Deck 12: Nutrient Cycles and Soil Fertility

Question 1

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

Answer 1

D

Question 2

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

Answer 2

D

Question 3

To be practical, a nitrification inhibitor should kill or inhibit _____.

A) Nitrosomonas
B) Nitrobacter
C) either A or B
D) none of the above

Answer 3

A

Question 4

The opposite process from mineralization is _______.

A) immobilization
B) nitrification
C) denitrification
D) ammonification
E) none of the above

Question 5

Ammonium fixation would be expected to be greatest in soils containing a lot of______.

A) Rhizobium bacteria
B) Frankia
C) vermiculite
D) iron oxides
E) both C and D

Question 6

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

Question 7

Nitrogen is a component of which essential plant compounds?

A) proteins
B) chlorophyll
C) enzymes
D) DNA
E) all of the above

Question 8

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

Question 9

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

Question 10

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

Question 11

A deficiency of N typically ______ the maturity of annual plants.

A) hastens
B) delays
C) does not affect

Question 12

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
E) none of the above

Question 13

The principal form of sulfur taken up by plants is ____.

A) sulfate
B) sulfur esters
C) sulfides
D) elemental sulfur
E) gypsum

Question 14

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

Question 15

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

Question 16

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

Question 17

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

Question 18

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

Question 19

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

Question 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

Question 21

Loss of P to groundwater is likely to be most significant for which type of soil?

A) highly weathered tropical soils
B) silt loam soils formed in windblown loess
C) cultivated organic peat soils
D) sandy soils under pine forests (Spodosols)
E) calcareous soils

Question 22

Compared to land that is not disturbed by tillage, conventionally plowed cropland usually loses much more ______.

A) dissolved P
B) particulate P
C) total P
D) both B and C are correct
E) none of the above is correct

Question 23

Other things being equal, a soil with 30% clay of the ____ type would be expected to have the greatest phosphorus -fixing capacity.

A) allophanic
B) 2:1
C) 1:1
D) crystalline iron oxide

Question 24

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%

Question 25

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

Question 26

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

Question 27

In acid soils the principal chemical form of potassium available for plant uptake is ____.

A) K₂O
B) H₂KO_2-
C) K⁺
D) HKO_22- E. P^-

Question 28

You would be most likely to find P deficient plants in which location?

A) a vegetable garden in India
B) a corn field in sub-Saharan Africa
C) a pasture in the Netherlands
D) a Douglas Fir forest in Oregon
E) an apple orchard in New York.

Question 29

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
C) hydroxy apatites
D) hydrous iron and aluminum phosphates
E) phospholipids

Question 30

In most soils, mineralization of soil organic matter is an important source of plant available ____.

A) potassium
B) phosphorus
C) both A and B
D) none of the above

Question 31

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

Question 32

Compared to the same soil used for cropland, a forested soil would be expected to lose _____ total P to streams draining the watershed.

A) less
B) about the same amount of
C) more

Question 33

The total phosphorus lost from various watersheds is most closely correlated with _____.

A) high soil permeability
B) low soil CEC
125
C) high percentage of forested land
D) extent of artificial drainage
E) high soil erosion

Question 34

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

Question 35

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

Question 36

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

Question 37

In acid soils the principal chemical form of phosphorus available for plant uptake is ____.

A) P₂O₅
B) H₂PO_4-
C) P³⁺
D) HPO_42-
E) P^3-

Question 38

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

Question 39

Non-point source losses of which element are considered to be a serious water pollution problem because the resulting high concentration of the element in stream water is toxic to most fish.

A) potassium
B) phosphorus
C) both a and b
D) neither a nor b

Question 40

The sites in certain clay minerals which fix potassium ions are also capable of fixing which other ion?

A) NO_3- B. NH₄₊
C) H₂PO_4-
D) Ca²⁺
E) H⁺

Question 41

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

Question 42

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

Question 43

Applying 10 kg/ha of which of the following nutrients would most likely cause toxicity to plants?

A) manganese
B) iron
C) copper
D) boron
E) chlorine

Question 44

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

Question 45

Which micronutrient element is found in the greatest quantity in most soils?

A) B
B) Cu
C) Fe
D) Mn
E) Zn

Question 46

When soil pH is between 4.5 and 5.5, which micronutrient most commonly causes plant toxicity?

A) Zn
B) Cu
C) Fe
D) Mn
E) Mo

Question 47

Which of the following nutrient elements is usually present in the soil solution as a simple cation?

A) B
B) Zn
C) Cl
D) Mo
E) all of the above

Question 48

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

Question 49

Which of the following nutrient elements is usually present in the soil solution as an undissociated acid?

A) B
B) Cu
C) Zn
D) Fe
E) Mo

Question 50

Molybdenum toxicity is most likely to occur under which soil conditions?

A) soil with pH 4.3 and subject to frequent flooding
B) well drained calcareous soil with pH 8.0
C) excessively 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 8.0

Question 51

Plant symptoms such as aborted fruits, dead terminal buds, and misshapen new leaves suggest a deficiency of which micronutrient?

A) B
B) Cu
C) Zn
D) Fe
E) Mn

Question 52

Which of the following micronutrients becomes more available for plant uptake as soil pH is increased from pH 6 to pH 8?

A) manganese
B) iron
C) zinc
D) boron
E) none of the above

Question 53

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

Question 54

Which of the following micronutrients is least commonly found to be deficient in plants?

A) manganese
B) iron
C) copper
D) boron
E) chlorine

Question 55

Plant symptoms such as interveinal chlorosis on new leaves suggest a deficiency of which micronutrient?

A) Zn
B) Fe
C) Mn
D) all of the above
E) none of the above

Question 56

In an alkaline soil, much of the iron in most iron chelates is rapidly replaced in the chelate complex by which other metallic nutrient?

A) Ca
B) Zn
C) Mn
D) Cu
E) K

Question 57

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

Question 58

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

Question 59

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

Question 60

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

Question 61

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

Question 62

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

Question 63

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

Question 64

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

Question 65

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

Question 66

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.

Question 67

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

Question 68

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

Question 69

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

Question 70

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.

Question 71

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.

Question 72

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

Question 73

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.

Question 74

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.

Question 75

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

Question 76

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

Question 77

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

Question 78

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

Question 79

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

Question 80

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