EAS 430 Soils

Question 1

Soil definition

Answer 1

A dynamic natural body composed of mineral matter, organic matter, gases and living organisms in which plants grow.

Question 2

Factors Influencing Soil Formation

Answer 2

1. Climate - Temperature & precipitation
2. Living Organisms - Animals (humans too), Plants, & Microorganisms
3. Parent Material - Physical & chemical properties of geologic materials
4. Topography - Landform, slope & aspect
5. Time - Duration over which climate and living organisms have influenced parent material

Question 3

3 important soil properies

Answer 3

texture, structure, color

Question 4

soil texture

Answer 4

proportion of sand, silt & clay

Question 5

soil structure

Answer 5

aggregation of sand, silt & clay into secondary structures called aggregates

Question 6

soil color

Answer 6

insight into organic matter content and other soil properties

Question 7

sand

Answer 7

portion of soil texture measuring 0.05 - 2 mm

[ADD composition]

Question 8

silt

Answer 8

portion of soil texture measuring 0.002 - 0.05 mm

[ADD composition]

Question 9

clay

Answer 9

portion of soil texture measuring < 0.002 mm

[ADD composition]

Question 10

granular

Answer 10

description of soil structure with high permeability

Question 11

blocky

Answer 11

description of soil structure with moderate permeability

Question 12

platey

Answer 12

description of soil structure with low permeability

Question 13

massive

Answer 13

description of soil structure with low permeability

Question 14

components of macroaggregate

Answer 14

micro-aggregates (plant and fungal debris, silt-sized aggregates, clay microstructures), particulate organic matter decomposed by saprophytic fungi, and mycorrhizal fungal hyphae. Pore space and organic binding agents.

Question 15

A-horizon

Answer 15

surface horizon.

Mineral horizons that formed at the surface or below an O horizon and (1) are characterized by an accumulation of humified organic matter intimately mixed with the mineral fraction and not dominated by properties characteristic of E or B horizons (defined below) or (2) have properties resulting from cultivation, pasturing, or similar kinds of disturbance.

Ap - Plowing or other disturbance

Question 16

O-horizon

Answer 16

organic horizon. On the surface, but can be buried.
Layers dominated by organic material. Some are saturated with water for long periods or were once saturated but are now artificially drained; others have never been saturated.

Oa - Highly decomposed organic material
Oe - Organic material of intermediate decomposition
Oi - Slightly decomposed organic material

Question 17

B-horizon

Answer 17

subsoil. Horizons that formed below an A, E, or O horizon and are dominated by obliteration of all or much of the original rock structure 11/ and by (1) illuvial concentration of silicate clay, iron, aluminum, humus, carbonates, gypsum, or silica, alone or in combination; (2) evidence of removal of carbonates; (3) residual concentration of sesquioxides; (4) coatings of sesquioxides that make the horizon conspicuously lower in value, higher in chroma, or redder in hue than overlying and underlying horizons without apparent illuviation of iron; (5) alteration that forms silicate clay or liberates oxides or both and that forms granular, blocky, or prismatic structure if volume changes accompany changes in moisture content; or (6) any combination of these.

Bh - Illuvial accumulation of organic matter
Bs - Illuvial accumulation of sesquioxides and organic matter
Bt - Accumulation of silicate clay

Question 18

C-horizon

Answer 18

Horizons or layers, excluding hard bedrock, that are little affected by pedogenic processes and lack properties of O, A, E, or B horizons. Most are mineral layers, but limnic layers, 10/ whether organic or inorganic, are included. The material of C layers may be either like or unlike that from which the solum presumably formed. A C horizon may have been modified even if there is no evidence of pedogenesis.

Question 19

E-horizon

Answer 19

eluviation layer. O-A-E-B-C.
Mineral horizons in which the main feature is loss of silicate clay, iron, aluminum, or some combination of these, leaving a concentration of sand and silt particules of quartz or other resistant minerals.

Used for horizons with significant loss of minerals.

Question 20

idealized soil proportion of solid, liquid, and fas

Answer 20

45% mineral
25% water
25% gas
5% organic matter

Question 21

water properties

Answer 21

polar (local positive and negative charge)

Question 22

hydrogen bonding

Question 23

field capacity

Question 24

wilting coefficient