Talk:1938 USDA soil taxonomy

Raw material to use to expand article
ZONAL SOILS
 * PEDOCALS
 * LIGHT COLORED SOILS OF ARID REGIONS
 * DARK COLORED SOILS OF SEMIARID, SUBHUMID, AND HUMID GRASSLANDS
 * PEDALFERS
 * LIGHT COLOR PODZOLS OF FORESTS REGIONS
 * LATERITIC FOREST SOILS OF THE TROPICS

INTRAZONAL SOILS
 * HALOMORPHIC SOILS OF IMPERFECTLY DRAINED ARID REGIONS
 * HYDROMORPHIC SOILS OF SWAMPS & MARSHES

AZONAL
 * NO SUBORDERS

(simple information about class systems)

Zonal soils
These mature soils form were the land surface and climate have been stable. They have defined soil horizons and developed soil profiles. Zonal soils are divided into 8 sub-types: tundra, podzols, brown earths, chernozems (prairie and chestnut), Mediterranean, red yellow desert, ferruginous and ferrallitic.

Intrazonal soils
These soils are influenced by parent material rock type, drainage or other factor, to a degree that prevents the development of a zonal or azonal soil. There are 3 major sub-types, 2 of which have 2 further sub-types each.


 * Calcimorphic or calcareous soils develop from a limestone. It has two sub-types:
 * Rendzina Thin soil with limited available water capacity.
 * Terra Rossa Deep red soil associated with higher rainfall than Rendzina.
 * Hydromorphic soils form in wetland conditions. There are two sub-types:
 * Gley soils - These occur when the pore spaces between the grains become saturated with water and contain no air. This lack of oxygen leads to anaerobic conditions which reduce the iron in the parent rock. This gives the soil a characteristic grey/blue colour with flecks of red.
 * Peat Forms under circumstances that prevent the break down of vegetation completely.
 * Halomorphic soils form due to soil salination.

Azonal soils
These young soils form where the land surface and climate have been unstable. Their characteristics are highly dependent on parent rock and mode of deposition. They have poorly developed soil profiles. Typical sub-types include: scree, alluvium, till, sands and gravels, desert and marine sand dune, salt marsh and volcanic/tectonic.