Question 1

Reduced forms of iron and manganese along with soil organic matter largely control the color of well-drained soils.

Accepted Answer

Well-drained soils are typically oxidized, leading to the presence of iron oxides that give the soil a reddish or yellowish color, rather than reduced forms of iron and manganese.

Question 2

A soil on the south facing slope in Canada is likely to be drier and warmer than a comparable soil on a north facing slope.

Accepted Answer

South facing slopes receive more direct sunlight and warmth than north facing slopes, leading to drier and warmer soil conditions.

Question 3

The specific heat of soil solids is significantly higher than that of water.

Accepted Answer

The specific heat of soil solids is generally much lower than that of water. Soil has a lower heat capacity than water, which means it takes less energy to raise the temperature of soil compared to water. This is why soil tends to heat up and cool down faster than water.

Question 4

A wildlife biologist in South Africa notes that the soils on south-facing slopes are wetter and deeper than those on north-facing slopes,and therefore support more wildlife.What likely accounts for this difference?

Accepted Answer

South-facing slopes in the Southern Hemisphere receive less direct sunlight compared to north-facing slopes, leading to cooler temperatures and reduced evaporation, which results in wetter and deeper soils.

Question 5

Soil temperatures under an organic mulch will likely be lower than that of bare soils in the summer but higher than that of bare soils in the winter.

Accepted Answer

Organic mulch acts as an insulator, keeping the soil cooler in the summer by reducing evaporation and preventing heat from penetrating the soil. However, in the winter, the mulch acts as an insulator and keeps the soil warmer than bare soil.

Question 6

In natural wetlands one would expect the redox potential to be high because of the low oxygen content.

Accepted Answer

In natural wetlands, the redox potential is expected to be low because of low oxygen content. This is because wetlands are waterlogged environments where oxygen cannot penetrate deep into the soil. As a result, anaerobic (oxygen-depleted) conditions prevail, leading to a low redox potential.

Question 7

Wildfires in forested areas result in the formation of organic compounds that enhance the percolation of water through the soil.

Accepted Answer

Wildfires in forested areas often lead to the formation of a water-repellent layer in the soil, which can reduce the percolation of water, increasing runoff and erosion.

Question 8

In acid soils you would be concerned if the redox potential was low since it could mean a deficiency of some plant nutrients such as iron and manganese.

Accepted Answer

Low redox potential in acid soils typically indicates reducing conditions, which actually increases the availability of iron and manganese, making them more soluble and accessible to plants.

Question 9

Some 40 to 50% of the solar radiation in humid regions is used to heat the soil.

Accepted Answer

In humid regions, a significant portion of solar radiation is used for evaporation and transpiration processes, not primarily for heating the soil.

Question 10

The great bulk of gaseous interchange between the soil pores and the atmosphere occurs by mass flow of the concerned gases.

Accepted Answer

The great bulk of gaseous interchange between the soil pores and the atmosphere occurs primarily through diffusion, not mass flow, as gases move from areas of high concentration to areas of low concentration.

Question 11

Anaerobic conditions commonly prevail in liberally watered flower pots with mineral soil as the growing medium even though the containers have holes for drainage in the bottom of the pot.

Accepted Answer

Even though the containers have drainage holes, the soil could still become too saturated with water, leading to anaerobic conditions. This can be addressed by adjusting watering practices and improving soil quality.

Question 12

Heat pumps can take advantage of the fact that subsoils are generally warmer in the winter and cooler in the summer than the atmospheric air.

Accepted Answer

This is true. Heat pumps can use the constant temperature of the subsurface to provide heating in the winter and cooling in the summer. This is known as geothermal heat pump technology.

Question 13

The redox potential is a measure of the tendency of a substance to accept or donate electrons.

Accepted Answer

The redox potential is indeed a measure of the tendency of a substance to accept or donate electrons.

Question 14

The partial pressure of CO₂ in the soil pores is higher than the partial pressure of this gas in the atmosphere.

Accepted Answer

This statement is true. Gases in the soil pores can have different partial pressures than in the atmosphere due to factors such as microbial activity, root respiration, and soil moisture content.

Question 15

Conservation tillage is not practical in some areas of the Northern part of the United States because the practice lowers the surface soil temperature in the spring of the year.

Accepted Answer

Conservation tillage reduces the amount of soil disturbance, which can lead to lower soil temperatures in the spring. This can be problematic for crops that require warmer soil temperatures to germinate and grow, especially in cooler areas of the Northern United States.

Question 16

If the CO₂ content of soil air is 3.5%,it is 100 times higher than that of the atmosphere.

Accepted Answer

The statement says that the CO₂ content in soil air is 100 times higher than that of the atmosphere. Therefore, if the CO₂ content in soil air is 3.5%, it must be higher than the atmosphere, which is typically less than 0.03%. Therefore, the statement is true.

Question 17

An abundance of macropores in soils helps assure an abundance of oxygen in the soil.

Accepted Answer

Macropores are large soil pores that allow for the movement of air, water, and nutrients through the soil. These pores help to improve soil aeration and can lead to an abundance of oxygen in the soil. Thus, an abundance of macropores in soils can help assure an abundance of oxygen in the soil.

Question 18

The most important management factors influencing soil aeration in well-drained soils are those that determine the volume of the soil's macropores.

Accepted Answer

Well-drained soils rely on macropores for soil aeration, so the management factors that influence the volume of these pores are crucial in maintaining soil aeration.

Question 19

The alternate freezing and thawing of soils results in the upward heaving of plants and building foundations.

Accepted Answer

The process is known as frost heaving, and it occurs due to the expansion of water as it freezes in soil pores. This expansion can cause the soil to push upward, resulting in the heaving of plants and building foundations.

Question 20

You would expect the installation of an effective tile drainage system in a naturally poorly drained soil in Iowa to increase soil temperatures in the spring of the year.

Accepted Answer

Tile drainage can help to remove excess water from soil, which can help it warm up faster in the spring. This is because water has a higher heat capacity than air or soil, meaning it takes longer to warm up and retains heat longer. Therefore, removing excess water can help the soil warm up more quickly.

Quiz 7: Soil Aeration and Temperature