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Why is soil important?

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Why is soil important? Nutrient cycling: soil controls the release and uptake of nutrients (soil can trap carbon reducing greenhouse gas) Water relations: Soil ... – PowerPoint PPT presentation

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Title: Why is soil important?


1
Why is soil important?
  • Nutrient cycling soil controls the release and
    uptake of nutrients (soil can trap carbon
    reducing greenhouse gas)
  • Water relations Soil acts as a filter to protect
    the quality of water and air
  • Biodiversity and habitat soil supports the
    growth of a variety of plants, animals and
    microorganisms ( The soil is an ecosystem)
  • Physical stability and support Soil allows plant
    roots to anchor in the ground and structural
    support for buildings, roads and parking.

2
How does soil form?
  • Soil erodes from parent material (rock) 1cm in
    250 -2,500 years

3
Weathering
  • Physical/mechanical wind and rain, temperature
    change
  • Chemical accelerated by warm wet conditions
    (acid rain)
  • Biological lichens, tree roots

4
Biological activity
  • Detritivores and decomposers cycle nutrients and
    produce organic matter (humus)
  • Humus rich soils hold water and are nutrient rich

5
What lives in the soil?
  • Each shovel of soil holds more living things than
    all the human beings ever born!
  • We know more about the movement of celestial
    bodies than about the soil underfoot. ---
    Leonardo daVinci
  • Yet, every plant and animal depends on this vast
    ecosystem

6
Worms!
  • Up to 1, 750, 000 per acre in good agricultural
    soil!
  • The weight of worms might outweigh the weight of
    livestock on a farm!
  • Worms break down plant material into nutrient
    rich humus
  • Burrowing improves soil structure for plant
    growth
  • Earthworms aerate the soil
  • Earthworms bring minerals from lower levels to
    the plant root zone

7
The soil profile
  • Soil forms distinct layers called horizons
  • Soil scientists classify soils according to their
    profiles
  • O organic matter/litter
  • A topsoil with organic and mineral content
  • E zone of leaching
  • B subsoil (minerals accumulate
  • C weathered parent material
  • R parent material

8
Alfisol
Andisol
9
oxisol
Vertisol
10
Iowa - Mollisols
  • Soils of grassland ecosystems
  • Fertile surface horizon formed from long term
    addition of plant material
  • Most widespread soil order in the U.S.
  • Among the most productive agricultural soils of
    the world

11
What is soil made of?
  • 45 minerals
  • 25 air
  • 25 water
  • 5 organic matter
  • To describe soil we consider
  • Color
  • Structure
  • texture

Soil texture classification
Particle type Size (mm)
clay 0.002
silt 0.002-0.05
sand 0.05-2.0
12
Importance of Soil Texture
  • Determines soils workability
  • Porosity the size of the spaces between
    particles
  • Fine particles have few spaces between them
    water and air move slowly
  • Large particles water travels too fast
  • Silty soil with medium pores OR loamy soils are
    favored by farmers

13
Which has the most fertile soil?
Temperate Grassland
Tropical Rainforest
14
Soil Degradation and Conservation
  • Erosion the removal of material (by wind or
    water) and its deposition at a new location
  • 3 widespread practices lead to erosion
  • Overcultivation
  • Overgrazing
  • Clearing forest on slopes

15
Desertification
  • A loss of more than 10 productivity due to
    erosion, soil compaction, forest removal,
    overgrazing, drought etc.
  • Affects 1/3 of the planets land
  • Could result in the displacement of 50M people in
    10 years
  • 1930s dustbowl caused by drought, strong winds
    and poor farming practices

16
Soil Conservation
  • Crop Rotation
  • Cover cropping (Rye)
  • Contour Farming
  • Terracing
  • No-till or reduced tillage
  • Shelterbelts (rows of trees)

17
Salinization
  • Irrigation may lead to a buildup of salts in
    surface soil
  • Water evaporating from the A horizon may pull
    water from lower in the soil
  • When water evaporates it leaves behind salts
  • Overhead Irrigation

Drip Irrigation
18
Overgrazing A tragedy of the Commons
  • Too many animals eating too much ground cover
    leads to
  • Erosion
  • Soil compaction
  • Invasive species (often less palatable to
    livestock

Degraded dryland in Greece
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