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Soil Fertility > Physical Properties > Flashcards

Physical Properties Flashcards

1
Q

What is soil?

A

45% Mineral Matter
5% Organic Matter
25% Air
25% Water

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2
Q

Weathering

A

Breakdown of parent material (rock) into smaller pieces

2 types: chemical and physical

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3
Q

Physical weathering

A

Mica loses K+ and turns to vermiculite which loses more K+ and becomes smectite (montmorilinite being the most important smectite)

feldspars lose K+ and become kaolinite( a low CEC clay mineral)

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4
Q

Decomposition: Organic material to inorganic

A

biological process that includes physical breakdown and biochemical transformation of complex organic molecules of dead material into simpler organic and inorganic molecules

(C6H10O5)n+ O + F&B–> CO2 +H2O + Heat

Contributes to carbon cycling

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5
Q

Factors controlling rates of decomposition

A

Environment Factors:
Aeration, Temperature, Soil Moisture, Soil pH

Quality of added residues:

  1. Size of organic residues
  2. C/N of organic residues
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6
Q

Rate of decomposition of plant residue

A

in order from fastest to slowest decomposition rates:

  1. Sugars, starches, simple proteins
  2. Hemicellulose
  3. Cellulose
  4. Fats, waxes, oils, resins
  5. Lignin, phenolic compounds
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7
Q

Soil Texture:

A

Describes the proportion of soil particle sizes: Sand, Silt, Clay

influences other traits such as: Water holding capacity, Aeration

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8
Q

Effect of particle size

A

Smaller particles larger internal surface area

Small particles= many small pores (more pores= micropores)

Large particles= larger pores but fewer in number (Larger pores= macropores)

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9
Q

Soil Separates

A

Sand: 2.00-0.05mm
Silt: 0.05-0.002mm
Clay: <0.002mm

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10
Q

Textural Classification

A

12 Textural Classes, Textural Triangle

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11
Q

Soil Density and Permeability

A

Density: Mass per volume D=M/V

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12
Q

Two densities in Soil

A 
Particle Density (PD)
Bulk Density (BD)
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13
Q

Particle Density

A

PD average soils ~2.65 gm/cu cum

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14
Q

Bulk Density

A

BD average range from 1.0-1.8 gm/cu cm

Depends on amount of pore space
BD= wt.dry soil/ vol. dry soil = g/cu cm

eg. BD= 650g/500 cu cm= 1.3 g/cu cm

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15
Q

Soil Porosity

A

Usually expressed as a percentage

2 ways to determine porosity:

  1. Calculate ratio water volume to total core volume
  2. Calculate from bulk density and particle density
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16
Q

Soil Porosity examples

A

Water Volume to Core Volume

porosity= wet weight (g)-dry weight (g)/ soil volume (cu cm) * 100%

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17
Q

Soil Porosity ex

A

An oven-dry soil core, volume 500 cu cm, weighs 650g. When wet, it weighs 900g. Find its % porosity

Porosity= 900g-650g/500 cu cm *100%= 250g/500 cu cm * 100 = 50%

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18
Q

Bulk Density to Particle Density

A

Defines the percentage of the soil that is solid matter.
The percent solid matter is subtracted from 100% to give percent porosity:

Porosity= 100% - (BD/PD * 100%)

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19
Q

soil porosity ex.

A

an undisturbed oven-dry soil, BD of 1.3 g/cu cm, consists of average mineral composition (PD 2.65 g/cu cm) Find its % Porosity:

Porosity=100% - (1.3 g/cu cm /2.65 g/cu cm *100%)

Porosity=100% - (0.49 *100%) = 100%-49%=51%

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20
Q

What has greater porosity, Sand or Clay?

A

Clay at about 50%; sand is lower at about 30%

Why? clay has more surface ware and smaller particles so has more pores

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21
Q

Permeability

A

the ease with which air, water, and roots move through soil

depends on number, size, and continuity of pores

liken to a maze

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22
Q

Fine-textured soils would be impermeable if not for

A

Soil structure

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23
Q

Structure: def

A

the way soil particles clump together into large units called aggregate or peds

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24
Q

Examples of soil structure

A

Granular, Platy, Wedge, Blocky (Subangular or Angular) Prismatic, Columnar

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25
Q

Structure and texture

A

structure can alter the effects of texture

e.g. a fine-textured silty clay with good structure can be permeable

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26
Q

Structure is classified by three groups of traits

A

Type: refers to shape of aggregates (granular, Platy, blocky, prismatic, columnar)

Class: refers to size of peds (very fine, fine, medium, coarse, very coarse)

Grade: refers to strength and distinction of peds (weak/not visible vs strong/easily distinguished

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27
Q

Formation of soil structure

A

2-step formation:

  1. Individual soil particles loosely aggregate
  2. Weak aggregates are cemented to strengthen: clay, iron oxides, organic matter, microorganisms gums
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28
Q

Aspects of soil structure

A

The arrangement into aggregates of desirable shape and size

the stability of the aggregate

the configuration of the pores

29
Q

Factors that affect aggregate stability

A

Kind of clay

chemical elements associated with the clay

nature of the products of decomposition or organic matter

Nature of the microbial population

30
Q

Factors that affect soil structure

A

Kind of clay

Amount of organic matter

freezing and thawing

wetting and thawing

action of burrowing organisms

growth of root systems of plants

31
Q

Soil consistence

A

the behavior of soil when pressure is applied; measured at 3 different moisture levels: wet, moist, dry

32
Q

Soil Tilth

A

ease of tillage, seedbed preparation, and seedling/root movement

33
Q

Compaction

A

results from pressure applied at the soil surface

34
Q

Puddling

A

occurs when pressure is applied to very wet soils (esp. plowing)

35
Q

Crusts

A

occur when bare soil is struck by raindrops; disperses soil then dries to a hardened crust

36
Q

Clods

A

clumps in soil

37
Q

Improving Tilth

A

best accomplished by improving structure

tilth relates to texture, structure, permeability, and consistence; however texture and consistence cannot be altered

therefore, improve tilth by improving structure and avoiding compaction

38
Q

Soil Channels

A

Continuous macropores leading from surface to deep subsoil

39
Q

Soil pans

A

any layer of hardened soil; includes claypans, fragipans (clays), plinthite (tropics), caliche (Ca cemented)

40
Q

Soil Temperature

A

Varies with color, texture, O.M

41
Q

Soil Color

A

Munsell Soil color chart
Hue, Value, Chroma
e,g 10YR3/6

42
Q

Soil Color

A

wide range of colors (gray, black, white, red, brown, yellow and greens)

varies by horizon (helps with id)

Development and distribution results from weathering

Aerobic vs anaerobic soils

43
Q

Soil Color Aerobic soils……

A

Aerobic soils produce uniform color changes

44
Q

Soil color is

A

Influenced by the amount of proteins present

45
Q

Dark or black color

A

indicates high organic matter

46
Q

Water affects soil color

A

oxidation rate:

  • oxygen rich= red or brown
  • Low oxygen= usually gray
47
Q

Munsell Soil color chart

A

Separates color into components of:

hue (relations to red, yellow, and blue)

Value (lightness or darkness)

Chroma (paleness or strength)

ex. 10YR 3/6

48
Q

Determining soil color of our soils

A

Use the Munsell soil color book to determine the Hue, value and chroma

49
Q

Soil Profiles: Soil horizons

A

Soils consist of one or more distinct layers called horizons

upper limit is air or shallow water and its lower limit is the depth to which soil weathering has been effective

50
Q

A soil pedon

A

a 3D sample of a soil just large enough to show the characteristics of all its horizons

51
Q

O horizon

A

Layers dominated by organic material.

May or may not be present.

undisturbed Bangor series ex. O is typically 3 inches thick

52
Q

A horizon

A

The mineral soil horizon at the surface or below the O.

All surfaces resulting from agricultural practices are considered part of the A horizon.

This horizon may have accumulations of organic compounds leached from the O

undisturbed Bangor series ex. A is typically 1 inches thick

53
Q

E horizon

A

characterized by eluviation i.e removal of silicate clays, iron, aluminum and organic matter.

Frequently not present

Used to be called A2. AKA “albic” horizon.

Found in campus forest in Monarda series. Pale colored.

bangor= 2 inches

54
Q

eluviation

A

transportation of dissolved or suspended material within the soil by the movement of water when rainfall exceeds evaporation

55
Q

illuviation

A

accumulation of eluviation material in lower levels

56
Q

B horizon

A

Formed below A, E, or O.

Thicker than the above

Tree roots found here

Dominated by the obliteration of all or much of the original rock structure.

Concentrates clays, iron, Al, organic compounds.

Bangor=32 inches

57
Q

C horizons

A

horizons other than bedrock that are little affected by soil forming processes

no tree roots usually

Bangor=25 inches

58
Q

R

A

Hard bedrock

59
Q

In Waldo County

A

1/4 of the land is underlain by glacial till on top of gneiss, schist or phyllite rock

60
Q

Soil orders in Maine

A

Spodosols
Inceptisols
Histosols
Entisols

61
Q

Spodosols

A

Subsurface accumulation of humus typically high in Al and Fe

Form in coarse textured parent material:

  • Light colored E horizon overlaying a reddish brown spodic (illuvial accumulation of organic matter-due to eluviation) horizon
    • Formed by podzolization
62
Q

podzolization

A

principally involves leaching of upper layers with accumulation of material in lower layers

63
Q

Spodosols occur….

A

under coniferous forests in cool, moist climates

Occupy ~4% of the ice free land area

Naturally infertile
-require additions of lime in order to be agriculturally productive

64
Q

Inceptisols

A

Exhibit minimal horizon development

Widely distributed occurring across a wide range of ecological settings

65
Q

Inceptisols occur…..

A

Often on steep slops, young geomorphic surfaces and resistant parent materials

Often found in mountainous regions (forestry, recreation and watershed)

15% of ice free land area (second most extensive soil order)

66
Q

Histosols

A
  • Composed mainly of organic materials
    - 20-30% organic matter by weight
    - Low bulk density often less than 0.3 g/cm3

Inhibit decomposition which in turn accumulate over time

referred to as peats, mucks (mined for fuel and horticultural products

67
Q

Histosols occur

A

wetlands with restricted drainage

Very ecologically important:

  • Accumulate large quantities of carbon
  • less than 1.5% of ice free land area
68
Q

Entisols

A

Soils of recent origin

No horizons except A
-all soils which so not fit into other orders are Entisols

69
Q

Entisols occur

A

great diversity in both land use and setting

Many found in steep rocky settings

most extensive soils order
-~18% of ice free land area

Soil Fertility (4 decks)

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