soil orders

Entisols

ENT

• recent-little, if any, profile development, baby soils

• A over C

• fertile floodplain soils, thin mountain soils, sandy dune soils

Inceptisols

EPT

• few diagnostic features: inception of the B horizon

• often A, Bw, C

• 2nd youngest, slightly more developed than entisols

• common in mountain areas + floodplains

Vertisols

ERT

• shrink-swell clays, cracks

• deep wide cracks open during dry periods cause mixing

• poor infiltration when wet

Mollisols

OLL

• dark, soft grassland soils

• accumulation of Ca-rich org matter (mollic epipedons)

• rich in cations, non-acidic, may have carbonates at depth

• among the worlds most productive soils

Gelisols

EL

• permafrost and/or frost churning (cryoturbation)

• little profile development (too cold)

• often OM accumulation (cold = slow decomp)

Histosols

IST

• organic soils

• little profile development because anaerobic

• main process = accumulation of partially decomposed OM

• common in wetlands

• O horizons

Andisols

AND

• volcanic ash soils = unique properties

• rapid weathering creates amorphous or poorly crystalline silicate minerals (can rapidly accumulate OM)

• little leaching or other profile development

• young, light, fluffy soils (highly fertile except strongly bind to P)

Aridisols

ID

• dry soils (with B horizons)

• low leaching, high evaporation, limited moisture

• may have clay accumulation

• may accumulate carbonate, gypsum, soluble salts, sodium (can become carbonate cemented)

Alfisols

ALF

• clay accumulation, moderately weathered (Bt horizons)

• often in forests, CA grasslands

• more weathered than all except spodosols, ultisols, and oxisols

• often very fertile, non-acidic

Spodosols

OD

• acid, sandy, forest soils, highly leached

• E horizon, bright white

• spodic horizon = subsurface accumulation of illuvial organic matter + Al/Fe oxides(dark)

• cool, moist climates

• very acidic + infertile

Ultisols

ULT

• clay accumulation, highly weathered

• highly leached

• accumulation of Fe oxides (red)

• moderately fertile

Oxisols

OX

• clay accumulation, oxides, most weathered

• usually wet climates (tropical rainforests

• weathering + intense leaching = some quartz, certain clays, but mostly Fe and Al oxides (may be weathered to 20m or more)

• low nutrient retention, moderately acidic