Soil Properties and Formation

These flashcards cover key vocabulary related to soil properties, formation, texture, and their implications for agriculture and ecology.

A-horizon

The surface or top soil layer that is less compacted, with more sand and silt, darker in color due to more organic matter.

B-horizon

The subsurface or sub soil layer that is more compacted, contains more clay, lighter in color with less organic matter.

Field capacity (FC)

The percentage of water remaining in soil after gravitational water has drained, indicative of the soil’s ability to retain water.

Permanent wilting point (PWP)

The soil moisture content at which plants wilt and cannot regain turgor overnight, usually at tensions of -15 to -30 bars.

Infiltration

The process of water moving into and through the soil layers, influenced by soil texture and aggregation.

Organic matter additions

Applying dead plant and animal materials to soil to increase porosity, nutrients, and soil structure.

Matric potential (Ψm)

The measure of the energy status of water in soil relative to the solid phase, affecting water retention.

Soil colloids

Small particles in soil that possess a high surface area and charge, critical for nutrient and water retention.

Cation exchange capacity (CEC)

The ability of soil to hold and exchange positively charged ions, crucial for soil fertility.

Isomorphic substitution

The process in which one cation in a mineral is replaced by another cation of similar size and charge, affecting soil charge characteristics.

Mollic epipedon

A diagnostic surface horizon characterized by a thick, dark layer rich in organic matter, typically found in grassland soils.

Histic epipedon

A diagnostic layer composed of organic materials, typically found in wetlands.

Argillic horizon

A subsurface soil layer enriched with clay, indicative of translocation processes in soil formation.

Entisol

A very young soil with little to no diagnostic horizons, often having an ochric epipedon.

Mollisol

A soil type with a mollic epipedon, typically found in semi-arid to sub-humid grasslands.

Oxisol

Soils that are highly weathered, typically found in tropical regions, and characterized by an oxic horizon.

C:N ratio

The ratio of carbon to nitrogen in organic matter, influencing decomposition rates and nutrient availability.

Decomposers

Organisms that break down dead organic matter, facilitating nutrient cycling in ecosystems.