Soil Texture Flashcards
What are the classes of particle in soil texture? Give sizes.
Sand 2.0mm - 0.06mm
Silt 0.06mm - 0.002mm
Clay 0.002mm and smaller
Explain the different types of weathering that create soil.
Chemical - rainwater and carbon dioxide create carbonic acid
Physical - wind and water erosion. Freeze and thaw breaks up rock.
Biological - plant roots penetrate rock cavities and expand. Plants create CO2 through respiration which combines with rainwater to form carbonic acid.
Describe the different layers that form soil.
O horizon - surface soil
A horizon - topsoil
B horizon - subsoil
C horizon - partially broken down parent rock
Parent rock
How do you identify a clay soil, and what are its characteristics?
Clay soil will roll into a sausage in the hands and bend in a circle.
It is heavy to work, sticky in winter and hard in summer.
It has a high cation exchange capacity.
It is prone to compaction and structural damage if worked when wet. It is slow to drain and warm up in spring, and poorly aerated.
How do you identify a sandy soil, and what are its characteristics?
Sandy soils will feel gritty, and sandy loam may roll into a sausage but won’t bend.
Inert, free draining, well aerated, quick to warm and cool, easily leached of nutrients.
Easy to work.
How do you identify a silty soil and what are its characteristics?
Usually occur in alluvial valleys.
Behave like sandy soil but have a small CEC.
prone to surface capping.
Give the proportions of ingredients in a perfect loam.
50% sand, 30% silt, 20% clay
