Chapter 3 Flashcards
Material phase that in soil is mostly minerals and some humus
Roughly half of the soil volume
Gives nutrients and anchor to plants
Solid phase
Material phases in soil found between solid particles
Other half of soil volume
Ratio varies
Liquid and gas phases
Mineral particles classified by size
Soil separates
> 2 mm in diameter
Coarse earth
0.05 - 2.00 mm
Sand
0.002 - 0.05 mm
Silt
< 0.002 mm
Clay
Provides framework and stability in soil mixture
Easily eroded on its own
Mostly quartz (resistant to breakdown)
Small amount of nutritious minerals (ex. feldspar)
Mostly spherical grains, angularity depends on amount of rolling in water
Sand
Too small to see grains with naked eye
Smooth feel, not sticky
Suspended in fast flowing water, drops in slow flowing
Wind carries it when disturbed by sand
Spherical grains
Majority of parent material in loess
Similar minerals as sand
Silt
Very fine
High surface area on grains per volume
Made of secondary minerals derived from original rock by drastic alteration or recrystallization of weathered products
Flat plate-like shaped grains
Differentiated by arrangement of chemical elements
Clay
< 0.0001 mm
Colloidal clay
How firm or coarse
General ratio of sand/silt/clay
Soil texture
Texture when soil is mostly sand
Coarse
Texture when soil is mostly clay
Fine
Texture of soil when it’s influenced by more than one soil separate
Medium
Instrument that suspends soil in water to measure the density of each separate
Determines ratio of sand/silt/clay
Hydrometer
Soil with balanced amount of all sand, silt, and clay
Roughly 20% clay, 40% silt, 40% sand
Loam
Arrangement of soil particles in an aggregate
Soil structure
Unit of soil structure
Aggregates/peds
The 5 types of soil structure
-granular
-platy
-blocky
-prismatic
-columnar
The properties that make clay and humus act like glue in soil structures
-small
-high in surface area
-have electrical charges
Aggregates are mostly spherical
Generally porous, crumb-like texture
Acts like a sponge
Found commonly in dark surface soil
Some clay and plenty of humus
Ideal structure for farming
Granular
Aggregates are shaped like long, flat sheets that stack on top of each other
Restricts water percolation because of a lack of vertical pores
Platy structure
Cube shaped aggregates
Decent water percolation
Sharp edges when clay heavy, rounded edges when not
Most common in humid forests
Blocky structure
Variant of blocky structure with rounded edges
Subangular blocky structure
Aggregates shaped like long verticals rectangular blocks
Mostly in subsoils with a lot of clay that periodically dry out
Common in grasslands
Prismatic structure
Rounded variation of prismatic structure
Caused by too much sodium in soil
Restricts water percolation
Tops look like baking soda biscuits
Columnar structure
Spaces in between particles of soil
Micropores
Spaces in between aggregates
Macropores
How resistant an aggregate is to breaking down or erosion
Bonding strength/stability
The amount of volume taken up by pores in soil
Porosity
Small pores _____ water
Retain
Large pores ____ water
Drain
Good soil structure has ~___% volume made of pores
50
Tightness or looseness of soil
Density
Density of a soil including both solid particles and the pore between them
Bulk density
Density of a solid mineral
2.6 g/cm3
General density of soil
1.3g/cm3
Compacted layer of soil
Pan
During growing season, CO2 ______ in soil because of _____, and O2 _____ in soil because of _____.
Increases, plant respiration
Decreases, plant absorption
Describes how soil reacts to physical manipulation
Soil consistence
Soil consistency evaluated when soil is dry
Hardness/softness
Soil consistency evaluated when soil is moist
Flexibility/firmness
Soil consistency evaluated when soil is wet
Stickiness
Moisture content in soil when soil is rolled between a hand and glass and it crumbles
Plastic limit
Moisture content in soil when soil starts flowing in a rounded dish after 25 drops
Liquid limit
The difference between plastic limit and liquid limit
Plasticity index
Color of soil that has oxidized iron that isn’t hydrated
Red
Color of soil that has oxidized and hydrated iron.
Yellow
Color of soil caused by chemical reduction of iron caused by wet conditions and a lack of oxygen
Gray
