Conserving Land and Soil

1
Conserving Land and Soil
2
Types of Land Use

• Agriculture
• New farmland must be created by clearing forests,
  draining wetlands, and irrigating deserts.

3
Types of Land Use

• Development
• Every year in the US, about a million hectares of
  farmland are developed.
• Reduces the amount of farmland and destroys
  wildlife habitats.

4
Types of Land Use

• Mining
• Strip mining removes nonrenewable resources from
  the land.
• Expose the soil and causes erosion.
• In underground mining, minerals are carried up
  through shafts of tunnels that have been dug out.

5
Restoring the Land

• It is possible to restore land damaged by erosion
  or mining. (land reclamation)
• In some cases, subsoil and topsoil are replaced
  and grass is planted so that the area can be used
  as agricultural land.

6
Protecting the Soil

• Erosion
• Plant roots usually hold soil in place.
• Many uses of land expose the soil and can cause
  erosion
• logging
• mining
• farming

7
Protecting the Soil

• Desertification
• The advance of desertlike conditions into areas
  that previously were fertile
• Climate (drought)
• Overgrazing of grasslands by cattle and sheep
• Poor farming practices and excessive cutting of
  trees for firewood

8
Protecting the Soil

• Nutrient Depletion
• If farmers plant the same crops in a field year
  after year, nutrients are used faster than
  decomposers can replace them.
• Prevention
• Periodically leave fields fallow
• Leave the unused parts of crops in the fields
  rather than clearing them away.
• Crop rotation

9
The Nitrogen Cycle

• The process by which nitrogen is removed from the
  atmosphere, fixed in the soil by bacteria,
  incorporated in other living things, and then
  released back into the atmosphere.

10
The Nitrogen Cycle

• Nitrogen Fixation
• The process of changing free nitrogen gas into a
  usable form of nitrogen
• Done by bacteria, some of which live in bumps
  called nodules on the roots of certain plants
  (legumes)
• Clover, beans, peas, alfalfa, and peanuts

11
The Nitrogen Cycle

• Return of Nitrogen to the Environment
• Once the nitrogen is fixed into complex
  compounds, it can be used by organisms to build
  proteins and other substances.
• Decomposers break down these complex compounds in
  wastes and dead organisms and return nitrogen
  compounds in the soil.
• At some time, the bacteria completely break down
  the compounds and release free nitrogen back into
  the air.

12
The Nitrogen Cycle