Chapter3 - SOIL Why Study Soil? An essential natural...

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SOIL
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Why Study Soil? • An essential natural resource • Medium for crop production • Producer and absorber of gases • Filters water and waste
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How is soil formed • Soil is formed by weathering • Weathered soil is further modified by activity of soil organisms and may be transported • Soil is an open system that interacts with other components of the geologic cycle
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Why Study Soil? • Home to organisms • Source material for construction, art, and medicine • Waste decomposer
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Why Study Soil? • One of the most indispensable resources on Earth • Weathering of crustal minerals creates soil that is essential to all life • Called the “bridge between life and the inanimate world”
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History Lesson from Soil
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What is Soil? • Regolith – any loose surface sediment • Soil –a combination of mineral and organic matter, water, and air • Soils constituents can vary from location to location
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Soil Horizons O Horizon – organic material ( Decomposed and nondecomposed) A Horizon – Decomposed organics (dark color) E Horizon – zone of leaching B Horizon – zone of accumulation C Horizon – partial weathering R Horizon – unaltered bedrock
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In real life however, soil horizons may or may not be readily apparent to the eye.
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…horizons are often characterized by chemical differences that may or may not have a visual signature. Careful visual observations however are still useful to soil scientists.
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Relative soil development • Weakly developed soil profile A horizon over C – B horizon is not well developed. Several thousand years old • Moderately developed: A overlies B that overlies the C horizon. 10,000+ years old • Well developed: redder color in B horizon, more translocation of clay to B. 40,000 to 100,000 years old
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In some cases new river sediments can bury an old, previously formed soil.
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Soils generally are less than 2 meters thick
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Soil formed on unconsolidated river sediments.
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on igneous rock,
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on metamorphic rock
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And on sedimentary rock
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Soils may or may not develop uniformly
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They form a discontinuous membrane around the Earth .
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Soil Properties • Color • Texture • Structure • Fertility • Water Content
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Soil Color • Easily identified property • Used to relate chemical/physical properties such as watertable depth, drainage, chemical constituents, formations, horizons
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Soil Color Color due to • Organic matter (carbon) – Strong coloring agent making soil dark or black • Compounds and elements – Iron, Sulfur, Manganese
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Soil Fertility • Factors controlling fertility – Infiltration, retention, and drainage of water – Soil structure – Content of organic matter – Active soil life (organisms) – Minerals and Ph – Parent soil
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Dominant Soil Orders
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Soil Fertility • Nitrogen is a primary element in soil and is an
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This note was uploaded on 02/10/2011 for the course GEOL 103 taught by Professor Lakshmi during the Spring '10 term at South Carolina.

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Chapter3 - SOIL Why Study Soil? An essential natural...

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