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soil functions
medium for plant growth, regulator of water supplies, habitat for organisms/biota, public health, recycling/storage of raw minerals
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4 soil processes
additions (input organic matter), losses (erosion, decomposition), translocations (movement down), transformation (chemical/physical modifications of elements in soil)
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weathering
chemical/physical alteration and reorganization of rocks and minerals
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5 soil factors
parent material (original material), climate (temp/moisture), organisms/biota(vegetation, macro, micro) relief/topography (altitude, slope) time (controls extent of other factors)
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pedogenesis
the process of soil formation as the result of the combination of soil forming factors and processes
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sources of parent material
residual (formed in place from rocks and minerals), alluvial (deposited by rivers/streams), marine (oceans), eolian (wind), glacial (ice)
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Florida's parent material.
sandy marine/alluvial sediments which derived from clayey, silty sands
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rain & temp on soil formation
- water increases weathering rates and translocations
- heat increases rates of physicochemical processes
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soils horizons
O (above mineral soil),A (surface mineral, accumulation of OM, weathered, elluvial, p sub),E (zone of loss),B (zone of accumulation of clays, OM, salts, iron, t,h,w,g sub),C (resembles parent material),R (bedrock)
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subordinate
a (sapric highly decomposed),e (hemic mod),i (fibric slightly),g (gleying-wet, low oxygen),h (OM),p (disturbed, plowed),t (clay),w (weak)
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munsell soil color components
- hue-proportions of red and yellow
- value-reflected light
- chroma-strength of color
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3 particle size
- sand 2.0-0.05mm
- silt 0.05-0.002mm
- clay less than 0.002mm
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primary and secondary minerals
- primary dominate sand & silt, not ractive
- secondary dominate clay, very reactive
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total porosity
the total volume of pore space in a soil, indicates max volume of water and gasses a soil can hold (finer-textured soils have greater TP)
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pore size distribution
large particles yield large pores
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Stokes' Law
- settling velocity of particles in a fluid
- V=KD2 (K=11,241)
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soil bulk density & particle density
- BD=mass OD soil/volume soilds+pores
- range 1.0-1.6 g/cm3
- 1-5& OM
PD=2.65g/cm3 (no pores)
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important
- OM increases porosity, decreases BD
- compaction/depth decreases porosity, increases BD
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BD vs. PD
- % porosity=[1-(BD/PD)]x100
- BD high------porosity low
- BD low------porosity high
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