Chapter 7

The partial pressure of oxygen in the atmosphere is 0.21 bar and that of nitrogen 0.78. Which of the following partial pressure levels would you expect to find in the pores of moderately well-drained soil?

0.15 (oxygen)

The heat of vaporization of water is 540 cal/g. A soil containing 30kg water per 100kg solids lost one sixth of the water by evaporation. If one tenth of the energy needed to evaporate the water came from the soil solids how much would the temperature if those solids be lowered?

13.5 C

A mineral soil has a water content of 25 kg water per 100 kg dry soil. What is the approximate specific heat of this soil, expressed in calories per kilogram?

360

The bulk of gaseous interchange in soils takes place by___.

Diffusion

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.

False

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

False

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

False

Respiration by plant and animal cells along with photosynthesis releases oxygen and consumes carbon dioxide.

False

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

False

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

False

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

False

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

False

The redox potential of a soil is -250mV. Which of the following forms of the pertinent elements would you expect to find in the soil?

Fe2+

A wildfire biologist in South Africa notes that the soil 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?

High soil temperatures on the north slopes

Which of the following is considered necessary features for an area to be delineated as a wetland?

Hydric soils

8. Compared to upland soils, wetland soils would be characterized by and abundance of ___.

Methane

Soil A has a redox potential pf 400mV, soil B -200 mV. Of the two soils, Soil A is more apt to be characterized by an abundance of ____.

Molecular oxygen

The following is the reduced form of the essential element depicted

NH4+

A well aerated soil is characterized by a relative abundance of ___.

NO3+ ions

Which of the following is not a major factor in determining the soil aeration status?

Nitrogen gas

Forest fires result in sufficiently high soil temperature to cause the vaporization and movement of certain organic compounds in soils. The main effect of these compounds is to ____.

Reduce water infiltration and percolation through the profile

Which of the following actions would best assure good assure aeration in a soil?

Remove excess water

If you owned a dairy farm with poorly drained clay soils in a humid temperate region which of the following would be most satisfactory from the stand point of soil aeration and temperature

Ridge-till system

Alternate freezing and thawing of soils results in the "heaving" of plants and the destruction of shallow building foundations. This effect is due primarily to ___.

The expansion of water when it freezes

The primary characteristic of subsoil that accounts for ability of grounds circulating heat pumps to moderate temperatures in houses in both summer and winter is___.

The high specific heat of the soil

The redox potential is a measure of ___.

The tendency of a substance to accept or donate electrons

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

True

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

True

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

True

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

True

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

True

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.

True

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

True

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.

True

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

True

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

True

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

True

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.

True

Which of the following practices would encourage high soil temperatures in the spring in a humid-temperate area?

Use a plastic multh

The process of aerobic respiration is a significant source of which of the following gases?

Carbon dioxide

Which of the following processes are most apt to encourage good soil aeration?

Creation of more macropores