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SOILS FORMATION, EROSION, AND CONSERVATION. Miller Chapter 10. I. Soil: Formation Erosion, and Conservation. What is Soil ? complex mixture of eroded rock, minerals, decaying organic matter, water, air, and living organisms. Ratios Differ among various soil types… Average Ratios: - PowerPoint PPT Presentation
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SOILSFORMATION, EROSION, AND
CONSERVATION
Miller Chapter 10
I. Soil: Formation Erosion, and Conservation
A. What is Soil?complex mixture of eroded rock,
minerals, decaying organic matter, water, air, and living organisms.
Ratios Differ among various soil types…
Average Ratios:45% Minerals25% Water25% Air5% Humus
B. How Soil is Produced
-Weathering of rock -Depositing of sediment -Decomposition of matter
C. Soil Zones (MATURE)-Soil is arranged into
zones called… SOIL HORIZONS-A cross-section of soil
horizons is called… SOIL PROFILE-Most mature soils have
at least three of the possible horizons
LAYERS/HORIZONS
O Horizon – Top layer/Surface Liter Layer
-Characterized by debris and animal waste
-Brown/black in color
A Horizon – • Top Soil Layer -Consists of porous mixture of
partially decomposed organic matter called…
• HUMUS • Inorganic minerals -Most plant roots and organic
matter found here.
B Horizon – Subsoil Layer andC Horizon – Parent Material
• Contain most of soil’s inorganic matter and varying mixtures of sand, silt,clay, and gravel
• C Horizon lies on BEDROCK
Soils: zones
O horizonLeaf litterA horizonTopsoil
B horizonSubsoilC horizonParent
material
Mature soil
Young soil
Regolith
Immature soil
Bedrock
D. Soil Properties*Soils vary in content of … Clay Silt Sand Gravel-Relative amounts of different size and types determines SOIL TEXTURE-LOAMS – soils of equal mixture
100%clay
Increasingpercentage silt
Increasingpercentage clay
0
20
40
60
80
80
60
40
20
0100%sand 80 60 40 20 100%silt
Increasing percentage sand
CLAY
SILTSAND
1. Infiltration: Water moving through
the soil layers
2. Leaching: Soil components from upper layers being carried to lower layers
3. Porosity:
the measure of the volume of pores and distance of pores per volume of soil
4. Permeability:the rate at which water and air can move through soilWater Water
High permeability Low permeability
5. Soil Structure: The way in which soil particles
are organized and clumped together Texture Nutrient Infiltration Water-Holding Aeration Tilth
Capacity Capacity
Clay Good Poor Good Poor Poor
Silt Medium Medium Medium Medium Medium
Sand Poor Good Poor Good Good
Loam Medium Medium Medium Medium Medium
6. Soil pHA measure
of the acidity of the soil
II. Soil Erosion1. The movement of soil components, especially surface litter and topsoil, from one place to another*Two main agents are…
-Flowing water -Wind
2. Types Of Water ErosionA. Sheet – Moving of water in wide flow
B. Rill – Fast moving water that cuts small channels
C. Gully – • Ditches and gulley’s are
caused by fast moving water over steep, exposed soil
Areas of serious concern
Areas of some concern
Stable or nonvegetative areas
Global Soil Erosion
3. U.S. Soil Erosion -1/3 of the original top soil has been washed or blown away.
-USDA states that soil is eroding 16x faster than it can form.
-USDA estimated loss of $30 billion dollars from erosion in 1997
A.Desertification- The productive potential of
arid or semiarid land falls by 10% or more due to…
Human activities Climate changesMUST REDUCE…Overgrazing & deforestation
4. Other Problems Associated With Soil
Moderate Severe Very Severe
B. Salinization-• The accumulation of salts in soil
• Often associated with irrigation
• Effects:• Stunts crop growth• Lowers crop yields• Kills plants
Severe Salinization
C. Water logging- An over abundance of
water within the soilEvaporation
TranspirationEvaporation
Waterlogging
Less permeableclay layer
III. Soil Conservation1. Reducing soil erosion and restoring soil fertility.
2. Farming Techniques A. Conventional-tillage
farming*Tilling in the fall
B. Conservation-tillage farming
1. Minimum Tillage Farming
2. No Till Farming
3. Terracing – • Creation of broad, nearly level terraces that run across the contour of the lands
-Mostly used on very steep gradients.
4. Contour Farming- • Plowing/planting crops in rows across the sloped contour of the land.
5. Strip Cropping- • Alternating rows of crops with low, ground hugging vegetation.
6. Alley Cropping/Agroforestry-
• several crops planted together in strips or alleys between trees or shrubs
7. Windbreaks/Shelterbelts- Rows of trees to reduce wind erosion.
Conservation During Urban Development
IV. Soil Restoration-Fertility can be returned by using one of two major types of fertilizer… A. Organic B. Inorganic
-Animal manure-Green manure
Organic fertilizer
-Compost
Commercial inorganic fertilizer
Extreme Erosion