12 Soil Orders In Depth

-semi arid to moist areas-weathering leaches clay minerals and other constituents into subsoil-formed primarily under forest or mixed vegetation-usually productive
-cool areas with moderate to high ppt-especially associated with volcanic PM-weathering generates minerals with little crystalline structure-high water and nutrient holding capacity-highly productive
-soils that are too dry for mesophytic plant growth-common in deserts-lack of moisture restricts weathering and limits development-accumulates gypsum, CaCO3, and other soluble materials
(polygenetic)-many environments-little to no pedogenic horizon development-recently deposited PM or erosion/deposition is faster than soil development
-higher latitudes and elevations-soils with permafrost or cryoturbation or ice segregation
-usually saturated year round (bogs and moors)-high content of O matter (peat or muck)-decomposed plant matter accumulates in water
-semi arid to humid areas-moderate degrees of soil weathering and development-wide range of characteristics in a wide variety of climates
-moderate to pronounced seasonal moisture deficit areas-dark colored surface horizon-relatively high O matter content-base rich throughout-characteristically form under grass in appropriate climates (Steppes)
-tropical and subtropical areas-highly weathered-dominated by low activity minerals (quartz, kaolinite, iron oxides)-indistinct horizons-low natural fertility and low capacity to retain additions
-humid areas-coarse-textured deposits under coniferous forests in humid regions-weathering processes strip O matter combined with Al (and sometimes Fe) from surfaces and deposit in subsoil-gray eluvial horizon and dark subsoil sometimes-tend to be acidic and infertile
-humid areas-fairly intense weathering and leaching resulting in clay-enriched subsoils dominated by minerals (i.

e. quartz, kaolinite and iron oxides)-typically acid soils, most nutrients in upper few inches-moderately low capacity to retain additions

-high content of expanding clay minerals-undergo pronounced volume changes with change in moisture-cracks that open and close, show movement in soil profile-swell when wet (transmit water slowly, little leaching)-high natural fertility