Clays

Soil texture

The relative proportion of sand, silt, and clay in a soil.

Clay

Particles smaller than 0.002 mm that play a significant role in soil properties.

Silt

Soil particles ranging from 0.002 mm to 0.05 mm in size.

Sand

Soil particles ranging from 0.05 mm to 2 mm in size.

Physical weathering

The mechanical breakdown of rocks into smaller particles without changing their chemical composition.

Chemical weathering

The alteration of the chemical composition of rocks and minerals through chemical reactions, often involving water and acids.

Colloid

Very small particles (less than 1-2 µm) that remain suspended in water.

Crystalline silicate clays

Layered silicate clays with defined morphology, including types like smectite and kaolinite.

Amorphous silicate clays

Non-crystalline silicate clays such as allophane and imogolite.

Oxides of Fe and Al

Metal oxides that may occur as crystalline or amorphous layers and influence soil properties.

Cation exchange

The ability of soil particles to hold onto cations (positively charged ions) and exchange them with those in the soil solution.

Isomorphic substitution

A process where a cation in a clay mineral is replaced by another cation of similar size and charge without altering the mineral structure.

Surface charge

The charge at the surface of colloids, which can be permanent or variable depending on pH and chemical environment.

Oxisols

Soil order characterized by high concentrations of iron and aluminum oxides, typically found in highly weathered settings.

Kaolinite

A clay mineral that is a product of the weathering of feldspar and is significant in soil composition.

Weathering products

Materials released during the weathering process that can be synthesized into new soil components or contribute to soil fertility.

Soil parent material

The unconsolidated material from which soil develops, influencing its properties and composition.

Aggregate

The clumping of soil particles which affects porosity, drainage, and aeration in the soil.

Freeze/thaw cycles

Weathering processes caused by the repeated freezing and thawing of water in soil that lead to the breakdown of minerals.

Siltation

The process of sediment accumulation that can alter soil texture and affect water retention.

Heavy metals in soil

Metallic elements that can be toxic in high concentrations and are influenced by soil composition and weathering processes.

Soil solution

The liquid phase of soil that contains dissolved ions, essential for plant nutrient uptake.