Soils Flashcards
Soil
Organic and inorganic material located above bedrock and capable of supporting life.
Residual material
Stays in place. (Inorganic part)
Transported material
Weathered elsewhere and deposited.
Decomposer
Bacteria, fungi, worms, insects.. convert dead tissue to humus.
Humus
Stable and able to hold nutrients.
Texture
Combination of particle sizes.
Clay soils (smallest), silty soils (intermediate), sandy soils (largest).
Loamy soils are all mixed together.
Texture important in water holding.
Cation exchange capacity
Ability of soil to hold onto nutrients; measure of fertility (effected by clay and humus content).
Soil pH
Measure of acidity and alkalinity.
Soil horizons
Many soils develop distinct horizons.
O layer
Surface covered by organic material (decomposed and undecomposed).
A layer
Mix of organic and mineral material; most fertile part of soils (topsoil).
E layer
Soluble minerals leached out (zone of eluviation).
B layer
Most leached material accumulates in this layer (zone of illuviation).
C layer
Weathered bedrock.
Bedrock (D or R layer)
Base layer.
Leaching
Water carries soluble materials lower in soil.
Effects
Topography (steep slopes have much erosion, so little soil development/poor drainage).
Climate is most important.
Parent material: what minerals are available?
Vegetation: adds organic matter, may affect pH.
Time
Podzolization
Coniferous forests in humid mid latitudes.
Heavy leaching, so mostly silica in A layer.
Calcification
Dry regions; soluble minerals leached short distance and deposited.
Salinization
Desert soils with much salt.
Salts accumulate on surface when water evaporates.
Laterization
Tropical areas with very high rainfall; extreme leaching leaves soil of quartz, iron, and aluminum.
Gleization
Poorly drained soils accumulate organic matter (peat).
