Soils: Physical Properties & Water Relations

Flashcards on soil physical properties, water relations and terminology.

Soil

A mixture of living and non-living components including mineral particles, organic matter, water, and gases; a living habitat for plants and organisms, typically darker in color.

Mineralization

Return of organic nutrients to inorganic form by decomposers in the soil.

Edaphic Relationships

Vegetation-soil relationships that are often strongly correlated and form the basis for soil classification.

Weathering

A process involving the chemical and physical breakdown of rocks, influencing soil development.

Humus

Partially decomposed organic matter in the soil.

Eluviation

The leaching of material by water from the topsoil (A horizon).

Illuviation

The deposition of materials in the subsoil (B horizon).

Loess

Fine, wind-blown clay, common in grassland soil development.

Mollisol

Soft soils of grasslands; thick, fertile, dark organic horizon.

Ultisol

Intensely weathered soils of humid climates; acidic with substantial clay translocation.

Soil Order

The most inclusive and broadest category in soil taxonomy, with 12 orders worldwide.

Gravel

Soil particle size >2 mm in diameter.

Sand

Soil particle size 0.05-2 mm in diameter.

Silt

Soil particle size 0.002-0.05 mm in diameter.

Clay

Soil particle size <0.002 mm in diameter.

Texture

Particle size distribution in soil.

Gravimetric Moisture

Soil moisture content measured as mass H2O/mass dry soil.

Volumetric Moisture

Soil moisture content measured as vol H2O/vol soil.

Bulk Density

Mass soil/volume soil.

Field Capacity (FC)

Water content after drainage by gravity; maximum water holding capacity.

Permanent Wilting Point (PWP)

Water left in soil when plants wilt permanently; lower limit of available water.

Available Water

FC - PWP (the amount of water plants can access).

Matric Potential (Ψm)

A component of soil water potential related to the attraction of water to soil particles.

Osmotic Potential (Ψπ)

A component of soil water potential, particularly important in saline soils.

Pressure Potential (Ψp)

A component of soil water potential, usually minimal in well-drained soils.

Hydraulic Conductivity (K)

Measure of the soil's ability to transmit water.

Hydraulic Redistribution

Process where plants can move water from wetter to drier soil layers.