Presentation on theme: "Lecture 5a Soil Taxonomy Purpose of Soil Taxonomy: 1. Organize knowledge about soils 2. Understand relationships among different soils 3. Establish groups."— Presentation transcript:
Lecture 5a Soil Taxonomy Purpose of Soil Taxonomy: 1. Organize knowledge about soils 2. Understand relationships among different soils 3. Establish groups or classes for practical purposes. a. predicting behavior b. identifying best uses c. estimating productivity d. extending research results
Soil Taxonomy- 12 Soil Orders Soils are classified into into six categories based on diagnostic characteristics The last (largest) category will place the soils into one of the 12 Soil Orders.
Soil Taxonomy 1) Orders (12) 2) Suborders (54) 3) Great Groups (211) 4) Subgroups (1,100+) 5) Family (7,000+) 6) Series (a lot!) Fine-loamy mixed, superactive, mesic Aquic Argiudolls (This is the name of a specific soil in Soil Taxonomy) This is the name of one Of the 12 large categories Mollisol - oll Oder - root of order
Orders Highest and most general of the soil classification system (similar to the phylum in plant taxonomy) Based on conditions under which the soil developed Fine-loamy mixed, superactive, mesic Aquic Argiudolls Order oll = Mollisols
Suborders Grouped by similarities in soil formation such as wetter/dryer soil, colder/warmer soil, etc. Fine-loamy mixed, superactive, mesic Aquic Argiudolls Sub Order Ud = Udic Moisture
Great Groups (not required to know) Based on differences between soil horizons Fine-loamy mixed, superactive, mesic Aquic Argiudolls Great Group Sub Order Argi = Clay accumulation
Sub Groups (not required to know) Describes a profile characteristic, wetness, sand, tonguing of E, etc. Great Group Fine-loamy mixed, superactive, mesic Aquic Argiudolls Sub Group Sub Order Aquic = wet soil
Family (not required to know) Based on soil properties that affect management and root penetration, such as texture, temperature, and depth Great Group Fine-loamy, mixed, superactive, mesic Aquic Argiudolls Family Sub Group Sub Order Texture, clay minerals, CEC, temp,
Series = Le Sueur – this is where the soils of the week names are from – ie Lester, Clarion, Nashwauk etc. Named from the town or landscape feature near where the soil was first recognized (Lester = Lester Prairie, MN. Other examples = Clarion, Nashwauk, Milaca, Port Byron, Zimmerman. Le Sueur for Le Sueur County, MN.) Great Group Fine-loamy mixed, superactive, mesic Aquic Argiudolls Family Sub Group Sub Order
Diagnostics Horizons- Used to place soils into one of the 12 Soil Orders Surface (Epipedon) Mollic Umbric Histic Ochric Subsurface Argillic Natric Spodic Oxic Cambic None
Soil Taxonomy- Diagnostic Surface Epipedons Mollic Epipedon - thick, dark, soft, surface layer. ` Characteristics ` Thick - greater than 10 inches; High base saturation> 50%; ` Mineral soil ` Soils formed under prairie vegetation
Other Epipedons Umbric - like mollic, but low base saturation Histic - Organic Soil - saturated with water, > -% organic matter Ochric - thin, light colored - surface layers that do not fit any of the above Base Saturation = relative amount of bases (Ca, Mg, K) in the soil, Low %= few, high% = many
Comparison of Epipedons OchricHistic Mollic Umbric thinner lighter color more organic matter low base saturation
Diagnostic Subsurface Horizons Argillic - illuvial horizon of clay accumulation - Bt Natric - same as argillic but with > 15% exchangeable sodium (Na) - Btn
Diagnostic Subsurface Horizons Spodic - illuvial accumulation of oxides of Al and Fe (sesquioxides) and OM, red or dark red color - only found in acid sandy soils, with high rainfall- generally found below E horizon. Contains a Bhs or Bs horizon or Bhsm Oi E Bhs Bs C
subsurface horizons (cont.) Oxic - very weathered layer of only Fe and Al oxides and 1:1 clay minerals, low pH and not very fertile (found in tropical soils) Bo Cambic - slightly altered layer - not weathered enough to be argillic, Bw horizon designation or development of color and or structure NONE - no diagnostic subsurface horizon present
Comparison of Subsurface Diagnostic Horizons Oxic very weathered SpodicCambic Argillic Natric more Al and Fe less developed more sodium
12 Soil Orders - Each Order has a diagnostic epipedon and subsurface horizons – which could be none. WEB SITE for soil orders = Entisol Inceptisol Andisols Spodosols Mollisols Alfisols Ultisols Oxisols Aridisols Vertisols Histosols Gelisols
Entisol - ent Recent soils - minimal development, little horizonation, young soils. 12.5% of world, Ochric + none
Entisol - Idaho ARAR
Vertisol - ert Inverted - soils with high clay content, Large shrink swell potential - gradually invert on themselves, 2.1% of the world, Mollic or Ochric + none
Vertisol = Bss at slickenslide
Inceptisol - ept Inception - soil shows the beginning of horizon development, little or no illuviation, 15.8% of world, Ochric or Umbric + cambic.
Inceptisol Soil Formed in colluvial material in mountains of Idaho.
Aridisols - id Arid regions of the world (19%), < 10 in. of rainfall, usually contain carbonates, Ochric + cambic or argillic or other diagnostic feature. A Bw Bk C
Aridisol in Idaho A Bt Bk Bkqm R
Aridisol - Nevada Az Bz C1 C2 NaCl Salt accumulates on the surface and in the subsurface.
Mollisols - oll soils with thick, dark, soft surface - mollic + cambic, natric, argillic or none - high base saturation - soils of the prairie 9% of the world
Mollisol This mollisol formed in a new parent material (loess) that buried the original soil -the Btb (b = buried). Mollisol from Kansas that is developed in Limestone bedrock. A1 A2 Bw BC R
Spodosols- od acid sandy soils with thick E and red Bhs - ochric and spodic % of the world - infertile soils. Oi E Bhs Bs C
Alfisol -- alf fertile forested soils with ochric and argillic - high base saturation (> 35%) - forested soils 7% of the world.
Ultisols - ult soils more weathered than Alfisols - ochric and argillic - low base saturation < 35% - redder and more acid than Alfisols 8.5% of the world - less fertile than Alfisols A E Bt1 Bt2 BC
Alfisol & Ultisol
Histosols - ist peat soils - organic material - histic 0.8% of the world Histic Epipedon. Oe1 Oe2 Oe3 Oe4 Oa 2C Photo USDA
Dyad Describe the Soil Order that is most likely found in your home town.
Andisols - and soils from volcanic ash - very light - low bulk density – 1% or the world Andisol from Idaho A Bw 2BC 2C A Bw Ab Bwb Ab
Oxisols - ox Soils with Oxic horizon - very weathered - soils of the tropics. low pH - acid soils - high in 1:1 clay minerals 9.2% of world
Oxisol Ap1 Ap2 Bo1 Bo2 Bo3
Oxisol Puerto Rico Ap A Bo1 Bo2 BC C
Gelisol - el New Order as of soils with permafrost (formerly Cryochrepts - or frozen Inceptisols) Cf - horizon