Question 1

Sodic soils generally have a poor physical condition. To what is this most likely due?

Accepted Answer

A)  low organic matter content 
B)  impact of raindrops on the soil surface 
C)  dispersal of the Na saturated soil colloids 
D)  precipitation of the Ca2+ and Mg2+ ions as carbonates 
E)  high content of smectite in the soils

Question 2

In extremely acid soils (pH 3.0 to 4.0) most of the Al3+ and H+ ions are bound tightly by organic matter and silicate clays and are not readily exchangeable.

Accepted Answer

A) True 
 B)False

Question 3

The very high pH levels found in some arid region soils are most likely due to high levels of exchangeable _____.

Accepted Answer

A)  Al3+  
B) Al(OH)2+ 
C)  Ca2+  
D) Mg2+  
E) Na+

Question 4

In desert areas, the soil under scattered clumps of natural vegetation is usually depleted of nutrients compared to the unvegetated soil between clumps.

Accepted Answer

A) True 
 B)False

Question 5

Saline-sodic soils are characterized by all but which one of the following?

Accepted Answer

A)  soil pH less than 8.5 
B)  exchangeable sodium percentage greater than 15 
C)  EC 4 dS/m or higher 
D)  sodium adsorption ratio greater than 13 
E)  CaCO3 layer near the soil surface.

Question 6

You were advised to use elemental sulfur in the reclamation of a saline-sodic soil. Indicate how the sulfur helps bring about this reclamation.

Accepted Answer

A)  Sulfur leaches down into the soil and increases the soil pH. 
B)  Sulfur is oxidized to sulfates that will precipitate much of the exchangeable Na+. 
C)  Sulfur helps maintain high salt content while reducing exchangeable Na+ levels. 
D)  Sulfur is oxidized and forms sulfuric acid which, in turn, removes the exchangeable Na+. 
E)  Sulfur stimulates the formation of gypsum in the soil.

Question 7

The drainage of certain wetlands has resulted in extreme soil acidity. This is due primarily to which of the following processes that take place when the soil is drained?

Accepted Answer

A)  oxidation of organic materials to produce organic acids 
B)  reduction of iron to low valent states that stimulate acidity 
C)  release of nitric acid due to oxidation of nitrogen compounds 
D)  high redox potential characteristic of aerated soils 
E)  oxidation of sulfur-bearing minerals that produces sulfuric acid

Question 8

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

Accepted Answer

A) True 
 B)False

Question 9

Sulfuric acid is sometimes added to irrigation water to help in the reclamation of sodic soils.

Accepted Answer

A) True 
 B)False

Question 10

Which of the following does not describe aluminum hydroxy ions (such as Al(OH)2+) in the soil?

Accepted Answer

A)  They are more prominent in acid than in neutral soils. 
B)  They affect the pH of the soil solution through hydrolysis. 
C)  They block negative sites on some clays thereby reducing the cation exchange capacity. 
D)  They influence the swelling of some clays by entering into the interlayer spaces. 
E)  They are commonly applied to help reduce the soil pH for acid-loving plants.

Question 11

The ill effects of acidity in subsoils can be ameliorated by adding gypsum (CaSO4-2H2O) to the soil surface. Which of the following most likely helps account for this effect?

Accepted Answer

A)  The gypsum replaces hydrogen from colloids which moves down the profile and decreases the pH of the subsoil layers. 
B)  Calcium from the gypsum replaces hydrogen from colloids in the subsoil thereby increasing the soil pH. 
C)  Gypsum dissolves and leaches downward, increasing the Ca/Al ratio in the soil solution in subsoil layers. 
D)  Sulfate ions from the gypsum react with H ions in the subsoil to form H2SO4. 
E)  Gypsum stimulates root growth in the surface soil horizons.

Question 12

Which of the following would occur when lime is added to the surface of a soil at pH 6.0?

Accepted Answer

A)  Earthworms would help move the limestone down into the soil profile. 
B)  Conservation tillage would increase the pH of the subsoil.
83 
C)  CO2 from root and microbial respiration would quickly solubilize the CaCO3 and increase its rate of downward movement. 
D)  Aluminum toxicity would increase in the vicinity of the limestone. 
E)  The release of H+ ions from the exchange complex would help reduce the soil pH.

Question 13

If you want to reclaim a saline soil, which of the following practices would you most likely use?

Accepted Answer

A)  Add CaCO3 to reduce the exchangeable Na+ level. 
B)  Leach the soil with low salt containing water. 
C)  Leach the soil with water having a high SAR ratio. 
D)  Leach the soil with water high in Ca2+ and Mg2+. 
E)  Leach the soil with water high in bicarbonates.

Question 14

The drainage of some coastal wetland soils results in high pH due to underlying lime deposits.

Accepted Answer

A) True 
 B)False

Question 15

The degradation of irrigated soils across the once very productive "Fertile Crescent" of the Middle East was due primarily to _____.

Accepted Answer

A)  high calcium and magnesium levels in the irrigation waters 
B)  high levels of calcium-containing salt in the irrigation water 
C)  inadequate equipment and power to properly cultivate the soil 
D)  poor internal drainage of the soils 
E)  destructive wars in the region

Question 16

If you wanted to reduce the percentage sodium saturation from 30% to 5% in a sodic soil with a CEC of 20 cmolc/kg, how many cmolc's of CaSO4 would need to react with 1 kg of this soil?

Accepted Answer

A)  30 
B)  20 
C)  10 
D)  5 
E)  2

Question 17

Irrigation waters with high sodium adsorption (SAR) ratios are preferred over those with lower ratios.

Accepted Answer

A) True 
 B)False

Question 18

A farmer started irrigating a soil some 10 years ago but in recent years yields have declined and the soil physical condition has deteriorated. Which of the following most likely accounts for this situation?

Accepted Answer

A)  high content of Ca and Mg in the irrigation water 
B)  failure to use conservation tillage to reduce salt accumulation at the soil surface 
C)  high SAR of the irrigation water 
D)  excessive drainage of the soil 
E)  high gypsum content in the soil

Question 19

Which of the following characteristics of irrigation water is most apt to stimulate the formation of a sodic soil?

Accepted Answer

A)  high selenium content 
B)  high Ca2+ and Mg2+ content 
C)  high content of chlorides 
D)  low pH 
E)  high SAR values

Question 20

Which of the following trees would you expect to fare most poorly in a soil at pH 5.0?

Accepted Answer

A)  loblolly pine 
B)  aspen 
C)  sumac 
D)  walnut 
E)  white spruce

Exam 9: Soil Acidity, Alkalinity, Aridity and Salinity

Sodic soils generally have a poor physical condition. To what is this most likely due?

In extremely acid soils (pH 3.0 to 4.0) most of the Al³⁺ and H⁺ ions are bound tightly by organic matter and silicate clays and are not readily exchangeable.

The very high pH levels found in some arid region soils are most likely due to high levels of exchangeable _____.

In desert areas, the soil under scattered clumps of natural vegetation is usually depleted of nutrients compared to the unvegetated soil between clumps.

Saline-sodic soils are characterized by all but which one of the following?

You were advised to use elemental sulfur in the reclamation of a saline-sodic soil. Indicate how the sulfur helps bring about this reclamation.

The drainage of certain wetlands has resulted in extreme soil acidity. This is due primarily to which of the following processes that take place when the soil is drained?

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

Sulfuric acid is sometimes added to irrigation water to help in the reclamation of sodic soils.

Which of the following does not describe aluminum hydroxy ions (such as Al(OH) ₂₊) in the soil?

The ill effects of acidity in subsoils can be ameliorated by adding gypsum (CaSO_4-2H₂O) to the soil surface. Which of the following most likely helps account for this effect?

Which of the following would occur when lime is added to the surface of a soil at pH 6.0?

If you want to reclaim a saline soil, which of the following practices would you most likely use?

The drainage of some coastal wetland soils results in high pH due to underlying lime deposits.

The degradation of irrigated soils across the once very productive "Fertile Crescent" of the Middle East was due primarily to _____.

If you wanted to reduce the percentage sodium saturation from 30% to 5% in a sodic soil with a CEC of 20 cmol_c/kg, how many cmol_c's of CaSO₄ would need to react with 1 kg of this soil?

Irrigation waters with high sodium adsorption (SAR) ratios are preferred over those with lower ratios.

A farmer started irrigating a soil some 10 years ago but in recent years yields have declined and the soil physical condition has deteriorated. Which of the following most likely accounts for this situation?

Which of the following characteristics of irrigation water is most apt to stimulate the formation of a sodic soil?

Which of the following trees would you expect to fare most poorly in a soil at pH 5.0?

Exam 9: Soil Acidity, Alkalinity, Aridity and Salinity

Sodic soils generally have a poor physical condition. To what is this most likely due?

In extremely acid soils (pH 3.0 to 4.0) most of the Al3+ and H+ ions are bound tightly by organic matter and silicate clays and are not readily exchangeable.

The very high pH levels found in some arid region soils are most likely due to high levels of exchangeable _____.

In desert areas, the soil under scattered clumps of natural vegetation is usually depleted of nutrients compared to the unvegetated soil between clumps.

Saline-sodic soils are characterized by all but which one of the following?

You were advised to use elemental sulfur in the reclamation of a saline-sodic soil. Indicate how the sulfur helps bring about this reclamation.

The drainage of certain wetlands has resulted in extreme soil acidity. This is due primarily to which of the following processes that take place when the soil is drained?

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

Sulfuric acid is sometimes added to irrigation water to help in the reclamation of sodic soils.

Which of the following does not describe aluminum hydroxy ions (such as Al(OH) 2+) in the soil?

The ill effects of acidity in subsoils can be ameliorated by adding gypsum (CaSO4-2H2O) to the soil surface. Which of the following most likely helps account for this effect?

Which of the following would occur when lime is added to the surface of a soil at pH 6.0?

If you want to reclaim a saline soil, which of the following practices would you most likely use?

The drainage of some coastal wetland soils results in high pH due to underlying lime deposits.

The degradation of irrigated soils across the once very productive "Fertile Crescent" of the Middle East was due primarily to _____.

If you wanted to reduce the percentage sodium saturation from 30% to 5% in a sodic soil with a CEC of 20 cmolc/kg, how many cmolc's of CaSO4 would need to react with 1 kg of this soil?

Irrigation waters with high sodium adsorption (SAR) ratios are preferred over those with lower ratios.

A farmer started irrigating a soil some 10 years ago but in recent years yields have declined and the soil physical condition has deteriorated. Which of the following most likely accounts for this situation?

Which of the following characteristics of irrigation water is most apt to stimulate the formation of a sodic soil?

Which of the following trees would you expect to fare most poorly in a soil at pH 5.0?

In extremely acid soils (pH 3.0 to 4.0) most of the Al³⁺ and H⁺ ions are bound tightly by organic matter and silicate clays and are not readily exchangeable.

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

Which of the following does not describe aluminum hydroxy ions (such as Al(OH) ₂₊) in the soil?

The ill effects of acidity in subsoils can be ameliorated by adding gypsum (CaSO_4-2H₂O) to the soil surface. Which of the following most likely helps account for this effect?

If you wanted to reduce the percentage sodium saturation from 30% to 5% in a sodic soil with a CEC of 20 cmol_c/kg, how many cmol_c's of CaSO₄ would need to react with 1 kg of this soil?