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AGR 100 - Soil Science > Chapter 3 > Flashcards

Chapter 3 Flashcards

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1
Q

Material phase that in soil is mostly minerals and some humus

Roughly half of the soil volume

Gives nutrients and anchor to plants

A

Solid phase

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2
Q

Material phases in soil found between solid particles

Other half of soil volume

Ratio varies

A

Liquid and gas phases

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3
Q

Mineral particles classified by size

A

Soil separates

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4
Q

> 2 mm in diameter

A

Coarse earth

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5
Q

0.05 - 2.00 mm

A

Sand

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6
Q

0.002 - 0.05 mm

A

Silt

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7
Q

< 0.002 mm

A

Clay

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8
Q

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

A

Sand

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9
Q

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

A

Silt

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10
Q

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

A

Clay

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11
Q

< 0.0001 mm

A

Colloidal clay

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12
Q

How firm or coarse

General ratio of sand/silt/clay

A

Soil texture

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13
Q

Texture when soil is mostly sand

A

Coarse

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14
Q

Texture when soil is mostly clay

A

Fine

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15
Q

Texture of soil when it’s influenced by more than one soil separate

A

Medium

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16
Q

Instrument that suspends soil in water to measure the density of each separate

Determines ratio of sand/silt/clay

A

Hydrometer

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17
Q

Soil with balanced amount of all sand, silt, and clay

Roughly 20% clay, 40% silt, 40% sand

A

Loam

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18
Q

Arrangement of soil particles in an aggregate

A

Soil structure

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19
Q

Unit of soil structure

A

Aggregates/peds

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20
Q

The 5 types of soil structure

A

-granular
-platy
-blocky
-prismatic
-columnar

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21
Q

The properties that make clay and humus act like glue in soil structures

A

-small
-high in surface area
-have electrical charges

22
Q

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

A

Granular

23
Q

Aggregates are shaped like long, flat sheets that stack on top of each other

Restricts water percolation because of a lack of vertical pores

A

Platy structure

24
Q

Cube shaped aggregates

Decent water percolation

Sharp edges when clay heavy, rounded edges when not

Most common in humid forests

A

Blocky structure

25
Q

Variant of blocky structure with rounded edges

A

Subangular blocky structure

26
Q

Aggregates shaped like long verticals rectangular blocks

Mostly in subsoils with a lot of clay that periodically dry out

Common in grasslands

A

Prismatic structure

27
Q

Rounded variation of prismatic structure

Caused by too much sodium in soil

Restricts water percolation

Tops look like baking soda biscuits

A

Columnar structure

28
Q

Spaces in between particles of soil

A

Micropores

29
Q

Spaces in between aggregates

A

Macropores

30
Q

How resistant an aggregate is to breaking down or erosion

A

Bonding strength/stability

31
Q

The amount of volume taken up by pores in soil

A

Porosity

32
Q

Small pores _____ water

A

Retain

33
Q

Large pores ____ water

A

Drain

34
Q

Good soil structure has ~___% volume made of pores

A

50

35
Q

Tightness or looseness of soil

A

Density

36
Q

Density of a soil including both solid particles and the pore between them

A

Bulk density

37
Q

Density of a solid mineral

A

2.6 g/cm3

38
Q

General density of soil

A

1.3g/cm3

39
Q

Compacted layer of soil

A

Pan

40
Q

During growing season, CO2 ______ in soil because of _____, and O2 _____ in soil because of _____.

A

Increases, plant respiration
Decreases, plant absorption

41
Q

Describes how soil reacts to physical manipulation

A

Soil consistence

42
Q

Soil consistency evaluated when soil is dry

A

Hardness/softness

43
Q

Soil consistency evaluated when soil is moist

A

Flexibility/firmness

44
Q

Soil consistency evaluated when soil is wet

A

Stickiness

45
Q

Moisture content in soil when soil is rolled between a hand and glass and it crumbles

A

Plastic limit

46
Q

Moisture content in soil when soil starts flowing in a rounded dish after 25 drops

A

Liquid limit

47
Q

The difference between plastic limit and liquid limit

A

Plasticity index

48
Q

Color of soil that has oxidized iron that isn’t hydrated

A

Red

49
Q

Color of soil that has oxidized and hydrated iron.

A

Yellow

50
Q

Color of soil caused by chemical reduction of iron caused by wet conditions and a lack of oxygen

A

Gray

AGR 100 - Soil Science (3 decks)

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