Soils

fine material covering the earth's surface composed of both mineral & organic material;  dirt

Soil formation & development happens by?

weathering

Soil profile

 the array of soil layers; their sequence from top (surface) to bottom (bedrock)

Soil horizon

 a distinct layer of soil within the soil profile

Soil Properties

Soil Formation

Components of Soil

 *Minerals

*Organic matter

*Water

*Air

Minerals

elements or compounds with a crystalline structure; the building-blocks of rocks; found in all soils
 

Organic matter

  that part originally from living matter; decaying matter of plants, animals & their waste products

Water

 fills spaces in the soil or forms a thin film around particles

Air

also fills pour spaces

Parent Material

the type of rock & minerals the soil was formed from

residual soil

made from the underlying rock

transported soil

made from material not found in underlying rock

Climate

if Temperature & precipitation (moisture) differ, will yield different soils, even from same parent material
 

Biological Agents

decomposers, microorganisms, bacteria, fungi, type of humus or organic matter
 

Topography

flat vs steep slopes;   windward vs leeward slopes;  sun exposure
 

Time

for a given place, more time means more complete development & increased thickness of soil
 

Factors involved in soil formation:

*Parent Material

*Climate

*Biological Agents

*Topography

*Time

What are the 4 development processes of soil horizons?

*Addition

*Transformation

*Depletion

*Translocation

Addition

grains of soil made by adding material to the soil already in place;  adding organic matter
 

Transformation

weathering of rock, minerals, & soil particles already present;  physically or chemically changing them
 

Depletion

particles are carried out of an area & downward thru soil by percolating water, the an area below
 

Translocation

deposition of particles in a lower area from an area above
 

Main Soil Horizons:

O, A, E, B, C, R

'O' horizon

organic horizon, consisting entirely of organic material

'A' horizon

upper most layer developed from parent material

'E' horizon

lighter colored layer just below the 'A' horizon

'B' horizon

created by translocation of particles from the 'A' & 'E' horizons above

'C' horizon

where the parent material is transformed by weathering into soil particles to become future soil

'R' horizon

where solid rock (bedrock) is first affected by weather

Solum

the 'A', 'E', & 'B' horizons; those layers in which plant roots are most active

*sol:  used as a suffix in soil classification

Pedon

column of soil, extending from the 'O' horizon into the 'C' horizon

*ped:  naturally occurring "clump" of soil

Soil texture is:

*size of the particles in the soil

*an indication of the soils compactness & amount of pore space

Largest to smallest:

Sand, silt, clay

Loam

a term used to describe a soil, similar to a clay or sand, but based on the percent of sand, silt, & clay and NOT on particle size

Field Capacity

ability of a soil to hold water against the downward pull of gravity

Sand=

=low field capacity

Clay=

=high field capacity

Soil structure does what?

*  the type or arrangement of a soils' peds;
also plays a role in determing a soils field capacity
 

Platy

layered peds, like flakes stacked horizontally

Prismatic

peds arranged in columns

Blocky or Angular

straight sided, irregularly shaped peds

Spheroidal or Granular

small, rounded shaped peds

 4 Basic Soil Structures

• Platy
• Prismatic
• Blocky or Angular
• Spheroidal or Granular

How many soil orders?

12

Entisols

soils of recent origin

Inceptisols

show the beginnings of a weakly developed

'B' horizon  

Vertisols

clay-rich soils which swell or shrink with moisture

Andisols

developed from volcanic ash

Histosols

water-saturated organic soils

Aridisols

dry soils found in most desert areas; salinization common

Mollisols

grassland soils of high agricultural value, such as under the Great Plains (US);  thick 'O' horizon

* very thick, sod houses made out of

Alfisols

moderately weathered deciduous forest soils; moist, highly mineral-rich soils

Spodosols

Utisols

warm, wet climate soils with a high clay content in the 'B' horizon, as found in the SE US
 

Oxisols

tropical areas with high rainfall;  rainforests; rich in FE & AL oxides; subject to laterization
 

Gelisols

cold & frozen soils subject to crytoturbation

(frost churning); found in high latitudes & elevations