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SOIL COMPOSITION
TYPES OF SOILS BASED ON COMPOSITION

A) Organic soil - contain 20% or more organic matter

     2 types
     1) peat soil - contains greater than 65% organic matter

     2) muck soil - contains 20-65% organic matter
 
 

B) Mineral soil (field soil) - contains less than 20% organic matter.

     4 Major Components (in a well watered, but well drained loam soil)

     1) air- approximately 25% of volume; in larger pores

     2) water - approximately 25% of volume; in smaller pores

     3) mineral particles - 44-49% of volume
 

Mineral Particle
Size
sand
0.05-2 mm
silt
0.002-0.05 mm
 clay
 <0.002 mm
 
    4) organic matter - typically about 1% in nature

         litter - partially decayed organic matter on the soil surface. 

         humus - highly decomposed, fine, amorphous organic matter in the soil.

         Functions of Organic Matter:
         1) stabilizes soil structure
         2) increases water retention and availability
         3) increases drainage and aeration
         4) increases cation exchange capacity
         5) supplies nutrients upon decay (only if low C:N ratio)
         6) stabilizes pH
 7) food source for microorganisms