Soil Conservation

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Soil Conservation

• S E C T I O N 2 - 3

2
Objectives

• Why is soil one of Earths most valuable
  resources?
• What caused the Dust Bowl?
• What are some ways that soil can be conserved?

3

• Soil is one of Earths most valuable resources
  because everything that lives on land depends
  directly or indirectly on soil.

4

• Plants depend directly on soil to live and grow.
• Animals depend on plants for food.

5

• Fertile soil is valuable because there is a
  limited supply.
• Less than one eighth of the land on Earth has
  soils that are well suited for farming.

6

• Soil is a renewable resource that can be found
  wherever weathering occurs.
• But it can take hundreds of years for just a few
  centimeters of soil to form.

7

• The prairie soils of the central United States
  took many thousands of years to develop.

8

• Prairies once covered a vast area, including
  Illinois and Iowa, as well as the eastern parts
  of Kansas, Nebraska, North Dakota, and South
  Dakota.

9

• The soil was rich with humus because it was
  covered with tall grass.
• The sodthe thick mass of tough roots at the
  surface of the soilkept the soil in place and
  held onto moisture.

10

• Today, farm crops have replaced the prairies.
• But the prairie soils are still among the richest
  in the world.

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• Soil can be damaged or lost.
• For example, soil can become exhausted, or lose
  its fertility.

12

• This occurred in large parts of the South in the
  late 1800s in areas where only cotton had been
  grown.

13

• In the early 1900s, a scientist named George
  Washington Carver developed new crops and farming
  methods that helped restore soil fertility in the
  South.

14

• Soil can be lost to erosion by water or wind.
• Water or wind erosion can occur wherever soil is
  not protected by plant cover.

15

• Plants break the force of rain, and plant roots
  hold soil in place.

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• Wind erosion was the cause of soil loss on the
  Great Plains in the 1930s.

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• The Great Plains cover an area from the prairies
  west to the base of the Rocky Mountains,
  including parts of North and South Dakota,
  Nebraska, Kansas, Oklahoma, and Texas.

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• By 1930, almost all of the Great Plains had been
  turned into farms or ranches.
• Plowing removed the grass from the Great Plains
  and exposed the soil.

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• In times of drought, the topsoil quickly dried
  out, turned to dust, and blew away.
• Wind blew the soil east in great, black clouds.

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• The problem was most serious in the southern
  Plains states.
• There, the drought and topsoil loss lasted until
  1938.

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• This area was called the Dust Bowl.
• Many people in Dust Bowl states moved away.

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• Soil conservation is the management of soil to
  prevent its destruction.
• Two ways that soil can be conserved include
  contour plowing and conservation plowing.

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• Contour plowing is the practice of plowing fields
  along the curves of a slope.
• This prevents rain from washing soil away.

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• Conservation plowing disturbs the soil and its
  plant cover as little as possible.
• Dead weeds and stalks of the previous years crop
  are left in the ground to help return soil
  nutrients, retain moisture, and hold soil in
  place.

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End