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It is a composite of inorganic minerals, organic humus, living organisms, moisture, and air. Soils are the product of interactions between abiotic and biotic processes and take thousands of years to form. |
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The study of soils is called? |
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what are factors that form soil? |
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1. The type of parent(source) material 2. The climate under which the soil components have existed since accumulation 3. The plant and animal life in and on the soil 4. The relief of the land 5. The length of time the other factors have interacted
the factors are inderdependent of each other |
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what is the process of the formation of soil? |
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Soil formation begins with the degradation of the parent material. The parent material is unconsolidated, chemically weathered mineral, rock, or organic matter. Precipitation, temperature, humidity, and wind are the climatic forces that act on the parent material to form soil. The relief of the land greatly influences how wind and water act upon parent material components as well as the types of plants and animals that inhabit the area. Animals, insects, bacteria, fungi, and other plants furnish organic matter. Differences in the amount of organic matter, nutrients, structure, and porosity of soil are caused by plant and animal actions. Time is an important factor in soil formation. |
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The O horizon is dominated by organic material. It contains fresh and decaying plant matter from leaves, needles, twigs, moss, lichens, and other organic accumulations. |
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The A horizon is formed at the surface or below the O horizon. It is an accumulation of organic matter and minerals. It is generally darker than the lower horizons because of the decaying organic matter. This horizon is where most plant root activity occurs. It may be referred to as the surface layer in a soil survey. |
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The main feature of the E horizon is the loss of silicate clay, iron, or aluminum, or some combination of these, leaving a concentration of sand and silt-sized particles. |
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The B horizon lies directly below an A, E, or O horizon. It is referred to as the subsoil. It is usually lighter colored, denser, and lower in organic matter than upper horizons. As the recipient of material from upper and lower soil layers, the B horizon is often called the “zone of accumulation.” As rain and irrigation waters percolate downward, they wash (leach) soil components through the A horizon and into the B horizon. The process by which these materials are moved downward by water is called leaching. For this reason, the A horizon is called the “zone of leaching.” Some minerals are drawn upward from lower soil layers by high evaporation rates and plant absorption. |
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Still deeper is the C horizon or the substratum. This layer may consist of less clay or other less-weathered sediments than the layers above. Partially disintegrated parent material and mineral particles are in this horizon. |
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The very lowest horizon, the R horizon, is bedrock. It can be within a few inches of the surface or many feet below. |
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the percentages of sand, silt, and clay in a sample of soil. Soil texture refers only to mineral particles smaller than 2 millimeters (mm). Each grouping of particle sizes is called a soil separate. Hence, sand, silt, and clay are soil separates
Very coarse sand 2.00–1.00 mm Coarse sand 1.00–0.50 mm Medium sand 0.50–0.25 mm Fine sand 0.25–0.10 mm Very fine sand 0.10–0.05 mm Coarse silt 0.05–0.005 mm Fine silt 0.005–0.002 mm Clay less than 0.002 mm |
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The process by which soil separates are obtained is called? |
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mechanical analysis. All mineral soils are made up of a mixture of soil separates. Textural class names of soils are based on the proportion of these separates. There are 12 major textural class names: sand, loamy sand, sandy loam, sandy clay loam, sandy clay, clay, clay loam, loam, silt loam, silty clay loam, silty clay, and silt. |
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remember how to use textural triangle |
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hue is written in letters like yr= yellow red
the value goes from 0 to 10, ten being white 0 being black
The notation for chroma consists of numbers beginning with 0 for neutral grays and increasing at equal intervals to a maximum of about 20.
Thus the notation for a yellowish-red colored soil of hue 5YR, value 5, and chroma 6 is yellowish-red (5YR 5/6). |
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Porosity refers to the amount and size of spaces between soil or rock particles. Porosity determines the amount of water that a soil can hold.Sands and gravels have high porosity. Clays are very porous |
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Permeability refers to the rate of water and air movement through soil or bedrock, if present. It is an indication of downward movement of water when the soil is saturated. This may be considered internal drainage.Permeability is measured in the number of inches per hour (in/hr) that water moves downward through a saturated soil.
Very slow less than 0.06 in/hr Slow 0.06–0.20 in/hr Moderately slow 0.20–0.6 in/hr Moderate 0.6–2.0 in/hr Moderately rapid 2.0–6.0 in/hr Rapid 6.0–20 in/hr Very rapid more than 20 in/hr |
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Soil pores are destroyed by tillage, intense agricultural operations, or heavy vehicle and foot traffic. This destruction is known as soil compaction.
The largest pores (macropores) are the most vulnerable to compaction. |
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macropores and micropores |
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The macropores are essential to the movement of gases and water.
The small pores (micropores) are important in holding and retaining water in the soil.
The loss of these pores lowers the permeability of the soil, thereby restricting percolation and increasing runoff, erosion, and flooding. |
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what does drainage patterns refer to? |
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Drainage classes refer to the periods of saturation or partial saturation during soil formation, as opposed to altered drainage. |
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Water is removed from the soil very rapidly. Excessively drained soils are commonly very coarse-textured, rocky, or shallow. Some are steep. All are free of mottling related to wetness. |
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Somewhat excessively drained |
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Definition
Water is removed from the soil rapidly. Many somewhat excessively drained soils are sandy and rapidly pervious. Some are shallow. Some are so steep that much of the water they receive is lost to runoff. All are free of the mottling related to wetness. |
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Water is removed from the soil readily, but not rapidly. It is available to plants throughout most of the growing season, and wetness does not inhibit growth of roots for significant periods during the growing seasons. Well-drained soils are commonly medium textured. They are mainly free of mottling. |
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Water is removed from the soil somewhat slowly during some periods. Moderately well drained soils are wet for only a short time during the growing season, but periodically they are wet long enough that most mesophytic crops are affected. They commonly have a slowly pervious layer within or directly below the solum or periodically receive high rainfall, or both |
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Water is removed slowly enough that the soil is wet for significant periods during the growing season. Wetness markedly restricts the growth of mesophytic crops unless artificial drainage is provided. Somewhat poorly drained soils commonly have a slowly pervious layer, a higher water table, additional water from seepage, nearly continuous rainfall, or a combination of these. |
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Water is removed so slowly that the soil is saturated periodically during the growing season or remains wet for long periods. Free water is commonly at or near the surface for long enough during the growing season that most mesophytic crops cannot be grown unless the soil is artificially drained. The soil is not continuously saturated directly below the plow depth. Poor drainage results from a high water table, a slowly pervious layer within the profile, seepage, nearly continuous rainfall, or a combination of these. |
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Water is removed so slowly that free water remains at or on the surface during the growing season. Unless the soil is artificially drained, most crops cannot be grown. Very poorly drained soils are commonly level or depressed, are frequently ponded, or have impermeable layers close to the surface. Yet where rainfall is high and nearly continuous, they can have moderate or high slope gradients. |
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what are some of the benefits of wetlands? |
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• They can store rain and slow runoff, which helps to control flooding and erosion. • They are valuable for recreation and beauty. • They filter and absorb pollutants and purify water. • They provide habitat for a wide variety of plants and animals, including 90 percent of the plants, 30 percent of the birds, 15 percent of the mammals, and 50 percent of the fish on the United States endangered species list. • They help stabilize shorelines and reduce coastal storm damage. • They provide important spawning and nursery grounds for approximately twothirds of the nation’s shellfish and important commercial and sport species of marine fish. • They provide important rest areas for the millions of migrating birds every year. |
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how many soil orders are there? |
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Well-developed soils with a relatively fine-textured subsoil horizon that has a base saturation of 35percent or more. |
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Soils of volcanic origin. |
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Dry soils that occur in arid or semi-arid regions |
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Soils with little or no horizon development |
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Soils of cold climates influenced by permafrost |
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Soils composed of relatively thick (usually 16 inches or more) organic materials (muck and peats). |
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Soils of humid regions with profile development sufficient to exclude them from the Entisols, but insufficient to include them in Spodosols, Ultisols, or other welldeveloped soils. Soils that appear to be like Mollisols but have less than 50 percent or more base saturation may also be Inceptisols |
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Soils with thick (usually 10 inches or more), dark surfaces that have a base saturation of 50 percent or more in the surface soil |
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Highly weathered soils of the tropics. |
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Soils with a spodic horizon (a dark-colored subhorizon with a mixture of organic matter and aluminum, with or without iron). |
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Well-developed soils with a relatively fine-textured subsoil horizon that has less than 35 percent base saturation |
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Soils with more than 30 percent clay which appreciably expand upon wetting and contract upon drying. |
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Land uses include crop and pasture lands, rangeland, forestry, recreation, wildlife habitat, and engineering uses, including building sites, sanitary facilities, water management, and construction materials. |
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Definition
Of particular concern in soil conservation is erosion control. Erosion is defined as the wearing away of the land surface by water, wind, ice, or other geologic agents and by such processes as gravitational creep.
Erosion my be classed as geologic or accelerated. Geologic erosion is caused by geologic processes acting over long geologic periods and resulting in the wearing away of mountains and the building up of such landscape features as floodplains and coastal systems. Geologic erosion is also known as natural erosion. Accelerated erosion is much more rapid than geologic erosion. Accelerated erosion is mainly the result of the activities of humans or other animals or of a natural catastrophe such as a hurricane or a wildfire |
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soil erosion control methods |
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The first principle in wind erosion control is to cover the soil. Vegetative cover slows the wind at ground level, protects soil particles from being detached, and traps other blowing soil particles. One of the most permanent wind erosion control methods is a wind barrier. There are also numerous agricultural practices such as crop residue management — leaving crop remains in the field as mulch — crop rotation, planting cover crops, strip cropping, and planting buffer strips that protect soil from erosion. |
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nonpoint source pollution |
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Nonpoint source pollution occurs when rain or irrigation water runs over the land or through the ground, picks up pollutants, and deposits them in lakes, rivers, and coastal waters or introduces them to groundwater. Usually, these pollutants are solely thought of as fertilizers, pesticides, other chemicals, oils, animal wastes, or heavy metals. Soil sediments also contribute to nonpoint source pollution. They clog waterways, reduce aquatic species habitat and spawning areas, and reduce water clarity, inhibiting aquatic plant growth. Erosion control practices have multiple benefits |
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look at the bacteria and animal section in the soil |
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