SSC 200: Exam 3

Plants can only obtain nitrogen from the soil by taking up soluble anions. In general cations cannot be absorbed by plants (TF)

False

_____ is not a characteristic of soil colloids.

a. Very small size

b. High surface area

c. Ability to exchange ions with the soil solution

d. Low water holding capacity

d. Low water holding capacity

Some nitrogen-containing fertilizers are significant sources of soil acidity in cultivated soils (TF)

True

Which of the following is a micronutrient?

a. Magnesium

b. Manganese

c. Nitrogen

d. Sulfur

b. Manganese

The conversion of the nitrate nitrogen to N2 is ____.

a. denitrification

b. immobilization

c. nitrification

d. mineralization

a. denitrification

Soil phosphorus is associated with eutrophication of fresh water lakes (TF)

True

Which of these ions would be held more tightly

than calcium within the cation exchange complex?

a. Aluminum

b. Magnesium

c. Potassium

d. Sodium

a. Aluminum

Micronutrient deficiencies are more likely to occur where inorganic chemical fertilizers, rather than organic manures, have been used to stimulate vigorous plant growth (TF).

True

What property of clays does isomorphic substitution affect?

a. The ability to shrink and swell

b. Whether it's classed as 2:1 or 1:1.

c. The amount of specific surface area.

d. The cation exchange capacity

d. The cation exchange capacity

Which of the following increases soil acidity.

a. Leaching of basic cations

b. Application of ammonium sources of nitrogen fertilizers

c. Weathering of clay minerals that release aluminum

d. All of the above

d. All of the above

In order for nitrate to form from soil organic matter, Nitrosomonas must be present in the soil but

Nitrobacter need not be present (TF)

False

Residual soil acidity is a measure of the _____.

a. hydrogen ion activity in the soil solution

b. aluminum and hydrogen ions attracted towards the charge of the clay and humus surfaces

c. aluminum and hydrogen bound to the charge of the clay and humus surfaces.

c. aluminum and hydrogen bound to the charge of the clay and humus surfaces.

In soil science, CEC is an abbreviation for _____.

a. Calcium Exchange Component

b. Carbonated Electrical Circuits

c. Cation Exchange Capacity

d. Cationic Eluviation Center

c. Cation Exchange Capacity

Most nitrogen leaching to groundwater is in the form of ammonium (TF)

False

When considering an appropriate lime recommendation, following variables should be considered:

a. Current soil pH

b. Crop to be grown

c. Organic matter content

d. All of the above

d. All of the above

Which cation does not promote soil flocculation?

a. Aluminum

b. Calcium

c. Potassium

d. Sodium

d. Sodium

The octahedron building unit of a clay crystal contains _____ atoms.

a. 1 aluminum and 4 oxygen

b. 1 aluminum and 6 oxygen

c. 1 silicon and 4 oxygen

d. 1 silicon and 6 oxygen

b. 1 aluminum and 6 oxygen

Which of the following is not a factor affecting CEC?

a. Type of clay

b. Organic matter content

c. Soil structure

d. Soil texture

d. Soil texture

On very acid soils, a chemical problem that can reduce plant growth is _____.

a. aluminum toxicity

b. calcium toxicity

c. iron deficiency

d. nitrate poisoning

a. aluminum toxicity

Conversion of the cationic form of soil nitrogen to the anionic form is _____.

a. ammonification

b. immobilization

c. nitrification

d. denitrification

c. nitrification

At extremely low pH values, well below 4.0, some colloids such as iron and aluminum oxides have positive surface charges, which increases the soil's ability to hold on to anions (TF)

False

A 2:1 type silicate clay has one tetrahedral sheet sandwiched between two octahedral sheets (TF)

False

In soil chemistry, CCE is an abbreviation for _____.

a. Calcium Carbonate Equivalency

b. Carbonated Cationic Elimination

c. Cation Capacity for Exchange

d. Cationic Center for Eluviation

a. Calcium Carbonate Equivalency

The sulfur dioxide in the atmosphere resulting from fossil fuel burning, volcanoes and forest fires can be an important source of sulfur nutrition for plants (TF)

True

_____ would be the preferred liming material for a soil low in Mg.

a. Calcitic lime

b. Dolomitic lime

c. Gypsum

d. Hydrated lime

b. Dolomitic lime

In acid soils the principal chemical form of phosphorus available for plant uptake is _____.

a. H2PO4-

b. P3+

c. CaPO42-

d. P3-

a. H2PO4-

The biological conversion of the ammonium form of

nitrogen into an unavailable form is _____.

a. denitrification

b. immobilization

c. volatilization

d. mineralization

b. immobilization

Which mineral colloid potentially has the lowest cation exchange capacity?

a. Humus

b. Montmorillonite, a 2:1 clay

c. Kaolinte, a 1:1 clay

d. Goethite, an iron oxide

d. Goethite, an iron oxide

Which ion hydrolyzes water molecules and causes some very low soil pH values?

a. Aluminum

b. Calcium

c. Magnesium

d. Potassium

a. Aluminum

Before plants can absorb nitrate-nitrogen that originated from residues of a previous crop, the following processes must have occurred: (Note: processes must be in correct sequence.)

a. denitrification, N-fixation

b. ammonification, nitrification

c. nitrification, denitrification

d. immobilization, mineralization

b. ammonification, nitrification

The total phosphorus lost from various watersheds is most closely correlated with _____.

a. high soil cation exchange capacity

b. low soil cation exchange capacity

c. low slopes and low erosion

d. high soil erosion

d. high soil erosion

Highly weathered soils low in available sulfur in their A horizons often have adequate supplies of

available sulfur in deeper, clay-rich horizons (TF)

True

Active soil acidity is a measure of the _____.

a. hydrogen ion activity in the soil solution

b. aluminum and hydrogen ions attracted towards the charge of the clay and humus surfaces

c. aluminum and hydrogen bound to the charge of the clay and humus surfaces

a. hydrogen ion activity in the soil solution

The quality of a lime is determined by its _____.

a. reserve acidity

b. cation exchange capacity

c. base saturation

d. calcium carbonate equivalency

d. calcium carbonate equivalency

The amount of limestone required to increase the pH from 5 to 7 would be higher for a Histosol than for an Alfisol (TF)

True

Cation exchange capacity can change as pH changes (TF)

True

The conversion of plant-available forms of nitrogen into microbial or plant biomass is an example of mineralization (TF)

False

Exchangeable soil acidity is a measure of the _____.

a. hydrogen ion activity in the soil solution

b. aluminum and hydrogen ions attracted towards the charge of the clay and humus surfaces

c. aluminum and hydrogen bound to the charge of the clay and humus surfaces.

b. aluminum and hydrogen ions attracted towards the charge of the clay and humus surfaces

Which colloid potentially has the highest cation exchange capacity?

a. Humus

b. Montmorillonite, a 2:1 clay

c. Kaolinte, a 1:1 clay

d. Goethite, an iron oxide

a. Humus

The lower the cation exchange capacity of a soil, the higher is its buffer capacity (TF)

False

Which of the following processes does not decrease the amount of nitrogen available to plants?

a. Denitrification

b. Immobilization

c. Symbiotic N-fixation

d. Volatilization

c. Symbiotic N-fixation

The amount of residual acidity is much larger than

the active acidity (TF)

True

Nitrogen use efficiency is consistent among all plants and averages about 75% (TF)

False

The "Ac" value is an estimate of

a. Active Acidity

b. Exchangeable Acidity

c. Ammonium Concentration

d. Anion Content

b. Exchangeable Acidity

In what range of soil pH is phosphorus generally most available to plants?

a. greater than 8.0

b. 5.5 to 7.0

c. 7.0 to 8.0

d. 4.5 to 5.5

e. 3.5 to 4.5

b. 5.5 to 7.0

Which of the following increases soil acidity.

a. Leaching of basic cations

b. Application of ammonium sources of nitrogen fertilizers

c. Weathering of clay minerals that release aluminum

d. all of the above

d. all of the above

When soil chemistry shows the soil to be basic, applying compounds containing aluminum results in the water molecule being split, thereby reducing pH.

True

The natural microbial oxidation of nitrogen released by organic matter mineralization is a major source of soil acidity.

True

A 2:1 type silicate clay has one octahedral sheet sandwiched between two tetrahedral sheets.

True

A pure clay crystal of kaolinite contains one octahedral layer and one tetrahedral layer. Which of these descriptions best describes the individual tetrahedrons that form the tetrahedral layer:

a. 6 aluminums and 1 oxygen

b. 1 silicon and 4 oxygens

c. 4 silicons and 1 oxygen

d. 1 aluminum and 6 oxygens

b. 1 silicon and 4 oxygens

Which mineral colloid has the largest cation exchange capacity?

a. Montmorillonite, 2:1 clay

b. Goethite, an iron oxide

c. Humus

d. Kaolinte, a 1:1 clay

a. Montmorillonite, 2:1 clay

Some nitrogen-containing fertilizers are significant sources of soil acidity in cultivated soils.

True

The higher the cation exchange capacity of a soil, the greater its buffer capacity.

True

Which of these statements is false about nitrification?

a. Is a part of the immobilization process

b. Bacteria are involved

c. Produces a leachable end-product

d. Oxygen is required

a. Is a part of the immobilization process

Volatilization is the process by which _____ is lost from the surface of a soil.

a. clay

b. phosphorous

c. ammonia

d. nitrate

c. ammonia

Which of these choices correctly lists ions in the order decreasing (strongest to weakest) order of attraction to clay colloids?

a. sodium - magnesium

b. calcium - sodium

c. potassium - calcium

d. aluminum - magnesium

d. aluminum - magnesium

In a soil with a very low cation exchange capacity, the most efficient approach to using potassium fertilizer would be to apply frequent small doses rather than a single large dose.

True

Which of these essential elements is it most likely to be toxic to plants in a soil at pH 5.0?

a. Molybdenum

b. Boron

c. Nitrogen

d. Manganese

e. Phosphorus

d. Manganese

On very acid soils, a chemical problem that can reduce plant growth is _____.

a. nitrate poisoning

b. aluminum toxicity

c. iron deficiency

d. calcium toxicity

b. aluminum toxicity

Liming materials neutralize soil acidity by converting the hydrogen ion into

a. carbon dioxide

b. a reserve form of acidity

c. a basic cation

d. water

d. water

If you want to quickly (in just a few days) increase the pH of a soil from 5.5 to 7.0, which of the following would you use?

a. Calcitic limestone

b. Calcium oxide

c. Calcium sulfate

d. Dolomitic limestone

b. Calcium oxide

If soil pH was observed to gradually increase and then gradually decrease over a 4-6 year period, what chemical(s) had probably been added to the soil at the start of this period:

a. An excess of hydrogen ions

b. An ammonium containing nitrogen fertilizer

c. Aluminum

D. calcium carbonate

D. calcium carbonate

Carbon dioxide evolution from microbes and plants into the soil solution will _____ soil pH.

a. lower

b. not affect

c. raise

a. lower

Which of the following micronutrients is least commonly found to be deficient in plants?

a. Boron

b. Chlorine

c. Manganese

d. Copper

e. Iron

b. Chlorine

The process of _____ releases soluble nitrogen as the result of the breakdown of nitrogen-rich organic

a. denitrification

b. symbiosis

c. mineralization

d. volatilization

c. mineralization

Active soil acidity is a measure of the H+ ion activity in the soil solution.

True

The nitrification reaction is:

NH4+ + 2O2 ---->> 2H+ + NO3- + H2O

This reaction _____ soils acidity.

a. decreases

b. does not affect

c. increases

c. increases

Hydrogen ions dominate the exchange complex of very acid soils (pH<5).

False

Which major plant nutrient has both an organic and inorganic unavailable pool in unfertilized soil?

a. Molybdenum

b. Hydrogen

c. phosphorous

d. Oxygen

c. phosphorous

In acid soils the principal chemical form of phosphorus available for plant uptake is _____.

a. P3-

b. CaPO42-

c. P3+

d. H2PO4-

d. H2PO4-

Which process in the nitrogen cycle describes the conversion of a plant available soil nitrogen form into the microbial tissue pool:

a. Mineralization

b. immobilization

c. Denitrification

d. Nitrification

b. immobilization

The particle size of limestone, in part, determines its _____.

a. effective calcium carbonate rating

b. shrink-swell clay content

c. cation exchange capacity

d. purity

a. effective calcium carbonate rating

The acidity of "acid rain" can be partially traced to the reaction of CO2 in the atmosphere forming carbonic acid (H2CO3).

True

Although only about 2 to 5 percent of the total P in most surface soils is in organic form, this form supplies nearly all the P taken up by plants.

False

Which ion hydrolyzes water molecules and causes some very low soil pH values. _____.

a. Potassium

b. Aluminum

c. Magnesium

d. Calcium

b. Aluminum

The amount of exchangeable acidity is much smaller than the active acidity.

a. True

b. False, because there is no such thing as exchangeable acidity

c. False, exchangeable acidity is much larger than active acidity

d. False, because there is no such thing as active acidity

c. False, exchangeable acidity is much larger than active acidity

A soil testing lab reports a soil pH of 6.1. From that value you can directly calculate the _____.

a. aluminum and hydrogen on clays

b. hydrogen ions in the soil solution

c. buffering capacity

d. hydrogen ions on cation exchange sites

b. hydrogen ions in the soil solution

The effective calcium carbonate (ECC) rating of a liming material is determined by its

a. cation exchange capacity

b. base saturation and pH

c. active and reserve acidity

d. purity and fineness

d. purity and fineness

Ammonification is a process by which much needed nitrogen is transformed from an organic form to a inorganic form.

False

Nitrogen use efficiency is consistent among all plants and averages about 95%.

True

The electronegative charge on 2:1 type silicate clays is due primarily to _____.

a. extremely small size of the individual colloid particles

b. the preponderance of tetrahedron sheets compared to octahedron sheets

c. the effect of pH on the presence of H+ ions in the exchange complex

d. substitution of one metallic atom for another in the crystal structure of the clay

e. ionization of surface OH- groups

d. substitution of one metallic ion for another in the crystal structure of the clay

What property of clays does isomorphism affect?

a. The ability to shrink and swell

b. The amount of specific surface area.

c. Whether it's classed as 2:1 or 1:1.

d. the cation exchange capacity

d. the cation exchange capacity

pH is a measure of _____ acidity.

a. active

b. exchangeable

c. reserve

d. total

a. active

The lower the cation exchange capacity of a soil, the higher is its buffer capacity.

False

Once limestone is applied to an acid soil and the pH changes to near optimum, the pH can be expected to

a. never revert to the original acidity

b. gradually decline

c. revert to the original acidity within a year

d. remain constant for the next 15-20 years

b. gradually decline

In the future, as food production is increased in countries around the world, micronutrient deficiencies are likely to become less of a problem than they are today.

False

A pure clay crystal of kaolinite contains one octahedral layer and one tetrahedral layer. Which of these descriptions best describes the individual octahedrons that form the octahedral layer?

1 aluminum and 6 oxygens

In the neutralization reactions involving limestone and acid soil, the acid component of the soil (H+) is neutralized by

becoming part of the water molecule

Limestone application should be mixed thoroughly with the soil to increase the

rate of the neutralization reaction

Which of the following is not a characteristic of soil colloids?

small surface area

The cation exchange capacity (CEC) of humus is not affected by soil pH.

False, the CEC of humus is entirely dependent on pH

Isomorphic substitution describes a phenomena in soils that produces

cation exchange sites

Which of these essential elements is most likely to be toxic to plants in a soil at 4.0?

Manganese

A 2:1 clay is more active than sand because the clay has

negative charge

The opposite process from mineralization is

immobilization

Active soil pH describes the concentration of hydrogen ions found

in the soil solution

________ is considered a micronutrient

Boron

The nitrification reaction is:

NH_4+ + 2O_2 --> 2H+ + NO_3- + H_2O

This reactions _______ soils acidity.

increases

Which process describes the conversion of unavailable, atmospheric nitrogen to plant available form?

Symbiotic fixation

Rank the following soil components in order of pH buffering capacity, lowest to highest:

sand--> clay--> organic matter