9-Soil_and_Agriculture

9-Soil_and_Agriculture - Soil and Agriculture Ecology &...

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Soil and Agriculture Ecology & Environmental Problems Biology 1305
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Soil as a system Soil consists of mineral matter, organic matter, air, and water Dead and living microorganisms, and decaying material Bacteria, algae, earthworms, insects, mammals, amphibians, and reptiles S ince soil is composed of living and non-living matter, it is considered an ecosystem
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Soil formation is slow and complex Parent material = the base geologic material of soil Lava, volcanic ash, rock, dunes Bedrock = the continuous mass of solid rock comprising the Earth’s crust Weathering = the physical, chemical, or biological processes that break down rocks to form soil Physical (mechanical) = wind and rain, no chemical changes in the parent material Chemical = substances chemically interact with parent material Biological = organisms break down parent
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Weathering produces soil
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Other processes affect soil formation Erosion = the dislodging and movement of soil by wind or water Occurs when vegetation is absent Biological activity includes deposition, decomposition, and accumulation of organic matter Humus = a dark, spongy, crumbly mass of material formed by partial decomposition
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A soil profile consists of horizons Horizon = each layer of soil Soil profile = the cross- section of soil as a whole Up to six major horizons may occur in a soil profile Topsoil = inorganic and organic material most nutritive for plants
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Soils are characterized in many ways Soils are classified based on color, texture, structure, and pH Soil color = indicates its composition and fertility Black or dark brown = rich in organic matter Pale gray or white = indicates leaching Soil texture = determined by the size of particles From smallest to largest = clay, silt, sand Loam = soil with an even mixture of the three Influences how easy it is to cultivate and let air
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Soil texture classification Silty soils with medium-size pores, or loamy soils with mixtures of pore sizes are best for plant growth and crop agriculture
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Soil structure and pH Soil structure = a measure of soil’s “clumpiness” Large clumps can discourage plant roots Repeated tilling compacts soil, decreasing its water-absorbing capabilities Plowpan = a hard layer resulting from repeated plowing that resists water infiltration and root penetration Soil pH = influences a soil’s ability to support plant growth Soils that are too acidic or basic can kill plants
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Cation exchange is vital for plant growth Cation exchange = process that allows plants to gain nutrients Negatively charged soils hold cations (positively charged ions) of calcium, magnesium, and potassium Cation exchange capacity = a soil’s ability to hold cations, preventing them from leaching, thereby increasing their availability to plants A useful measure of soil fertility Greatest in fine soils
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Regional differences in soils affect agriculture
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This document was uploaded on 10/27/2011 for the course BIO 1305 at Texas Tech.

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9-Soil_and_Agriculture - Soil and Agriculture Ecology &...

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