VOCABULARY: soil; weathering; non-renewable resource; renewable resource; humus; residual; transported; ground water; parent material; climate; topography; organisms; chronological factors; texture; clay; sand; silt; gravel; loam; structure; ped; acidic; alkaline; color; profile; horizon; eluviation; illuviation; leaching; solum; regolith; pedogenic regimes; laterization; podzolization; calcification; caliche; salinization; Great Soil Groups; zonal; pedalfer; pedocal; azonal; alluvium; intrazonal; United States Comprehensive Soil Classification System; Seventh Approximation; generic; genetic; soil orders; entisol; inceptisol; aridisol; mollisol; spodosol; alfisol; ultisol; oxisol; vertisol; histosol

soil--end product of weathering--breakdown of existing surface and near surface materials by natural processes

composed of fine rock particles and organic matter; contains gasses and liquids
formed by organic and inorganic processes
partially decomposed organic matter--humus
soil is well developed where water and vegetation plentiful

permeability--rate at which water passes through a porous material like soil
porosity--amount of space between grains in a rock

ground water--the water contained in the ground and moving through it
usually ground water sinks until a solid or impermeable layer, backs up above it, becomes saturated, forms the water table

water may flow within the permeable layer

Ground Water and the water table
 

factors which influence soil development
• 1) parent material--bedrock from which it forms, same different soil; same soil different rock; residual soils or transported soils
• 2) climate--very important, controls vegetation type, chemical reactions, weathering and erosion
• 3) site [topography, land surface configuration]--influences texture and depth, flow water etc.
• 4) organic activity (biological factors)
• 5) time (chronological factors)--non-renewable resource 1' in 10,000 years

classified by 5 properties
• 1) texture--size distribution of mineral particles

% of fine--clay, med.-silt, large-sand, very large-gravel, LOAM-mixture
• 2) structure--shape and size of peds-clumps, plate-like, granular, block, prismatic
• 3) chemistry--is it acidic or alkaline; (how many colloids--chemically active soil particles; influence water retention; greater the colloidal content, the greater inherent fertility)
• 4) color--function of amount and state of iron and organic matter
• 5) profile--layers of development, well developed 5 horizons


O undecomposed plant debris

A zone of eluviation or zone of depletion--material is translocated to lower levels, leaching

B zone of illuviation or zone of accumulation, rich with minerals and organic matter from above, more compact, lighter in color

(A and B together--SOLUM)

C weathered rock

R unweathered broken bedrock [D]

beneath is the solid rock of the crust, the bedrock

5 pedogenic (soil-forming) regimes--correlate with climate
• laterization--tropics--leaching of silica; maximum chemical weathering; nonsoluable oxides (like iron) collect; reddish color, coarse texture, porous; produces latosols
• podzolization--cool humid--eluviation of iron by acidic soil moisture, does not affect silica; ash gray color
• calcification--semiarid--calcium carbonate accumulates in B horizon by water evaporation--caliche
• salinization-arid--accumulation of salts near surface through evaporation
• gleization--waterlogged--oxygen poor condition limits bacterial action and reduces iron to ferrous state
2 ways to classify soils

Great Soil Groups -- 1938 -- environment and genesis, amount of adjustment to climate and vegetation--genetic

• zonal--good horizons climate and vegetation yes

pedalfers--enriched with aluminum and iron, leached forests
pedocals--semiarid, calcium carbonate concentration
 
• azonal--not typical profile not equilibrium with climate like volcanic ash, not yet; immature; alluvium--deposition from running water
• intrazonal--nonclimatic--drainage, parent material; something else
U.S. Comprehensive Soil Classification System--Seventh Approximation -- 1960 -- properties or qualities of soil--generic; 10 general soil orders

order, new system meaning of name traditional system equivalent
 

entisol	recent soil	azonal soil & some gley soils
inceptisol	young soil	some brown forest soils & gley
aridisol	arid soil	mainly red & gray desert soils
mollisol	soft soil	mainly Chernozem, Prairie, Chestnut and Brown soils
spodosol	ashy soil	podzols
alfisol	pedalfer soil	gray-brown podzol, prairie soils, weak Chernozems, some intrazonal
ultisol	ultimate soil	red-yellow podzolic, reddish-brown lateric, and some intrazonal
oxisol	oxide soil	latosols
vertisol	inverted soil	no equivalent
histosol	organic (tissue)	intrazonal bog soils
andisol	volcanic ash	young soils from weathering of volcanic parent materials
gelisol	frozen	soils with top mixed by freeze/thaw processes

Soil descriptions
 

• entisols--recent origin

geomorphically active or recently active environments
(floodplains, mountain slopes, sand dunes)
horizons weak to none

any bioclimatic region

• inceptisols--horizons just beginning

weak eluviation and illuviation
all climatic zones, Arctic tundra

volcanic ash in tropics; alluvium, tundra 

• aridisols--arid lands

eluviation weak and shallow
low organic content; highly alkaline
CaCO₃ accumulates near surface to form a calcic horizon; caliche old system

about 1/5 surface of earth; Sahara; southwestern United States; central Asia; southern Australia

• mollisols--boarders aridisols, (soft soils)--grass cover, substantial organic buildup

not enough moisture for strong leaching; subhumid and semiarid so bases build up (calcium)
among best agriculturally

Great Plains, Pampas of Argentina, Kirgiz Steppe

• spodosols-(ashy soils)--strong horizons, zone of illuviation made of colloids, iron and aluminum

humid continental and subarctic climate, sandy parent material
strong eluviation
A horizon may be ashy gray
acidic (podzols)

northern Great Lakes, Leningrad area

• alfisols--moist versions of mollisols, humid continental , mid-latitudes, and mediterranean, less acidic than spodosols

under tree covers, bases are leached out replaced from organic layer
illuviation characterized by clay accumulation

Sahel; South Africa; Moscow east; eastern "corn belt" of the United States

• ultisols-(ultimate)-warm humid tropical climate, advanced state of development

positive moisture balance at least part of year
pronounced leaching
few bases but abundant aluminum
red and yellow color from iron and aluminum oxides
trees recycle nutrients

southeastern United States; southeastern China

• oxisols-warm humid tropical climate, also advanced, long stable environment

heavy rainfall, prolonged leaching
no reserve of bases
nutrients from vegetation, rainforest, savanna, woodland
illuviation--concentrations of clay, iron, aluminum oxic (laterite) horizon
end product of laterization

Brazil; central Africa

• vertisols-(inverted)--poor horizons; clay montmorillonite, expansion and contraction with wetting and drying

slough into cracks, cracks close invert soil--equatorial, subtropical, and tropical savanna
dark color

Australia, India, East Africa

• histosols--organic soils--saturated all or part of year

characteristics depend on nature of vegetation
where organic matter accumulates

local poorly drained areas, Scandinavia, Canada, Scotland

• andisols--volcanic soils--weathered volcanic ash

fertile
where volcanic ash has fallen

Philippines, West Indies, Indonesia, Pacific Northwest of the U.S.

• gelisols--frozen soils--permafrost

subsoil remains frozen
surface defrosts and freeze/thaw cycle churns up the soil
water saturated when defrosting of the surface occurs


northern Alaska, northern Canada, Siberia

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