Deck 13: Nitrogen and Sulfur Economy of Soils

Question 1

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

Answer 1

C

Question 2

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

Answer 2

E

Question 3

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

Answer 3

C

Question 4

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 5

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 6

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 7

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

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

Question 8

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 9

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 10

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 11

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

A)hastens
B)delays
C)does not affect

Question 12

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

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

Question 13

The opposite process from mineralization is _______.

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

Question 14

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

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

Nitrogen is a component of which essential plant compounds?

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

Question 17

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 18

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

Question 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
E)none of the above

Question 20

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 21

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 22

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

Question 23

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 24

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 25

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

Question 26

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

Question 27

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

Question 28

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

Question 29

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

Question 30

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

Question 31

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

Question 32

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 33

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 34

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

Question 35

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

Question 36

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

Question 37

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

Question 38

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

Question 39

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 40

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

Question 41

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