Exam 2
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What is soil texture?
The distribution of particles into different size classes less than 2 mm and then divided into sand, silt, and clay.
What particle is greater than 2 mm?
coarse fragment or gravel
How large are sand particles?
2-0.05 mm
How large are silt particles?
0.05-0.002 mm
How large are clay particles?
<0.002 mm
What makes a good ribbon?
A soil containing more than 40% clay is sticky enough to form a ribbon 2 inches long or longer.
What makes a fair ribbon?
A soil containing 27-40% clay is sticky enough to form a ribbon at least 1 inch long but not longer than 2 inches.
What makes no ribbon?
The ribbon formed by a soil containing less then 27% clay will be less than 1” long
What does a gritty soil texture tell you?
The individual particles are large enough that one can feel a significant number of particles in a moist soil sample.
What does a smooth or slippery soil texture tell you?
A soil high in silt will feel smooth (lacking the grittiness of sand) or slippery without feeling sticky (a property of clay).
What does a sticky soil texture tell you?
–The feel of a moist soil sample which contains significant amounts of clay. Stickiness of clay allows one to form a ribbon.
What is the hydrometer method?
Soil particles are dispersed with a sodium meta-phosphate and then agitated. The different soil particle will then settle at different speeds. Smaller particles settle slowly. Larger particles settle fast.
What soil separate has the largest surface area? a) Gravel b) Sand c) Silt d) Clay
d) clay
What soil separate would have a particle diameter of 0.2 mm? a) Gravel b) Sand c) Silt d) Clay
b) sand
What is the difference between soil texture and structure?
Texture refers to the sizes of the individual particles that make up the soil (i.e., sand, silt & clay). – Structure refers to how these particles may be stuck together to form crumbs or larger structures.
What is soil structure?
the shape that the soil takes based on its physical and chemical properties.
What is the name of soil aggregates (clumps) that are bound together?
Peds
How does soil structure develop?
Wetting and drying, burrowing of macroorganisms, and Growth of plant roots.
What soil structure is broken into individual particles that do not stick together. Commonly found in sandy soils and C horizons.
Single grained soil structure
What soil structure has no visible structure. Is hard to break apart, appears in very large clods, and is commonly found in the C horizon?
Massive soil structure
What soil structure is thin, flat plates of soil that lie horizontally, which are usually found in compacted soil?
Platy soil structure.
What soil structure has vertical columns of soil that have a salt “cap” at the top and found in soils of arid climates and generally in the subsoils (B-horizon).
Columnar soil structure
What soil horizon has vertical columns of soil that might be a few cm long and usually found in B-horizon.
Prismatic Soil structure
What soil structure has Irregular blocks that are usually 1.5 to 5.0 cm in diameter and commonly found in the B-horizon.
Blocky soil structure?