Download Introduction to Soils

Introduction to Soils
The most important natural
resource around the earth!
1
What is soil?
Defined as:
• Mineral & Organic material that supports
plant growth on the earth’s surface
• Mixture of particles of rock, organic
materials, living forms, air, water
2
What soil resources help in
supporting life?
• Oxygen: needed for adequate root growth
• Temperature: soil absorbs heat from the
sun – loses heat to atmosphere (plant
growth and seed germination)
• Water: plant growth
• Carbon: organic matter
• Nutrients: minerals
3
Briefly explain the process of soil
origin.
• All soil originated as rocks.
• Powerful forces act on the rocks to break
them down into smaller fragments.
• Water penetrates the cracks in the rock
and when it freezes the water acts as a
wedge to split the rock.
4
Soil origin cont.
• Rivers, glaciers, landslides and
avalanches cause rock particles to grind
against each other wearing them down.
• Chemicals mix with water to further break
the rocks down.
• Plants began to grow in the weathered
rocks and as they die, they add organic
matter to the soil which attracts soil microorganisms.
5
Soil origin cont.
• When this happens, the soil is capable of
supporting plant life and can then truly be
called soil.
6
What does the term weathering
mean?
• Weathering is the processes that occur to
break down rock into soil. This process
includes water freezing, thawing,
landslides, wind and chemical action.
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What is parent material?
• Rock material that has undergone some
weathering and change, but not enough to
be called true soil, as it is not capable of
sustaining plant life.
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List the 5 factors responsible for
soil development.
1. Parent material
2. Climate
3. Variation in the earth’s surface
(topography)
4. Plant & animal life
5. Time
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Components of Soil
• Mineral Matter: about 45% of soil (partially
decomposed rock material (sand, silt, clay)
• Organic Matter: about 5% of soil (partially
decomposed plant & animal matter)
• Air: about 25% of soil (constant fluctuation
as soil is dry and wet)
• Water: about 25% of soil
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Water in the soil
• Infiltration: process of water soaking into
the soil
• Percolation: water movement downward
• Permeable: quality soil allows for both
infiltration and percolation – then it is said
to be permeable
11
Living Organisms in the soil
• Forms of life:
– Earthworms
– Insects
– Bacteria
– Fungi
– Other organisms
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Bacteria & Fungi Jobs
• Break down organic matter and release
nutrients
13
Earthworm & other soil organism
jobs
• Improve soil tilth
– Ease at which soil can be worked
– Create openings in soil as they tunnel
– Enhances drainage and improves air
exchange
14
Plants use soil
A. Anchorage – roots
B. Water – absorbed through roots
C. Oxygen – all living organisms need
oxygen
-plants release oxygen during photosynthesis
and consume oxygen during respiration
-good soil aeration needed for below ground
plant parts to get oxygen
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Plants use soil cont.
D. Nutrients – of the 16 essential nutrients
for plant growth – 13 are obtained from the
soil
-root hairs absorb the nutrients dissolved in soil
water
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Soil uses in agriculture
•
•
•
•
Cropland
Grazing land
Forest
Water structures
• Agriculture depends on soil to grow food,
fiber, and ornamental plants.
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Nonagricultural uses of soil
• Recreation: playgrounds, sports fields,
jogging paths, golf courses, parks,
campgrounds
• Foundations: buildings have to have solid
base
• Waste Disposal
• Building materials
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