When a soil has a Textural Profile this means the subsoil has accumulated clay from above by leaching. This is called an illuvial clay zone or these soils have had clay translocated by water from the A and or E horizons into the B horizon.
This soil has a Bt horizon below the eluvial E horizon and based on the % clay increase from 8 to 35 has a very distinct textural profile. Generally a 3% increase is sufficient to be considered a textural profile.
Soils with an accumulation of clay or a B/E clay ratio greater than 1.2 have an argillic horizon ( the argillic horizon is a diagnostic subsurface horizon for Soil Taxonomy) and are said to have a textural profile.
Let's graph the textural profile for the soil in this photo. The percent
clay going down the profile would be 10, 8, 8, 12, 15, 25, 34, 40, 32, 25,
& 24. A graph of the % Clay from 0 to 100 cm is shown, note the clay bulge
at the Bt. This graph is visual description of the textural profile.
As you go down the profile at about 45 cm the clay content begins to increase until 90 cm is reached, where clay reaches a maximum. This zone of maximum clay accumulation is the Bt horizon. If the B/E clay ratio is > 1.2, the Bt horizon qualifies as an argillic horizon horizon .
Bt horizons have a larger number of smaller pores and fewer total pores than horizons above. This is significant for they will hold more water for plant growth than sandy horizons above. Bt horizons will also have a much slower water permeability than horizons above. Thus, Bt horizons may have saturated soils above them after heavy rains.
The hardwood forests of the central U.S. belong to the
Alfisol soil order. These soils occur in the
forested areas of Minnesota, Iowa, Illinois, Michigan, and Wisconsin. The
presence of a textural profile increases the nutrient retention capacity of the
soils, making them highly productive for crop production after forest removal.
A close-up of the Bt horizon shows that the clay has accumulated on the surface of the peds as glossy clay coatings. These coatings are known as clay skins and are proof that clay has moved from the E horizon into the Bt horizon. Clay migrates downward in water and is deposited on pore or channel walls when water is withdrawn into dry soil. Alternate wet and dry seasons favor argillic horizon formation. You will have a chance to see some clay films in the laboratory investigations under the microscope.
Sandy soils are noted for the rapid movement of water
due to the large pores that exist between sand grains. They also have low water
storage for plant growth. Some of the extensive sandy areas of Minnesota are
located on sandy outwash plains, for example the
Anoka
Sand Plain, which is just north of the Twin Cities.
Sandy soils do not have a textural profile and are in the soil order Entisols and Suborder Psammnents.
Another sandy profile is the USGA Putting Greens soil
mix. For information about constructing a putting green see
USGA GREEN SECTION - Construction
Review Chapter 1- Mechanical Analysis
Review Chapter 2- Texture by Feel
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