Question 1

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 typically have abundant macropores that provide good soil aeration. Therefore, management factors that affect the volume of macropores, such as soil compaction and organic matter content, are crucial in maintaining soil aeration.

Question 2

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 system removes excess water from the soil, which can increase soil temperatures in the spring by promoting soil drying and warming.

Question 3

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

Heat pumps work by transferring heat from a warmer source to a cooler source, and in the case of ground-source heat pumps, the subsoil provides a more stable and consistent source of heat than atmospheric air. In the winter, the heat pump extracts heat from the relatively warm subsoil and transfers it into the building, while in the summer, the process is reversed and heat is transferred from the building into the cooler subsoil.

Question 4

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 5

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 6

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

Accepted Answer

The answer of Reduced forms of iron and manganese along...

Question 7

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

Accepted Answer

Macropores in soil are larger openings that allow air and water to move more freely through the soil. This promotes good soil aeration and helps ensure the presence of oxygen in the soil, which is vital for plant growth and microbial activity.

Question 8

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 if flower pots have drainage holes, they can still become anaerobic if the soil is too wet and does not allow enough air to circulate.

Question 9

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 because the concentration of gases in the soil pores can differ from the concentration in the atmosphere due to various factors such as microbial respiration, plant root respiration, and chemical reactions in the soil. Therefore, the partial pressure of CO₂ may be higher in the soil pores than in the atmosphere.

Question 10

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 11

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 typically low due to the anaerobic conditions created by the low oxygen content. Anaerobic conditions promote the reduction of oxygenated compounds, which lowers the redox potential.

Question 12

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 13

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, which means it can help regulate the temperature of the soil underneath it. In the summer, it can help prevent the soil from getting too hot, while in the winter, it can help keep the soil from getting too cold. However, the insulating properties of the organic mulch mean that the soil temperatures underneath may not fluctuate as much as bare soils.

Question 14

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

A south-facing slope receives more direct sunlight and therefore has higher temperatures and more evaporation, resulting in a drier soil. Conversely, a north-facing slope receives less direct sunlight and has lower temperatures and less evaporation, resulting in a moister soil.

Question 15

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

Accepted Answer

This process is known as frost heaving and it occurs when water in the soil freezes and expands, pushing the soil and anything above it upward. This can cause damage to building foundations and uproot plants.

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 is true. A CO₂ content of 3.5% in soil air is 100 times higher than the typically measured atmospheric concentration.

Question 17

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. This results in wetter and deeper soils on south-facing slopes, supporting more wildlife.

Question 18

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 19

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

Accepted Answer

The statement is true. The redox potential is a measure of the relative ability of a substance to accept or donate electrons. It is used to determine the direction and extent of oxidation and reduction reactions.

Question 20

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 involves leaving crop residue on the soil surface, which can reduce the amount of sunlight that reaches the soil and lower the surface temperature. In some areas of the Northern United States, this can delay the warming of the soil in the spring, which can negatively impact crop growth and development. Therefore, conservation tillage may not be practical or effective in these regions.

Quiz 7: Soil Aeration and Temperature