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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
Structure and texture
structure can alter the effects of texture e.g. a fine-textured silty clay with good structure can be permeable
26
Structure is classified by three groups of traits
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
27
Formation of soil structure
2-step formation: 1. Individual soil particles loosely aggregate 2. Weak aggregates are cemented to strengthen: clay, iron oxides, organic matter, microorganisms gums
28
Aspects of soil structure
The arrangement into aggregates of desirable shape and size the stability of the aggregate the configuration of the pores
29
Factors that affect aggregate stability
Kind of clay chemical elements associated with the clay nature of the products of decomposition or organic matter Nature of the microbial population
30
Factors that affect soil structure
Kind of clay Amount of organic matter freezing and thawing wetting and thawing action of burrowing organisms growth of root systems of plants
31
Soil consistence
the behavior of soil when pressure is applied; measured at 3 different moisture levels: wet, moist, dry
32
Soil Tilth
ease of tillage, seedbed preparation, and seedling/root movement
33
Compaction
results from pressure applied at the soil surface
34
Puddling
occurs when pressure is applied to very wet soils (esp. plowing)
35
Crusts
occur when bare soil is struck by raindrops; disperses soil then dries to a hardened crust
36
Clods
clumps in soil
37
Improving Tilth
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
Soil Channels
Continuous macropores leading from surface to deep subsoil
39
Soil pans
any layer of hardened soil; includes claypans, fragipans (clays), plinthite (tropics), caliche (Ca cemented)
40
Soil Temperature
Varies with color, texture, O.M
41
Soil Color
Munsell Soil color chart Hue, Value, Chroma e,g 10YR3/6
42
Soil Color
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
Soil Color Aerobic soils......
Aerobic soils produce uniform color changes
44
Soil color is
Influenced by the amount of proteins present
45
Dark or black color
indicates high organic matter
46
Water affects soil color
oxidation rate: - oxygen rich= red or brown - Low oxygen= usually gray
47
Munsell Soil color chart
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
Determining soil color of our soils
Use the Munsell soil color book to determine the Hue, value and chroma
49
Soil Profiles: Soil horizons
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
A soil pedon
a 3D sample of a soil just large enough to show the characteristics of all its horizons
51
O horizon
Layers dominated by organic material. May or may not be present. undisturbed Bangor series ex. O is typically 3 inches thick
52
A horizon
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
E horizon
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
eluviation
transportation of dissolved or suspended material within the soil by the movement of water when rainfall exceeds evaporation
55
illuviation
accumulation of eluviation material in lower levels
56
B horizon
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
C horizons
horizons other than bedrock that are little affected by soil forming processes no tree roots usually Bangor=25 inches
58
R
Hard bedrock
59
In Waldo County
1/4 of the land is underlain by glacial till on top of gneiss, schist or phyllite rock
60
Soil orders in Maine
Spodosols Inceptisols Histosols Entisols
61
Spodosols
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
podzolization
principally involves leaching of upper layers with accumulation of material in lower layers
63
Spodosols occur....
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
Inceptisols
Exhibit minimal horizon development Widely distributed occurring across a wide range of ecological settings
65
Inceptisols occur.....
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
Histosols
- 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
Histosols occur
wetlands with restricted drainage Very ecologically important: - Accumulate large quantities of carbon - less than 1.5% of ice free land area
68
Entisols
Soils of recent origin No horizons except A -all soils which so not fit into other orders are Entisols
69
Entisols occur
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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