Spodosols

Soils with spodic horizon (organic with or w/out Fe) >10 cm thick, within 200 cm of surface Commonly coarse-textured Albic horizon above is common, NOT required Bhs—often cemented in parts (orstein-like), difficult to dig (Fe-cemented) Two temperature regimes– cryic/frigid thermic

State Factor Considerations Parent material and vegetation are the overriding factors Acid, sandy parent material Coniferous vegetation to produce acid leachate high in fulvic acids Time is also a factor since development of a well-expressed spodic horizon requires a minimum of 3 to 5,000 years Weakly expressed spodic horizons may form in a few hundred years. Spodosols are found on a variety of landscapes and reliefs Climate must be such that conifers can grow, but there are no other restrictions

Distribution Occur in humid tropical, sub-tropical, cool temperate and boreal areas with coarse-textured parent materials Occupy about 4.2% of the earth's land surface

Distribution

Problems and Use Acidity is the major problem Most Spodosols are either in cold climates or need drainage for agricultural production Used for forest, blueberries (acid tolerant crop), and citrus (in Florida if soil is drained). Spodosols have been used for other agricultural crops with addition of lime and fertilizers

Aridisols Central concept: soils with pedogenic development in arid regions. They either have an aridic moisture regime, or they are saline. Aridisols must have a diagnostic subsurface horizon If no diagnostic horizon is present, the soil is an Entisol Soils that do not supply water to plants for long periods Calcic, petrocalcic, and salic horizons are common Lack of leaching from low rainfall results in subsoil accumulation of the more soluble salts State factor considerations: Climate is the overriding factor Time is important since the soil must have a diagnostic horizon Can have any parent material, relief, and vegetation (xerophyllic)

Aridisols Problems and use: Most obvious limitation is lack of water Accumulation of salts more soluble than gypsum is also serious problem in some areas Soluble salts are toxic to certain plants and can limit availability of water for plants (high osmotic potential) Salt accumulations can cause structural damage to buildings and corrosion of steel and concrete. The major use for Aridisols is for rangeland grazing Motorcycles and dune buggies are also a major use in some areas

Distribution

Aridisols

Andisols Soils developed from volcanic ejecta and composed of andic soil materials Only order criterion is 36 cm of andic soil materials in the upper 60 cm of the soil Any vegetation, landscape position, or climate

Andic Soil Materials Soil material with properties characteristic of volcanic ash, cinders, and other pyroclastic materials Volcanic materials have an abundance of amorphous silicate components such as allophane and imogolite Low bulk density High P fixation High amounts of Fe and Al extracted with acid oxalate Oxalate extraction will dissolve amorphous Fe, Si, and Al components but not crystalline components Andic criteria are designed to separate soils with a high content of amorphous components from soils with crystalline components

Andisols Dominant pedogenic processes are weathering and mineral transformation Translocation is minimal. State factor considerations The only important factor is parent material. Time is a minor factor A few 10's or 100's of years to weather fresh ash to produce oxalate soluble components Biology, climate, and relief are not important Transitional soils With enough weathering, amorphous components will transform to crystalline minerals and properties associated with andic soil materials will be lost

Andisols Andisols are generally highly productive soils Favorable physical and chemical properties P fixation may high Few engineering problems.

Andisol Distribution 124 million hectares worldwide Pacific Rim of Fire Rift Valley of Africa, the west coast of Italy, the West Indies, and Iceland

Andisols

Vertisols Soils with combination of amount and type of clay to have a high shrink-swell potential Occur in an environment with wet and dry periods to induce shrink-swell Three requirements must be met for a soil to classify as a Vertisol: cm thick layer in the upper 100 cm of soil that has either slickensides close enough to intersect or wedge shaped peds with their long axis tilted 10 to 60 o from horizontal; and 2. 30% or more clay in all horizons between the soil surface and a depth of 50 cm or to a lithic or paralithic contact or petrocalcic horizon, if shallower than 50 cm; and 3. cracks that open and close periodically.

Vertisols The most common feature of Vertisols is occurrence in an environment with seasonal drying of the soil profile Also common among Vertisols are parent materials with a basic reaction, i.e. basic igneous rocks, chalks, marls, basalt, etc. Vertisols also often occur in basins Accumulation of basic cations and Si from mineral weathering in upslope positions Maintainence of high Si in soil solution is important for smectite stability Vegetation is commonly grassland or savannah - rarely forest. Vertisols are often referred to as self-mulching Strong structure at surface behaves more like sand than clay

Vertisols Genesis of Vertisols requires substantial volume changes 2 models for slickenside formation Self-swallowing

Soil Mechanics σ 0 = σ V = σ L σ0σ0 σ 0 = cohesion + internal friction σVσV σLσL σLσL σVσV Dry Soil σ0σ0 σ 0 = σ V > σ L σ L > σ 0 > σ V Moist and Shallow σ0σ0 σLσL σLσL σVσV Moist and Deep σ0σ0 σ 0 < σ L ≤ σ V = shear failure σVσV σLσL σLσL =

Vertisol Features

Gilgai

State Factor Considerations Parent material and climate are the overriding factors. The parent material must have either minerals that weather to clays that induce shrink-swell or this type of clay Climate must result in Either continually moist or dry and no volume change Relief is sometimes a factor Basins and other low position where cations and Si accumulate Vegetation and time are not important

Shrink Swell Clays with high shrink-swell are not necessarily smectitic Volume change is not from changes in interlayer spacing Volume change is due to change in thickness of the water shell surrounding clay particles and packets Clay particle size is more important than type Kaolinite – 1-2 µm Smectite <0.2 µm Flexibility of the clay also has an influence Fine-grained kaolinite (volcanic derived) may have high shrink-swell

Distribution

Problems and Use Vertisols are one of the most difficult classes of soils to manage Shrink-swell creates many engineering problems Foundation stability Roads Lime stabilization Ca vs. Na saturated clays Agronomic problems include water erosion water excess and deficiency low trafficability when wet high P fixation high energy demand for tillage

Histosols Histosols are soils composed of organic soil materials To be a Histosol, more than half of the upper 80 cm of the soil must be organic soil materials (>40 cm) Organic Soil Material Mineral Soil Material

Fiber Fragment or piece of plant tissue, excluding roots, that is retained on a 100-mesh sieve (0.15 mm) after dispersion separate with sodium hexametaphosphate. Fiber content of organic material determined in the field is rubbed fiber Material is rubbed 10 times between the thumb and forefinger Fiber content is estimated Decomposition state has a large impact on many soil properties including water holding capacity, bulk density, hydraulic conductivity, etc.

Fiber Content Affect on Soil Properties

Control Section Surface to either 130 or 160 cm thick depending on kind of organic material Unconsolidated mineral substratum does not limit the depth of the control section Lithic or paralithic contact, water, or frozen soil is lower limit Control section divided into 3 tiers: Surface tier - upper 30 cm (60 cm if the organic material is fibric) Subsurface tier - next 60 cm from base of surface tier Bottom tier - next 40 cm from base of subsurface tier

Properties that Affect Classification Hydric - soils that have a layer of water within the control section Limnic - limnic materials >5 cm thick within control section Lithic - organic materials rest on lithic contact within the control section Terric - a mineral layer other than limnic materials is 30 cm or more thick and its upper boundary is within the control section

Suborders Saprists - sapric material dominant Hemists - hemic material dominant and/or have sulfuric horizon within 50 cm of the soil surface or sulfidic materials within 1 m or the surface Fibrists - fibric material dominant Folists - not saturated with water for more than a few days and is composed of leaf litter, twigs, and branches resting on rock or fragmental materials

Family Criteria Particle-size class - refers to mineral layer of terric subgroups Mineralogy class - Ferrihumic - Fe oxides mixed with organic materials Terric subgroups - mineral mineralogy classes applied to mineral part of soil Limnic subgroups - limnic layers within the control section 5 cm or more thick Coprogenous Diatomaceous Marly Reaction classes Euic - pH is 4.5 or more in 0.01 M calcium chloride in at least some part of the subsurface tier Dysic - pH less than 4.5 throughout subsurface tier Soil temperature classes - same as mineral soils Soil depth classes - same as mineral soils

State Factor Impacts Time - needed to accumulate and decompose organic matter Parent Material Rock type is not important Type of organic material can affect accumulation and decomposition rates Relief Important in warm climates Flat landscapes and depressions with saturated conditions Less important for Folists and Fibrists in cold climates Blanket bogs Climate - affects organic matter decomposition Cold Wet Organics - various types of plants will contribute to Histosol formation Sphagnum mosses are common precursor to Fibrists

Distribution Boreal climates Warm wet climates with low relief landscapes South Florida Southeast Asia

Distribution

Use Considerations Drainage Saturation is a limitation for most soil uses Saturated conditions cause Histosol formation Drainage leads to Histosol destruction Subsidence through organic matter decomposition is a major problem Subsidence rates up to 3 cm per year in Florida

Use Considerations In areas of crop production, the water level is controlled to prevent the soil's destruction Water table is maintained at the surface during most of the year Soil only drained when necessary for a production operations In addition to subsidence, organic materials are not rigid. and as water in pores is removed, the material collapses

Use Considerations Histosols are used in many areas for vegetable or citrus production Fertile with high CEC, adequate moisture, good tilth, etc. Mostly high-value crops because of cost of drainage and to control the water table Histosols have been historically and are still being used for fuel Demand for use as potting soil, wrapping material, etc. Histosols have severe limitations for use in roads, buildings, etc. High water tables Low bearing capacity and strength Subsidence.

Series Lowest category in Soil Taxonomy More than 19,000 series in the United States Purpose is mainly pragmatic Closely related to interpretations Differentiae used for series are the same as those used for classes in other categories Series properties cannot range across limits of classes in higher categories Cecil must be a fine, kaolinitic, thermic Typic Kanhapludult Rion must be a fine-loamy, siliceous, themic Typic Kanhapludult Cataula must be a fine, kaolinitic, themic Oxyaquic Kanhapludult Many families only have one series

Greater Restriction within a Family Fine, kaolinitic, thermic Typic Kanhapludults Cecil – Bt horizon has hue of 2.5YR or redder Appling – Bt horizon has hue of 5YR or yellower fine-loamy, siliceous, thermic Plinthic Kandiudults Tifton – common Fe stone in upper Bt Dothan – no Fe stone in upper Bt Distinctions within a family are restrictions in the range of one or more properties of the family Only those differences that serve to distinguish one series from another are included in statements of series differences

3 Tests of Series Differentiae Properties serving as differentiae can be observed or can be inferred with reasonable assurance Differentiae must create soil series having a unique range of properties Difference among series should be greater than normal errors made by qualified pedologists Differentiae must reflect a property of the soils Can be reflected in the nature or degree of expression of one or more horizons. Can be almost any horizon or soil property May also be Landscape property Commonly associated soils Climate We may not be as smart as we think

Phase Properties that may influence certain but not all uses of a soil Slope Stoniness Aspect “Wind swept” Not a part of Soil Taxonomy Utilitarian classification that can be superimposed at any categorical level to permit more precise interpretations for soil use

Competing Series Statement - Cecil These are the Appling, Bethlehem, Madison, Nankin, Pacolet, Tumbleton, and Wedowee series in the same family Those in closely related families are the Aragon, Braddock, Cataula, Chestatee, Cullen, Georgeville, Hayesville, Herndon, Hulett, Kolomoki, Lloyd, Mayodan, Mecklenburg, Spotsylvania, Tatum and Wedowee series Appling soils have dominant hue of 7.5YR or yellower or where hue is 5YR it has evident patterns of mottling in a subhorizon of the Bt or BC horizon Aragon soils contain fragments of chert, and have a cherty limestone C horizon. Bethlehem soils are moderately deep to weathered bedrock of sillimanite schist, phyllite schist, or mica schist. Braddock and Hayesville soils are mesic Cataula soils have a fragipan, Chestatee soils contain more than 15 percent, by volume, of coarse fragments throughout the pedon

Piedmont Series Key Upper 50 cm of Bt horizon has >35% clay Bt horizon has hue of 5YR or redder Upper part of Bt horizon has common mica flakes - Madison Bottom of Bt horizon with more than 35% clay is 45 to 75 cm below the surface – Pacolet Bottom of Bt horizon with more than 35% clay is more than 75 cm below the surface – Cecil