Its more than just dirt -Mr. Shefferly 3.4 The Soil System
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The Soil System Soil is a complex mixture of Eroded rock
Mineral nutrients Decaying organic matter Water Air Billions of
living organisms (DECOMPOSERS!!)
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Soil Formation Over Time
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Soil Formation Very Slow Process 1. Weathering of rock
(mechanical) 2. Deposition of sediments by erosion (mechanical) 3.
Decomposition of organic matter (chemical)
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Soil System Food Web
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Soil horizons (layers) Soil Layers O - (Organic) Freshly fallen
leaves, twigs, animal waste, fungi A- Mixture of partially
decomposed organic matter B- (Subsoil) Nutrients leached from A
Plant Roots C- (Parent Material) largely inorganic material
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Important Cycles (Nitrogen Cycle)
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Nitrogen Cycle Terms Nitrogen Fixation: Atmospheric N2 is made
available to plants Nitrification: Bacteria in soil convert
ammonium to nitrates Denitrification: Bacteria in soil nitrates to
nitrogen gas Assimilation: Living organisms take in the nitrogen to
make proteins
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Carbon Cycle
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Soil Content Clay (very fine particles >0.002mm) Silt (fine
particles 0.05mm-0.002) Sand (medium-sized particles 2mm-0.05mm)
Gravel (large coarse particles < 2mm) Soil Texture is determined
by the relative amounts of the different types and sizes of mineral
particles Smallest Largest
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Soil Texture Triangle
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Soil Permeability Rate at which air and water flow from upper
layers of soil to lower layers of soil
Soil Erosion Movement of soil, especially surface litter and
topsoil Two main agents of erosion Wind Flowing water Occurs due to
loss of plant in soil from: Overgrazing Deforestation
Irrigation
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Global Soil Erosion Stable or nonvegetative Some concern
Serious concern
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Top Soil Erosion and Run Off from Farm
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Gully Erosion In Bolivia
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Wind removes topsoil
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Erosion Continued Erosion is harmful 1. Leads to loss of soil
fertility and ability to hold water 2. Increases runoff of sediment
that pollutes water and kills fish.
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Desertification Enlargement of deserts through human activities
Causes: Overgrazing, deforestation, irrigation, and erosion
Consequences: Worsening drought, famine, economic losses
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Other Soil Issues SalinizationWaterlogging Irrigation water
contains small amounts of dissolved salts Evaporation and
transpiration leave salts behind Salt builds up in soil
Precipitation and irrigation water move downward Water table
rises
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Soil Issues SalinizationWaterlogging
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Toxification An increase in soil acidity ( low pH = more
acidic) Caused by leaching of metals Burning of plant material
increases soil pH Can be counteracted by using lime stone to raise
the pH and reduce acidity Large problem in the Ohio valley in the
USA due to coal power plants
Slide 24
Acidity of precipitation measured by the National Atmospheric
Deposition Program in 2006. Notice that precipitation is most
acidic downwind of the large concentration of power plants in the
Ohio Valley. Effect on Soils Neutralization: The effect of acid
rain on the environment depends greatly on the ability of soils to
neutralize the acid. Limestone and other rocks and soils containing
calcium carbonate are most effective. Acids react with calcium
carbonate to produce neutral compounds and carbon dioxide. For
example, sulfuric acid and hydrochloric acid react with calcium
carbonate: CaCO 3 + H 2 SO 4 > CaSO 4 + H 2 CO 3 H 2 CO 3 >
CO 2 gas + H 2 O 2HCl + CaCO 3 -> CO 2 + CaCl 2 + H 2 O The
extent to which soils can neutralize acid rain depends on several
factors: type of soil, thickness, weather, and water flow patterns.
If the ground is frozen, as in the winter, soil process cannot
work, the acid is not neutralized. If the soil is mainly quartz,
such as sand, it is resistant to weathering and no bases are
present to neutralize acid. If the soil has very little base such
as limestone, the acid is neutralized only slightly or with the
passage of time, not at all. In the slightly acidic soils in
typical evergreen forests in the Northeastern U.S., Canada, and
Europe, two other effects can neutralize the acid rain. The acid
can be immobilized as the soil or vegetation retains the sulfate
and nitrate ions (from sulfuric and nitric acids). Very deep soils
have a large capacity to retain sulfate and nitrate ions. From
Virtual ChemBook, Elmhurst College: Acid Rain Soil
Interactions.Acid Rain Soil Interactions Mature forest soils are
also able to neutralize the acids in rain. Such soils are acidic
and rich in humic acids. Krug (1983) reports that mature soils in
New England or Norwegian forests have a pH of 3.8, and they may
contain as much acid as would fall in 1000 years of rain at 1m/year
with a pH of 4.3. These soils are highly resistant to acid rain. In
contrast, thin alpine soils lacking carbonates and humic acid and
overlying granite rocks are not able to neutralize acid rain. The
same is true for disturbed forests where forest fires and logging
have reduced the organic material in the soil, which also make the
soil more susceptible to damage by acid rain. Leaching of Nutrients
Acids leach nutrients from the soil. They are carried deeper into
the ground or into streams, depriving plants of essential elements
calcium, potassium, magnesium and trace metals. Normally, metals
are attached to clay particles produced by weathering of rocks. The
H + anion of the acid replaces the metal ions in the clay in a
process called ion exchange. The metals occur in groundwater as
sulphates and nitrates. Two H + anions displace one Ca 2+ or Mg 2+
anion or two K + anions. Release of Aluminum Aluminum in soils and
rock is very insoulable if the pH is greater than 5. More acidic
solutiona dissolve aluminum from the soil, and the aluminum is
carried into streams and lakes by runoff and groundwater. Effect on
Vegetation Bavaria, Germany, high-altitude forest damaged by acid
rain. Photo by Spitzbergler. From AccuWeather. More photos of
Bavarian forest by Spitzbergler.AccuWeatherSpitzbergler In some
regions, especially regions where granite is close to the surface
and where soils have been degraded by logging and forest fires, the
soil has little ability to neutralize the acid. In these regions,
acid deposition depletes the available plant- nutrient cations Ca
2+, Mg 2+, and K +, it increases the leaching of aluminum, and it
increases the amount of sulfur and nitrogen in the soil. All lead
to weakening of trees, leading to their death by bark beetle
infestations and disease. Some of the most dramatic effects on
forests have been observed in Europe. In 1983, a survey in West
Germany showed that 34% of the country's total forest is damaged by
air pollution. This included about one half of the famous Black
Forest. Switzerland has recorded damage to 14 % of her forest
trees... Vogelmann, measured the reproductive capacity of the
forest by counting the total trees in an area. Red spruce dropped
from 6,000 trees to 1,000 trees, a decline of 80 % from 1965 to
1983. Very few pine cones and young trees were found. Sugar maple
tree counts dropped 84 % and beech tree counts dropped 63% over the
same time period... Acid rain or acid cloud droplets that fall on
the leaves and needles of trees leaches the nutrients from them.
Calcium, magnesium, and potassium ions may be removed from the
leaves faster than the roots can resupply them. Acid rain in
combination with ozone may damage the waxy coating on leaves and
needles. This may weaken, damage them, and provide opportunities
for diseases to enter the tree. From Virtual ChemBook Elmhurst
College Charles E. Ophardt Acid Rain Effects on Forests.Acid Rain
Effects on Forests Effect on Aquatic Animals When nutrients and
metals, including heavy metals and aluminum, are leached from the
soil, they are carried by runoff and groundwater into streams and
lakes where they kill aquatic life. Aluminum dissolved by acid rain
is highly toxic to many aquatic animals, especially young animals
including eggs and larvae. Not all species of animals are equally
sensitive to acids and aluminum. Some fish species (such as (brown
bullhead, yellow perch, golden shiner, brook trout, and white
sucker) are tolerant of water with pH < 6, while others (such as
Atlantic salmon, tiger trout, redbreast sunfish, bluegill, tiger
musky, walleye, and alewife) cannot tolerate such waters. Most fish
are killed if pH falls below 5.2 (Driskoll, 2001). In areas where
soils have little capacity to buffer acids in water, acidic
precipitation can be a problem because the infiltrating acidic
water can increase the solubility of metals, which results in the
flushing of high concentrations of dissolved metals into surface
water. Increased concentrations of naturally occurring metals such
as aluminum may be toxic to aquatic organisms. Studies of
watersheds have indicated that the length of subsurface flow paths
has an effect on the degree to which acidic water is buffered by
flow through the subsurface. For example, studies of watersheds in
England have indicated that acidity was higher in streams during
storms when more of the sub-surface flow moved through the soil
rather than through the deeper flow paths. Moreover, in a study of
the effects of acid precipitation on lakes in the Adirondack
Mountains of New York, the length of time that water was in contact
with deep subsurface materials was the most important factor
affecting acidity because contact time determined the amount of
buffering that could take place. US Geological Survey. Circular
1139, Ground Water and Surface Water A Single Resource. Effects of
Atmospheric Deposition on the Quality of Ground Water and Surface
Water.Effects of Atmospheric Deposition on the Quality of Ground
Water and Surface Water Further Reading 1.A good review article
article on acid rain in North America by Driscoll (2001) in
BioScience. This is a 700kByte PDF file.review article article on
acid rain in North America 2.For information on acid rain
deposition check the acid rain web pages at the EPA. More
information is at the National Atmospheric Deposition Program web
pages.acid rain web pagesNational Atmospheric Deposition Program
3.To understand how emissions trading works and how it has led to a
reduction of acid rain in the US, read Clearing The Air: The Truth
About Capping and Trading Emissions (a 0.6 MByte PDF file).Clearing
The Air: The Truth About Capping and Trading Emissions 4.The USGS
has a site on acid rain with examples from Washington DC,
especially the effects of acid precipitation on buildings. There is
an active monitoring program in the US called the National Acid
Precipitation Assessment Program (NAPAP) and they have a brief
summary on their web site. Environment Canada has also a very
informative web page on acid rain (as well as other environmental
issues including ozone hole over the Arctic Ocean).acid rain active
monitoring programacid rain 5.The EPA publishes Emission Reports
listing the amounts of pollutants emitted by individual power
plants.Emission Reports 6.A European perspective with many good
links can be found at the Swedish NGO Secretariat on Acid
Rain.European perspective References DRISCOLL, C. T., G. B.
LAWRENCE, et al. (2001). Acidic Deposition in the Northeastern
United States: Sources and Inputs, Ecosystem Effects, and
Management Strategies. BioScience 51(3): 180--198. Krug, E. C. and
C. R. Frink (1983). Acid Rain on Acid Soil: A New Perspective.
Science 221 (4610): 520-525. Acid rain is widely believed to be
responsible for acidifying soil and water in areas of North America
and northern Europe. However, factors commonly considered to make
landscapes susceptible to acidification by acid rain are the same
factors long known to strongly acidify soils through the natural
processes of soil formation. Recovery from extreme and widespread
careless land use has also occurred in regions undergoing
acidification. There is evidence that acidification by acid rain is
superimposed on long-term acidification induced by changes in land
use and consequent vegetative succession. Thus, the interactions of
acid rain, acid soil, and vegetation need to be carefully examined
on a watershed basis in assessing benefits expected from proposed
reductions in emissions of oxides of sulfur and nitrogen. Revised
on: 5 January, 2009
Slide 25
Soil Conservation Reduce Erosion by Wind Reduction: Plant trees
or bushes as windbreaks near edges of open fields Improving
irrigation: Prevent evaporation of water Soil Conditioners : Add
lime to raise the pH and prevent the soil from become too acidic
Soil Fertility: Rotate crops to prevent the depletion of nitrogen
in the soil and add natural manure as fertilizer
Terracing Reduces soil erosion by controlling water runoff by
holding water at each level
Slide 28
Contour Planting/ Strip Cropping Each row acts as a small dam
to help slow water runoff and reduce soil erosion
Slide 29
Alley Cropping Crops are planted in alleys between trees/shrubs
Provides shade and helps to slow down the release of soil
moisture
Slide 30
Windbreak in field Barrier of trees planted around the edge of
the crop Prevents wind erosion, provides habitat for birds, and a
supply of fuel wood
Slide 31
A soil Lab Must!! Simpsons Diversity Index Review Use the
Simpsons diversity index below D = ____________N
(N-1)___________________ n1(n11) + n2(n2 1) + n3(n3 1) +nk(nk 1) D
= Diversity N = Total number of organisms of all species n = number
of individuals of a particular species The higher the D value the
more diverse the sample is!!!!!
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Now You Try Abundance of Organism Ecosystem AEcosystem B
species 135 species 274 species 32612 species 497 species 575
Diversity3.27
Slide 33
Vermicomposting Vermicomposting is the process of having
redworms and other decomposer organisms process our organic waste
and turn it into a great natural fertilizer (called worm castings).
Worm cast = worm poop Creates Healthy Topsoil from waste that would
end up in a landfill.