Introductory Soil Science Review

Comprehensive vocabulary flashcards covering soil components, horizon classification, formation factors, chemical weathering, and physical properties based on Chapters 1, 2, and 4.

Mineral Soils

Soils predominantly composed of inorganic components such as quartz, feldspar, and biotite, making up approximately $45\%$ of the soil volume.

Sand

The largest soil particle size class, ranging from $0.05$ to $2.0\,mm$, which is gritty to the touch and visible to the eye.

Silt

A soil particle size class ranging from $0.002$ to $0.05\,mm$, characterized by a smooth or silky feel.

Clay

The smallest soil particle size class ($< 0.002\,mm$) which has a large surface area and high capacity to retain water and nutrients.

Soil Organic Matter (SOM)

Living organisms and plant/animal residues representing about $5\%$ of soil volume but having the largest impact on soil functions such as aggregation and water holding capacity.

Soil Air

The gaseous component of soil ($25\%$) which typically contains more $CO_2$, more water vapor, and less $O_2$ than the atmosphere.

CLORPT

An acronym representing the five soil-forming factors: Climate, Organisms, Relief (topography), Parent material, and Time.

Soil Profile

A $2D$ vertical section of soil showing its various horizons extending down to the parental material.

Regolith

The layer of unconsolidated debris and partially weathered rock that overlays the solid bedrock.

Solum

The active part of the soil above the C horizon, specifically the O, A, E, and B horizons, which are affected by climate and biota.

Pedon

The smallest $3D$ unit of soil that contains all the horizons of a particular soil type.

O Horizon

The organic layer at the soil surface consisting of leaf litter and humus.

A Horizon

Commonly known as topsoil; it is a mineral horizon darkened by the accumulation of organic matter.

E Horizon

The elution or leaching layer where clay, iron, and aluminum oxides have been washed out, leaving a concentration of resistant minerals.

B Horizon

Known as subsoil or the zone of illuviation, where minerals and metal salts from upper layers accumulate.

C Horizon

The layer of unconsolidated parent material that is least affected by soil-forming processes and lacks the properties of the horizons above it.

Macronutrients

Essential elements used by plants in relatively large amounts ($> 0.1\%$ of dry plant tissue), including $C$, $H$, $O$, $Ca$, $Mg$, $N$, $K$, $P$, and $S$.

Micronutrients

Essential elements used by plants in relatively small amounts ($< 0.1\%$ of dry plant tissue), including $Fe$, $Cu$, $Mn$, $Ni$, $Zn$, $B$, $Cl$, and $Mo$.

Hydrolysis

A chemical weathering process involving the separation of water into $OH^{-}$ and $H^{+}$ at a mineral surface, often releasing a nutrient cation.

Oxidation-Reduction (Redox)

Chemical reactions involving electron transfer; oxidation is the loss of an electron, while reduction is the gain of an electron.

Primary Minerals

Minerals that have not been chemically altered since their formation from molten lava, such as quartz, mica, and feldspar.

Secondary Minerals

Minerals formed from the weathering of primary minerals, such as silicate clays and iron oxides.

Catena

A group of soils that commonly occur together in a landscape sequence.

Toposequence

A specific type of catena where the differences in soil development are primarily influenced by topography.

Residuum

Parent material that develops in place from the underlying rock rather than being transported.

Colluvium

Parent material transported down slopes by the force of gravity, often consisting of poorly sorted rock fragments.

Alluvium

Parent material transported and deposited by flowing water in floodplains, fans, or deltas.

Eolian

Parent material transported and deposited by wind, including dune sand, loess, and aerosolic dust.

Stoke's Law

The principle stating that the larger the soil particle, the faster it falls when suspended in water.

Munsell Color Chart

A system used to describe soil color based on three variables: Hue (dominant spectral color), Value (lightness or darkness), and Chroma (color intensity or purity).

Eluviation

The process of leaching or translocation of silicate clays, iron, and aluminum oxides out of an upper soil horizon.

Illuviation

The accumulation or deposition of leached materials in a lower soil horizon, typically the B horizon.