Moderately well drained
Water is removed from the soil somewhat slowly during
some periods. Moderately well drained soils are wet for only a short time during the
growing season, but periodically they are wet long enough that most mesophytic crops
are affected. They commonly have a slowly pervious layer within or directly below the
solum or periodically receive high rainfall, or both
Somewhat poorly drained
Water is removed slowly enough that the soil is wet for
significant periods during the growing season. Wetness markedly restricts the growth
of mesophytic crops unless artificial drainage is provided. Somewhat poorly drained
soils commonly have a slowly pervious layer, a higher water table, additional water
from seepage, nearly continuous rainfall, or a combination of these.
Poorly drained
Water is removed so slowly that the soil is saturated periodically
during the growing season or remains wet for long periods. Free water is commonly at
or near the surface for long enough during the growing season that most mesophytic
crops cannot be grown unless the soil is artificially drained. The soil is not continuously
saturated directly below the plow depth. Poor drainage results from a high water table,
a slowly pervious layer within the profile, seepage, nearly continuous rainfall, or a
combination of these.
Very poorly drained
Water is removed so slowly that free water remains at or on the
surface during the growing season. Unless the soil is artificially drained, most crops
cannot be grown. Very poorly drained soils are commonly level or depressed, are
frequently ponded, or have impermeable layers close to the surface. Yet where rainfall
is high and nearly continuous, they can have moderate or high slope gradients.
what are some of the benefits of wetlands?
• They can store rain and slow runoff, which helps to control flooding and erosion.
• They are valuable for recreation and beauty.
• They filter and absorb pollutants and purify water.
• They provide habitat for a wide variety of plants and animals, including 90 percent
of the plants, 30 percent of the birds, 15 percent of the mammals, and 50 percent of
the fish on the United States endangered species list.
• They help stabilize shorelines and reduce coastal storm damage.
• They provide important spawning and nursery grounds for approximately twothirds
of the nation’s shellfish and important commercial and sport species of
marine fish.
• They provide important rest areas for the millions of migrating birds every year.
how many soil orders are there?
12. listed in next cards
Well-developed soils with a relatively fine-textured subsoil horizon that has a
base saturation of 35percent or more.
Soils of volcanic origin.
Dry soils that occur in arid or semi-arid regions
Soils with little or no horizon development
Soils of cold climates influenced by permafrost
Soils composed of relatively thick (usually 16 inches or more) organic
materials (muck and peats).
Soils of humid regions with profile development sufficient to exclude them
from the Entisols, but insufficient to include them in Spodosols, Ultisols, or other welldeveloped
soils. Soils that appear to be like Mollisols but have less than 50 percent or
more base saturation may also be Inceptisols
Soils with thick (usually 10 inches or more), dark surfaces that have a base
saturation of 50 percent or more in the surface soil
Highly weathered soils of the tropics.
Soils with a spodic horizon (a dark-colored subhorizon with a mixture of
organic matter and aluminum, with or without iron).
Well-developed soils with a relatively fine-textured subsoil horizon that has
less than 35 percent base saturation
Soils with more than 30 percent clay which appreciably expand upon wetting
and contract upon drying.
soil uses
Land uses include crop and pasture lands, rangeland, forestry, recreation, wildlife
habitat, and engineering uses, including building sites, sanitary facilities, water
management, and construction materials.
soil conservation

Of particular concern in soil conservation is erosion control. Erosion is defined as the
wearing away of the land surface by water, wind, ice, or other geologic agents and by
such processes as gravitational creep.

Erosion my be classed as geologic or accelerated. Geologic erosion is caused by geologic
processes acting over long geologic periods and resulting in the wearing away of
mountains and the building up of such landscape features as floodplains and coastal
systems. Geologic erosion is also known as natural erosion.
Accelerated erosion is much more rapid than geologic erosion. Accelerated erosion is
mainly the result of the activities of humans or other animals or of a natural catastrophe
such as a hurricane or a wildfire

soil erosion control methods
The first principle in wind erosion control is to cover the soil. Vegetative
cover slows the wind at ground level, protects soil particles from being detached, and
traps other blowing soil particles. One of the most permanent wind erosion control
methods is a wind barrier. There are also numerous agricultural practices such as crop
residue management — leaving crop remains in the field as mulch — crop rotation,
planting cover crops, strip cropping, and planting buffer strips that protect soil from
nonpoint source pollution
Nonpoint source pollution occurs
when rain or irrigation water runs over the land or through the ground, picks up
pollutants, and deposits them in lakes, rivers, and coastal waters or introduces them to
groundwater. Usually, these pollutants are solely thought of as fertilizers, pesticides,
other chemicals, oils, animal wastes, or heavy metals. Soil sediments also contribute to
nonpoint source pollution. They clog waterways, reduce aquatic species habitat and
spawning areas, and reduce water clarity, inhibiting aquatic plant growth. Erosion
control practices have multiple benefits
look at the bacteria and animal section in the soil
pages 31-45