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Soil & Water Conservation Merit
Badge
1a. Tell what soil is. Tell how it is formed.
There are three different definitions of soil. To a soil scientist,
soil is solid earth material that has been altered by physical, chemical, and
organic processes, such that it can support rooted plant life. To a geologist,
soil is any unconsolidated earth material that forms from rocks; with or
without organic material. Finally, to engineer, soil is any solid earth
material that can be removed without blasting. All soil is formed from weathering
which is the physical and chemical breakdown of rocks. Different rock types can
determine what soil type will be present in a given area. Soil also is then
worked by biological components, which include soil organisms, bacteria, fungi,
and plants. Soil also can be transported and worked by liquid water or frozen
water. Soil is transported by rivers and streams and can also be scoured and
transported by glaciers.
1b. Describe three kinds of soil. Tell how they are different.
There are many different ways of classifying soils. Engineers,
farmers, geologists all have their own unique way of looking at soils based on
their specific needs. Engineers usually look at the soil ability to hold water,
creep or move, and its ability to hold different types of structures.
Farmers, or people in agribusiness look how fertile a soil is and its ability
to support years of grazing or crop farming. Finally, geologists look at soil permeability
for ground water resources. They also examine soil texture for building dams
and for determining the erosion rates for certain streams.
Soil Taxonomy is a classification system for soils that emphasizes the
chemical and physical properties of soils. This system is used for agriculture
purposes. Another classification system used is the unified soil
classification system that is used by engineers (and sometimes geologists)
by classifying soil grain sizes and whether or not they would be fit to build a
particular type of structure. Soil texture is used to give a very general class
to soils and is actually used by both soil classification systems.
The three textures are clay, silt, and sand. Clay is the
finest in terms of the size of the soil particle, sand is the largest, and silt
is in the middle. Sand is familiar to most people since it occurs in abundance
at the seashore. In fact, beach sand is 100% sand on the soil texture chart.
Silt is a term given to soil particles that are suspended in rivers during
floods. Another terms for silt is mud, which is actually a term applied
to a mixture of silt and clay together. Clay particles are too small to be seen
with your eye. Some of them are so small, even a good microscope cannot resolve
clay particles. An equal mixture of sand, silt, and clay is called loam.
Loam is an excellent soil for farming and is usually formed where there has
been glaciation. Many states in the Mid-West have excellent loamy soils.
1c. Name the three main plant nutrients in fertile soil. Tell how they can be put back when used up.
Nitrogen (N):
This plant nutrient
is probably the most important of all of the macronutrients, or
nutrients plants need a lot of. Nitrogen is put back into the soil by three
main ways. First, certain plants host bacteria or fungi in their roots that
have the ability to “fix” atmospheric Nitrogen (N2), or Nitrogen
found in the air, into “usable” Nitrogen called Nitrates (NOx).
These nitrates are absorbed into the plant through its roots and are used in
making essential amino acids, or “the building blocks of life.” When a
plant or animal dies, bacteria and fungi immediately begin to break down the
dead organism. One of the by-products of decay is Ammonia, which
contains Nitrogen. Further decay of Ammonia makes usable nitrates in the soil.
Also, manure releases Ammonia into the soil, which is, in turn broken down into
usable nitrates. Finally, a neat way Nitrogen is fixed into the soil is by lighting.
This process is what some scientists believe started the life on land. Without
nitrogen fixed in the soil, plants would not be able to grow.
Phosphorus (P):
Many people often
overlook phosphorus as an essential soil nutrient. But it is important in
plants as well as animals for the transfer of energy in our bodies. Phosphorous
is used in a molecule known as ATP. This molecule helps transfer energy
in cells so that we have the ability to move about and live. Phosphorus is
usually weathered out of rocks. Usually, rocks that were once of the seafloor
contain an abundance of phosphorus. Bones from dead vertebrates also contain an
abundance of phosphorus. Bones are used to store additional reserves of
phosphorus in many animals. When these creatures die, bacteria release the phosphorus
stored in the bones into the soil. Manure and some plant remains also contain
some phosphorus.
Potassium (K):
Also called, “potash”,
Potassium is usually found in abundance in soil. The main sources of potassium
in the soil are from a mineral called “Potassium-rich Feldspar.” This mineral is
found in granite and many other rock types and easily weathers when it is
exposed at earth’s surface. This is called hydrolysis:
2KAlSi3O8
(K-spar) + 2H+ (acid ions) + 9H2O → Al2Si5O5
(OH)4 (clay) + 4H4SiO4 (silicic acid) + 2K+
(Free Potassium)
This generalized chemical reaction can occur in any rock containing feldspar or another potassium-rich rock. Small amounts of potassium are returned to the soil by decay and manure. But this is the main way by which soil is replenished with potassium.
Magnesium (Mg) is a micronutrient or a nutrient a plant
needs in small amounts. This should not detract from this nutrients importance.
Magnesium is essential to plants since it is the building block of chlorophyll,
the component in plant cells that drive photosynthesis. Iron (Fe) in animals is
used in the same way to make hemoglobin, or the component in red
blood cells that carry oxygen throughout our bodies.
2a. Define soil erosion
Erosion is simply the removal and transportation of
weathered or unweathered materials by wind, running water, waves, glaciers,
underground water, and gravity.
2b. Tell why soil erosion is important. Tell how it affects you.
The removal of every square inch of soil on earth would kill just
about every land organism. It would take millions of years to develop usable
soil once again to grow plants and support numerous different plant
communities. But that scenario will probably never happen. But targeted soil
erosion in areas can change the type of plant community found there and therefore
alter the animal populations. This can affect the number of plants and animals
found in an area or radically change the types of organisms found there. To
humans, soil erosion is bad since it carries away readily available soil to use
for crops and transports it to another body of water (lake, pond, ocean). The
reduction is arable or usable soil is a key environmental issue that is
often overlooked. The dust bowl during the 1930’s in the Mid-West devastated this
country and added insult to injury during the Great Depression. This poor
management of the soil led Aldo Leopold to write A Sand County Almanac,
which contains many sections on soil conservation.
Without careful management of soil around the world, the world’s
food supply could be placed in jeopardy. This could even affect people living
in the more developed countries like the United States and Europe. Locally,
soil erosion removed land that could otherwise be used for recreation (beaches
and parks).
2c. Name three kinds of soil erosion. Describe each.
Often overlooked as a mode of erosion, it was the major culprit of the Dust Bowl in the 1930’s. Winds as light as 3 mph can kick up small clay and silt particles and carry them. NASA has neat satellite photographs of winds sweeping soil off the West coast of Africa from the Sarah Desert. Winds that blow off of glaciers help produce loamy soils called loess.
Running water:
This is the easiest type of soil erosion
to spot. When heavy rains fall, soil from your lawn is carried off by torrents of
running water. This also called sheet erosion. Sometimes fast moving
water carves of gully in your lawn, and it is called exactly that, gully
erosion (or rill erosion). By far, running water in rivers does the most
damage in terms of soil erosion. During great floods, tons and tons of soil can
be removed from the river floodplain and surrounding areas.
Waves:
This type of
erosion is always seen at the seashore, especially during Nor’easters. Waves
are a constant force along beaches, but they also help to replenish beaches
also. This process however is slow and does not meet human needs for
recreation. Waves also cause erosion along riverbanks and lakeshores. This is
often overlooked and can become a problem if human caused waves are not
controlled.
Glaciers:
Glaciers can
transport soil over great distances, but the process if often slow and takes
thousands of years. Ice scours the rocks and soils it moves over. As the
glaciers retreat, the materials are dropped out of the ice and a soil starts to
form in its place. Glaciers transported the soils of Northern Pennsylvania
during the most recent glaciation.
Underground water:
This is an unseen
mostly chemical erosion type. Rain or melt waters penetrate deep down to the
bedrock and since it is naturally acidic, the bedrock can either go through
hydrolysis (see above) or if it hits a Carbonate rock, the rock will dissolve
forming sink holes. The ions from the weathering are carried away by
groundwater.
Gravity:
What goes up
must come down. When rocks fall, gravity moves down slope to rest. Soil can
also “fall” by either creep or another process called slump. Heavy rains
and cause landslides can always activate these processes. This is very common
in areas that are devoid of vegetation to hold the soil.
3a. Tell what is meant by “conservation practices.”
Conservations practices are methods employed by people to help
keep soil where it will do the most good. Most conservation practices are used
on farms to keep fertile soil on the farm to grow crops. Other conservation
practices are used in recreational areas to keep rivers or streams from
removing soil from the floodplain to allow for optimal recreational activities.
