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Soil Taxonomy and Classification

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Presentation on theme: "Soil Taxonomy and Classification"— Presentation transcript:

1 Soil Taxonomy and Classification

2 Soil Taxonomy Hierarchy
Kingdom Phylum Class Order Family Genus Species Order Suborder Great group Sub group Family Series 12 63 250 1400 8000 19,000

3 Diagnostic Surface Horizons
Epipedons Mollic Umbric Ochric Histic Melanic Plaggen Anthropic Very common “specialized” Human-derived

4 Organic Matter Accumulation
O.M. accumulation Histic Mollic, Umbric ochric time Parent material Vegetation established tmax = 3000 yrs

5 Diagnostic Sub-surface Horizons

6 Diagnostic Subsurface Horizons
Formation Translocation Transformation Clays Organic Matter Oxides

7 Subsurface Horizons Organic Matter Clays Oxides Formation
Translocation Transformation Subsurface Horizons Organic Matter Clays Oxides Dark colors Metals (Fe, Al) smectites Iron Aluminum Kaolinite Also: salts, carbonates, sulfides

8 Diagnostic Subsurface Horizons
Albic Argillic Spodic Oxic Kandic Cambic Sombric sulfuric Natric Agric Calcic Gypsic Salic Duripan Fragipan Placic Subordinate Distinctions

9 Diagnostic Subsurface Horizons
Albic (white) Horizon Light-colored (Value > 6 moist ) Elluvial (E master horizon*) Low in clay, Fe and Al oxides Generally sandy textured Low chemical reactivity (low CEC) Typically overlies Bh or Bt horizons albic *not all E horizons are albic horizons

10 Diagnostic Subsurface Horizons
Argillic Horizon Illuvial accumulation of silicate clays Illuvial based on overlying horizon Clay bridges Clay coatings Bt horizon Accumulation based on absolute increases compared to relevant horizon above or below. Argillic horizon. An argillic horizon is an illuvial horizon in which layer-silicate clays have accumulated to a significant extent by illuviation. They have formed below the surface of a mineral soil but may be exposed at the surface by erosion. In general, this is a B horizon which has an increase in clay content of at least 1.2 times that of the eluvial horizon above and is, in general, parallel to the surface of the polypedon. This increase of 20% in clay content occurs most in soils within a vertical distance of less than 30 cm. In case of clayey soils, this requirement would be unreasonable. If the surface horizon is greater than 40% clay, the increase of clay needed is only 8%. For sandy soils with less than 15% clay, an increase of 3% is required for meeting the criteria of an argillic horizon. In other words, if the clay content of the eluvial horizon is between 15 and 40%, an increase in clay of 20% is needed to meet the requirements for an argillic horizon.

11 Diagnostic Subsurface Clay Horizons
Argillic Horizon Kandic Horizon High Low Activity of Clays Necessary Illuviation of clay Not Necessary

12 Diagnostic Subsurface Horizons
Spodic Horizon Illuvial accumulation of organic matter and aluminum (+/- iron) Dark colored (value, chroma < 3) Low base saturation (acidic) Formed under humid acid conditions Bh horizon Spodic

13 Elluviation and Illuviation
Elluviation (E horizon and A horizons) Organic matter Clays A Bt A E Bh E Bh horizon Bt horizon Spodic horizon Argillic horizon

14 Diagnostic Subsurface Horizons
Oxic horizon Highly weathered (high temperatures, high rainfall) - High in Fe, Al oxides - High in low-activity clays (kaolinite < smectite < vermiculite) activity Bo horizon

15 Diagnostic Horizons Surface Horizons:
Mollic- thick, dark colored, high %B.S., structure Umbric – same, but lower B.S. Ochric – pale, low O.M., thin Histic – High O.M., thick, wet, dark Sub-Surface Horizons: Argillic – illuvial accum. of clay (high activity) Kandic – accum. of clay (low activity) Spodic – Illuvial O.M. accumulation (Al and/or Fe) Oxic – highly weathered, kaolinite, Fe and Al oxides Albic – light colored, elluvial, low reactivity

16 Diagnostic Subsurface horizons
Soil Taxonomy Diagnostic Epipedons Diagnostic Subsurface horizons Moisture Regimes Temperature Regimes Age Texture Depth

17 Soil Orders Order 12 Suborder Great group 63 Sub group Family 250
Soil forming processes, presence or Absence of major diagnostic horizons Similar genesis Order Suborder Great group Sub group Family Series 12 63 Grasslands – thick, dark epipedons High %B.S. 250 1400 8000 19,000

18 Soil Orders Entisols Histosols Inceptisols Andisols Gelisols Alfisols
Mollisols Ultisols Spodosols Aridisols Vertisols Oxisols

19 Soil Orders Entisol Histosol Inceptisol Alfisol Ultisol Spodosol
Mollisol Oxisol Andisol Gelisol Aridisol Vertisol Ent- Hist- Incept- Alf- Ult- Spod- Moll- Ox- And- Gel- Arid- Vert- Recent Histic (organic) Inception Television alien Ultimate Spodos (wood ash) Mollis (soft) oxide Ando (black) Gelid (cold) Arid (dry) Verto (turn)

20 Soil Orders in Florida Entisols – little development, usually A-C horizons, ochric epipedon Inceptisols – A little more development, Bw horizons, ochric, umbric epipedon Alfisols – Argillic/Kandic horizon (Bt) less than 2 m, base saturation is > 35% Ultisols – Argillic/Kandic horizon (Bt) less than 2 m, base saturation is < 35% Mollisols – Mollic epipedon, dark, high organic matter Spodosols – Spodic horizon (Bh), ochric, umbric epipedon Histosols – Organic soil, histic epipedon Entisols Inceptisols Alfisols Ultisols Mollisols Spodosols Histosols A A A A A O A E C Bw E E Bt Bw meters Bt Bh C C C C C 2

21 Entisols Young Soils Weaklly developed Sandy or clayey Ochric Epipedon
A – C profiles

22 Taxonomic Peculiarity
A horizon C horizon 2 meters (200 cm) Bt

23 Entisols

24 Inceptisols Little Development Ochric, Histic, or Umbric epipedon
Ap horizon Little Development Ochric, Histic, or Umbric epipedon One or more subsurface horizons Weakly developed Contains many unweathered minerals Bw horizon C horizon

25 Histosols Peat or muck > 20% organic matter Agriculturally valuable
Sometimes used as fuel Often over impermeable material

26 Histosols

27 Alfisols Mollic/Umbric/Ochric epipedon A horizon E horizon
Bt horizon (argillic, kandic) base saturation > 35% Btg horizon

28 Ultisols A horizon E horizon Bt horizon Mollic/umbric/Ochric epipedon
Argillic or Kandic horizon Base saturation < 35%

29 Ultisols and Alfisols Mixed Hardwood Forests

30 Spodosols State Soil of Florida Associated with acidic vegetation
Subsoil accumulation of organic matter with aluminum and/or iron Formed under Wet acidic conditions Poorly or Very poorly drained Pine Flatwoods State Soil of Florida

31 Spodosols Pine Flatwoods (wet, acidic)

32 Mollisols Many with argillic Poorly-drained Surface % B.S. > 50%
Mollic Epipedon High organic matter Thick surface horizon Highly productive Many with argillic Poorly-drained Surface % B.S. > 50%

33 Mollisols Grasslands

34 Soil Orders slight Entisols Histosols Inceptisols Andisols Gelisols
Strong Weathering and development Entisols Histosols Inceptisols Andisols Gelisols Aridisols Vertisols Alfisols Mollisols Ultisols Spodosols Oxisols

35 Geographic Distribution

36 Florida Soil Orders Spodosols 8.4 million acres Entisols 7.5
Ultisols 6.9 Alfisols 4.6 Histisols 4.0 Inceptisols 1.0 Mollisols 1.0

37 Soil Taxonomy Order 12 Suborder Great group 63 Sub group Family 250
Series 12 Soil forming processes / diagnostic horizons Genetic similarity: Wetness, climate, vegetation 63 250 1400 8000 19,000

38 Temperature Conditions
Moisture Conditions Wet Dry Aquic – poor aeration, reduced iron Udic- dry < 90 total days Ustic - limited but is present Aridic- moist <90 total days Xeric - dry Temperature Conditions cold Hot Cryic – icy cold Frigid – lower than 8oC Mesic – between 8 and 15oC Thermic – between 15 and 22oC Hyperthermic - > 22oC

39 Suborders Temperature, moisture, diagnostic horizons Suborder Examples
Aquod very wet spodosol Udult wet ultisol Udoll wet mollisol Xeroll dry mollisol Ochrept Umbrept alboll

40 Soil Taxonomy Order 12 Suborder Great group 63 Sub group Family 250
Series 12 Soil forming processes / diagnostic horizons Soil moisture conditions, diagnostic horizon Arrangement of Diagnostic horizons 63 250 1400 8000 19,000

41 Great Groups Based on diagnostic horizons and their arrangements or
other features like age, color, texture Arg - argillic horizon present Pale - old Kand - kandic horizon present Hapl - minimum horizonation quartzi – quartz sand Hum - humid

42 Greater Specificity Order Suborder Great Group Udult paleudult Aquoll argiaquoll Udalf paleudalf Udult hapludult Ultisol Mollisol Alfisol

43 Sub group Moisture, sandiness, depth, color Typic shallow sand
Expresses the core concept of the great group Moisture, sandiness, depth, color Typic shallow sand Arenic deeper sand Grossarenic deep sand Aquic Typic hapludult Grossarenic quartzipsamment Subgroup Great group suborder order

44 Families Particle size mineralogy temperature oC Sandy Loamy
Properties important to growth of plant roots Particle size mineralogy temperature oC Sandy Loamy Fine loamy Clayey Siliceous Kaolinitic Smectitic Oxidic Frigid < 8 Mesic 8-15 Thermic Hyperthermic > 22

45 Series Horizon number, order, thickness, texture, structure,
Color, Organic matter, pH, accumulations Order Sub-order G. Group Sub-group Family Series Mollisol Aquoll Argiaqoll typic Argiaquoll typic argiaquoll Brookston loamy siliceous Cordova Westland

46 Alachua County paleudult order Suborder great group albaqualf
Apopka loamy, siliceous, hyperthermic grossarenic paleudult Ledwith fine, smectitic, hyperthermic mollic albaqualf Surrency loamy, siliceous, thermic, arenic paleaquult Pomona sandy, siliceous, hyperthermic, ultic, haplaquod paleudult order Suborder great group sub-group family albaqualf paleaquult haplaquod

47 Alachua County paleudult Great group suborder order albaqualf Great group suborder order

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