soils formation, erosion, and conservation
DESCRIPTION
SOILS FORMATION, EROSION, AND CONSERVATION. CHAPTER 10. I. Soil: Formation Erosion, and Conservation. A. Soil – Defined as a complex mixture of eroded rock, minerals, decaying organic matter, water,air , and living organisms. 1. Produced by… -Weathering of rock - PowerPoint PPT PresentationTRANSCRIPT
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SOILSFORMATION, EROSION, AND
CONSERVATION
CHAPTER 10
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I. Soil: Formation Erosion, and Conservation
A. Soil – Defined as a complex mixture of eroded rock, minerals, decaying organic matter, water,air , and living organisms.
1. Produced by…-Weathering of rock
-Depositing of sediment -Decomposition of matter
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B. Soil Zones (MATURE)
-Mature Soil is arranged into zones called SOIL HORIZONS, each with distinct textures and compositions
-A cross-section of soil horizons is called a SOIL PROFILE
-Most mature soils have at least three of the possible horizons
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LAYERS/HORIZONS
O Horizon – Top layer/Surface Liter Layer
-Characterized by debris and animal waste
-Dark Brown/Black in color
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A Horizon – Top Soil Layer -Consists of porous mixture of partially
decomposed organic matter called HUMUS and *inorganic minerals -Generally darker and more loosely compact than lower levels.
-Most *plant roots and organic matter found here.
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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
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Soils: Zones
O horizonLeaf litterA horizonTopsoil
B horizonSubsoilC horizonParent
material
Mature soil
Young soil
Regolith
Immature soil
Bedrock
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-Spaces, pores, between particles contain varying amounts of water and air.
-Some of the precipitation that reaches the soils moves down through layers by a process known as… Infiltration- Water moving through the soil layers
-Leaching- Soil components from upper layers being carried to lower layers when water moves through soluble soil layers. Ex: dumping oil in yard
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C. Soil Properties1. Soils vary in content of … Clay - very fine particle Silt – fine particles Sand – medium particles Gravel – coarse/very course
particles-Relative amounts of different size and types determines SOIL TEXTURE-LOAMS – soils of equal mixture….not a particle size used to determine soil texture.
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2. Soil texture(s) can be determined by…A. Feel – Mixing a small sample of top soil and water, rub it between the fingers and thumb.
-Gritty = a lot of sand-Sticky = high amounts of
clay, rolls-Silt = smooth like flour-Loams = between the
extremesB. Use of “texture chart”
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CLAY
SAND SILT
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3. Soil texture helps to determine… - SOIL POROSITY, the measure of the volume of pores and distance of pores per volume of soil.
(important for water/air amounts)
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-Porosity helps to determine SOIL PERMEABILITY, the rate at which water and air can move through soil.
Water Water
High permeability Low permeability
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-Porosity also is influenced by SOIL STRUCTURE, the way that particles are organized.
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Texture Nutrient Infiltration Water-Holding Aeration TilthCapacity 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
Loams – best for cropsSands – easy to work but decrease waterClay – soils can easily become water-logged
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-pH can be changed by adding LIME to acidic soils and SULFUR to those soils that are basic/alkaline
4. pH- Measure of alkalinity or acidity
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II. Soil Erosion1. Defined as the movement of soil components, especially surface litter and topsoil, from one place to another*Two main agents are…
-Flowing water -Wind
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2. Types Of Water Erosion A. Sheet – Moving of water in wide
flow
B. Rill – Fast moving water that cuts small channels
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C. Gully – Ditches and gulleys caused by fast moving water over steep, exposed soil
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Areas of serious concern
Areas of some concern
Stable or nonvegetative areas
Global Soil Erosion
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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 in 1997
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A. Desertification- Process whereby the productive potential of arid or semiarid land falls by 10% or more due to human activities and climate changes. **Can be caused by prolonged drought, overgrazing, and soil compaction
B. Salinization-The accumulation of salts in soil -often a result of irrigation-stunts growth, decrease productivity, kills
plants making the land unproductive
4. Other Problems Associated With Soil
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C. Waterlogging- An over abundance of water within the soil
-Often caused from trying to “wash out” salts.
-Occurs due to decrease drainage
-Irrigation often results in waterlogging
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EvaporationTranspiration
Evaporation
Waterlogging
Less permeableclay layer
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III. Soil Conservation
Soil Conservation involves reducing soil erosion and restoring soil fertility.
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A. Farming Techniques 1.Conventional-tillage farming-plowing, breaking up, and smoothing soil in fall to plant in the spring. 2. Conservation-tillage farming-decreases erosion Tillage refers to the workability of soil
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C. Terracing – Creation of broad, nearly level terraces that run across the contour of the lands
-Mostly used on very steep gradients to prevent erosion.
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D. Contour Farming- Plowing/planting crops in rows across the sloped contour of the land at 90 degree angles.
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E. Strip Cropping- Alternating rows of crops with low, ground hugging vegetation.
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F. Alley Cropping/Agroforestry- several crops planted together in strips or alleys between trees or shrubs that are used for fuel wood or fruits.
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G. Windbreaks/Shelterbelts- Rows of trees to reduce wind erosion.
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H. Organic fertilizer
-Compost
-Animal manure-Green manure
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Commercial inorganic fertilizer
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Drawbacks to Commercial Inorganic Fertilizers
- They don’t add humus to soil- Show decreased ability to hold
water- Lower oxygen content in soil- Supply 2 or 3 of 20 needed
nutrients.