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            to accompany

Elements of the Nature and
    Properties of Soils
             Second Edition




         Nyle C. Brady, Ph.D.
     Emeritus Professor of Soil Science
             Cornell University
             Ithaca, New York


                    and



          Ray R. Weil, Ph.D.
         Professor of Soil Science
          University of Maryland
          College Park, Maryland
                            TABLE OF CONTENTS

Chapter 1   The Soils Around Us                                                   3

Chapter 2   Formation of Soils from Parent Materials                              8

Chapter 3   Soil Classification                                                   13

Chapter 4   Soil Architecture and Physical Properties                             19

Chapter 5   Soil Water: Characteristics and Behavior                              24

Chapter 6   Soil and the Hydrologic Cycle                                         29

Chapter 7   Soil Aeration and Temperature                                         34

Chapter 8   The Colloidal Fraction: Seat of Soil Chemical and Physical Activity   39

Chapter 9   Soil Acidity, Alkalinity, and Salinity                                44

Chapter 10 Organisms and Ecology of the Soil                                      52

Chapter 11 Soil Organic Matter                                                    55

Chapter 12 Nitrogen and Sulfur Economy of Soils                                   62

Chapter 13 Soil Phosphorus, Potassium, and Micronutrients                         67

Chapter 14 Practical Nutrient Management                                          72

Chapter 15 Soil Erosion and Its Control                                           78




                                                     2
The Soils Around Us                                                             Chapter 1

                            Multiple Choice Questions
                    (Circle the single best answer for each question.)

1. Most of the different nutrients essential for growth are supplied to plants directly from
   the ______.
   A. rain water               B. soil solution C. atmosphere
   D. cosmic radiation         E. soil humus

2. In a load of 10 cubic meters of topsoil, approximately how many cubic meters of the
   volume would be solid material?
   A. 1        B. 2.5     C. 4       D. 5        E. 7.5

3. Which of the following is (are) essential plant nutrients?
   A. Cu      B. Al      C. Sr        D. Pb      E. all of the above

4. Which of the following is considered to be a plant macronutrient?
   A. N       B. P       C. S        D. Ca      E. all of the above

5. Soil occupies the ______part of the regolith.
   A. upper B. lower C. younger D. both B and C

6. The lithosphere is made up of _________.
   A. air             B. rock           C. water
   D. plants and animals        E. all of the above

7. The layers of contrasting material found when one digs a hole in a soil are called
   _______.
   A. pseudoliths B. regoliths C. pedons
   D. horizons        E. soil structure

8. A soil profile consists of _________.
   A. the sum of chemical and physical data known about a soil
   B. the way a soil "feels"
   C. the boundaries of a particular soil
   D. the set of layers seen in a vertical cross section of a soil
   E. the general outline of a soil or group of soils when viewed from the side

9. "Topsoil" is generally equivalent to which soil horizon?
   A. A        B. B        C. C       D. D       E.     E

10. "Subsoil" is generally equivalent to which soil horizon?
    A. A        B. B       C. C        D. D       E.      E

11. In a typical mineral soil in optimal condition for plant growth, approximately what
    percentage of the pore space would be filled with water and what percentage filled
    with air?
    A. 10% water and 90% air            B. 90% water and 10% air
    C. 25% water and 25% air            D. 50% water and 50% air
    E. 25% water and 75% air


                                             3
12. The amount of different sizes of mineral particles in a soil defines the soil ________.
    A. structure      B. texture         C. pore space
    D. solution       E. profile

13. The water in the soil typically differs from pure water because the soil water
    ________.
    A. contains organic compounds
    B. contains mineral nutrients
    C. is restrained in its flow by attraction to particle surfaces
    D. all of the above
    E. none of the above

14. Compared to silt, clay-sized soil particles are characterized by ______.
    A. greater attraction for water
    B. greater proportion of primary minerals
    C. less tendency to form hard clods when dry
    D. less capacity to hold nutrients in plant-available forms

15. Which of the following pH values represents a neutral condition?
    A. 1.0     B. 5.0     C. 6.0     D. 7.0     E. 10

16. Which of the following pH values represents the most acid condition?
    A. 1.0     B. 10.0 C. 7.0        D. 100     E. 5.55

17. Most (usually 80% or more) of soil potassium and calcium can be found in the form
    of _________________.
    A. dissolved substances
    B. structural components of minerals
    C. exchangeable ions
    D. organic compounds

18. Increasing the organic matter content of a soil is likely to _____.
    A. have no effect on water holding capacity
    B. increase the soil's water holding capacity
    C. decrease the soil's water holding capacity

19. Hydroxyl ion concentrations are greatest in a soil solution with a pH value of ______.
    A. 0.1        B. 4.0         C. 5.0          D. 6.5

20. In a given soil, the horizon with the highest organic matter content is generally the
    _____ horizon.
    A. E        B. C        C. D        D. B       E. A

21. Information about conditions at 2 to 4 meters deep in a soil is most helpful for
    understanding ____ ___.
    A. how best to design a building foundation
    B. the diversity of animal life in the soil.
    C. the proper classification of the soil.
    D. fertility requirements of most crops



                                              4
                               True or False Questions
                             (Write T or F after each question.)

22. Except for some kinds of foods, modern industry has made human dependence on
    soils a thing of the past.

23. Most of the water in our rivers and lakes has come in contact with and has been
    affected by soils.

24. Soil air usually has a higher carbon dioxide content than the air in the atmosphere.

25. Plants can be grown without any soil.

26. Hydroponics will likely be a key element in enabling the world to feed and clothe its
    increasing human population in the next few decades.

27. Practices that tend to increase the amount of organic matter in soils would be
    expected to reduce the global greenhouse effect.

28. Soil, like concrete and steel, is a standard construction material. Its properties are
    well characterized and predictable so that standard building foundation designs can
    be used uniformly at all building sites of a given topography.

29. Although subsoil is more difficult to obtain, it is generally equally as good as topsoil
    for landscaping purposes.

30. Subsoil is typically equivalent to the O horizon.

31. The mineral particles in soil consist of sand, silt, and clay.

32. Where organic matter constitutes only 1 or 2 percent of the soil by weight, it has only
    negligible influence on soil properties.

33. The dark brown and black humus found in many soils does not mix well with clay
    minerals so there is very little contact between these two soil components.

34. Soil horizons, like alluvial sediments, generally have a horizontal orientation,
    regardless of the slope of the land.

35. A, B, C, and E horizons can be found in any true soil.

36. For any soil in which it is present, the C horizon is the parent material for the B
    horizon.

37. While many organisms depend on the soil for nutrients and water, only a few very
    specialized organisms live in the soil itself.

38. If supplied with a suitable nutrient solution, plants can grow normally without any soil
    at all.




                                               5
39. Natural soils (as opposed to modern farm soils) can recycle organic compounds, but
    not inorganic elements.

40. Most of the water flowing in rivers passed through a soil profile or over soil surfaces
    before reaching the river.

41. Most, if not all, of the nutrient supply stored in a fertile soil is in forms readily
    available to plants.

42. In humid regions most rainwater that soaks into the soil and is not used by plants
   eventually flows into rivers and streams.




                                                 6
        Answers to Chapter 1 Questions

1. A                      22.   F
2. D                      23.   T
3. A                      24.   T
4. E                      25.   T
5. A                      26.   F
6. B                      27.   T
7. D                      28.   F
8. D                      29.   F
9. A                      30.   F
10. B                     31.   T
11. D                     32.   F
12. B                     33.   F
13. D                     34.   F
14. A                     35.   F
15. D                     36.   F
16. A                     37.   F
17. B                     38.   T
18. B                     39.   F
19. D                     40.   T
20. E                     41.   F
21. A                     42.   T




                      7
Formation of Soils from Parent Materials                                                      Chapter 2


                                   Multiple Choice Questions
                           (Circle the single best answer for each question.)

1. Igneous rocks can best be characterized as:
   A. rocks formed when molten magma solidifies.
   B. rocks containing both feldspars and micas.
   C. rocks formed from the recrystallization of sedimentary material.
   D. rocks containing a mixture of primary and secondary minerals.
   E. rocks found primarily near volcanoes.

2. What mineral is most resistant to weathering under humid temperate conditions?
   A. dolomite B. muscovite C. gypsum          D. gibbsite   E. biotite

3. Which of the following is not a secondary mineral?
   A. silicate clay   B. microcline C. calcite D. hematite      E. gypsum

4. Mechanical weathering processes result in:
   A. the decomposition of primary minerals.
   B. the hydrolysis of minerals through frost action.
   C. the disintegration of rocks due to differential expansion of minerals.
   D. the oxidation of iron and manganese compounds.

5. Which of the following is not considered one of the five major factors influencing soil formation?
   A. native parent materials B. living organisms C. climate
   D. valence state               E. topography

6. Residual parent materials are best described as __________.
   A. materials formed under organic residues
   B. materials formed by weathering of rocks and minerals in place
   C. materials transported from one location to another by water, ice, or wind
   D. materials more dominant in Iowa than in the Southern United States
   E. upland materials formed with relatively little chemical weathering

7. Glacial till is a term used to describe parent materials that:
   A. were transported by water gushing from glacial fronts.
   B. were laid down in the bottom of former glacial lakes.
   C. were transported by high winds during glacial periods.
   D. are sorted by rapidly flowing melt waters.
   E. contain a heterogenous mixture of mineral debris dropped by receding glaciers.

8. If you wanted to find a soil where physical weathering dominated over chemical breakdown you
   would be most apt to find it in ______.
   A. a desert region of Arizona      B. a humid region in Brazil C.       the hill lands of Georgia
   D. a lacustrine deposit in Minnesota      E. a coastal plain area of Delaware

9. Igneous, sedimentary, and metamorphic are three _________.
   A. types of rocks       B. basic classes of soils  C. master horizon names
   D. forms of minerals    E. processes of weathering

                                                    8
10. The element most often involved in oxidation reactions as minerals weather is _____.
    A. copper    B. silicon      C. aluminum        D. magnesium                 E.     iron

11. In which of the following horizons has the process of illuviation most likely occurred?
    A. O horizon        B. C horizon      C. A horizon        D. E horizon           E.     B horizon

12. Organic matter accumulation is most pronounced in the ____.
    A. O horizon B. A horizon C. E horizon       D. B horizon E. C horizon

13. Silicate clay accumulation is most common in the ____.
    A. A horizon B. B horizon C. C horizon D. O Horizon             E. E horizon

14. Which of the following statements is not correct?
    A. Grasslands are found in semi-arid and sub-humid areas.
    B. Coniferous forests are found mostly in cool humid areas.
    C. The type of native vegetation is controlled primarily by climate.
    D. Deciduous forests are mainly found in warm humid areas.
    E. Tropical forests protect the soil from excessive weathering.

15. Which of the following statements is correct?
    A. Soils on hillsides tend to be deeper than those on level lands.
    B. Lacustrine parent materials have been subject to weathering for shorter periods of time than
       residual parent materials nearby.
    C. Limestone parent materials enhance the process of acidification.
    D. Nutrient cycling in forested areas contributes little to soil formation.
    E. Calcium carbonate accumulation is more prominent in humid than in arid regions.

16. Secondary minerals are most prominent in the       fraction of soils.
    A. organic      B. sand        C. silt      D. clay

17. The presence of rocks such as shale and sandstone indicate the existence of _______.
    A. a high water table   B. ancient seas              C. old mountain ranges
    D. iron-rich minerals   E. highly weathered soils

18. "Illite-->kaolinite-->iron/aluminum oxide" represents a ________.
    A. catena                     B. weathering sequence     C. silicate mineral sequence
    D. both A and B               E. none of the above

19. Granite is an example of a(n) ________.
    A. primary mineral       B. sedimentary rock       C. secondary mineral
    D. igneous rock          E. eolian parent material

20. The transformation of gneiss into mica, quartz, and feldspar crystals is an example of:
    A. physical weathering B. chemical weathering           C. disintegration
    D. hydrolysis            E. both A and C

21. The reaction: mica + H2O  K+ + OH- + acid clay is an example of ________.
    A. hydrolysis     B. acid solution weathering     C. oxidation
    D. hydration      E. exfoliation

22. Exfoliation is caused by changes in _________.
    A. hydration                     B. oxidation               C. temperature

                                                    9
   D. carbon dioxide dissolution       E. all of the above

23. The mixed angular gravel, rock, and soil found at the foot of a slope is typical of what type of parent
    material?
    A. eolian    B. colluvial        C. fluvial     D. glacial        E. lacustrine

24. Alluvial fans are usually characterized by ______ soils.
    A. sandy and gravelly B. clay textured
    C. poorly drained          D. nearly level


                                      True or False Questions
                                     (Write T or F after each question.)

25. Igneous rocks are formed when molten magma cools and solidifies.

26. Sandstones are good examples of metamorphic rocks.

27. Secondary minerals are recrystallized products of the chemical breakdown and/or alteration of
    primary minerals.

28. Iron and aluminum oxides are major components of igneous rocks.

29. Chemical weathering is accelerated by water, oxygen, and organic and inorganic acids moving
    down through the regolith.

30. Hydrolysis involves the splitting of water into its H+ and OH- components while hydration attaches
    intact water molecules to a compound.

31. The presence of iron in a mineral generally increases its resistance to chemical breakdown.

32. Alluvial parent materials are those that have been laid down in former lake bottoms.

33. Residual parent materials have formed in place and have not been transported from one area to
    another.

34. Glacial till is laid down by melt waters gushing out from the front of glaciers.

35. Marine sediments are typical parent materials in coastal plain areas.

36. Organic deposits are most common in areas where water flow over the soil surface is restricted.

37. Climate influences not only the rate of weathering but the type of native vegetation dominant in an
    area.

38. Living organisms affect soil formation primarily by their constraining the level of oxygen in the soil.

39. Residual parent materials have generally been subjected to weathering for a longer period of time
    than have lacustrine or alluvial parent materials.

40. The O horizons of a soil are dominantly organic horizons occurring above mineral horizons.


                                                     10
41. The A horizons are more apt to be cultivated than the E horizons.

42. In most B horizons one of the dominant processes of soil formation has been eluviation.

43. The C horizons are generally more completely weathered than the other horizons.

44. Even if all the glaciers present today in the world were to melt, the melt water would have no
    measurable effect on the level of the world’s oceans.

45. Glacial till can be recognized by the distinct layering of different kinds of particles.

46. Soils developed in wind-blown parent materials such as loess are generally of little agricultural
    value.

47. Sapric and fibric are terms used to describe peat parent materials.

48. A soil developed in residual parent materials will likely have properties related to the properties of
    the rock below the C horizon.

49. A soil developed in transported parent materials will likely have properties related to the properties
    of the rock below the C horizon.

50. The topmost horizon in most humid region forest soils is the A horizon.

51. Eluviation of clay, iron, and other materials is the principal process responsible for the formation of
    an E horizon.

52. Weathering of rocks usually is most intense in the center of a rock fragment, and gradually
    decreases toward the outside.

53. The parent materials for most coastal plain soils are residual in nature.




                                                      11
        Answers to Chapter 2 Questions

1. A      18. B                          35. T
2. D      19. D                          36. T
3. B      20. E                          37. T
4. C      21. A                          38. F
5. D      22. C                          39. T
6. B      23. B                          40. T
7. E      24. A                          41. T
8. A      25. T                          42. F
9. A      26. F                          43. F
10. E     27. T                          44. F
11. E     28. F                          45. F
12. A     29. T                          46. F
13. B     30. T                          47. T
14. E     31. F                          48. T
15. B     32. F                          49. F
16. D     33. T                          50. F
17. B     34. F                          51. T
                                         52. F
                                         53. F




                      12
Soil Classification                                                                             Chapter 3


                                    Multiple Choice Questions
                            (Circle the single best answer for each question.)

1. A soil pedon is ____.
   A. a category of Soil Taxonomy
   B. a three-dimensional unit that embodies the primary characteristics of an individual soil
   C. generally larger in area than a polypedon
   D. a diagnostic subsurface horizon prominent in arid regions and in sandy parent materials
   E. a surface horizon used to characterize soil suborders and great groups

2. Soil scientists from which country first conceived the idea that soils were natural bodies?
   A. United States       B. France       C. Russia      D. Great Britain           E.     Belgium

3. In which of the following epipedons is the organic matter level generally lowest?
   A. mollic           B. umbric     C. histic         D. ochric           E.     melanic

4. Which soil moisture regime has the highest soil moisture levels?
   A. udic       B. ustic      C. aquic        D. aridic      E. xeric

5. Which of the following subsurface diagnostic horizons would you expect to find in a highly
   weathered soil of the humid tropics?
   A. cambic B.        oxic      C. natric     D. salic      E. spodic

6. Which of the following diagnostic horizons would likely not restrict root growth in soils?
   A. albic       B. fragipan C. salic         D. placic        E. petrocalcic

7. Which of the following soil temperature regimes would provide the warmest and least variable soil
   temperatures?
   A. Thermic B. Mesic            C. Isomeric D. Isohyperthermic E. Hyperthermic

8. Which of the following categories of Soil Taxonomy provides the greatest specificity of soil
   properties?
   A. series      B. suborder C. order          D. family    E. great group

9. The nomenclature of Soil Taxonomy is characterized by all but which one of the following
   statements?
   A. Soil names (except for series level) identifies major soil characteristics.
   B. The names of the orders all end with the letters sols.
   C. The subgroup name also tells you the great group, suborder, and order names.
   D. The names give a clear indication of the modes of genesis of the soil.
   E. The names are based on measurable properties and not on presumed modes of genesis.

10. A soil has a thick black A horizon, a distinct B horizon, has reasonably stable soil structure, and was
    formed under grassland natural vegetation. In which suborder is it most likely classed?
    A. udolls       B. ustalfs     C. cambids D. aquents              E. udults.

11. In which of the following soil orders would recent alluvium most likely be a common parent
    material?
    A. Ultisols    B. Entisols C. Andisols           D. Alfisols    E.              Aridisols

                                                    13
12. Soils in this order are commonly sandy in texture, quite acidic and develop primarily under
    coniferous trees in cool to cold climates
    A. Mollisols        B. Andisols        C. Spodosols          D. Alfisols               E. Ultisols

13. Argillic horizons are characterized by ___.
    A. accumulation of silicate clays
    B. high level of Na+ ions
    C. high levels of iron and aluminum oxides
    D. impervious hardpan layers
    E. organic matter accumulation

14. Soils in which of the following suborders would be more likely to occur in Minnesota than in Texas?
    A. Fluvents         B. Cryolls     C. Udalfs        D. Usterts          E.     Cambids

15. You are seeking a soil with high clay content but one that is not sticky when wet nor hard and
    cloddy when dry. In which of the following suborders would you most likely find this soil?
    A. Udert         B. Ustalfs       C. Aquands        D. Ustox                E. Cambids

16. Which of the following describes a soil likely to contain a significant content of low activity clays?
    A. an Alfisol in New York
    B. a Mollisols in Central Brazil
    C. an Oxisol in Minnesota
    D. an Ultisol in the Congo River basin in Africa
    E. an Inceptisol in Mississippi

17. Which of the categories in the Soil Taxonomy system indicates properties that have implications for
    root growth as well as for the construction of building foundations?
    A. suborder            B. family          C. series
    D. great group         E. subgroup

18. Soils in which of the following soil suborders would most likely have a prominent E horizon under
    the A horizon?
    A. Ustox            B. Udalfs       C. Orthents      D. Aquepts                E.     Udolls

19. If the soils are to be used for crop production, for which soil order would land drainage be most
    critical?
    A. Mollisols         B. Inceptisols     C. Aridisols       D. Oxisols             E.    Histosols

20. The map units on a detailed soil map in a county soil survey report are most likely to be labeled with
    names from which category of Soil Taxonomy?
    A. order      B. suborder C. great group D. subgroup E. series

21. In soils of which great group would you most likely find wide surface cracks during periods of dry
    weather?
    A. Calciusterts         B. Albaqualfs    C. Argiaquolls      D. Kandiaquults       E. Haplustox

22. Investigating the soils of northern Canada on summer, you dig a soil pit easily though fairly uniform
    peat material until, at 75 cm deep, your shovel hits a layer that is frozen solid. Into which type of soil
    are you most likely digging?
    A. Histosol     B. Cryent       C. Fibrist   D. Histel        E. Cryert


                                                     14
23. Which of the following soil map units consists of the most nearly level land?
    A. BeC2            B. CgE2       C. BeC3         D. CgE         E. BeB2

24. Which of the following soil map units consists of the most severely eroded soils?
    A. BeC2 B.         CgE2 C.        BeC3 D.        CgE E.         BeB2

25. If you wanted to choose a site for an irrigation project and were primarily concerned that the slope
        be less than 2%, but also needed soils with good internal drainage and high water holding
        capacity, you could feed all the relevant soils data into a(n) ______ to help you choose the best
        site available.
    A. G.I.S       B. G.P.S      C. T.D.R.         D. Thematic Mapper        E. G.P.R.

26. To constitute a soil association, a group of soils must all _____.
   A. be classed in the same soil order
   B. have the same soil series name
   C. be found together in the landscape
   D. have the same surface horizon texture and be in the same slope class
   E. all of the above

27. In making the detailed soils map in a county soil survey, soil scientists typically obtain most of the
        necessary soil profile information by using _____.
    A. soil pits
    B. ground penetrating radar
    C. satellites
    D. soil augers
    E. electro-magnetic induction

28. In the United States, the government lead agency for most soil survey work is the _____.
    A. National Bureau of Soil Survey
    B. Department of Land Reclamation
    C. Agency for Soil Resource Inventory
    D. Department of the Interior
    E. Natural Resources Conservation Service

29. Which of the following could likely be a "layer" of information in a GIS?
    A. data on rainfall changes over time
    B. soil drainage classes
    C. land capability classes
    D. B and C
    E. all of the above

                                      True or False Questions
                                    (Write T or F after each question.)

30. Russian scientists were the first to develop the concept of soils as natural bodies.

31. Soil Taxonomy, the classification system used in the United States, was developed by C. E. Marbut
    and associates in the 1940s.

32. Epipedons are diagnostic subsurface horizons that are one of the primary means of classifying soils
    in the United States.


                                                     15
33. Organic matter distribution in the profile is a significant criterion for differentiating epipedons.

34. The soil and a soil are two extremes in the concept of soils that is basic to most classification
    schemes.

35. A pedon is a three dimensional field unit occupying about 1000 square meters (1 hectare) of land
    area.

36. A polypedon or individual soil is a group of closely related pedons that conceptually approximates
    what in the United States is called a soil series.

37. The two most significant characteristics of the classification system used in the United States are a
    unique system of terminology and focus on measurable soil properties as a primary basis for the
    classification.

38. For agricultural use in a given region, a soil with an ochric epipedon could generally be expected to
    be more productive than one with a mollic epipedon.

39. An argillic horizon is a diagnostic horizon characterized by the subsurface accumulation of silicate
    clays.

40. An aquic soil moisture regime connotes a higher degree of soil moisture saturation than an ustic
    one.

41. The broadest category of classification in Soil Taxonomy specifies 12 soil orders, 11 of which are
    for mineral soils.

42. The categories of Soil Taxonomy can be listed from the broadest (first) and most specific (last) as:
    order, suborder, great group, subgroup, series, family.

43. The name of a subgroup indicates the order, suborder, and great group of which it is a member.

44. Soils classified as Inceptisols have the least well-developed profiles of those in any order in the Soil
    Taxonomy system.

45. Soils in the Oxisols order are deeply weathered and have deep subsurface horizons of silicon
    oxide.

46. Andisols are found mostly near recently active volcanoes.

47. Mollisols are characterized by a deep epipedon that is high in organic matter.

48. Because soil development is just beginning in Entisols, these soils are generally less variable in
    properties than are those in the Andisols or Ultisols orders.

49. Vertisols are characterized by high contents of swelling-type silicate clays.

50. Spodosols are generally less acidic and less sandy than are Alfisols.

51. The family category focuses on properties affecting plant roots and suitability for engineering uses
    of soils.


                                                      16
52. You would be more apt to find a Gelisol in Alaska than in Iowa.

53. Oxisols are more highly weathered than are the soils of any other order.

54. Histosols generally have higher organic matter contents than Mollisols.

55. Geographic information about soils addresses primarily changes in field soil properties in the
    vertical direction.

56. A soil association is a group of soils found together in a landscape that may differ in minor ways,
    but must all belong to the same soil order.

57. The map unit "152C2" indicates that the soils in this complex have two types of C horizons.

58. Modern county soil survey reports provide information on the suitability of soils for construction of
    such projects as sewage lagoons, roads and streets, and septic tank drainage fields.




                                                    17
                Answers to Chapter 3 Questions


1.    B   22.   D                  43.   T
2.    C   23.   E                  44.   F
3.    D   24.   C                  45.   F
4.    C   25.   A                  46.   T
5.    B   26.   C                  47.   T
6.    A   27.   D                  48.   F
7.    D   28.   E                  49.   T
8.    A   29.   D                  50.   F
9.    D   30.   T                  51.   T
10.   A   31.   F                  52.   T
11.   B   32.   F                  53.   T
12.   C   33.   T                  54.   T
13.   A   34.   T                  55.   F
14.   B   35.   F                  56.   F
15.   D   36.   T                  57.   F
16.   D   37.   T                  58.   T
17.   B   38.   F
18.   B   39.   T
19.   E   40.   T
20.   E   41.   T
21.   A   42.   F




                              18
Soil Architecture and Physical Properties                                                         Chapter 4

                                     Multiple Choice Questions
                            (Circle the single best answer for each question.)

1. Brown and red colors in subsurface horizons are caused by __ in the soil.
   A. manganese         B. aluminum oxides
   C. organic matter    D. clay
   E. iron oxides

2. Dull gray colors are characterized by _____.
   A. gray hues           B. low chromas
   C. high color values D. low color values
   E. mixed hues

3. Soil colors are scientifically described by ____ color designations such as 10YR3/4.
   A. USDA         B. wavelength C. Parson's D. Munsell E. structural

4. Which color would be typical of a well drained, low-organic matter sandy surface soil?
   A. 10YR5/8 B. 7.5YR6/2 C. 2.5YR6/1 D. 7.5YR2/2                 E. 10YR8/4

5. Texture describes the ____ of particles in a soil.
   A. sizes B. colors C. arrangement D. mineralogical makeup                        E. roughness

6. Colloidal properties are exhibited by the ___ fraction of soils.
   A. gravel      B. sand C. silt         D. clay

7. The percentages of which soil components represent the minimum information necessary in order
   to determine the textural class of a soil?
   A. gravel and sand         B. silt and sand C. clay and organic matter
   D. clay, water and air     E. sand, silt and clay

8. Because of their greater surface area per unit of soil mass, silt loams soils generally have a greater
   capacity than loamy sand soils to ___.
   A. adsorb water                                  B. adsorb gases
   C. release nutrients by mineral weathering       D. support bacterial growth
   E. all of the above

9. Which of the following is not a textural class name?
   A. sand B. silt C. loam D. clay E. sandy silt

10. A sticky, putty-like feel indicates a high percentage of which soil separate?
    A. sand B. silt C. clay D. humus E. none of the above

11. Which type of soil structure is typically found in surface soil (A horizons)?
    A. platy B. sub-angular blocky C. prismatic D. columnar                    E.      granular

12. Which type of structure is typically found in sodium-rich sub-surface horizons?
    A. platy B. sub-angular blocky C. prismatic D. columnar                 E.     granular




                                                     19
13. For which substance would the particle density equal the bulk density?
    A. an organic soil   B. a wet soil
    C. a quartz pebble D. a soil clod E. a well-aggregated surface soil

14. If a dry soil high in certain types of ____ is moistened, it is likely to swell up with enough force to
    crack pavements and building foundations.
    A. humus         B. iron     C. clay D. silt E. any of the above

15. Using a textural triangle chart, it can be determined that a soil with 45% sand and 20% clay belongs
    to the ___textural class.
    A. sandy loam B. loamy sand C. sandy clay loam D. loam                       E. sandy clay

16. A landscaping contractor wants to change the texture of a silt loam soil to meet the specifications
    for a loam. S/he would most likely do so by adding ______ to the soil and mixing it well.
    A. humus       B. compost C. clay D. sand E. either A or B

17. In many soil profiles, the subsoil is high in clay, but is also quite permeable to percolating water.
    Why?
    A. Clay generally promotes free water movement.
    B. The subsoil may have an organic texture.
    C. Prismatic structure may be well developed.
    D. The water table may be present in the subsoil.
    E. All of the above are common reasons.

18. A soil with a bulk density equal to 0.35 Mg/m3 is most likely what type of soil?
    A. an Ultisol                          B. a Vertisol      C. a compacted urban soil
    D. a well-structured garden soil       E. a peat soil

19. Practices that add organic matter and reduce tillage can be expected to most significantly increase
    the _____ in a soil.
    A. macropores B. total porosity C. bulk density D. fineness of texture

20. Fungal hyphae have an important influence on soil structure because they ______.
    A. help to flocculate the soil colloids
    B. stabilize macro aggregates
    C. are active in the formation of soils crusts
    D. create large channels that enhance water flow and aeration
    E. all of the above

21. Which of the following practices is(are) useful in stabilizing surface soil structure?
    A. use of organic mulches B. use of green manure crops
    C. growing grass sod          D. minimizing tillage        E. all of the above

22. Soil tilth refers to _____.
    A. the bearing strength of a soil under a given downward force
    B. the moisture content at which a soil is best suited for tillage
    C. ratio of bulk density to particle density
    D. the physical suitability of a soil for plant growth
    E. micro-aggregates produced as a by-product of tillage

23. The difference between the liquid and plastic limits of a soil is _______.
    A. that one is a moisture variable while the other is a density variable

                                                      20
    B.   that one is applicable to natural soils the other to artificial growth media
    C.   greater than the difference between the solid and liquid limits
    D.   the plasticity index
    E.   none of the above


                                        True or False Questions
                                      (Write T or F after each question.)

24. Light-colored surface soils are likely to be warmer than dark-colored surface soils if soil moisture
    and other conditions are the same.

25. Fungal hyphae play an important role in stabilizing surface soil aggregates.

26. Flocculation is the process by which certain chemicals in the soil stabilize large soil aggregates.

27. The drainage class of a soil (the degree to which the soil becomes water-saturated during the year)
    can be judged by the presence and location of gley in the soil profile.

28. Tillage when the soil is too wet is likely to increase the soil bulk density.

29. Roots of most plants have difficulty growing through soil if the bulk density is greater than 1.0
    Mg/m3.

30. The percent of total pore space in a soil can be calculated if only the particle density and the
    organic matter content are known.

31. Compared to a similar soil under native vegetation, a soil with a long history of conventionally tilled
    cropping would have less micropore space.

32. Soils of good tilth and high productivity are usually characterized by stable aggregation and a high
    percentage of macropores.

33. When preparing a surface soil seedbed, the soil should generally be in the loosest, least dense soil
    condition in the row where the seed is placed.

34. Polysaccharides produced by soil microbes and similar synthetic polymers applied to soils are
    largely responsible for the crusts that form when rain follows tillage.

35. Proper timing of tillage is generally more difficult for a clayey than for a sandy soil.

36. A chroma greater than 4 generally indicates a soil in good tilth.

37. For most soils, plowing and harrowing every year improves soil tilth in the long run.

38. A friable soil is usually more likely to be indurated.

39. The plasticity index is the difference between the plastic limit and the liquid limit.

40. The plasticity index is used to determine soil texture.

41. For any soil, the bulk density is always lower than the particle density.

                                                       21
42. Soil consistence changes with changes in soil water content.

43. Subsoiling is a primitive deep tillage technique that results in extremely high subsoil bulk density.




                                                     22
        Answers to Chapter 4 Questions
1. E      15. D                          29.   F
2. B      16. D                          30.   F
3. D      17. C                          31.   F
4. A      18. E                          32.   T
5. A      19. A                          33.   F
6. D      20. B                          34.   F
7. B      21. E                          35.   T
8. E      22. D                          36.   F
9. E      23. D                          37.   F
10. C     24. F                          38.   F
11. E     25. T                          39.   T
12. D     26. F                          40.   F
13. C     27. T                          41.   T
14. C     28. T                          42.   T
                                         43.   F




                      23
Soil Water: Characteristics and Behavior                                                      Chapter 5

                                    Multiple Choice Questions
                            (Circle the single best answer for each question.)

1. The following are characteristics of a water molecule.
   A. The H to O to H angle is approximately 90o C.
   B. The two H atoms are on diametrically opposite ends of the molecule.
   C. It has a positive and a negative side.
   D. It is attracted to surfaces with negative but not positive charges.
   E. It is held in soils by adhesion but not adsorption.

2. Capillarity in soils _____.
   A. involves both adhesion and cohesion
   B. is enhanced by the symmetrical nature of the water molecule
   C. is independent of the matric potential in soils
   D. is not involved in the process of water uptake from soils
   E. does not account for unsaturated water movement in soils

3. Two soil samples, A & B, at different soil moisture levels are placed in contact with each other.
   Water will more likely move from soil A to soil B if their water potentials, expressed in kPa, are:
   A. A=-5;      B=+5
   B. A=-5;      B=-5
   C. A=-20;     B=-10
   D. A=-30;     B=-40
   E. A=-100; B=-50

4. Which of the following expressions in kPa is most apt to characterize the gravitational potential of a
   clay loam surface soil?
   A. -5          B. -30        C. 0       D. +5           E. -3100

5. The osmotic potential would likely be lowest in soils of which of the following orders
   A. Aridisols     B. Histosols        C. Oxisols           D. Ultisols            E.       Spodosols

6. The matric potential of soil water is _____.
   A. influenced greatly by the content of salts in the soil
   B. not influenced appreciably by the force of gravity
   C. is generally higher than that of pure water outside the soil
   D. is little affected by soil solids
   E. is lower in a sandy soil with 20 percent soil water than in a clay soil with same percentage of
      moisture

7. Which of the following best characterizes the field capacity of a soil?
   A. Maximum capacity of a soil to hold water
   B. Water content of a soil with water potential of about -10 kPa
   C. The total capillary water in a soil
   D. A wetted soil prior to the removal of the gravitational water
   E. Soil with water potential of -1500 kPa

8. Which of the following means of estimating soil water levels gives a direct measurement of the
   water content?
                                                    24
   A. gypsum blocks                   B. neutron scattering C. gravimetric determinations
   D. tensiometer                     E. pressure membrane

9. Unsaturated water flow _____________.
   A. is faster than saturated flow
   B. is driven primarily by the force of gravity
   C. is stimulated by the osmotic potential
   D. is slower on sands than on clays if the soil moisture content is high
   E. occurs on soils that are at field capacity

10. In which of the following situations would you expect downward movement of soil water through the
    profile to be most rapid?
    A. uniformly textured sandy loam profile
    B. sandy loam in upper layers with a clay band underneath
    C. sandy loam in upper layers with a layer of coarse gravel underneath
    D. clay texture throughout the profile
    E. silt loam in upper layers underlain by a sandy layer

11. At which of the following soil moisture potentials (expressed as kPa) is the soil water held most
    tightly?
    A. +5      B. 0        C. -31      D. -1500       E. -3100

12. At which of the following soil moisture potentials (expressed as kPa) is the waters' energy level
    lowest?
    A. +5      B. 0        C. -31      D. -1500       E. -3100

13. The water content in a soil is known to be .2 m3/m3 and the potential of pure water outside the
    system is assumed to be 0. If the soil is a clay loam you would calculate the soil water potential (in
    kPa) to be
    A. 0       B. -5      C. 20       D. -20      E. impossible to calculate with the data given

14. Soils high in organic matter commonly hold more available water than comparable soils with lower
    organic matter levels. This is most likely due to what characteristics of the high O.M. soils?
    A. larger micro pore space        B. lower permanent wilting percentage
    C. higher field capacity          D. higher capacity of the O.M. to hold water tightly
    E. higher clay content

15. In which of the following "forms" of soil water are pesticides, excess plant nutrients and waste
    chemicals most apt to move through soils?
    A. gravitational        B. unsaturated         C. available D. hygroscopic E.               capillary

16. Plant roots obtain access to soil water in which of the following ways?
    A. The roots contract and leave room in the pores for the water to move in.
    B. Roots extend into moist soil area.
    C. Water vapor moves from the wet soil areas to the root surfaces.
    D. Water flows to the roots by capillarity.
    E. both B and D.

17. Which of the following statements concerning applications or capabilities of soil moisture measuring
    devices is (are) true for the neutron probe?
    A. Requires "destructive sampling" for each measurement.
    B. Good to turn on automatic irrigation at -50 kPa.

                                                    25
   C. Used to turn on irrigation when soil moisture potential reaches -200 kPa.
   D. Would give the same reading for both a loamy sand and a silt loam if both contained 15%
      moisture.
   E. both A and D.

18. Which of the following statements concerning applications or capabilities of soil moisture measuring
    devices is (are) true for the electrical resistance block?
    A. Requires "destructive sampling" for each measurement.
    B. Good to turn on automatic irrigation at -50 kPa.
    C. Used to turn on irrigation when soil moisture potential reaches -200 kPa.
    D. Would give the same reading for both a loamy sand and a silt loam if both contained 15%
       moisture.
    E. Both A and D.

19. Which of the following statements concerning applications or capabilities of soil moisture measuring
    devices is (are) true for the use of a drying oven and balance?
    A. Requires "destructive sampling" for each measurement.
    B. Good to turn on automatic irrigation at -5.0 kPa.
    C. Used to turn on irrigation when soil moisture potential reaches -20.0 kPa.
    D. Gives same reading for loamy sand and silt loam if both contained 15% moisture.
    E. Both A and D.

20. Which of the following statements concerning applications or capabilities of soil moisture measuring
    devices is (are) true for the tensiometer?
    A. Requires "destructive sampling" for each measurement.
    B. Good to turn on automatic irrigation at -50 kPa.
    C. Used to turn on irrigation when soil moisture potential reaches -200 kPa.
    D. Would give the same reading for both a loamy sand and a silt loam if both contained 15%
       moisture.
    E. Both A and D.


                                      True or False Questions
                                     (Write T or F after each question.)

21. The polarity of water helps account for the attraction of water molecules for each other.

22. The hydrogen end of a water molecule is attracted to positively charged cations such as Na+ and
    Ca2+.

23. The property of cohesion in water stems from the attraction of water molecules for soil solids.

24. The adsorption of water on soil surfaces encourages capillarity.

25. Gypsum or nylon blocks are most useful in estimating the soil water content if the soil is quite dry.

26. The magnetic resonance technique of estimating soil moisture levels can also be used to estimate
    salt contents.

27. The tenacity with which water is held in soils is directly related to the soil moisture content, the
    higher the moisture level the greater the attraction of the water to the soil.


                                                     26
28. Water molecules have polarity primarily because each contains two H atoms and only one O atom.

29. The soil water potential is a measure of the potential of a soil to hold water.

30. The osmotic potential is dependent upon the presence of salts and other solutes in the soil.

31. The matric potential is due to the attraction of water molecules to soil solid surfaces.

32. Water will move from one site in a soil with a water potential of -5 kPa to an adjacent site with a
    water potential of -40 kPa.

33. Hysteresis is the phenomenon whereby a soil has the same water content/potential relationship
    when it is being dried as when it is being wetted.

34. The water potential at the field capacity for most soils is in the range of -10 to -30 kPa.

35. Although the total soil water content of a clay soil is about the same as a nearby well-structured silt
    loam, the clay will likely provide more available water to plants because of its higher volume of
    small pores.

36. The effect of soil organic matter on the amount of water available to plants is due to organic matter
    influence on total soil porosity as well as to the water-supplying power of the soil organic matter.

37. Plant roots gain access to soil water primarily by the growth of the roots into moist soil.

38. Capillary movement is made possible by the processes of cohesion and adhesion.

39. Osmotic and matric potentials are commonly negative because the soil water has a lower energy
    level than that of pure water.

40. Filling the bottom half of a flower pot with gravel will greatly improve the aeration of the soil-mix in
    the top half.




                                                      27
        Answers to Chapter 5 Questions

1. C
2. A      14.   C                        27.   F
3. D      15.   A                        28.   F
4. D      16.   E                        29.   F
5. A      17.   D                        30.   T
6. B      18.   C                        31.   T
7. B      19.   E                        32.   T
8. C      20.   B                        33.   F
9. E      21.   T                        34.   T
10. A     22.   F                        35.   F
11. E     23.   F                        36.   T
12. E     24.   T                        37.   F
13. E     25.   T                        38.   T
          26.   T                        39.   T
                                         40.   F




                      28
Soil and the Hydrologic Cycle                                                                  Chapter 6

                                   Multiple Choice Questions
                           (Circle the single best answer for each question.)

1. Which of the following is not true with respect to the hydrologic cycle?
   A. More than 85% of the water evaporated from the earth's surface comes from oceans.
   B. There is a net migration of some 40,000 km3 of water in clouds from the land area to the ocean
      areas.
   C. The average residence time of water in clouds is about 10 days.
   D. Some 78% of the total precipitation falls onto the oceans.
   E. About one third of the readily accessible water in the hydrologic cycle is in the soil.

2. Which of the following sources of water have the shortest average residence time?
   A. Soil moisture B. Clouds.      C. Oceans and ice caps        D.     groundwater

3. The expression, P - ET -SS estimates the ________ a watershed.
   A. soil water content of B. discharge volume from C. evaporation from                 D. interception in

4. The water potential at the leaf surfaces expressed in kPa is most likely to be _____.
   A. -10    B. 33          C.     -33       D. -500     E. -31,000

5. If the average transpiration (T) loss from leaf surfaces in a particular watershed is 10 mm/day, you
   expect the evaporation (E) from the soil surface to be _____.
   A. 10 mm/ day B. 5 mm/ day C. 15 mm/day D. 100 mm/day
   E. impossible to calculate from the data given

6. The evapotranspiration (ET) from a pine forest was found to be 50 cm during a growing season. If
   the evaporation from the soil surface during this period of time was 5 cm, what is the level of loss
   from leaf surfaces?
   A. 55 cm           B. 45 cm           C. 50.0 cm
   D. 10 cm           E. Impossible to calculate from the data given.

7. In a field experiment you noted that 300 tons of water were transpired to produce 1 ton of corn (dry
   weight). If alfalfa had been grown in the same field instead of corn, which of the following would
   most likely have been the amount of water transpired?
   A. 500 tons          B. 300 tons      C. 275 tons        D. 250 tons
   E. depends on the climate in the area of the experiment

8. Which of the following would you expect to have the highest leaf area index?
   A. Bare fallowed area B. Corn three weeks after planting
   C. Corn, knee high       D. Alfalfa just before harvest        E. Either B or C (equal)

9. Plant transpiration efficiency at a given location is markedly influenced by _____.
   A. organic residue cover on the soil       B. tillage practices used
   C. fertilization practices used            D. the plant species being grown
   E. both C and D

10. The transpiration ratio of a native meadow is 550 kg per kg of dry matter produced. If 4 Mg of dry
    matter is produced on a hectare of land, how many centimeters of water will be required (rounded
    to the nearest cm) ?
    A. 46       B. 220     C. 14       D. 22        E. Not possible to calculate
                                                   29
11. Which of the following will increase the evaporation (E) from the soil surface?
    A. adding a straw mulch to the soil surface
    B. the use of no-till culture
    C. stubble mulch farming
    D. plastic mulch
    E. none of the above

12. Which of the following locations in the United States would have the highest evaporation (E) from
    the soil surface in July?
    A. a bare, unirrigated dry land soil in Colorado
    B. an unirrigated soil in South Carolina growing cotton
    C. a furrow-irrigated cotton field in Arizona
    D. a forest woodland in Illinois
    E. a corn field in New York

13. Eutrophication _____.
    A. is a process of enriching ponds and lakes with plant nutrients
    B. enhances the production of fish in ponds
    C. decreases the growth of weeds in ponds
    D. is discouraged by the application of farm manures
    E. increases the loss of soil by erosion

14. The likelihood of polluting groundwater with pesticides and plant nutrients is enhanced by _____.
    A. the presence of macropores in the soil
    B. light tillage of the upper centimeter or so of soil
    C. the use of tillage to control weeds
    D. the production of oats rather than wheat
    E. conventional tillage as a choice compared with conservation tillage

15. Which of the following irrigation systems produces the most biomass per unit of water applied?
    A. flood irrigation
    B. furrow irrigation
    C. drip irrigation
    D. sprinkle irrigation
    E. furrow-dike irrigation

16. Groundwater _____.
    A. is a source of water above the vadose zone in a soil
    B. moves downward in the vadose zone through the capillary fringe
    C. moves laterally but not vertically below the soil profile
    D. is found mostly in shallow layers just below the argillic
    E. is a major source of water for irrigation in the United States


17. Land drainage is beneficial because _____.
    A. it increases the alternate of expansion and contraction due to freezing and thawing of soils
    B. it increases the water-to-air ratio in the soil pores
    C. it slows down the rate of soil warming in the spring
    D. it increases the depth of root penetration in the soil
    E. it increases the availability of iron and manganese in acid soils


                                                    30
18. Which of the following will not increase the efficiency of water use by plants in an irrigation system?
    A. the use of concrete-lined delivery ditches
    B. the use of flood irrigation for forage crops
    C. the use of drip irrigation for fruit trees
    D. the use of crop residues to reduce evaporation
    E. the use of herbicides to control weeds

19. Drainage pipe comes in 200 ft long rolls. The number of rolls needed to construct a uniform buried
    drainage system for a nearly level 20 hectare field will depend primarily on _____________.
    A. the texture and structure of the soil
    B. the slope of the drain lines
    C. the annual rainfall
    D. rate of capillary movement in the soil
    E. the saturated moisture potential of the soil

20. Of the various types of drain systems, open ditch systems are most practical and economical for
    use on __________.
    A. Vertisols.                        B. soils which do not freeze during the winter
    C. soils with a deep water table     D. poorly drained soils with sandy profiles
    E. clay soils with poor drainage

21. If you dug a deep hole in your back yard and water started to seep into the hole it would fill the hole
    up to ________.
    A. the infiltration rate      B. the percolation rate
    C. field capacity             D. the water table
    E. the liquid limit

22. The most common form of on-site waste water treatment for homes not hooked up to sewer lines is
    the _______.
    A. active composting method       B. septic tank and drain field
    C. chemical “flush” system        D. electrical induction sterilization
    E. soil enrichment process

23. Where high-value crops or individual ornamental shrubs are to be grown and water is expensive,
    the most efficient type of irrigation to use would be ______.
    A. center pivot        B. basin flooding       C. furrow D. drip or trickle


                                      True or False Questions
                                    (Write T or F after each question.)

24. More than ninety-eight percent of the earth's water does not take part in the annual cycling known
    as the hydrologic cycle.

25. Some 2/3 of the solar energy reaching the earth is absorbed by water on or near the earth's
    surface.

26. The average residence time for water in clouds over the ocean is about one year.

27. There is a net movement of clouds from land areas to the ocean areas in the hydrologic cycle.



                                                    31
28. Some 60 percent of the water that is actively involved in the hydrologic cycle worldwide is found in
    soils.

29. Early snowfall that arrives before the cold winter weather has frozen the soil generally increases the
    penetration of water into the soil.

30. The water potential in soils is generally considered lower than that in the atmosphere.

31. Evaporation from the soil surface (E) is determined to a large degree by soil surface wetness.

32. Evapotranspiration includes vapor losses both from the soil surface and from the leaves of plants.

33. Soil and crop management generally has a greater influence on evaporation from the soil surface
    (E) than on transpiration (T) from leaf surfaces.

34. The leaf area index significantly affects the solar radiation reaching the soil surface.

35. Vapor loss from a south-facing slope in Australia would likely be higher than from a north-facing
    slope.

36. Atmospheric vapor pressure has little effect on the vapor losses from soil surfaces.

37. Corn plants are generally more efficient in the use of water than is alfalfa.

38. Conservation tillage can have a significant effect on transpiration of water from a rapidly growing
    crop of corn.

39. Drip irrigation would more likely be used in the production of apples or peaches than in the
    production of wheat.

40. Sprinkle irrigation is generally more efficient in the use of water than drip irrigation, especially for
    high valued crops.

41. The pollution of ground water is often increased by the presence of macropores in soils.

42. Eutrophication is enhanced by the pesticides in the water draining from agricultural soils.

43. Most irrigation systems are very inefficient with less than half the water that is taken from streams
    ever reaching the plants.




                                                      32
        Answers to Chapter 6 Questions

1. B      15.   C                        29.   T
2. B      16.   E                        30.   F
3. B      17.   D                        31.   T
4. D      18.   B                        32.   T
5. E      19.   A                        33.   T
6. B      20.   D                        34.   T
7. A      21.   D                        35.   F
8. D      22.   B                        36.   F
9. E      23.   D                        37.   T
10. D     24.   T                        38.   F
11. E     25.   F                        39.   T
12. C     26.   F                        40.   F
13. A     27.   F                        41.   T
14. A     28.   F                        42.   F
                                         43.   T




                      33
Soil Aeration and Temperature                                                                Chapter 7

                                    Multiple Choice Questions
                            (Circle the single best answer for each question.)


1. The process of aerobic respiration is a significant source of which of the following gases?
   A. methane B. oxygen         C. nitrogen      D. carbon dioxide          E.      ammonia

2. Which of the following is not a major factor in determining the soil aeration status?
   A. redox potential         B. volume of macropores        C. nitrogen gas
   D. carbon dioxide     E. oxygen

3. The bulk of gaseous interchange in soils takes place by _____.
   A. mass flow             B. partial pressure of N2     C. diffusion
   D. dissolution in water E. respiration

4. The redox potential is a measure of _____.
   A. molecular oxygen content
   B. the tendency of a substance to accept or donate electrons
   C. carbon dioxide content
   D. the ferric ion content
   E. soil pH

5. Soil A has a redox potential of 400 mV, soil B -200 mV. Of the two soils, Soil A is more apt to be
   characterized by an abundance of _____.
   A. Fe2+ ions B. Mn2+ ions C. H+ions          D. S2- ions   E. molecular oxygen

6. A well aerated soil is characterized by a relative abundance of _____.
   A. micropores      B. Fe2+ions C. NH4+ ions           D. NO3- ions              E.      methane gas

7. The following is the reduced form of the essential element depicted
   A. NH4+ B. Fe3+ C. CO2 D. SO42- E. Mn4+

8. Compared to upland soils, wetland soils would be characterized by an abundance of _____.
   A. methane B. CO2 C. NO3- D. SO42- E. Fe3+

9. 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 standpoint of soil aeration and temperature?
   A. no-till system      B. conventional moldboard plow system
   C. ridge-till system D. heavy organic residues           E. heavy chemical fertilization

10. Which of the following processes are most apt to encourage good soil aeration?
    A. root respiration
    B. organic matter decomposition
    C. diffusion of oxygen from the soil to the atmosphere
    D. creation of more macropores
    E. reaction of oxygen with organic matter

11. 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 a moderately well-
    drained soil?
                                                    34
   A. 0.21 (oxygen)       B. 0.80 (nitrogen)      C. 0.30 (oxygen)
   D. 0.50 (nitrogen)     E. 0.15 (oxygen)

12. The redox potential of a soil is -250 mV. Which of the following forms of the pertinent elements
    would you expect to find in the soil?
    A. NO3- B. SO42- C. Fe2+ D. Mn4+ E. CO2

13. Which of the following actions would best assure good aeration in a soil?
    A. increase the soil temperature
    B. add organic residues
    C. use a plastic mulch
    D. use cover crops, especially legumes
    E. remove excess water

14. Which of the following is (are) considered necessary features for an area to be delineated as a
    wetland?
    A. hydric soils       B. shallow standing water         C. aquatic vegetation
    D. organic soils      E. all of the above

15. Forest fires result in sufficiently high soil temperatures to cause the vaporization and movement of
    certain organic compounds in soils. The main effect of these compounds is to _____.
    A. reduce water infiltration and percolation through the profile
    B. enhance soil structural stability
    C. increase pH
    D. decrease water losses by surface runoff
    E. increase soil organic matter

16. 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 _____.
    A. the expansion of water when it freezes
    B. the wetting and drying of swelling-type clays
    C. pressure from upward movement of water from lower horizons
    D. the breaking down of soil aggregates due to freezing and thawing
    E. the hydration of adsorbed cations on the soil colloids

17. 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?
    A. 250     B. 450       C. 640     D. 360      E. impossible to calculate

18. The primary characteristic of subsoils that accounts for the ability of ground circulating heat pumps
    to moderate temperatures in houses in both summer and winter is _____.
    A. the high redox potential of the soil
    B. the high heat of the evapotranspiration
    C. the ready conduction of heat in the soil
    D. the high specific heat of the soil
    E. the low oxygen content of the subsoil

19. The heat of vaporization of water is 540 cal/g. A soil containing 30 kg water per 100 kg soil solids
    lost one sixth of that water by evaporation. If one tenth of the energy needed to evaporate the
    water came from the soil solids how much would the temperature of those solids be lowered?
    A. 5.2oC B. 32.4oC C. 20.5oC D. 10.5oC E. 13.5oC


                                                    35
20. Which of the following practices would encourage higher soil temperatures in the spring in a humid-
    temperate area?
    A. apply modest levels of organic residues
    B. follow no-till practices
    C. use a plastic mulch
    D. irrigate the soil
    E. use the moldboard plow

21. 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?
    A. differences in rainfall from one area to another
    B. more rapid plant growth on the south slopes
    C. higher soil temperatures on the north slopes
    D. more solar radiation on the south slopes
    E. sandier soils on the north slopes


                                      True or False Questions
                                    (Write T or F after each question.)

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

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

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

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

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

27. 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.

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

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

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

31. 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.

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



                                                     36
33. The alternate freezing and thawing of soils results in the upward heaving of plants and building
    foundations.

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

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

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

37. 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.

38. 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.

39. 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.

40. 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.

41. 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.




                                                      37
        Answers to Chapter 7 Questions

1. D      15. A                          29. T
2. C      16. A                          30. F
3. C      17. D                          31. T
4. B      18. D                          32. F
5. E      19. E                          33. T
6. D      20. C                          34. F
7. A      21. C                          35. F
8. A      22. F                          36. F
9. C      23. T                          37. T
10. D     24. F                          38. T
11. E     25. T                          39. T
12. C     26. T                          40. T
13. E     27. F                          41. T
14. A     28. T




                      38
The Colloidal Fraction: Seat of Soil Chemical and Physical Activity                           Chapter 8


                                  Multiple Choice Questions
                          (Circle the single best answer for each question.)

1.   Which of the following is not a characteristic of soil colloids?
     A.    very small size                          B.       high external surfaces
     C.    electronegative charges                  D.       ability to exchange ions with the soil solution
     E.    low water holding capacity

2.   The electronegative charge on 2:1 type silicate clays is due primarily to _____.
     A.     ionization of surface OH groups
     B.     substitution of one metallic atom for another in the crystal structure of the clay
     C.     extremely small size of the individual colloid particles
     D.     the effect of pH on the presence of H+ ions in the exchange complex
     E.     the preponderance of tetrahedron sheets compared to octahedron sheets

3.   If you were seeking a soil colloid with a high capacity to adsorb cationic pollutants, but also with
     a consistent capacity to do so even as the pH varied form 4.0 to 7.5, which of the following
     would you choose?
     A. montmorillonite    B. kaolinite C. fine-grained mica D. humus            E. chlorite

4.   Soils rich in which type of clay would provide the most troublesome site on which to build home?
     A. Fe, Al oxides       B. kaolinite C. fine-grained micas          D. chlorite    E. smectite

5.   Which cation would you expect to be mostly tightly held in a soil at pH 4.5?
     A. K+         B. Ca2+      C. Al3+         D. Mg2+          E. Na+

6.   If you were looking for a soil with high cation exchange capacity and were not concerned with
     the soils physical properties, which of the following would most likely fit your needs?
     A. Aridisol     B. Oxisol      C. Vertisol      D. Mollisol  E. Ultisol

7.   You are working with a soil colloid known to have a reasonably high potassium level, a cation
     exchange capacity of about 20 cmolc/kg of clay and little tendency to swell when wetted. Which
     of the following is it most apt to be the dominant clay mineral in this soil?
     A. vermiculite B. smectite C. kaolinite D. humus             E. fine-grained mica

8.   The negative charges associated with smectite clay crystals are due mostly to _____.
     A.    isomorphous substitution of Mg for Al in the octahedral sheet
     B.    substitution of Al for Mg in the tetrahedral sheet
     C.    high pH associated with the formation of the mineral
     D.    substitution of Si for Al in the tetrahedral sheet
     E.    OH groups on the external surface of the crystal

9.   The swelling/shrinking tendency of some silicate clay minerals is due primarily to _____.
     A.    the presence of cations attracted by the negative charges on the internal surfaces
     B.    the movement of water molecules in and out of the interlayers of the crystal
     C.    varying thickness of the film of water covering the external surface of the particles
     D.    expansion in the width of the interlayers due to movement of larger ions such as K+.
     E.    the high Mg2+ contents in the octahedral layers

                                                   39
10.   Which of the following silicate clays would be least apt to be formed from the alteration of
      primary minerals?
      A. smectite                  B. vermiculite              C. chlorite
      D. fine-grained micas        E. iron or aluminum oxides

11.   A well-drained soil under a rain forest in Brazil contains significant amounts of a silicate clay.
      Which of the following is it most apt to be?
      A. chlorite    B. fine-grained mica C. smectite D. kaolinite E. vermiculite

12.   As biotite weathers in soils, which of the following would not likely develop by mere alteration of
      this mineral?
      A. fine-grained mica B. kaolinite C. smectite D.chlorite              E. vermiculite

13.   Some soil colloids exhibit positive charges under highly acid conditions. To what are these
      charges likely due?
      A.    protonation of some hydroxy groups by excess H+ ions
      B.    the adsorption of Al3+ ions on the colloid
      C.    the release of some OH- ions leaving an unsatisfied positive charge on the colloid
      D.    substitution of lower valent atoms for higher valent atoms in the octahedral sheet
      E.    increase in the level of H+ ions on the exchange complex

14.   A 1 kg soil sample has 2 cmolc of Al3+ on the exchange complex. Addition of which of the
      following would most effectively replace about half of this Al?
      A. 2 cmolc H+                 B. 10 cmolc OH-        C. 8 cmolc Ca2+
                    +                             +
      D. 8 cmolc Na                 E. 2 cmolc Na

15.   An alkaline soil contains 20% clay and 3% humus. If the pure clay has a CEC of 40 cmolc/kg
      and the humus 200 cmolc/kg calculate the CEC/kg of the soil.
      A. 8           B. 30         C. 12        D. 16          E. 14

16.   Anion exchange by formation of outer sphere complexes is of least importance in the plant
      absorption of _____.
      A. NO3-        B. Cl-     C. SO42-      D. MoO4-2    E. H2PO4-.

17.   Humus is an important soil colloid. It differs from 2:1 type minerals in all but one of the following
      characteristics (select the one).
      A.     structural framework of the particles
      B.     CEC dependence on soil pH
      C.     influence of isomorphous substitution
      D.     capable of adsorbing cations
      E.     influence on soil aggregate stability

18.   Allophane differs from other silicate clays in all ways but one of the following (select the one).
      A.     nature of parent materials from which it forms
      B.     degree of crystallization of the particles
      C.     the presence of negative charges on the colloidal particles
      D.     widespread occurrence around the world
      E.     the period of time it has been subject to weathering

19.   Which of the silicate clays would likely have the highest level of potassium in the crystal
      structure?

                                                   40
      A.     kaolinite                      B.      chlorite        C.      smectite
      D.     fine-grained mica              E.      vermiculite

20.   Assume you find that the CEC of a soil at pH 5.0 is 8 cmolc/kg and at pH 8.2 it is 14 cmolc/kg.
      What is the most likely reason for this difference?
      A.     increase in the pH-dependent charges on 2:1 type silicate clays
      B.     removal of Al3+ ions from the exchange complex
      C.     ionization of carboxyl and phenolic groups to release H+ ions leaving negative charges
             on the colloid
      D.     removal of Al atoms from tetrahedral layers
      E.     replacement of trivalent Al3+ ions with divalent Ca2+ ions


                                    True or False Questions
                                  (Write T or F after each question.)

21.   Soil colloids are too small to be seen with an ordinary light microscope.

22.   While 2:1 type clays have significant internal surfaces, their external surfaces are generally
      much more extensive.

23.   For most soil colloids, electronegative charges predominate although vermiculite and associated
      silicate clays have a net electropositive charge in very acidic soils.

24.   Iron and aluminum hydrous oxides are characteristic of soils that are highly weathered
      chemically.

25.   Kaolinite is most prevalent in soils developed from volcanic ejecta (Andisols).

26.   The order of strength of adsorption of ions by most colloids when they are present in equivalent
      quantities is Al>Ca>K>Mg>Na.

27.   The leaf-like structure of silicate clays involves two kinds of horizontal sheets, one dominated by
      a plane of silicon atoms, the other by a plane of aluminum and/or magnesium.

28.   A tetrahedral sheet is characterized by a plane of aluminum atoms surrounded by oxygen and
      hydroxyl groups.

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

30.   Isomorphous substitution involves the substitution of a tetrahedral sheet for an octahedral sheet.

31.   The primary source of charge for 2:1 type clays minerals is ionization of the surface hydroxyl
      groups on the tetrahedral sheets.

32.   While kaolinite particles are larger than those of other major silicate clays, the surface area of
      kaolinite per kilogram is much smaller than that of the 2:1 type minerals.

33.   Humus has a much higher cation adsorption capacity at pH 5.5 than at pH 8.0.



                                                   41
34.   Of the silicate clays, smectite has the least tendency to expand upon wetting and shrink upon
      drying.

35.   Smectite and vermiculite are more prominent in extremely weathered soils than in soils where
      only modest weathering has occurred.

36.   In most soils of the arid regions of Nevada, smectite is more prominent than in most soils in
      warm, humid Georgia.

37.   The high cation adsorption capacity of vermiculite is due primarily to the substitution of silicon
      atoms for aluminum in the tetrahedral sheet.

38.   Even at pH values near 7.0 some colloids such as iron and aluminum oxides have modest
      positive surface charges.

39.   The cation exchange capacity of a soil is determined primarily by the amount and kind of
      colloids in the soil and by the pH.

40.   You would expect the cation exchange capacities of Ultisols to be lower than those of Aridisols if
      the soil textures are about the same.




                                                   42
        Answers to Chapter 8 Questions

1. E      14. C                          27. T
2. B      15. E                          28. F
3. A      16. E                          29. T
4. E      17. D                          30. F
5. C      18. C                          31. F
6. C      19. D                          32. T
7. E      20. C                          33. F
8. A      21. T                          34. F
9. B      22. F                          35. F
10. E     23. F                          36. T
11. D     24. T                          37. F
12. B     25. F                          38. T
13. A     26. F                          39. T
                                         40. T




                      43
Soil Acidity, Alkalinity, and Salinity                                                       Chapter 9
                                   Multiple Choice Questions
                           (Circle the single best answer for each question.)
1. The exchange complexes of strongly acid (pH 4.5) mineral soils are saturated mainly with _____.
   A. exchangeable H+ ions
   B. exchangeable Al3+ ions
   C. exchangeable Al(OH2)+ ions
   D. tightly bound H+ ions
   E. tightly bound Al3+ ions

2. What does not describe the role of aluminum hydroxy ions such as Al(OH)2+ in the soil?
   A. They are more prominent in acidic 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.

3. In the B horizon of which order would you most likely find a soil with the highest buffering capacity?
       A. Alfisol     B. Vertisol   C. Oxisol      D. Spodosol E. Ultisol

4. How does the amount of lime needed to neutralize the residual acidity in a clay loam soil compare
   to that needed to neutralize the active acidity in that soil?
       A.     residual takes considerably less                 B. residual takes about the same
       C.     residual takes about double                      D. residual takes 10 times greater
       E.     residual takes 5,000 times more

5. A soil has a maximum potential cation exchange capacity of 30 cmolc/kg and has a 50% acid
   saturation. If you want to decrease the percentage acid saturation to 10%, how many cmolc of
   calcium would it take to replace the exchangeable acid cations per kg of soil? Assume all the
   calcium exchanged with aluminum.
       A. 30          B. 40          C. 6          D. 12          E. 5

6. You are using pure limestone (CaCO3) to provide the Ca needed to exchange with acid cations in a
   soil with a maximum potential cation exchange capacity of 20 cmolc/kg. How many kg of this
   limestone would you need to add to a hectare furrow slice (2.0 x 106 kg) to reduce the percentage
   acid saturation from 40 to 10%, assuming that all the Ca added exchanged with Al or H ions?
       A. 20,000      B. 50,000     C. 12,000     D. 6,000        E. 16,000

7. Which of the following human actions is most apt to result in a long term increase in soil pH?
   A. application of NH4- containing fertilizers
   B. application of farm manure
   C. irrigation with high sodium salt-containing waters
   D. emission of gases from automobiles
   E. application of unlimed sewage sludge

8. The drainage of certain wetlands can resulted in extreme soil acidity because ____.
   A. oxidation of organic materials to produce organic acids
   B. reduction of iron to low valence 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
                                                   44
9. Which of these essential elements is it most likely to be toxic to plants in a soil at pH 5.0?
      A. nitrogen B. manganese              C. phosphorus            D. molybdenum           E. boron

10. Phosphorus availability is very low in most strongly acid soils because of its reactions with ______.
       A. iron       B. calcium       C. magnesium           D. sulfur      E. boron.

11. Which of the following trees would you expect to fare most poorly in a soil at pH 5.0?
       A. loblolly pine        B. aspen     C. sumac       D. walnut       E. white spruce

12. Which of the following would likely grow best on a soil with a pH of 6.0?
       A. alfalfa      B. sweet clover       C. tomatoes       D. blueberries           E. cranberries

13. Assume you want to grow azaleas in a soil with a pH of 6.0. The application of which of the
    following would be most appropriate to make this soil suitable for this ornamental?
         A.    chicken manure               B.     limestone        C.       elemental sulfur
         D.    iron oxide                   E.     hydrated lime

14. 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. sawdust              B. calcitic limestone C. dolomitic limestone
         D. burned lime          E. ammonium nitrate

15. Under which of the following conditions would you favor a finely ground dolomitic limestone as your
    choice among liming materials?
    A. need for a rapid reaction with the soil
    B. need to provide magnesium in addition to calcium
    C. need for a material with a low shipping cost
    D. need to obtain a high soil pH
    E. need to significantly reduce the exchangeable Al3+ level in the soil

16. Which of the following is likely to occur when lime is added to the surface of a soil at pH 6.0?
    A. Earthworms help move the limestone down into the soil profile.
    B. Conservation tillage increases the pH of the subsoil.
    C. CO2 in the soil air helps solubilize the CaCO3 and increase its rate of downward movement.
    D. Aluminum toxicity increases in the vicinity of the limestone.
    E. The release of H+ ions from the exchange complex helps reduce the soil pH.

17. 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?
    A. The gypsum replaces H+ ions from colloids and these move down the profile and decreases the
        pH of the subsoil layers.
    B. Calcium from the gypsum replaces H+ from subsoil colloids thereby increasing the soil pH.
    C. Gypsum moves down the profile and increases the dissolved Ca/Al ratio in the subsoil.
    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.

18. In humid regions, applications of limestone are repeated every few years primarily because of ____.
    A. the release of aluminum ions from the structure of silicate clays
    B. the annual loss of calcium and magnesium in drainage waters
    C. increases in soil acidity from acid rain
    D. increased rates of formation of carbonic acid (H2CO3)
    E. increases in phosphate fertilization

                                                     45
19. The very high pH levels found in some arid region soils are most likely due to high levels of
    exchangeable _____.
       A. Al3+        B. Al(OH)2+ C. Ca2+           D. Mg2+       E. Na+

20. Poor plant growth in a well-drained irrigated Aridisol (pH=8.0) is most likely due to ________.
       A. manganese toxicity                  B. iron deficiency             C. phosphate toxicity
       D. calcium toxicity                    E. molybdenum deficiency

21. Normal alkaline soils are characterized by all but which one of the following?
       A. low levels of available iron                       B. high levels of molybdenum
       C. high levels of exchangeable sodium                 D. low levels of available manganese
       E. low levels of available boron

22. The CEC of alkaline soils are generally higher than those of most acid soils of similar texture.
    Which of the following characteristics of alkaline soils most likely accounts for this high CEC?
       A. high humus content                  B. high content of hydrous oxides of iron and aluminum
       C. high exchangeable calcium           D. high exchangeable sodium content
       E. high content of 2:1 type clays

23. A homeowner in New Mexico attempted to grow azaleas in a well drained soil (pH 7.5) but the
    plants were stunted and the leaves were yellow. What is the most likely cause of this constraint?
    A. P deficiency B. Mn toxicity C. Fe deficiency       D. Ca toxicity        E. Na toxicity

24. Some irrigation systems have stimulated the formation of saline and saline-sodic soils. Which of
    the following contributes to this process?
    A. the low sodium adsorption ratio in the irrigation water
    B. high Ca and Mg contents in the irrigation water
    C. inadequate drainage systems to remove soluble salts
    D. high contents of sulfates and chlorides in the irrigation water
    E. low pH of the irrigation water

25. Which of the following correctly describes the relationship among the several methods available to
    measure electrical conductivity (EC) of soils?
    A. The saturated paste extract method is the best field method.
    B. The four electrode field sensor gives EC values about 2x those of the saturated paste method.
    C. The saturation extract procedure is more accurate than the saturated paste method.
    D. Electromagnetic induction method requires prongs to penetrate the soil.
    E. The saturated paste method takes more time than the four electrode field sensor.

26. Saline soils are characterized by _______.
    A. high CaCO3 levels near the soil surface
    B. sodium adsorption ratios of 13 or higher
    C. electrical conductivity of standard saturated paste of less than 4 dS/m
    D. pH values of less than 8.5
    E. low chloride and sulfate contents

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



                                                    46
28. Soil physical conditions began to deteriorate and crop yields began to decline several years after a
    farmer started irrigating a field. Which of the following most likely accounts for this situation?
    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

29. Which of the following plants would be most apt to tolerate high soil salinity?
       A. cotton       B. alfalfa    C. apples      D. corn         E. tomato

30. Which of the following characteristics of irrigation water is most apt to stimulate the formation of a
    sodic soil?
       A. high selenium content                B. high Ca2+ and Mg2+ content
       C. high content of chlorides            D. low pH              E. high SAR values

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

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

33. Gypsum is the most widely used chemical for the reclamation of sodic soils. What characteristic
    likely accounts for this popularity?
    A. Gypsum is abundant and low priced.
    B. Gypsum is quite insoluble so it remains in the soil for long periods of time.
    C. Gypsum provides sulfates that attract Na+ from the exchange complex.
    D. Gypsum forms sulfuric acid that helps reduce the soil pH.
    E. Gypsum reacts with Na+ ions to form insoluble Na2SO4.

34. Sodic soils generally have a poor physical condition. This is most likely due to:
    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.

35. 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?
         A. 30         B. 20         C. 10        D. 5           E.     2

36. Available phosphorus levels are constrained in alkaline and salt-affected soils because of _____.
       A. high iron and aluminum levels             B. high exchangeable sodium levels

                                                     47
        C. high calcium and magnesium levels            D. high manganese levels
        E. low hydrogen ion levels

37. Attempts to leach the excess salts from a saline-sodic soil resulted in a marked reduction of crop
    yields. This is most likely due to:
    A. deficiency of iron and manganese.
    B. increase in percentage sodium saturation.
    C. removal of Ca2+ and Mg2+ ions from the exchange complex.
    D. increase in the soil pH.
    E. increase in the Al3+ concentration.

38. Which of the following comparisons of the three different classes of salt-affected soils is correct?
    A. Sodic soils generally have the lowest pH.
    B. Saline soils are generally higher in soluble salts than saline-sodic soils.
    C. Sodic soils generally have the highest EC levels.
    D. The pH of saline soils is generally above 8.5.
    E. Sodic soils are commonly formed by leaching saline-sodic soils.

39. The growth of plants on sodic soils is constrained by all but one of the following:
    A. caustic influence of high pH caused by sodium carbonate and bicarbonate.
    B. toxicity of bicarbonate and other anions.
    C. low micronutrient availability due to high pH.
    D. oxygen deficiency due to breakdown of soil structure.
    E. toxicity of very high levels of calcium carbonate.

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


                                         True or False Questions
                                      (Write T or F after each question.)

41. Soil reaction indicates the degree of acidity or alkalinity in a soil.

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

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

44. In extremely acidic 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.

45. The cation exchange capacity of humus is mostly pH-dependent.

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

47. Residual soil acidity is that acidity remaining in the soil after limestone has been applied.


                                                      48
48. The amount of exchangeable acidity is much smaller than the residual acidity.

49. The presence of neutral salts in an alkaline soil has a tendency to increase the pH of the soil.

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

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

52. The buildup of excess salts in irrigated soils can result in increased pH if the salts are high in
    sodium bicarbonate.

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

54. Iron and manganese are commonly deficient in very acid soils.

55. Fungi are much more sensitive to strong acid conditions than are bacteria or actinomycetes.

56. Loblolly pine tolerates higher levels of acidity than beech or maple trees.

57. Sulfur can be used to increase soil acidity and to reduce alkalinity.

58. If you wanted to quickly increase the pH of a soil to 7.5 to combat a cabbage disease you would
    prefer hydrated lime over calcium carbonate.

59. The amount of limestone required to increase the pH from 5 to 7 would be higher for an Oxisol
    than for an Alfisol.

 60.   If you want to grow azaleas on a soil that initially has a pH of 6.5 and have been told that you
       should apply sulfur to reduce the soil pH, you would likely need more sulfur if the soil is a
       Vertisol than if it is an Alfisol.

 61.   Normal alkaline soils often exhibit deficiencies of available iron and manganese.

 62.   Phosphate availability is constrained in alkaline soils by the presence of iron and aluminum
       oxides.

 63.   The cation exchange capacities of alkaline soils are commonly lower than those of comparable
       soils in humid regions.

 64.   Saline soils are characteristic of arid and semiarid areas with poor internal drainage.

 65.   The source of salts for some naturally occurring saline soils are ancient fossil deposits of salts in
       old lake beds.

 66.   Lack of adequate drainage in irrigation projects leads to the accumulation of CaCO 3 that is
       responsible for the high pH values above 8.5.

 67.   The electrical conductivity (EC) of a paste of a saline soil and water is generally less than 4
       dS/m.



                                                     49
68.    Saline-sodic soils have electrical conductivities greater than 4 dS/m and a sodium adsorption
       ratio of less than 13.

69.    Irrigation of a saline-sodic soil with water very low in salts could lead to a sodic soil.

70.    The presence of neutral salts in salt-affected soils helps keep the pH from rising above 8.5.

71.    Sodic soils generally have better physical conditions than either saline or saline-sodic soils.

72.    The high pH of sodic soils is due to the high saturation of the colloidal complex with calcium.

73.    Sodic soils are sometimes referred to as white alkalis because of the white salt crusts that
       appear on the surface.

74.    Irrigation waters with high sodium adsorption ratios are preferred over those with lower ratios.

75.    Removal of excess salts from the soil profile is a requisite for the reclamation of a saline soil.

76.    Conservation tillage can help reduce salt build up by reducing surface evaporation.

77.    Elemental sulfur is the most widely used chemical for the reclamation of sodic soils.

78.    Gypsum plus irrigation reduces the pH of sodic soils by replacing sodium from the exchange
       complex and removing it from the soil.

79.    Soils with high sodium adsorption ratios commonly have very stable soil structures.

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




                                                     50
          Answers to Chapter 9 Questions

1.    B      40.   D                       79.   F
2.    E      41.   T                       80.   T
3.    B      42.   T
4.    E      43.   F
5.    C      44.   T
6.    D      45.   T
7.    C      46.   T
8.    E      47.   F
9.    B      48.   T
10.   A      49.   F
11.   D      50.   T
12.   C      51.   F
13.   C      52.   T
14.   D      53.   F
15.   B      54.   F
16.   A      55.   F
17.   C      56.   T
18.   B      57.   T
19.   E      58.   T
20.   B      59.   F
21.   C      60.   T
22.   E      61.   T
23.   C      62.   F
24.   C      63.   F
25.   E      64.   T
26.   D      65.   T
27.   E      66.   F
28.   C      67.   F
29.   A      68.   F
30.   E      69.   T
31.   D      70.   T
32.   D      71.   F
33.   A      72.   F
34.   C      73.   F
35.   D      74.   F
36.   C      75.   T
37.   B      76.   T
38.   E      77.   F
39.   E      78.   T




                        51
Organisms and Ecology of the Soil                                                      Chapter 10

                                   Multiple Choice Questions
                           (Circle the single best answer for each question.)


1.    Soil detritivores feed principally on ___.
      A.      smaller organisms                     B.     plant roots
      C.      larger, but defenseless animals       D.     dead tissues E.      microorganisms

2.    Which of the following groups is not considered to include important primary consumers in the
      soil ecosystem?
      A. detritivores         B. herbivores        C. fungi       D. saprophytes       E. predators

3.    An organism that subsists by eating predators would function as a(n) _____ in the soil
      ecosystem.
      A.     primary consumer
      B.     detritivore
      C.     tertiary consumer
      D.     decomposer
      E.     all of the above

4.    Which of the following groups of organisms are responsible for greatest amount of organic
      matter decomposition in soils?
      A.     macrofauna                    B.     microfauna
      C.     mesofauna                     D.     microflora
      E.     autotrophs

5.    Meso- and macrofauna contribute to organic matter decomposition primarily by ______.
      A.    enzymatic digestion of plant residues       B.   enhancement of microbial activity
      C.    predation     D.      synthesis of humus E.      none of the above

6.    Which of the following microorganisms can commonly be seen with the unaided eye in organic
      matter-rich soils?
      A. fungi        B. bacteria C. nematodes        D. actinomycetes      E. none of the above

7.    Compared to the bulk soil in which the earthworms live, earthworm casts contain ____.
      A.   less of most plant-available nutrients
      B.   more nitrogen but less of other plant-available nutrients
      C.   more of most plant-available nutrients
      D.   more sand and silt
      E.   less organic matter

8.    Which group of soil organisms includes the largest number of autotroph species?
      A. bacteria B. fungi        C. actinomycetes        D. detritivores      E. protozoa

9.    Organisms which use carbon dioxide or carbonates for their carbon source and either sunlight
      or inorganic chemicals for their energy source are called ____.
      A. facultative anaerobes      B. heterotrophs       C. detritivores    D. autotrophs
      E. actinomycetes

10.   In nature, beneficial mycorrhizae form with the roots of _____.

                                                   52
      A. coniferous trees    B. grasses     C. legumes      D. broad leaf trees    E. all of the above

11.   The fungal symbiont generally benefits from the mycorrhizal relationship by obtaining ____ from
      the higher plant.
      A. water       B. phosphorus        C. micronutrients     D. A-C          E. none of the above

12.   Vesicles and arbuscules are structures typically formed ____.
      A.     in bacterial cells when attacked by protozoa.
      B.     above ground by certain soil fungi
      C.     by mesofauna when they incorporate organic materials into the soil
      D.     in root cells by fungi when they form mycorrhizae
      E.     none of the above

13.   In most soils the overall population (numbers) of microorganisms changes with time, generally
      following changes in the _____.
      A.      supply of decomposable organic matter
      B.      supply of oxygen
      C.      pore space
      D.      availability of root infection sites
      E.      concentrations of antibiotics

14.   The addition of large quantities of plant residues to the soil generally ____ the incidence and
      severity of soil-borne plant diseases.
      A. increases            B. reduces C. has no effect on

15.   In which soil situation are the actinomycetes likely to be most?
      A.     extremely acid conditions too severe for most other microorganisms
      B.     low organic matter soils
      C.     cold, wet soils
      D.     soil with lots of fresh, easily decomposed residues
      E.     neutral, moist, warm soil with lots of partially decomposed residues

16.   Many members of which group of soil microorganisms are anaerobic?
      A. actinomycetes   B. bacteria C. fungi         D. both A and C              E. all of the above

17.   This (these) group(s) of microorganisms usually predominate(s) in sandy, acid soils.
      A. actinomycetes      B. bacteria C. fungi         D. both A and C       E. all of the above

18.   Members of this (these) microbial group(s) are responsible for a major proportion of the nitrogen
      fixed globally in symbiosis with higher plants.
      A. actinomycetes       B. bacteria    C. fungi     D. A and B E. all of the above

19.   Oxidation or reduction of inorganic soil constituents such as iron and sulfur is carried out by
      members of which group(s) of microorganisms.
      A. actinomycetes      B. bacteria C. fungi            D. A and C E. all of the above

20.   Disease suppressive soil often results from ____.
      A.    proper fumigation with a strong volatile biotoxin.
      B.    heating the soil by natural solarization or by steam heat.
      C.    repeated tillage to keep a soil free of living plants for at least one year.
      D.    regular addition of a variety of organic material that stimulate diverse microorganisms.
      E.    all of the above

                                                   53
                                    True or False Questions
                                  (Write T or F after each statement.)

21.   Termites tend to enrich soils in the tropics much the same way as earthworms do in temperate
      region soils.

22.   The total number of microorganisms in a hectare of soil is far greater than the number of
      macroorganisms, but the reverse is true for biomass of the two groups.

23.   Where conditions are favorable, earthworms are known to add several hundred kg/ha of several
      important nutrients to the soil system.

24.   Most soil organisms are heterotrophs.

25.   A significant portion of the global production of methane comes from the activity of termites.

26.   All but a few nematodes are pests, attacking either economic or wild plants.

27.   Compared to the rest of the soil, the rhizosphere is kept relatively sterile by the action of plant
      roots.

28.   Plant roots are an important source of carbon for many soil organisms which are beneficial to
      plants.

29.   Mucigel is thought to improve the contact between plant roots and soil particles, thus enhancing
      the plant uptake of water and nutrients.

30.   Algae are single-celled plants that function principally as primary producers in the soil
      ecosystem.

31.   Mycorrhizae involve a symbiotic combination of certain bacteria and plant cells.

32.   Mycorrhizae do not normally kill their host plants, but merely reduce the efficiency of the plant
      root system.

33.   Certain soil fungi and actinomycetes are known to produce specialized organic compounds that
      inhibit or kill other, competing microorganisms in the soil, but so far scientists have not been
      able to put any of these compounds to practical use.

34.   Of all the groups of soil organisms, bacteria have the most diverse metabolic capabilities.

35.   Fungi tend to be the dominant group of microorganisms in acid, sandy soils.

36.   Actinomycetes tend to dominate soils that are either very acid, very cold, or very dry.

37.   Most anaerobic organisms in soils are bacteria.

38.   Research has shown that most herbicides and insecticides used in agriculture drastically reduce
      the numbers of living meso- and microorganisms in soils for several years after the application
      of these chemicals.

                                                   54
39.   Soil microorganisms often compete with higher plants for mineral nutrients, such as nitrogen.

40.   The deeper that they are placed in the soil, the more rapidly organic compounds such as
      pesticides are decomposed by the soil microflora.

41.   Earthworms generally are most abundant in sandy, acid soils typically under coniferous forest
      vegetation.




                                                 55
        Answers to Chapter 10 Questions

1. D      15. E                           29. T
2. E      16. B                           30. T
3. C      17. C                           31. F
4. D      18. D                           32. F
5. B      19. B                           33. F
6. A      20. D                           34. T
7. C      21. F                           35. T
8. A      22. F                           36. F
9. D      23. F                           37. T
10. E     24. T                           38. F
11. E     25. T                           39. T
12. D     26. F                           40. F
13. A     27. F                           41. F
14. B     28. T




                      56
Soil Organic Matter                                                                         Chapter 11

                                   Multiple Choice Questions
                           (Circle the single best answer for each question.)


1.    Nearly all organic compounds from which living beings are made have as their backbone,
      chains or rings of _____ atoms.
      A. aluminum B. oxygen        C. carbon      D. nitrogen E. none of the above

2.    Which of the following pools contain the largest amount of the world's carbon?
      A. soil               B. vegetation          C. atmosphere         D. animals

3.    Which of the following is (are) major sources of the carbon dioxide now being added to the
      atmosphere in excess of the amount taken out by plants?
      A.    loss of soil organic matter                    B.     burning of fossil fuels
      C.    destruction of natural forests                 D.     all of the above
      E.    none of the above

4.    Which of the following is a greenhouse gas contributed to the atmosphere by soils?
      A.    nitrous oxides          B.    carbon dioxide         C.    methane
      D.    all of the above        E.    none of the above

5.    Which of the following added to a soil would be likely to result in the greatest level of soil organic
      matter after several years of decomposition?
      A.     5 Mg of carbon in plant roots
      B.     5 Mg of carbon in plant tops
      C.     the manure produced by feeding cattle 5 Mg carbon in plant residues
      D.     the compost made by composting 5 Mg of carbon in plant residues

6.    Green plant residues such as grass clippings or a green manure crop generally have a water
      content of about ____% by weight.
      A. 10         B. 25         C. 45          D. 75          E. 95

7.    After drying to eliminate the water in plant litter, which two elements account for about 80% of
      the dry weight?
      A. N and C B. N and S C. C and H D. C and O E. Ca and C

8.    To avoid a nitrate depression period when it is added to a garden soil, about how many kg of
      nitrogen must be added to a load of grass clippings that contains 1000 kg of C and 25 kg of N?
      A. 15          B. 35          C. 50          D. 75          E. 100

9.    Suppose leaves containing 1000 kg of carbon fell to the forest floor in a humid temperate
      environment. After a year or so, how many kg of that carbon would you expect to remain in the
      soil as microbial biomass and humus?
      A. 10          B. 20          C. 200       D. 400          E. 800

10.   Humic substances consists of _____.
      A.    living organisms and cells               B.     dead plant and animal tissues
      C.    identifiable biomolecules                D.     polymerized, non-identifiable molecules
      E.    all of the above


                                                   57
11.   Soil organic matter consists of ______.
      A.      living organisms and cells            B.     dead tissues and wastes
      C.      identifiable biomolecules             D.     polymerized, non-identifiable molecules
      E.      all of the above

12.   Biomass consists of ______.
      A.    living organisms and cells              B.     dead tissues and wastes
      C.    identifiable biomolecules               D.     polymerized, non-identifiable molecules
      E.    all of the above

13.   Detritus consists of ______.
      A.      living organisms and cells            B.     dead tissues and wastes
      C.      identifiable biomolecules             D.     polymerized, non-identifiable molecules
      E.      all of the above

14.   Non-humic substances consist of ____.
      A.    living organisms and cells              B.     dead tissues and wastes
      C.    identifiable biomolecules               D.     polymerized, non-identifiable molecules
      E.    all of the above

15.   One would expect well drained soils to have the highest organic matter contents where the
      climate is _______.
      A. warm and dry             B. warm and humid              C. cool and dry
      D. cool and humid

16.   The active fraction of soil organic matter largely accounts for which of the benefits of adding
      organic matter to soils?
      A.     increased CEC                           B.     increased water holding capacity
      C.     increased microbial activity            D.     increased aggregate stability
      E.     both c and d

17.   Under natural vegetation, about 60 to 90% of soil organic matter is in the _____fraction.
      A.    active          B.     slow          C.       passive

18.   Soils with thick horizons consisting mainly (> 30% by weight) of organic matter and that form in
      topographic depressions or low-lying places usually belong to the order ______.
      A. Alfisols     B. Vertisols C. Histosols D. Umbrasols              E. Spodosols

19.   When fresh plant residues are added to soils, the "priming effect" may result in the
      decomposition of _______.
      A.    stable humus                          B.      sugars and starch
      C.    waxes and fats                        D.      lignin and cellulose
      E.    proteins and other nitrogen-rich compounds

20.   Alcohols, methane and organic acids of various kinds often accumulate as a result of ______
      decomposition of residues in soil.
      A. nitrogen-limited B. acidic      C. fungal       D. anaerobic         E. abiotic

21.   Given this table of plant residue analyses, choose the “highest quality” residue in terms of
      suitability to support an active community of soil organisms and rapid nutrient cycling.


                                                  58
                                    A              B            C              D             E
          C/N ratio                 15             15           15             45            45
          Polyphenol content,%      0.5            6.0          6.0            0.5           0.5
          Lignin content,%          10             40           10             40            10



                                     True or False Questions
                                  (Write T or F after each statement.)

22.   The soils of the world contain more carbon than all the world's vegetation and the entire
      atmosphere, combined.

23.   Microbial metabolism in the guts of termites and in waterlogged soils are two major sources of
      excess methane that is contributing to the global greenhouse effect.

24.   Removing all the straw with the harvest of paddy rice would increase the amount of methane
      produced by the paddy soil microorganisms.

25.   The species of microorganisms that are able to sustain themselves by slowly attacking stable
      soil organic matter are the most active decomposers of freshly added organic materials because
      of the head start they enjoy over other organisms which were present only in inactive forms prior
      to the addition.

26.   The priming effect refers to the excretion of growth promoting substance by certain bacteria
      during decomposition of fresh organic residues.

27.   As decomposition of added organic material proceeds, the C/N ratio in the remaining
      undecomposed material steadily increases.

28.   Mineralization of soil organic matter results in the addition of inorganic nutrient ions to the soil
      solution.

29.   The cation capacity of soil humus is two to three times greater than that of an equal volume of
      high CEC silicate clays.

30.   Humus is an important nutrient, essential for healthy plants.

31.   Allelopathic chemicals, once added to soil, usually make the affected soil unsuitable for any
      plant life for periods of years.

32.   Non-humic substances formed during organic matter decomposition probably play a more
      important role than do humic compounds in the mineralization of N and S as well as in the
      solubilization of iron and other micronutrients.

33.   Fulvic acids are a major type of non-humic substances.

34.   Practices that increase the soil organic matter level generally have favorable effects on the
      chemical and biological properties of soils, but have little or no effect on soil physical properties.

                                                    59
35.   Aridisols generally contain more organic matter than Mollisols.

36.   Poorly drained soils generally contain more organic matter than well drained soils.

37.   Sandy soils generally are higher in organic matter than fine textured soils.

38.   When native prairie soils are brought under cultivation, the fraction of soil organic matter which
      disappears most quickly is the passive fraction.

39.   The main contributions of the active fraction of soil organic matter are increased CEC and water
      holding capacity of the soil.

40    In the United States, a national goal of maintaining 5% organic matter in all agricultural soils
      would be a practical and beneficial policy in the long term.

41.   Humus indirectly affects plant growth through its effects on soil physical and chemical
      properties, but humic substances have not been shown to affect plant growth processes
      directly.

42.   Well aerated soils enriched with organic amendments can help reduce the methane load in the
      atmosphere.




                                                   60
        Answers to Chapter 11 Questions


1. C      15. D                           29. F
2. A      16. E                           30. F
3. D      17. C                           31. F
4. D      18. C                           32. T
5. A      19. A                           33. F
6. D      20. D                           34. F
7. D      21. A                           35. F
8. A      22. T                           36. T
9. C      23. T                           37. F
10. D     24. F                           38. F
11. E     25. F                           39. F
12. A     26. F                           40. F
13. B     27. F                           41. F
14. C     28. T                           42. T




                      61
Nitrogen and Sulfur Economy of Soils                                                         Chapter 12

                                  Multiple Choice Questions
                          (Circle the single best answer for each question.)


1.    Nitrogen is a component of which essential plant compounds?
      A. proteins B. chlorophyll          C. enzymes           D. DNA               E. all of the above

2.    A deficiency of N typically ______ the maturity of annual plants.
      A. hastens             B. delays             C. does not affect

3.    Applied to agricultural crops, the term lodging refers to ________.
      A.     pre-mature fruit drop as a result of N deficiency
      B.     infestation with a high number of insect larvae lodged in the fruits or seeds
      C.     short, stubby plants starving for N or S
      D.     plants falling over, often as a result of too much N
      E.     plants losing their leaves because of a N imbalance

4.    Grass clippings from a healthy lawn can be expected to contain approximately ___% N (on a
      dry weight basis).
      A. 0.01       B. 0.2         C. 0.5         D. 3.0        E. 7.5

5.    In the early stages of plant nitrogen deficiency, the most obvious symptoms are _____.
      A.      yellowing of the youngest leaves
      B.      brown spots and tiny holes on the underside of most leaves
      C.      purpling of the youngest leaves
      D.      yellowish colors in the oldest leaves
      E.      brown edges on leaves scattered randomly all over the plant

6.    Plants obtain nitrogen from the soil by taking up ______.
      A.     soluble anions                         B.     soluble cations
      C.     soluble organic compounds              D.     all of the above
      E.     none of the above

7.    The great majority of nitrogen (95 to 98%) in soils can be found in the form of _____.
      A.     primary minerals               B.     secondary minerals
      C.     dissolved cations              D.     dissolved anions
      E.     organic compounds

8.    The process of ______ releases soluble nitrogen as the result of the breakdown of nitrogen-rich
      organic compounds.
      A.     nitrification               B.      denitrification
      C.     symbiosis                   D.      volatilization
      E.     mineralization

9.    The opposite process from mineralization is _______.
      A.    immobilization        B.     nitrification  C.        denitrification
      D.    ammonification        E.     none of the above

10.   Ammonium fixation would be expected to be greatest in soils containing a lot of______.
      A.   Rhizobium bacteria           B.     Frankia                                 C. vermiculite
                                                  62
      D.    iron oxides                   E.       both C and D
11.   Ammonia losses are likely to be greatest if a nitrogen source is placed about 10 cm deep in
      ____.
      A.    an acid, sandy loam soil      B.       a calcareous sandy loam soil
      C.    an acid, clay loam soil       D.       a calcareous clay loam soil

12.   In order for nitrate to form from soil organic matter, _____ must be present in the soil.
      A.     Nitrosomonas                     B.      Nitrobacter                 C.      either A or B
      D.     both A and B                     E.      none of the above

13.   To be practical, a nitrification inhibitor should kill or inhibit _____.
      A.     Nitrosomonas              B.       Nitrobacter
      C.     either A or B             D.       none of the above

14.   Wetlands and forests growing along the banks of rivers remove much nitrogen from
      groundwater by the process of _________.
      A.    immobilization        B.      nitrification               C.      denitrification
      D.    ammonification        E.      none of the above

15.   Methemoglobinemia is principally a potential threat to _____.
      A.    babies drinking water high in sulfate
      B.    adults drinking water high in sulfate
      C.    babies drinking water high in nitrate
      D.    adults drinking water high in nitrate
      E.    all of the above

16.   Assume an A horizon depth of 15 cm. A well drained silt loam soil on an Iowa farm has 3.5%
      organic matter which is about 5% N. Estimate the kg/ha of nitrogen that this soil horizon will
      make available for plant use from soil organic matter in one year (without the addition of
      fertilizer).
      A. 17.5               B. 88          C. 263         D. 175          E. 38

17.   The principal form of sulfur taken up by plants is ____.
      A.     sulfate
      B.     sulfur esters
      C.     sulfides
      D.     elemental sulfur
      E.     gypsum

18.   Compared to gypsum, elemental sulfur is sometimes considered a more desirable fertilizer
      material because _____.
      A.     plants respond to sulfur more rapidly
      B.     it is less dependent on warm, moist conditions for availability
      C.     it contains more nutrient sulfur, kilogram for kilogram, than gypsum
      D.     it causes less soil acidity than gypsum
      E.     all of the above

19.   The sulfur dioxide in the atmosphere ______.
      A.     can be an important source of sulfur nutrition for plants
      B.     is a major contributor to "acid rain"
      C.     comes from fires such as fossil fuel burning, volcanoes and forest fires
      D.     all of the above

                                                      63
      E.     none of the above

20.   Because of _______, soils developed in marine marshes can become extremely acid if drained
      for agriculture or used as topsoil.
      A.      oxidation of sulfates
      B.      reduction of sulfates
      C.      oxidation of sulfides
      D.      reduction of elemental sulfur
      E.      all of the above


                                    True or False Questions
                                  (Write T or F after each question.)

21.   Applying heavy dressings of N fertilizer will tend to produce sugary-sweet fruits and vegetables.

22.   About half the nitrogen in the A horizon of most soils becomes available to plants over the
      course of a whole year in a warm, humid climate.

23.   Nitrogen taken up by plants growing in a compost-treated soil is indistinguishable from the
      nitrogen taken up by plants growing in a fertilizer-treated soil.

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

25.   Nitrification requires the presence of a source of readily available carbon, such as manure.

26.   The terms "ammonium fixation" and "biological nitrogen fixation" refer to the same soil process.

27.   Ammonium fixation occurs to the greatest extent in the O and A horizons.

28.   Ammonia volatilization is a process by which much needed nitrogen is added to the pool of
      plant-available nitrogen in soils.

29.   Ammonia losses from the shallow, algae-filled water of a non-tidal wetland are likely to be much
      greater at night than during the day.

30.   Pesticides and other chemicals added to soils would be more likely to slow down nitrification
      than mineralization.

31.   Nitric acid deposited on forest soils with "acid rain" can increase the leaching of nutrient cations.

32.   In most temperate, humid regions, the period of greatest potential for nitrate leaching is during
      the summer when nitrogen fertilizer is applied to crops.

33.   Most nitrogen leaching to groundwater is in the form of ammonium.

34.   Leguminous forest trees, such as Locust, enrich the soil in nitrogen, to the benefit of non-
      nitrogen fixing plants growing nearby.

35.   Unlike Rhizobium bacteria, Bradyrhizobium bacteria are effective at fixing N, regardless of the
      type of plants present.

                                                   64
36.   Because of their huge numbers and direct access to soil organic matter, free living
      microorganisms such as Azotobacter typically fix more nitrogen per hectare of land than do
      nitrogen-fixing bacteria living in plant roots.

37.   Forests in decline because of acid deposition can often be brought back to high productivity with
      just a few applications of nitrogen fertilizer.

38.   On the average, agricultural soils in the US are currently being depleted of their nitrogen supply.

39.   Although slow release fertilizers take longer to have an effect, they are more economical than
      regular nitrogen fertilizers and so are favored by foresters and farmers.

40.   Highly weathered soils low in available sulfur in their A horizons often have adequate supplies of
      available sulfur in deeper, clay-rich horizons.

41.   Soluble organic N compounds are taken up by plants and are lost in leaching and runoff waters.




                                                  65
        Answers to Chapter 12 Questions

1. E      15. C                           29. F
2. A      16. B                           30. T
3. D      17. A                           31. T
4. D      18. C                           32. F
5. D      19. D                           33. F
6. D      20. C                           34. T
7. E      21. F                           35. F
8. E      22. F                           36. F
9. A      23. T                           37. F
10. C     24. T                           38. F
11. B     25. F                           39. F
12. D     26. F                           40. T
13. A     27. F                           41. T
14. C     28. F




                      66
Soil Phosphorus, Potassium, and Micronutrients                                                Chapter 13

                                    Multiple Choice Questions
                            (Circle the single best answer for each question.)


1. In various parts of the world, soil phosphorus is associated with which of the following
   environmental problems?
   A. soil degradation because of depletion of soil phosphorus
   B. eutrophication of lakes because of a build-up of soil P in the watersheds
   C. toxic levels of phosphate in groundwater supplies
   D. both A and B
   E. all of the above

2. Approximately what percentage of the P in surface soils is typically found in organic forms?
   A. 0.1 to 0.5%          B.      1 to 5%                C.       5 to 15%
   D. 25 to 75%            E.      95 to 98%

3. In a soil at pH 5.0, most of the inorganic P is likely to be in the form of _______.
   A. monocalcium phosphates                  B.       tricalcium phosphates
   B. hydroxy apatites                        D.       hydrous iron and aluminum phosphates
   C. phospholipids

4. The amount of P lost from agricultural soils by the process(s) of _____ is generally considerably
   greater than the corresponding losses of potassium.
   A. leaching                                       B.     harvest removal
   C. gaseous evolution                              D.     both b and c are correct
   E. none of the above are correct

5. Mycorrhizae improve the nutrition of many plants by ______.
   A. transporting phosphorus through the soil to the plant root
   B. fixing atmospheric phosphorus into forms readily used by plants
   C. masking P-fixation sites on the surface of certain soil minerals
   D. readily dissolving iron and aluminum phosphate compounds
   E. making the root cell membrane more permeable to phosphate ions

6. Other things being equal, a soil with 30% clay of the ____ type would be expected to have the
   greatest potassium -fixing capacity.
   A. allophanic             B. 2:1         C. 1:1         D. crystalline iron oxide

7. If a manager can afford only a limited amount of soluble P fertilizer for a calcareous soil with low
   phosphorus availability, the best plant growth is likely to be obtained if the P fertilizer is applied
   _____.
   A. well in advance of the plant's main period of nutrient uptake
   B. evenly across the entire area to be fertilized and mixed thoroughly with the soil in the root zone
   C. in narrow bands or localized concentrations
   D. in combination with ground limestone
   E. a combination of both B and D would be best

8. In acid soils the principal chemical form of phosphorus available for plant uptake is ____.
   A. P2O5 B. H2PO4-            C. P3+        D. HPO42-    E. P3-

                                                    67
9. The nutrient most often limiting the growth of aquatic plants and algae in unpolluted fresh water
   lakes is ______.
   A. N              B. S             C. P          D. K           E. none of the above

10. The sites in certain clay minerals which fix potassium ions are also capable of fixing which other
    ion?
    A. NO3- B. NH4+            C. H2PO4-      D. Ca2+        E. H+

11. In what range of soil pH is phosphorus generally most available to plants?
    A. 3.5-4.5        B. 4.5-5.5     C. 5.5-7.0     D. 7.0-8.0     E. >8.0

12. The total phosphorus lost from various watersheds is most closely correlated with _____.
    A. high soil permeability                      B.     low soil CEC
    C. high percentage of forested land            D.     extent of artificial drainage
    E. high soil erosion

13. Manganese toxicity is most likely to be a problem under which soil conditions?
   A. clay loam Ultisol, pH 4.3, subject to frequent flooding
   B. well drained calcareous soil, pH 8.1
   C. well drained humid region loamy sand, pH 5.0
   D. muck soil (Saprist) with pH 5.5
   E. poorly drained calcareous soil with pH 7.6

14.    Iron deficiency is most likely to occur under which of the following soil conditions?
      A. soil with pH 4.3 and subject to frequent flooding
      B. leached humid region sandy soil limed to pH 8.0
      C. well drained humid region loamy sand (Spodosol) with pH 5.0
      D. muck soil (Saprist) with pH 5.5
      E. silt loam Mollisol with pH 7.5

15. Copper deficiency is most likely to occur under which of the following soil conditions?
    A. soil with pH 4.3 and subject to frequent flooding
    B. well drained loamy sand Ultisol with pH 6.1
    C. silt loam soil with pH 7.0
    D. muck soil (Saprist) with pH 5.5
    E. poorly drained calcareous soil with pH 7.6

16. Molybdenum deficiency is most likely to occur under which of the following soil conditions?
    A. soil with pH 6.3 and subject to frequent flooding
    B. well drained calcareous soil with pH 8.1
    C. well drained humid region loamy sand with pH 5.0
    D. muck soil (Saprist) with pH 5.5
    E. poorly drained calcareous soil with pH 7.6

17. The availability of which of the following micronutrients is commonly affected by soil redox
       potential?
    A. manganese B. zinc                       C. cobalt       D. boron     E. all of the above

18.    Which of the following micronutrients is least commonly found to be deficient in plants?
      A. manganese B.           iron    C.      copper       D.     boron E.         chlorine



                                                       68
19. Which method of application generally would require the greatest amount of iron to alleviate an iron
     deficiency in an orange grove?
    A. application of iron chelate to the soil in localized pockets
    B. application of iron chelate to soil evenly with thorough mixing
    C. foliar spray of iron chelate
    D. application of iron sulfate to soil in localized pockets
    E. application of iron sulfate to soil evenly with thorough mixing

20. Plants that are efficient at taking iron up from a calcareous soil are known to employ which of the
       following methods?
   A. lower pH of their rhizosphere
   B. produce reducing agents that reduce Fe3+ to Fe2+ in the rhizosphere.
   C. produce organic compounds that can form stable chelates with iron.
   D. all of the above
   E. none of the above

21. Which micronutrient is particularly critical for legume plants because of its place in the nitrogenase
    enzyme that allows Rhizobia-infected legumes to utilize atmospheric nitrogen?
   A. B      B. Mo           C. Cu             D. Mn          E. Zn

22. Simply spraying a solution to coat the seeds before planting often provides enough of which
    micronutrient to meet the needs of the crop?
    A. B              B. Mo         C. Cu          D. Mn           E. Zn


                                      True or False Questions
                                    (Write T or F after each question.)

23. Application of phosphorus fertilizer usually makes plants more susceptible to diseases.

24. Annual plants deficient in P usually flower and mature more rapidly than P-sufficient plants.

25. 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.

26. During the last several decades, modern agriculture in the industrialized countries has tended to
    deplete cropland soils of their supply of available P.

27. The amount of K lost in subsurface drainage waters from humid region forested watersheds is
    generally far greater than the amount of P lost in this manner.

28. Water running off from a bare field whose soil had an EPC of 0.1 mg/L would be expected to be
    lower in P concentration than runoff from a field whose soil had an EPC of 2 mg/L.

29. Eroded sediment usually contains about half as much P per kg as does the soil remaining on the
    eroded site.

30. Deep rooted vegetation such as forest trees can increase the available potassium content of
    surface soil horizons even though no potassium is added to the soil profile.

31. Because of the complimentary ion effect, potassium is more readily leached from an acid soil than
    from a neutral soil.

                                                     69
32. In a soil with a very low potential buffering capacity, the most efficient approach to using potassium
    fertilizer would be to apply frequent small doses rather than a single large dose.

33. For an unfertilized temperate region forested soil with a large amount of interlayer fixed potassium,
    but a low amount of readily available potassium, the level of readily available potassium is expected
    to be higher in early spring than in late fall.

34. Application of FeSO4 or ZnSO4 to many soils is much less effective than the addition of the same
    amount of micronutrient in the form of a chelate.

35. Mycorrhizae help plants overcome deficiencies of zinc, copper, and other micronutrients by
    increasing the plant uptake of these elements from soil.

36. Mycorrhizae help plants avoid toxicities of zinc, copper, and other micronutrients by decreasing the
    uptake of these elements from soil into the plant shoot.

37. When organic amendments such as animal or green manures are added to soils, micronutrient
    availability generally is enhanced by the production of natural chelating agents.

38. Most micronutrients play essential roles in plant metabolism as enzyme activators.

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

40. Boron is commonly deficient in acid soils because chemical reactions under acid conditions make it
    less available for plant uptake .

41. The data in the following table show the occurrence of synergism between two nutrients.

                   Height (cm) of subterranean clover plants with and without
                   Mo and P fertilizer.
                                        No Mo added       Mo added

                   No P added          24                   32
                   P added             38                   42


42.    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.




                                                    70
        Answers to Chapter 13 Questions

1. D     15. D                            29. F
2. D     16. C                            30. T
3. D     17. A                            31. T
4. E     18. E                            32. T
5. A     19. E                            33. T
6. B     20. D                            34. T
7. C     21. B                            35. T
8. B     22. B                            36. T
9. C     23. F                            37. T
10. B    24. F                            38. T
11. C    25. F                            39. T
12. E    26. F                            40. F
13. A    27. T                            41. F
14. B    28. T                            42. F




                      71
Practical Nutrient Management                                                               Chapter 14

                                  Multiple Choice Questions
                          (Circle the single best answer for each question.)

1.   Modern nutrient management is designed to _____________.
     A.    cost-effectively produce quality plants
     B.    protect or improve environmental quality
     C.    protect or improve soil quality
     D.    conserve nutrient resources
     E.    all of the above

2.   Of the macronutrients, which can be most correctly said to be a renewable resource?
     A.     potassium
     B.     nitrogen
     C.     phosphorus
     D.     calcium
     E.     iron

3.   Concentrated animal production as is practiced in modern industrial agriculture usually results in
     ______.
     A.    nutrient excesses in the area of the livestock operation
     B.    depletion of nutrients from the soils in the vicinity
     C.    insufficient manure production to properly fertilize cropland on the livestock farm
     D.    nutrient exports from the operation that exceed imports
     E.    both C and D

4.   Buffer strips principally function in nutrient management to _______.
     A.      recycle non-renewable nutrients
     B.      enrich the soil with nutrients that are needed for optimum plant growth
     C.      prevent the transport of nutrients from fields to streams
     D.      slow the movement of potential pollutants to the groundwater
     E.      all of the above

5.   Fertilization to supply the nutrient element iron is often accomplished by which type of
     application?
     A.       injection of a gas into the soil
     B.       broadcast of a chloride salt
     C.       broadcast of the nearly pure element as a solid
     D.       incorporation of powdered limestone rock
     E.       application of a chelate to the soil

6.   Within the technical capabilities of the particular lab, most soil test results can be best
     interpreted as indicating the _______________________.
     A.      total amount of each nutrient in the soil
     B.      amount (lbs or kg ) of nutrient present in plant available forms
     C.      amount or concentration of nutrient in the soil solution
     D.      probability (likelihood) that nutrient application will improve plant growth
     E.      amount of nutrient needed to achieve balanced soil fertility

7.   A cover crop is usually grown for the purpose of _________.
     A.     improving soil quality               B.      saving or recycling nutrients

                                                   72
      C.     covering expenses for pollution control measures
      D.     A and B                              E.     all of the above

8.    A grass cover crop grown on cropland over the winter season in a humid temperate region can
      be expected to ______.
      A.     increase nutrient concentrations in runoff water
      B.     significantly reduce the amount of water percolating to the water table
      C.     significantly reduce the amount of nitrogen fertilizer that will be needed to grow the
             following crop
      D.     reduce the amount of nutrients leached to the groundwater
      E.     all of the above

9.    Well-vegetated buffer strips 10 to 20 meters wide can be expected to reduce the total N content
      of runoff water by about ______.
      A.      10% B.        20% C.          40%    D.     60% E.       90%

10.   Fertilization to supply the nutrient element sulfur is often accomplished by which type of
      application?
      A.       injection of a gas into the soil
      B.       broadcast of a chloride salt
      C.       broadcast of the nearly pure element as a solid
      D.       incorporation of powdered limestone rock
      E.       application of a chelate to the soil

11.   Fertilization to supply the nutrient element nitrogen is often accomplished by which type of
      application?
      A.       injection of a gas into the soil
      B.       broadcast of a chloride salt
      C.       broadcast of the nearly pure element as a solid
      D.       incorporation of powdered limestone rock
      E.       application of a chelate to the soil

12.   Fertilization to supply the nutrient element potassium is often accomplished by which type of
      application?
      A.       injection of a gas into the soil
      B.       broadcast of a chloride salt
      C.       broadcast of the nearly pure element as a solid
      D.       incorporation of powdered limestone rock
      E.       application of a chelate to the soil

13.   The nutrient element magnesium is often supplied by which type of application?
      A.     injection of a gas into the soil
      B.     broadcast of a chloride salt
      C.     broadcast of the nearly pure element as a solid
      D.     incorporation of powdered limestone rock
      E.     application of a chelate to the soil

14.   If soil test results for P are available, the optimum amount of P fertilizer to apply to a crop can be
      best recommended by __________.
      A.        comparing the cost of P fertilizer to the yield responses measured in the past when P
                was applied to similar soils with similar soil test P levels
      B.        subtracting the available soil test P from the total P uptake for the desired yield goal

                                                   73
      C.     subtracting the soil test P level measured from the soil test P level considered to be on
             the border of "high" and "very high"
      D.     calculating the amount of P needed to bring the ratios of soil test P to N, P to K, and P to
             Mg into balance with the proper ratio for the type of soil in question
      E.     these days, all four of the above a done, in order, by a computer program

15.   In recent years, a soil test for nitrogen has been developed and widely used in humid regions in
      predicting how much nitrogen will need to be applied to supplement natural mineralization in the
      soil. This test is called the _______.
      A.      Melich II nitrogen test
      B.      Differential Nitrate Extraction Test (DNET)
      C.      diagnosis and recommendation integrated system (DRIS)
      D.      pre-sidedress nitrate test (PSNT)
      E.      soil nitrogen partial analysis (SNPA)

16.   The PSNT nitrogen soil test is designed to be used in growing _____.
      A. corn      B. turfgrass C. alfalfa        D. fruit trees E. any of the above

17.   The place where the manure pile was stored last year, a narrow strip that used to be a
      limestone gravel farm road, and the spot where fertilizer is usually transferred from a nurse truck
      to the tractor spreader are all examples of parts of a 25 hectare field that should be treated as
      follows when sampling soil for the soil test lab.
      A.       included, like all other areas, in the sample sent in for analysis
      B.       carefully avoided while sampling
      C.       more intensively sampled (more cores per hectare) than other areas
      D.       sampled more deeply than other areas
      E.       sampled and sent in separately

18.   For a year or so after clearcut (even-aged) harvesting large areas of mature forest, the streams
      draining the watershed can be expected to carry ______ than before the harvest.
      A.     much less water
      B.     a much greater total nitrate load
      C.     much less calcium and other cations
      D.     away enough pollutants to reduce the toxic load to levels lower
      E.     all of the above

19.   To monitor the effects of management on soil fertility, it is best to sample the soils in an area
      _______.
      A. every one to three years               B. at the same season every time
      C. from the same depth every time         D. all of the above E. none of the above

20.   Perforation placement is usually used to fertilize _____.
      A. row crops         B. turfgrass C. landscape trees          D. forests




                                                   74
21.   Consider the data in the accompanying table giving the average height of 10 trees planted in
      order to revegetate a disturbed soil. What was the first limiting factor for tree growth on this soil?
      A. water       B. soil pH     C. nitrogen D. phosphorus

                Average height of 10 trees planted on reclaimed, mined-over land.
      Growth factor added      Nothing added     100 kg/ha N   50 kg/ha P    2 cm / wk water

      no lime                  56                45            63            50

      lime added               85                170           58            62



22.   Based on the data given in the table, if the revegetation site were limed and fertilized with
      nitrogen, would you also recommend the addition of P fertilizer to improve tree growth?
      A. no          B. yes                C. no basis to judge

                Average height of 10 trees planted on reclaimed, mined-over land.
      Growth factor added      Nothing added     100 kg/ha N   50 kg/ha P    2 cm / wk water

      no lime                  56                45            63            50

      lime added               85                170           58            62




                                     True or False Questions
                                    (Write T or F after each question.)


23.   Integrated nutrient management seeks to apply, as fertilizer, enough of each nutrient to replace
      that removed from the soil by plant uptake.

24.   The cost of fertilizer is the main consideration of nutrient management for most ornamental
      landscaping applications.

25.   Land application of treated sewage sludge is an effective means of recycling nutrients back to
      the soil from which they were originally taken.

26.   Routine soil testing on a regular basis allows landowners to monitor most changes in soil
      quality.

27.   The primary means to avoid non-point source nitrogen and phosphorus pollution in agricultural
      watersheds is to avoid applications that bring the available supply of these nutrients in soils to
      amounts higher than can be used by crop plants.

28.   Buffer strips are usually a last-resort mechanism of pollution control because of their expense
      and unfavorable side-effects.

29.   As runoff water flows across a grassed buffer strip, the concentrations of N and P in the water
      decrease slowly at first, but if the buffer strip is sufficiently wide, major reductions in these
      concentrations will occur just before the water leaves the buffer.

                                                      75
30.   Broadcast application usually requires less fertilizer to achieve a given level of plant response
      than does banding.

31.   Many years of research have confirmed that the quadratic (parabolic curve) model is the best
      method of making fertilizer recommendations based on response curves, especially if
      environmental quality is a high priority.

32.   When banding fertilizer, the material should be placed about 1 or 2 cm below the seed being
      planted.

33.   For most plants the relationship between plant tissue concentration of a nutrient and the dry
      matter production of the plant is linear until toxicity begins to have an effect.

34.   To enable the most consistent and appropriate interpretations, all soil samples submitted to a
      particular soil test lab should be taken from the same soil depth, regardless of differences in the
      type of tillage used or plants grown.

35.   Soil test interpretations have been developed so that for most fields testing "low" in a nutrient,
      addition of that nutrient will increase yield enough to more than pay for the cost of applying the
      fertilizer.

36.   Soil test interpretations have been developed so that for most fields testing "high" in a nutrient,
      addition of that nutrient will not increase yield enough to more than pay for the cost of applying
      the nutrient.

37.   For most soils, even if they test "high" in a nutrient such as potassium or nitrogen, it is
      necessary to apply at least as much of each nutrient as is removed in the harvest, if the soil is
      not to eventually become infertile and unproductive.

38.   Most research has shown that at both high and low fertilization levels, about 15 to 20% of the
      nitrogen applied as fertilizer will be lost by leaching from medium textured soils growing corn.

39.   The forestry industry uses fertilizers most often to treat old growth stands that will produce
      valuable lumber

40.   Most chemical fertilizers are inorganic salts.




                                                   76
        Answers to Chapter 14 Questions

1. E      14. A                           27. T
2. B      15. D                           28. F
3. A      16. A                           29. F
4. C      17. B                           30. F
5. E      18. B                           31. F
6. D      19. D                           32. F
7. D      20. C                           33. F
8. D      21. B                           34. F
9. E      22. C                           35. T
10. C     23. F                           36. T
11. A     24. F                           37. F
12. B     25. F                           38. F
13. D     26. F                           39. F
                                          40. T




                      77
Soil Erosion and its Control                                                                Chapter 15

                                  Multiple Choice Questions
                          (Circle the single best answer for each question.)

1.   Which of the following statements about soil erosion is not true?
     A.    Soil erosion losses per hectare of cropped land are higher in Asia and Africa than the
           United States.
     B.    The rate of soil erosion loss in the United States declined from 1980 to 1995.
     C.    Downstream off-site costs of erosion are often higher than those in upstream fields from
           which the soil came.
     D.    Soil erosion losses of potassium exceed those of nitrogen and phosphorus.
     E.    Less than 20 percent of the total soil erosion in the United States comes from croplands.

2.   In explaining erosion processes to a friend, which of the following would you say about
     accelerated erosion?
     A.      It refers to sediment carried by water flowing at ever greater velocity.
     B.      It involves a much less rapid process than geological erosion.
     C.      It is greatly enhanced by the splash effect of raindrops impacting bare soil.
     D.      It is increasing in intensity in the United States, especially in the past 10 years.
     E.      it removes more nitrogen from the surface soil than calcium.

3.   Which of the following statements is true?
     A.    Sheet erosion is most obvious from a distance.
     B.    Gully erosion carries the most sediment away from lands in the United States.
     C.    Rill erosion is the most serious in forested areas.
     D.    Rill erosion is initiated before water concentrates in small 1-2 cm channels.
     E.    Rill erosion channels can be removed by ordinary cultivation.

4.   The universal soil-loss equation (USLE) suggests that soil erosion loss is a product of all but
     one of the following factors:
     A. soil drainage                     B. climate
     C. slope length                      D. sloped steepness
     E. vegetative cover

5.   The key to preventing soil erosion by water on both farms fields and landscaping job sites is
     ______.
     A.    to keep the soil surface covered with vegetation
     B.    to provide adequate surface and subsurface drainage
     C.    to grade or till the soil until a smooth surface is achieved
     D.    to keep the soil moist (with irrigation if necessary)
     E.    to practice good landscape sanitation such as clearing away weeds and old plant
           residues

6.   The P factor in the Universal soil-loss equation is concerned with all but one of the following:
     A. contour tillage    B. strip-cropping
     C. soil erodibility   D. terraces                     E. vegetative covers

7.   If you want to maximize the quantity of vegetative cover on soil which of the following tillage
     practices would you use?
     A.      conventional moldboard plow
     B.      no-tillage
                                                   78
      C.     ridge tillage
      D.     stubble mulch
      E.     strip till

8.    To be classified as a conservation tillage practice, a system must leave at least what portion of
      the soil surface covered with plant residues?
      A. 10%          B. 20%        C. 30%          D. 40%         E. 50%

9.    A soil has been managed using a no-till system for 10 years following many years of
      conventional tillage operations. Which of the following changes in surface soil properties would
      you expect due to the no-till management system?
      A.      the earthworm population would decline
      B.      soil pH would increase
      C.      aggregate stability would decline
      D.      organic matter content would increase
      E.      bulk density would increase

10.   You have been asked to produce continuous corn on five different soils using both no-till and
      conventional management systems. Yields on the no-till and conventional-till systems are about
      the same on all but one of the soils. In which of the following suborders would the poor-
      performing soil most likely be classified?
      A. Orthods             B. Eutrox              C. Borolls
      D. Udalfs              E. Xerolls

11.   In one field trial comparing no-till and conventional tillage, soil samples taken after 15 years
      without liming revealed that the pH of the upper 15 cm was lower on the no-till plot than on the
      conventional plot. Which of the following most likely accounts for this difference?
      A.      organic decomposition produced more organic acids in the no-till plot
      B.      earthworms were more active in the no-till plot
      C.      acidifying effects of nitrogen-containing fertilizers
      D.      Al3+ ions are tied up by the organic matter thereby releasing H+ ions
      E.      plowing mixes the surface soil more thoroughly

12.   Conservation tillage systems are said to have all of the following advantages but one over
      conventional tillage systems
      A.    its labor and energy requirements are lower
      B.    it encourages higher microbial population numbers in the soil
      C.    it involves the use of less toxic weed control practices
      D.    it increases the hydraulic conductivity of the soil
      E.    it reduces soil erosion

13.   Wind erosion accounts for about what percent of the total soil erosion losses in the United
      States?
      A.     5%     B.    10% C.         20% D.          35% E.           75%

14.   Wind erosion is generally not affected by _____.
      A.    soil moisture B.        soil crusting C.       bulk density of the soil
      D.    soil pH        E.       soil texture

15.   The R factor of the Universal soil-loss equation is concerned with _____.
      A.     soil erodibility       B.      residue cover on the soil
      C.     terraces               D.      climate         E.    slope steepness

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16.   "Living" terraces involving rows of deep rooted grasses planted on the contour would be
      considered as contributing to which factor in the Universal soil-loss equation?
      A. R            B. K           C. L           D. S           E.      P

17.   The U.S. Department of Agriculture has developed soil-loss tolerance limits (T values) for
      different soils. Which of the following is the highest T value assigned for most soils in this
      country (Mg/ha)?
      A. 5.0           B. 15         C. 11           D. 20          E. 2

18.   Which of the USDA land use capability classes (LUC) is most suitable for the production of row
      crops?
      A. I          B. II        C. VI           D. IV         E. VIII

19.   On which of the land use capability classes is suggested use restricted to non-production
      purposes, only wildlife and recreational purposes being appropriate?
      A. I          B. II           C. VI          D. IV         E. VIII

20.   About what percentage of the total non-federal government owned rural lands is considered
      suitable for cultivation according to USDA land use capability classes (if appropriate
      management practices are employed)?
      A. 75%                   B. 55%              C. 35%                 D. 20%          E. 2%


                                       True/False Questions
                                   (Write T or F after each question.)

21.   In the United States, losses of soil due to wind and water erosion decreased by about 1/3
      between 1982 and 1992.

22.   Some 3/4 of the total soil loss from erosion in the United States is carried away by water.

23.   The total global soil lost through erosion is generally greater from gully erosion than from sheet
      erosion.

24.   Slope length is generally of greater significance in determining erosion rate than is steepness of
      slope.

25.   The soil erodibility factor in the Universal soil-loss equation (USLE) relates primarily to the soil's
      infiltration capacity and structural stability.

26.   The Revised Universal Soil-Loss Equation (RUSLE) is more location specific, more accurate in
      predicting soil loss, and provides answers on alternative procedures more quickly than does
      USLE.

27.   Vegetative barriers planted on the contour have been found to create low-cost "natural"
      terraces.

28.   Compared to conventional tillage systems, most conservation tillage systems rely more heavily
      on herbicides to control weeds.



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29.   Ridge-till systems show promise in the management of somewhat poorly drained soils of the
      Midwest.

30.   Yields of row crops on poorly drained soils are generally somewhat higher with no-tillage
      systems than with conventional tillage systems.

31.   Conservation tillage has generally positive effects on soil physical properties.

32.   Hydraulic conductivity is commonly higher in soils on which conventional tillage systems have
      been used than where no-tillage systems have been followed.

33.   The effects of conservation tillage on soil erosion would be more pronounced in fields cropped
      continuously to corn than in fields cropped to soybean.

34.   The surface soil pH is generally higher on no-tillage plots than on comparable conventionally
      tilled plots.

35.   Conservation tillage systems are now in use on some 75% of the cropland in the USA.

36.   Saltation is the process of wind movement of salt-affected soils from one location to another in
      arid regions.

37.   Although transportation of soil particles in suspension in the atmosphere is very spectacular,
      less than 40% of the wind erosion losses generally occur in this manner.

38.   The T values are the maximum losses of soil by erosion that can be tolerated without a
      reduction in the soil's long term productivity.

39.   In the U.S. Department of Agriculture's land capability classification systems, some 15% of the
      Nation's cultivated land is in Class I.

40.   Soils in Land Capability Class VIII areas are less subject to erosion than any other class.




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          Answers to Chapter 15

1. E    14. D                     27. T
2. C    15. D                     28. T
3. E    16. E                     29. T
4. A    15. C                     30. F
5. A    18. A                     31. T
6. C    19. E                     32. F
7. B    20. B                     33. T
8. C    21. T                     34. F
9. D    22. F                     35. F
10. C   23. F                     36. F
11. C   24. F                     37. T
12. C   25. T                     38. T
13. D   26. T                     39. F
                                  40. F




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