Soil Chemistry and Hydrology CRSS3060 EXAM 1

Iron oxides are primarily responsible for what soil color?

Red

Type of parent material that is weathered in place; not transported

Residual

Type of parent material that is moved by water, laid down in floodplains

Alluvium

Type of parent material that is deposited at the base of slopes by gravity

Colluvial

Type of parent material that is laid down on ocean floors, later exposed

Marine

Feldspar + (H+) -> Clay minerals + (K+) is an example of what?

Hydrolysis

In addition to iron, name another agent that provides color to soil

Mn (Manganese)

Which of the following would provide the thickest A horizon with dark brown color?
A. Pine trees in North Florida
B. Oak and hickory trees in Tennessee
C. Grassland in Nebraska
D. Cropland in Maryland
E. Cactus and shrubs in New Mexico

C. Grassland in Nebraska

What is the acronym for remembering the 5 soil forming factors published by Hans Jenny in 1941?

Cl, O, R, P, T

Which of the following is properly ordered from most soluble to most stable in the soil environment?
A. calcite, clay minerals, quartz
B. feldspar, muscovite, iron oxide
C. Iron oxide, muscovite, gypsum
D. halite, muscovite, feldspar

B. Feldspar, muscovite, iron oxide

Athens GA is predominantly on what type rock?

Gneiss

Most common soluble salt?

CaCO3 (Calcite)

Folistic Epipedon

occur primarily in cool, humid regions of the world. The folistic epipedon is like the histic except it is not saturated with water for more than 30 days.

Histic

High O.M, thick, wet, dark

Ochric Epipedon

Fails to meet the definitions for any of the other epipedons because it is too thin, has too high a chroma or value, and contains too little organic matter

Umbric Epipedon

a relatively thick, dark colored, humus-rich surface horizon, the % base saturation is less than 50% due to leaching of basic cations. The umbric develops in areas with higher rainfall than the mollic. If the surface layer of organic material is so thick that the soil is recognized as a Histosol

Mollic Epipedon

a relatively thick, dark colored, humus-rich surface horizon (or horizons) in which bivalent cations are dominant on the exchange complex and the grade of structure is weak to strong. If the surface layer of organic material is so thick that the soil is recognized as a Histosol

Mollic and Umbric Value and Chroma

≤3

Most of Georgia is what type of soil?

Ultisol

Soil Taxonomy Categories

order, suborder, great group, subgroup, family, series

Gelisols

soil order that is limited geographically to poles & to mountainous regions where permafrost is close to surface (within 2 meters). decomposition occurs very slowly, so there is a high amount of organic matter

Histosols

Soils composed of relatively thick (usually 16 inches or more) organic materials (muck and peats). >20% organic matter

Spodosols

acid forest soils with a subsurface accumulation of metal-humus complexes

Andisols

developed from volcanic material, particularly ash

Oxisols

intensely weathered soils of tropical and subtropical environments. low base saturation

Vertisols

clayey soils with high shrink/swell capacity

Aridisols

dry soils found in most desert areas; salinization common. Arid environments w/ subsurface development.

Ultisols

strongly leached soils with a subsurface zone of clay accumulation and <35% base saturation

Mollisols

grassland soils with high base status

Alfisols

soil order in semi-arid to humid regions, often in hardwood forests
Very fertile & imp to food production
Typically have not been heavily leached unlike ultisols

Inceptisols

soils with weakly developed subsurface horizons

Entisols

"young" soils with little or no morphological development

Soil Colloids

organic and inorganic matter with very small particle size and a correspondingly large surface area per unit of mass. Most chemically active portion of the soil. (Humus, clay, Fe and Al oxides)

Isomorphous substitution

Results in permanent charge because it is not affected by fluctuations in pH. It is the replacement of one atom by another of similar size in a crystal lattice without disrupting or changing the crystal structure of the mineral. Results in a deficit of charge. Extra (-) from O-2
Examples are:
Al+3 -> Si+4 (tetra)
Fe+2 or Mg+2 -> Al+3 (octa)

Permanent Charge

due to isomorphous substitution and is not dependent on pH

Variable Charge

pH dependent - related to hydrolysis
Releasing H+
Edges of clay
Common in humus, 1:1 clays, oxides, and amorphous minerals

Silicate clay groups

Smectite Group
Hydrous Mica Group
Kaolinite Group

Montmorillonite is part of what Silicate Clay group?

Smectite Group

Montmorillonite

2:1 Clay with high nutrient capacity
Low bearing strength
Prone to high swell/shrink capacity
Variations are due to the differences in ferrous iron and magnesium for aluminum in the alumina layer

Alumina

aluminum oxide

Pedogenesis

process of soil formation

Silicates

Made of mostly silicon and oxygen and are the most common mineral in rocks

Most common silicates are

aluminosilicates, e.g. Feldspar

Feldspar weathering is responsible for most of the what in soil

potassium and calcium

ferromagnesian silicates

Contain single or paired tetrahedra bonded iron (Fe+2) and/or magnesium. Typically dark and relatively heavy

Hydrolysis in soil

Rain absorbs CO2 when it falls, this increased the rate of hydrolysis. When H+ ions replace mineral ions. Example: H2O + Potassium Feldspar -> Silicons Acid + Potassium Hydroxide
KAlSi3O8 + H2O -> HAlSi3O8 + KOH

Oxidation in soil

Certain multivalent ions lose an electron, becoming more positive. Iron is capable of two valence states
Fe+2 = Fe+3 + (1e-)
4Fe+3 + 3O2 = 2FeO3

Hydration in soil

Water enters minerals and rocks and causes expansion. Follows oxidation in nature

Reduction in soil

Opposite of oxidation, gain of electron

Solution reaction in soil

Whenever water acts as a solvent. Carbonic acid in water can speed up this reaction

eolian sediments

Materials transported and accumulated by wind (for example, dunes).

loess

A wind-formed deposit made of fine particles of silt

cation exchange capacity

the ability of a particular soil to absorb and release cations. This is sometimes referred to as the nutrient holding capacity

Common soil bases

Ca +2, Mg +2, Na +2, K +

base saturation %

Sum(Bases)/CEC

@ pH = 7, BS% = ?

100%

Sodic soil

A soil with an exchangeable sodium percentage of 15 percent or greater and a pH between 9.5 and 10.0.

T/F Surface area increases as soil particles get bigger.

False

In which one of the following landscapes would you expect to find Mollisol?

a. The rolling upland hills of the Piedmont

b. The floodplain of the Mississippi River

c. The rolling loess prairies of Iowa

d. The nearly level topography of the Atlantic Flatwoods region

e. The Alaskan tundra with permafrost

c. The rolling loess prairies of Iowa

Which of the following minerals is most soluble in a humid, temperate climate?

a. kaolinite

b. gypsum

c.feldspar

d. quartz

b. gypsum

T/F Anion exchange is the ability of a soil to attract positively charged ions.

False

Which of the following is not a function of soil?

a. serves as a foundation for building roads

b. regulate floodwater from hurricane Florence

c. Modify atmospheric composition

d. store carbon from the atmosphere

e. none of the above

e. none of the above

A soil with both low chroma and low value in the Munsell color system tell you that a soil…

a. has high calcium carbonate content

b. has a high humus level

c. has a high Fe content

d. has oxidized forms of Fe in it

e. is well drained

b. has a high humus level

T/F Bg is appropriate for a horizon with few 10YR 5/1 mottles

False

Which element is primarily responsible for the formation of visible redoximorphic features in soils that have fluctuating water table?

a. aluminum

b. magnesium

c.iron

d.calcium

c.iron

Two soil components that have appreciable pH- dependent charge are (circle Two)

a. kaolinite

b. Fe oxides

c. montmorillonite

d.humus

e. muscovite

b.Fe oxides and d.humus

Which pool of acidity is the greatest in soil?

a. exchangeable

b. active

c. residual

d.pH

c. residual

Which of the following does not provide an appreciable coloring pigment for the soil?

a. Iron oxides

b. humus

c.Calcium carbonate

d. aluminum oxides

e. organic matter

d. aluminum oxides

soil with upland hills formed in metamorphic rocks; Ultisols

Piedmont

Atlantic Coast flatwoods physiographic region

Flatwoods

Steep mountains with sedimentary rocks; Ultisols and inceptisols

Valley and Ridge

resistant primary mineral common in sand fraction

quartz

metamorphic rock common in the piedmont

gneiss

2:1 clay mineral with very high CEC

Montmorillonnite

primary mineral with platy morphology found in granite

mica

parent material deposited at base of slopes by gravity

colluvium

element that commonly substitutes for Al in octahedral layer of clay minerals

Mg^2+

name of the process that causes permanent negative charge on soil colloids

isomorphous substitution

term for particle 0.002-0.05 mm in size

silt

chemical process that involves splitting a water molecule to attack a primary mineral

hydrolysis

Name the five soil forming factors

Climate

Organism

Relief

Parent material

Time

weathered in place; not transported

residue

deposited at base of slopes by gravity

colluvial

Igneous rocks -

a. form from cooled magma

b. are the most common type of rock around Athens

c. contain only secondary minerals

d. are mostly deposited on the sea floor

e. none of the above

a. form from cooled magma

Which of the following impacts landscape development?

A. climate

B. Time

C. Tectonic activity

D.Erosional processes

E.all of the above

E. all of the above

Name the four soil forming processes and example

S=(A,L,T,T)

Addition: Organic matter input

Losses: Nutrient leaching

Transpiration: mineral weathering

Translocation: clay movement

In which physiographic region in Georgia would you find flat landscapes with sandy deposits that are the youngest in geologic history?

Flatwoods

Water balance Equation

P= ET+Q+triangleS

Which of the following has the lowest surface area for the same volume of soil?

a.sand

b.silt

c.clay

a. sand

Which of the following is most likely to be eroded by wind?

a. sand

b. silt

c. clay

b. silt

term for particles 0.05 - 0.002 mm in size; primarily size in loess parent material

silt

dominant mineral in sand size fraction; a primary mineral

quartz

Bulk density

Mass/ Volume = BD

You perform hand texture of a soil that produces a ribbon that is 0.5” long and feels gritty. What is the texture class?

Sandy Loam