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Lecture 5b, 6, & 7a: Soils I, II, & III Spring 2006 WVU GEOL 321 ((J.S. Kite) Soil: Assemblage of natural bodies on the Earth’s surface (natural or artificial) capable of supporting plant life outdoors Pedon: Area on Earth’s surface w/ single type of soil Also: soil mapping unit. Soil Development Is a Function of 5 Factors S = ƒ (Cl,O,R,P,T) 1. 2. 3. 4. 5. Climate Organisms Relief Parent material Time 1 Factors of Soil Development 1. Climate Temperature & Moisture Affect Eh & Redox Reactions Fe (Iron) Depletions Gray Reduced Iron (Water-Logged) Fe (Iron) Concentrations Red “Mottles” of Oxidized Iron (= Redoximorphic features) Factors of Soil Development 2. Organisms Microorganisms (Bacteria, Fungi) Decompose organic material into humus Macroorganisms Bioturbation by Trees, Worms, Crayfish, Groundhogs, Gophers, Grizzly Bears Organisms Supply material Leaves (Conniferous vs. Deciduous Forests) Roots (Grasslands) Factors of Soil Development 3. Relief Slope Steep Slopes: Well Drained, Erosion Low Slopes: Poorly Drained, Deposition Aspect Direction slope faces affects temperature & moisture 2 Factors of Soil Development 4. Parent Material Material from which soil develops Types of Parent Material Residual Soil = Residuum Bedrock weathers in situ, on low relief & little erosion Parent Material, (cont.) Colluvial Transported by Gravity Alluvial Material Transported by Streams Glacial Transported by Glaciers Eolian Transported by Wind Factors of Soil Development 5. Time Needed to Form Soils Depends on Other Factors Warm Climates Form Soil Faster Than Cold Biological & Geochemical Reactions Act 2X Faster for Every 10oC Increase Water = a ‘must’ in Pedochemical Reactions, Translocation Parent Material Affects Time to Form Soil 3 Increasing Soil Development Soil Properties Through Time Geometric Logarithmic Steady State Increasing Time Soil Characteristics 1. Color Typically Formed by three substances 1. Humus Decomposed organic material 2. Iron (Fe) 3. Carbonate Munsell soil color chart Soil Characteristics cont. 2. Texture (USDA) = size of soil particles in “matrix” Sand = 2.0 to 0.05 mm Silt = 0.05 to 0.002 mm Clay = less than 0.002 mm Excludes particles >2 mm Loam = Significant percentage of all three (2 sand: 2 silt: 1 clay) 4 Soil Characteristics cont. Textural Triangle Texture determined by two methods 1. Particle Size Analysis Laboratory method 2. By Feel (Field method) Takes lots of practice High clay content will cause soil to form ribbon when rolled. 20 30 80 S nt rce Pe Soil Texture Triangle 10 100 90 ilt 70 24 Jan 2006 50 40 Clay 60 50 yS an d 90 80 Silt 10 0 Sand 70 60 Pe rce n tC l ay Silty Clay Silty Clay Clay Loam Loam 30 Sandy Clay Loam 20 Loam Silt Loam 10 Loam Sandy Loam Sandy Clay 40 10 20 30 40 50 60 70 80 90 0 10 Percent Sand Soil Characteristics cont. 3. Soil Structure PEDS: aggregates of particles Types of Structure Blocky (well developed) Platy Prismatic Columnar Granular (high organics) 5 Soil Horizons Soil Profile Described from the surface down Solum “True soil” = A &/or E & B horizons Soil & Ground Water Distribution Eastern USA • Soil Moisture Belt • Unsaturated (= Vadose = Aeration) Zone Capillary Fringe • Water Table • Saturated (= Phreatic) Zone Soil & Ground Water Distribution Western USA Phreatophytes • Soil Moisture Belt • Unsaturated (= Vadose = Aeration) Zone Capillary Fringe • Water Table • Saturated (Phreatic) Zone 6 Soil Horizons Idealized Soil Profile Surface Solum = A, E, and B { L Horizon Leaf Litter O Horizon Decomposed Organics A Horizon Top Soil E Horizon Leached Horizon B Horizon Subsoil Weathered (?) C Horizon Parent Material R Horizon Bedrock Soil Horizons cont. L = New leaf litter In forest soils O = Organic Layer Partly decomposed organic matter A = Top Soil Mix of inorganic & organic material Eluvial horizon Most fertile soil horizon Soil Horizons cont. E = Eluvial Horizon Organics & minerals even more elluviated, light color horizon B = Subsoil Illuvial horizon High clay content? Maximum soil development 7 Soil Horizons (cont.) C = “Weathered” Parent Material or “Unweathered” Transported Material Has NOT undergone soil formation R = Bedrock Unweathered Bedrock Diagnostic Horizons EPIPEDONS Mollic: dark, > 1% O.M. in upper 7”, >50% base saturation Ochric: light, < 1% O.M. Umbric: dark, <50% base saturation Histic: peaty surface layer Plaggen: >20” of manure applied over long time Diagnostic Horizons cont. SUBSURFACE HORIZONS Spodic: buildup of humus Argillic: buildup of clay Cambic: incomplete argillic or spodic horizon Oxic: high clay, 1:1 clay, low CEC Petrocalcic: Concentration of carbonates Albic: light colored E horizon Other Common Soil “Horizons” Fragipan: brittle layer with high bulk density Saprolite: soil mineralogy w/ relict bedrock structure 8 Fragipan:Top view of truncated soil - Canaan Valley Btx horizon J.S. Kite Photo Fragipan: Side view showing reduced tongues J.S. Kite Photo Subdivisions of Horizons: • A • B • B2 • B3 • BC • 2 BC • 2C • 3C “1” not written Change in Parent Material Change in Parent Material 9 lower case notations to horizons: • • • • • • • Ap Bw C Ab Bt BC C p = disturbed (plowed?) A w = incipient (weak) B b = buried A t = argillic clay build-up Catena Sequence of soils of about the same age, derived from similar parent material, and occurring under similar climate conditions, but having different characteristics due to variation in relief and in drainage. SSSA Internet Glossary of Soil Science Terms http://www.soils.org/sssagloss/ Catena, Alberta www.soils.rr.ualberta.ca/soa/catena3.cfm 10 Soil and Soil Development Soil Handout Soil Taxonomy 6 Levels of Classification Order Suborder Great Group Subgroup Family Series Soil Taxonomy “Tucker County Mine Soil” Loamy-skeletal, mixed, acid, frigid Typic Udorthent ent = Entisol (ent as in recent) [Soil Order] orth = Common (typical entisol) [Suborder] Ud = Humid climate [Great Group] Typic = Common (typical udorthent) [Subgroup] frigid = Cold climate acid = pH less than 4.0 mixed = mixed mineralogy of materials in the soil skeletal = greater than 35% rock fragments in soil Loamy = textural classification = LOAM 11 ORDER FORMATIVE ELEMENT Entisol ent no horizons Inceptisol ept incipient horizons - Cambic horizon Alfisol alf argillic horizon, high B.S. >35% Ultisol ult argillic horizon, low B.S. <35% Oxisol ox oxic horizon Mollisol oll mollic epidedon Spodosol od spodic horizon Vertisol ert shrink-swell soils Aridisol id dry >50% of year Histosol ist >30% organic matter Andisols and tephras Gelisols el permafrost Suborder Formative Elements • • • • • Alb Aqu Arg Ferr etc. - White Albino Wet Argillic Horizon Iron Examples of Suborders (2 Formative Elements): • • • • • Albolls Aquolls Rendolls Xerolls Borolls - Albic Horizon Wet (Aqueous) Rendzina (Lots O. M. + Hi pH) Xeric Dry Season Boreal Cool 12 Mon-Marion County Soil Survey West Virginia State Soil (1997) feet • See P. 157 Monongahela Silt Loam Fine-loamy, mixed, semiactive, mesic Typic Fragiudults Source of image & text for 2 slides: www.statlab.iastate.edu/soils/ photogal/statesoils/wv_soil.htm Monongahela soils occur on >100,000 acres in 45 counties in West Virginia. These very deep, moderately welldrained soils are on alluvial or glaciallake terraces (after NRCS w/ JSK modif.) Generalized Distribution 13 TYPE LOCATION: 2.7 mi E of Beverly, 100 ft N of church on N boundary of 4-H Camp, Randolph Co., WV; MLRA OFFICE: Morgantown, WV SERIES ESTABLISHED: Greene County, Pennsylvania, 1921. DIAGNOSTIC HORIZONS, etc. Ochric epipedon - 0 to 12 inches (Ap & BA horizons). Argillic horizon - 12 to 22 inches (Bt horizon). Fragipan - 22 to 52 inches (Btx horizon). Source of image and text for 3 slides: www.statlab.iastate.edu/soils/ osd/dat/M/MONONGAHELA.html Ap--0 to 7 inches; dark grayish brown (10YR 4/2) silt loam; moderate fine granular structure; friable; many roots; slightly acid; abrupt smooth boundary. (6 to 10 inches thick) BA--7 to 12 inches; yellowish brown (10YR 5/4) silt loam; weak fine subangular blocky structure; friable; common roots; slightly acid; clear smooth boundary. (0 to 7 inches thick) Bt--12 to 22 inches; yellowish brown (10YR 5/6) silt loam; weak to moderate fine subangular blocky structure; friable; common roots; few distinct clay films on faces of peds; moderately acid; clear wavy boundary. (8 to 20 inches thick) Btx1--22 to 31 inches; yellowish brown (10YR 5/4) loam; common fine distinct yellowish brown (10YR 5/8) and light brownish gray (2.5Y 6/2) mottles; weak coarse prismatic structure parting to weak coarse platy; firm; few distinct clay films; very strongly acid; clear irregular boundary. (7 to 14 inches thick) Btx2--31 to 42 inches; light yellowish brown (10YR 6/4) loam; many medium distin\ct yellowish brown (10YR 5/8) and light brownish gray (2.5Y 6/2) mottles; weak very coarse prismatic structure parting to weak coarse platy; very firm, brittle; few distinct clay films; very strongly acid; clear wavy boundary. (8 to 15 inches thick) Btx3--42 to 52 inches; light yellowish brown (10YR 6/4) cobbly loam; many distinct yellowish brown (10YR 5/8) and light brownish gray (2.5Y 6/2) mottles; weak very coarse prismatic structure parting to weak coarse platy; very firm, brittle; few distinct clay films; numerous fine pores; 25 percent sandstones cobbles; very strongly acid; clear wavy boundary. (0 to 12 inches thick) C--52 to 65 inches; mixed strong brown (7.5YR 5/8) and light gray (N 7/ ) clay loam, pale yellow (2.5Y 7/4) crushed massive; firm; 35 percent weathered shale, sandstone fragments and cobbles; very strongly acid; clear smooth boundary. Ap--0 to 7 inches; dark grayish brown (10YR 4/2) silt loam; moderate fine granular structure; friable; many roots; slightly acid; abrupt smooth boundary. (6 to 10 inches thick) BA--7 to 12 inches; yellowish brown (10YR 5/4) silt loam; weak fine subangular blocky structure; friable; common roots; slightly acid; clear smooth boundary. (0 to 7 inches thick) Bt--12 to 22 inches; yellowish brown (10YR 5/6) silt loam; weak to moderate fine subangular blocky structure; friable; common roots; few distinct clay films on faces of peds; moderately acid; clear wavy boundary. (8 to 20 inches thick) Btx1--22 to 31 inches; yellowish brown (10YR 5/4) loam; common fine distinct yellowish brown (10YR 5/8) and light brownish gray (2.5Y 6/2) mottles; weak coarse prismatic structure parting to weak coarse platy; firm; few distinct clay films; very strongly acid; clear irregular boundary. (7 to 14 inches thick) Btx2--31 to 42 inches; light yellowish brown (10YR 6/4) loam; many medium distinct yellowish brown (10YR 5/8) and light brownish gray (2.5Y 6/2) mottles; weak very coarse prismatic structure parting to weak coarse platy; very firm, brittle; few distinct clay films; very strongly acid; clear wavy boundary. (8 to 15 inches thick) Btx3--42 to 52 inches; light yellowish brown (10YR 6/4) cobbly loam; many distinct yellowish brown (10YR 5/8) and light brownish gray (2.5Y 6/2) mottles; weak very coarse prismatic structure parting to weak coarse platy; very firm, brittle; few distinct clay films; numerous fine pores; 25 percent sandstones cobbles; very strongly acid; clear wavy boundary. (0 to 12 inches thick) C--52 to 65 inches; mixed strong brown (7.5YR 5/8) and light gray (N 7/ ) clay loam, pale yellow (2.5Y 7/4) crushed massive; firm; 35 percent weathered shale, sandstone fragments and cobbles; very strongly acid; clear smooth boundary. 14 Ap--0 to 7 inches; dark grayish brown (10YR 4/2) silt loam; moderate fine granular structure; friable; many roots; slightly acid; abrupt smooth boundary. (6 to 10 inches thick) BA--7 to 12 inches; yellowish brown (10YR 5/4) silt loam; weak fine subangular blocky structure; friable; common roots; slightly acid; clear smooth boundary. (0 to 7 inches thick) Bt--12 to 22 inches; yellowish brown (10YR 5/6) silt loam; weak to moderate fine subangular blocky structure; friable; common roots; few distinct clay films on faces of peds; moderately acid; clear wavy boundary. (8 to 20 inches thick) Btx1--22 to 31 inches; yellowish brown (10YR 5/4) loam; common fine distinct yellowish brown (10YR 5/8) and light brownish gray (2.5Y 6/2) mottles; weak coarse prismatic structure parting to weak coarse platy; firm; few distinct clay films; very strongly acid; clear irregular boundary. (7 to 14 inches thick) Btx2--31 to 42 inches; light yellowish brown (10YR 6/4) loam; many medium distinct yellowish brown (10YR 5/8) and light brownish gray (2.5Y 6/2) mottles; weak very coarse prismatic structure parting to weak coarse platy; very firm, brittle; few distinct clay films; very strongly acid; clear wavy boundary. (8 to 15 inches thick) Btx3--42 to 52 inches; light yellowish brown (10YR 6/4) cobbly loam; many distinct yellowish brown (10YR 5/8) and light brownish gray (2.5Y 6/2) mottles; weak very coarse prismatic structure parting to weak coarse platy; very firm, brittle; few distinct clay films; numerous fine pores; 25 percent sandstones cobbles; very strongly acid; clear wavy boundary. (0 to 12 inches thick) C--52 to 65 inches; mixed strong brown (7.5YR 5/8) and light gray (N 7/ ) clay loam, pale yellow (2.5Y 7/4) crushed massive; firm; 35 percent weathered shale, sandstone fragments and cobbles; very strongly acid; clear smooth boundary. Distribution of Soil Orders The distribution of Soil Orders depends on all of the 5 factors of soil formation S = ƒ (Cl,O,R,P,T) Climate has the most influence on a global or continental scale Climate Climate Soil Orders 15 Soil Orders - USA Soil Orders. Entisols “Ent” For Recent; Very Little Development New Surficial Deposits Soil Orders cont. Inceptisols “Incept” for inception Cambic Horizon 16 Soil Orders cont. Alfisols “Alf” for Aluminum ‘Al’ and Iron ‘Fe’ Argillic horizon, high (>35%) base saturation Well-developed soil Common West Virginia soil Alfisol Wisconsin J.S. Kite Photo Soil Orders cont. Ultisols “Ult” for ultimate Highly weathered, but less than Oxisols Argillic horizon & low (<35%) base saturation Dominant soil type in SE USA 17 Ultisol http://www.statlab.iastate.edu/ soils/photogal/orders/soiord.htm Ultisol Shenandoah Valley, Virginia 70 ft J.S. Kite Photo Soil Orders, cont. Oxisols “oxi” for oxides Red soils due to oxidized iron Highly weathered Warm, moist tropics 18 Oxisol Oxisol Cornfield Mollisol Shenandoah Valley, Virginia J.S. Kite Photo 19 Mollisol Great Plains Calcite Soil Orders cont. Spodosols Light-colored E horizon & Dark illuvial B horizon Mostly loamy to sandy soils Common in acidic soils of coniferous forests organic acids aid translocation Spodosols at high elevation in WV J.S. Kite Photo Spodosol Allagash River Terrace, Maine 20 Soil Orders cont. Vertisols “Vert” for invert Contain smectite Shrink-swell properties causes Turnover Slickensides, “Tee-pee” Structures Texas Gulf Coast Vertisol, Zambia Soil Orders cont. Aridisols Dryland Soils Highly alkaline (high pH), commonly saline Typical in SW U.S. 21 Aridisol Soil Orders cont. Histosols “Hist” means fiber Dark, organic soils May be muck or peat Anaerobic, Negative Eh Highly acidic Histosol, Carrying Place Bog, Maine J.S. Kite Photo 22 New (1998) Soil Orders Andisols Soils in Tephras Gelisols Soils Under Permafrost) Andisol Aquic Vitrixerands Washington http://www.statlab.iastate. edu/soils/photogal/ statesoils/wa_soil.htm J.S. Kite Photo Gelisol: Victoria Valley, Antarctica 23 Gelisol http://www.statlab.iastate.edu/ soils/photogal/orders/soiord.htm Proposed Soil Order Anthrosols Proposed soil order for artificially disturbed material 24