12 Soil Orders

Entisols

• most limited soil development

• horizons are absENT

• ochric epipedon

Inceptisols

• minimal soil development (INCEPTion of soil development)

• ochric epipedon

• cambic Bw horizon

• variable productivity

• mountainous & arid regions

Histosols

• wetland soils

• high organic content

• water saturation; lack oxygen; slows down decomposers

• gleying (Bg)

• geographically widespread

• agriculture

Alfisols

• well developed

• moderately weathered & leached

• argillic/kandic or natric

• brown ochric or umbric epipedon

• forests

Ultisols

• highly leached with clay accumulation

• umbric epipedon & argillic

• low base saturation

• reddish color

• warm/humid climate

Vertisols

• shrinking & swelling of clays

• deep/wide cracks

• dry/wet seasons

• grasslands

Aridosols

• salt accumulation

• arid regions (low precipitation)

• poorly developed

• ochric epipedon

Mollisols

• highly fertile

• >50% cation saturation (nutrients)

• deep, dark A horizon (mollic)

• grasslands

Andisols

• volcanic ash deposit

• young soil

• melanic epipedon

• andic soil properties (glass, Al, Fe)

• can be highly productive

• Western MT

Gelisols

• permafrost

• minimal soil development

• mollic, histic, umbric

• high organic matter content

• low rates of chemical weathering

• limited productivity

• crytoturbation (freeze & thaw cycles churn & mix horizons)

Spodosols

• Sandy, acidic

• humus accumulation

• albic E horizon

• highly leached (light color)

• Al & Fe oxides (spodic horizon)

• cold, wet climates

Oxisols

• Most highly weathered

• low nutrient content

• oxic (Bo)

• yellowish-red

• humid, tropical climates

• limited productivity