Soil Use and Abuse

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Soil Use and Abuse

• Chapter 11
• APES January 2007

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Objectives

• Define the roles of living organisms, physical
  forces, and other factors on creating and
  maintaining fertile soil.
• Differentiate between the sources and effects of
  land degradation including erosion, nutrient
  depletion, waterlogging, and salinization.

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SO what does that really mean?

• How is soil made?
• How is it destroyed?
• What role are we playing as humans?

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What is soil?

• Soil is made of three things
• Water
• Eroded rock material
• Dead stuff
• Live stuff

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The water component

• The moisture content of the soil will depend upon
  several factors
• How well drained the soil is
• The rock composition/particle size
• How much it rains

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The rock component

• Bigger rock particles such as gravel and sand
  (see chart page 237) provide good drainage and
  aeration. Its easier for roots to push through
  this type of soil.
• Smaller rock particles such as clay and silt tend
  to pack and offer less air spaces, but are better
  at holding the minerals.

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Humus (dead stuff) in the soil

• The dead animal and plant parts in soil act like
  a sticky glue holding the tiny rock particles
  together, making the spongy conditions needed for
  roots to grow.
• It also holds the water and minerals needed by
  plants.

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Soil Organisms in the soil

• Soil aeration by worms and bugs
• Decomposing humus by fungi and bacteria
• Algae makes new organic compounds
• Burrowing mammals help aerate as well
• Plant roots penetrate the soil and secrete acids,
  breaking down rock further

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The Soil Profile/Soil Horizons

• Field trip flashback
• Remember all
• The differences?
• The E layer is also
• Called the
• Zone of Leaching

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Types of Soils

• Your text discusses the types of soils, please
  study them pg. 238-239.
• 12 soil orders, I will discuss three common to
  WI. You should be aware of and be able to
  discuss the rest.

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Mollisols under grasslands
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Spodosols under pine forests
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Alfisols deciduous forests
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How do we use our soil?

• 11 of our land areas is under agriculture.
• 4 times that could be crops but it would affect
  the wildlife populations.
• Many areas cannot support agriculture due to soil
  chemistry, topography, and rainfall.

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How are we using our land?

• Land use comparison
• Wisconsin land use
• Satellite land use
• Study chart
• Page 240
• Of your text.

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Land use correlations

• Developed countries through technology are
  tilling less land.
• Developing countries are destroying forests to
  create agricultural areas that are not
  sustainable.
• 2/3 crop gains have come from better genetics and
  methods.

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Ecological Trade offs

• Be sure to read about the challenges facing
  developing countries.
• How do you decide between saving the rainforest
  and feeding your people?
• Just because you CAN cultivate land SHOULD you?

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The Sad Truth about some areas

• When you clear the trees from the land
• And there isnt very deep soil
• And theres lots of rain
• You have about 5 years
• Until the soil is ALL gone
• Washed away
• It will take 100s of years to rebuild.

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If we acted as a team.

• Theres plenty of land that COULD be farmed
  safely and we could feed the world.
• I have often thought.what if we tried to feed
  the world as hard as we are trying to liberate
  Iraq? What would happen?

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Degradation of the Land

• What does that really mean?
• It means the land
• gets ruined.
• Hmmm..how?
• Fertilizers , overgrazing, and erosion.
• Why does that happen?

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Every year our land takes a hit

• 3 million hectares are ruined by erosion
• 4 million hectares are turned into desert
• 8 million hectares are turned into something
  other than crop land such as malls, homes,
  highways and parking lots

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World Statistics on Land Degradation

• 3oo million hectares strongly degraded
• 910 million hectares moderatelydegraded
• 9 million hectares not usable anymore
• Causes
• Water, wind, salts

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Signs of Degradation

• Soil is impoverished or eroded

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Signs of Degradation

• Water runs off the land or is contaminated

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Signs of Degradation

• Vegetation is diminished

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Signs of Degradation

• Biomass production is decreased

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Signs of Degradation

• Wildlife diversity diminishes

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Impacts

• Ranches fewer livestock
• Farms poor crop yields
• Nature less species
• Page 241 of the text shows the percentages of
  degradation by country and region.

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Major Issues to Tackle

• Water 55
• Wind 29 these happen naturally
• but can be exacerbated
• Chemical 12
• Nutrient depletion, Salinization, acidification,
  pollution
• Physical 4
• Heavy machinery, cattle, waterlogging,
  solidification

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What exactly is erosion?

• Its the transport of soil from one place to
  another.
• How does it happen?
• Wind and Water carrier soil parts from high
  places to low places.
• It has shaped the surface of our planet.
• Is it really bad?

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Wind Erosion
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Wind Erosion
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Wind
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Wind
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Water Erosion
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Water Erosion across the World
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Types of Erosion

• Rill Erosion
• Tiny rivers of running water make small channels
  in the soil
• Gully Erosion
• Rills enlarge to form big channels in the soil

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Where is it happening?

• Agricultural Fields/runoff
• The fields loose soil twice as fast as it is
  being replaced.
• Dust Storms
• Wind carries the soil away and dumps it
  elsewhere. This can be worse than water in some
  ways.

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US and Canada are big culprits

• Intensive cropping/row crops
• Deep plowing
• Heavy herbicide applications
• Machines create gullies
• Abandonment of crop rotations/ issues
• Monoculture cropping
• check out these stats in your text pg. 242

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What are we to do?

• You tell me gang.
• What can we do as individuals to help stop the
  washing away of our future?