SOILS What is soil Soil relatively thin surface
- Slides: 57
SOILS
What is soil? • Soil – relatively thin surface layer of the Earth’s crust consisting of mineral and organic matter
Soil Composition • Soil is composed of 4 distinct parts: – Mineral particles (45% of “typical” soil) – Organic matter (about 5%) – Water (about 25%) – Air (about 25%)
Importance of Soil • Organisms inhabit the soil & depend on it for shelter, food, & water. • Plants anchor themselves into the soil, and get their nutrients and water. • Humans need plants and, therefore, need soil.
Soil is a renewable resource • Soil is a slowly renewed resource • Soil formation begins when bedrock is broken down by weathering. • Mature soils (soils that have developed over a long time) are arranged in a series of horizontal layers called soil horizons.
Soil Formation • Soils form from parent material • Parent material (rock) is slowly broken down into smaller particles by biological, chemical, and physical weathering. • It takes a long time to form soil. – Example: To form 2. 5 cm (1 in. ) it may take from 200 -1000 years.
Physical Weathering • Physical breakdown by wind, water, ice, etc.
Chemical Weathering • Chemicals interact with rock and break it down. • Example: A plant’s roots or animal cells undergo cell respiration and the CO 2 produced diffuses into soil, reacts with H 2 O & forms carbonic acid (H 2 CO 3). This eats parts of the rock away.
Biological Weathering • Parent material is broken down by tree roots or lichens. • Lichens play a big role in primary succession.
Soil Properties: Texture • The percentages (by weight) of different sized particles of sand, silt and clay that it contains.
Soil Properties: Texture, Cont. • Grain Size – 0. 05 to 2 mm = sand (the largest soil particles) – 0. 002 to 0. 05 mm = silt (about the size of flour) – <. 002 mm = clay (only seen under and electronic microscope)
Soil Properties: Texture, Cont. • To tell the difference in soil, take the soil, moisten it, and rub it between your fingers and thumb. – Gritty: has a lot of sand – Sticky: high clay content and you should be able to roll it into a clump – Silt: smooth, like flour.
Soil Structure • How soil particles are organized and clumped together. – Sand – Silt – Clay
Friability • How easily the soil can be crumbled.
Porosity • A measure of the volume of soil and the average distances between the spaces.
Permeability • The rate at which water and air moves from upper to lower soil layers. • The Distances between those spaces.
Variability • Soils (Sand, Silt, & Clay) vary in – the size of the particles they contain – the amount of space between these particles – how rapidly water flows through them.
Big spaces, not a lot of them LESS surface area AL U EQ SITY O R PO Little spaces but lots of them GREATER surface area IMPORTANT TO REMEMBER The size of the rock particle DOES NOT change the porosity!
1 st trial: look at red yellow green only Demo #1 Which size held the most water?
Soil Texture (descriptions) • Sand • Silt • Clay
Shrink-Swell Potential • Some soils, like clays, swell when water gets in them, then they dry and crack. This is bad for house foundations, etc.
Slope • Steep slopes often have little or no soil on them because of gravity. • Runoff from precipitation tends to erode the slope also. • Vegetation?
Depth • Some soils are very shallow. It can be only two inches of soil and then you hit rock. Other areas can have soil 36 inches deep or more.
Color • Dark soil is rich with lots of organic matter. • Light soil (like sand) is not so rich with very little organic matter.
Soil Horizons
Organic Layer (O-horizon) • The uppermost layer; it is rich in organic material. • Plant litter accumulates in the O-horizon and gradually decays. • In desert soils the O-horizon is completely absent • In certain rich soils it may be the dominant layer.
Topsoil (A-horizon) • It is dark and rich in accumulated organic matter and humus. • It has a granular texture and is somewhat nutrient-poor due to the loss of many nutrient minerals to deeper layers and by leaching.
Eluvial(E-horizon) • Mineral horizon in upper part of soil • Below A-Horizon and above B-Horizon • Generally forested areas, light color
Subsoil (B-horizon) • The light-colored subsoil beneath the Ahorizon; • Accumulation of minerals occurs here • It is typically rich in iron and aluminum compounds and clay.
Parent Material (C-horizon) • Contains weathered pieces of rock and borders the unweathered solid parent material. • Most roots do not go down this deep • often saturated with groundwater.
Oak tree Wood sorrel Lords and ladies Fern O horizon Leaf litter Dog violet Grasses and small shrubs Earthworm Millipede Honey fungus Mole Organic debris builds up Rock fragments Moss and lichen A horizon Topsoil B horizon Subsoil Bedrock Immature soil Regolith Young soil Pseudoscorpion Mite Nematode C horizon Parent material Root system Mature soil Red Earth Mite Springtail Actinomycetes Fungus Bacteria Fig. 3 -23, p. 68
Mosaic of closely packed pebbles, boulders Weak humusmineral mixture Desert Soil (hot, dry climate) Dry, brown to reddish-brown with variable accumulations of clay, calcium and carbonate, and soluble salts Alkaline, dark, and rich in humus Clay, calcium compounds Grassland Soil (semiarid climate) Fig. 3 -24 a, p. 69
Acidic light-colored humus Iron and aluminum compounds mixed with clay Tropical Rain Forest Soil (humid, tropical climate) Fig. 3 -24 b, p. 69
Forest litter leaf mold Humus-mineral mixture Light, grayishbrown, silt loam Dark brown firm clay Deciduous Forest Soil (humid, mild climate) Fig. 3 -24 b, p. 69
Acid litter and humus Light-colored and acidic Humus and iron and aluminum compounds Coniferous Forest Soil (humid, cold climate) Fig. 3 -24 b, p. 69
Erosion • Erosion is the movement of soil components, especially surface litter and topsoil, from one place to another.
Importance of Erosion • In undisturbed ecosystems, the roots of plants help anchor the soil, and usually soil is not lost faster then it forms. • But, farming, logging, construction, overgrazing by livestock, off-road vehicles, deliberate burning of vegetation etc. destroy plant cover and leave soil vulnerable to erosion. This destroys in a few decades what nature took hundreds to thousands of years to produce.
Soil Erosion & Degradation Figure 13 -9
Global Outlook: Soil Erosion • Soil is eroding faster than it is forming on more than one-third of the world’s cropland. Figure 13 -10
- The rate of weathering depends upon the area's ____.
- Classification of soils
- Porosity of soil
- Aridisols are soils characteristically found in _______.
- How does the study of soils help evaluate natural hazards?
- Red latosols
- Ashley soils
- Timbering in dry loose soils
- Components of soil
- Soils alive
- Pedalfer soil
- What is clorpt?
- Which is not true of laterite soils
- The finest grained soils are richest in
- Living soil vs dead soil
- Living soil vs dead soil
- Lateral surface area prism
- High surface tension vs low surface tension
- Volume and surface area of cone
- Greenyar
- Ego reality principle
- Relatively new concept
- Are complex relatively brief responses
- Relatively orderly meaning
- Learning is any relatively permanent change
- Gas particles are separated by relatively large distances
- Douglas merritte
- A relatively permanent change of behavior is called
- In 1500 mainland southeast asia was a relatively
- Is defined as a distinctive and relatively stable pattern
- It refers to the stable pattern or configuration
- Objects that radiate relatively well
- Principles of remedial teaching
- A loop of relatively cool incandescent gas
- To increase fan-out of the gate in dtl
- Relatively permanent change
- We are usually referring to species diversity
- The sun converts matter into energy in what zone
- The relatively permanent and limitless storehouse
- Floors should be relatively smooth and non-absorbent.
- Source traits example
- A relatively permanent change in behavior
- A relatively permanent change of behavior is called
- Relatively new concept
- Stimulus learning
- Relatively permanent
- Principles of developmentally appropriate practice
- The maintenance of a stable internal environment
- Permanent learning examples
- Film interference
- Fiber texture pole figure
- Thin filament
- A red big plastic hat
- Thin gate oxide
- Conoit
- Ectomorph sports persons
- Thin
- A long thin light bulb illuminates a vertical aperture