Soil Architecture and Physical Properties

Brown and red colors in subsurface horizons are caused by ________ in the soil.

iron oxides

A sticky, putty-like feel indicates a high percentage of which soil separate?

 

clay

Which type of soil structure is typically found in surface soil (A horizons)?

granular

Which type of structure is typically found in sodium-rich (Na) sub-surface horizons?

columnar

If a dry soil high in certain types of ________ is moistened, it is likely to swell up with enough force to crack pavements and building foundations.

clay

Using a textural triangle chart, it can be determined that a soil with 45% sand and 20% clay belongs to the ________ textural class.

loam

A landscaping contractor wants to change the texture of a silt loam soil to meet the specifications for a loam. S/he would most likely do so by adding ________ to the soil and mixing it well.

sand

In many soil profiles, the subsoil is high in clay, but is also quite permeable to percolating water. Why?

Prismatic structure may be well developed.

Practices that add organic matter and reduce tillage can be expected to most significantly increase the ________ in a soil.

macropores

Dull gray colors are characterized by ________.

low chromas

Fungal hyphae have an important influence on soil structure because they ________.

stabilize macro aggregates

Flocculation is the process by which certain chemicals in the soil stabilize large soil aggregates. (T/F)

False

Texture describes the ________ of particles in a soil.

sizes

Colloidal properties are exhibited by the ________ fraction of soils.

clay

Because of their greater surface area per unit of soil mass, silt loams soils generally have a greater capacity than loamy sand soils to ________.

all of these properties

What does the hue of the soil color indicate?

how red the soil is: a hue of 2.5 means the color is 2.5 parts yellow to 1 part red

_________ are typical for the colors of poorly drained (anoxic) mineral soils.

low chromas