sw25 - Soil Morphology and Classification Soil Purpose The...

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Unformatted text preview: Soil Morphology and Classification Soil Purpose The Language of Soils Loamy, siliceous, hyperthermic grossarenic paleudult Morphology and Classification of Soils Based on physical and chemical properties Color Texture Structure Density/Porosity Water Movement Reactivity of mineral and organic colloids Soil acidity and pH All are used to classify soils Soil Formation Factors Affecting Soil Formation The 5 soil forming factors Climate Organisms/Vegetation Parent material Relief/Topography Time Alteration of Parent Material Climate Organisms Relief (Topography) Time Additions, Losses, Translocation, Transformation Pedogenesis: The process of soil formation as the result of the combination of soil forming factors and processes. Parent Material Affects texture, vegetation, nutrients clay mineralogy, CEC Deposition Colluvial (gravity) Alluvial (streams) Marine (oceans) Lacustrine (lakes) Glacial (ice) Eolian (wind) silt and clay Florida: Loamy Marine Sediments Sea Levels +150 ft -300 ft Shaping of the landform Deposition of materials Climate Temperature and Precipitation Rates of chemical, physical, biological processes Cold dry climates – weaker, more modest profile development Warm, humid climates – strong, deep profile development Organisms/Vegetation O.M. accumulation Profile mixing Nutrient cycling Soil structure Soil solution constituents Plants (roots, O.M.), Earthworms, Burrowing Organisms, Bacteria, Fungi, Microorganisms Topography Configuration of land surface – elevation, slope, depressions Hastens or delays climatic forces. Impacts depth of profile development. Slope Aspect Water Erosion Vegetation Time Duration of weathering and all other factors Additions Losses Translocations Transformations Soil Horizons: first step in classification Alteration of Parent Material Sands Clays Iron The O Horizon Organic horizon formed above the mineral soil. Derived from plant and animal residues Range in thickness from absent to meters thick. The A Horizon • • • • • Topmost mineral horizon Accumulates organic material Often darker than soil below. high in plant roots, biotic activity Zone of gas and water exchange A horizon A horizon Additions, Losses, Translocation, Transformation The E horizon - Zone of Eluviation Elluviation = exit Maximum Losses by Translocation •Organic matter •Clay •Carbonates •Fe, Al oxides •color A horizon E horizon (Elluvial) Contains resistant materials (e.g. quartz) The B Horizon - Accumulates material lost from above, or forms in place. (translocation, transformation) Zone of Illuviation (additions, translocation). Clay, O.M., Fe/Al, salts soil structure Potential color development Potentially high reactivity - B horizon Soil Horizon designations O horizon Master Horizons Master Organic matter Sandy Clays/iron O A E B C R A horizon E horizon B horizon organic topsoil, O.M., cycling elluvial developed/accumulation parent material bedrock C horizon Parent Extra Credit: 1. Identify 2 of the soil forming factors 2. Identify 1 important feature of the A master horizon 3. Identify one major feature of the B master horizon 4. Identify one major feature of the E master horizon Master Horizons Enough information? O horizon A horizon R horizon E horizon (Elluvial) C horizon B horizon (Illuvial) B horizon Subordinate Distinctions Subordinate Distinctions b – buried horizon c – concretions d – root restrictive g – gleying h – illuvial organic matter k – carbonates m – cementation o - oxic p – plowing/disturbance q – secondary silica r – soft bedrock (saprolite) s – illuvial sesquioxides and O.M. t – clay accumulation v – plinthite w – development of color/structure x - fragipan Subordinate Distinctions Subordinate g – gleying h – illuvial organic matter p – plowing/disturbance t – clay accumulation w – development of color/structure o – oxic Subordinate Distinction p = plowed Disturbed surface horizon (cultivation, pasture, forestry) Used with the A master horizon (e.g. Ap horizon) Ap horizon Subordinate Distinction t = clay accumulation Translocation of clay or formed in place Coatings or discrete Used with the B master horizon (e.g. Bt) Subordinate Distinction h = organic accumulation • Accumulation of illuvial organic matter-metal complexes • Coatings on sand and discrete particles • h = “humic” • value and chroma approximately 3 or less • Used with the B master horizon (e.g. Bh horizon) Bh horizon “spodic horizon” * Subordinate Distinction (g = gleying) (g • Oxygen deprived or reduced state due to water saturation. • Reduction of iron (Fe III to Fe II) • low chroma • Often used with B master horizon (Bg horizon), also E and C horizon. oxidized material oxidized Fe2+ Iron is Depleted Subordinate Distinction w = color or structure Non-illuvial development of color or structure “w” can = “weak” Commonly used with the B master horizon (e.g. Bw) Bw Subordinate Distinction o = oxic horizon Low activity clays Few weatherable materials Little rock structure Fe and Al oxides Subordinate Distinctions Subordinate g – gleying h – illuvial organic matter p – plowing/disturbance t – clay accumulation w – development of color/structure o – oxic Subordinate Distinctions and Organic Matter Subordinate Distinction a, e, i Denotes the degree of organic matter decomposition in the O horizon. Oa – highly decomposed (sapric) Oe – moderately decomposed (hemic) Oi – slightly decomposed (fibric) Sapric –most decomposed, low plant fiber, low water content Hemic – intermediate decompostion Fibric – least decomposed, recognizable fibers Summary Summary Master: O, A, E, B, C, R Subordinate symbols: g, h, p, t, w and a,e,i Examples: Oa, Oe, Oi Bt Bg Btg Bw Ap ...
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This note was uploaded on 02/04/2011 for the course SWS 3022 taught by Professor Bonczek during the Spring '11 term at University of Florida.

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