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Sustainable Nutrient Management > Midterm 2 > Flashcards

Midterm 2 Flashcards

1
Q

P mineralization is most effective in soils with pH (</>) 7.

A

<7

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2
Q

(Ammonium/nitrate) inhibits phosphate uptake.

A

Nitrate.

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3
Q

C;N cutoff between organic and synthetic fertilizers.

A

2:1

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4
Q

Step two of N mineralization:

A

Ammonification

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5
Q

The main P minerals in acid and neutral soils.

A

Al/Fe phosphates

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6
Q

SOM contains about ____% N.

A

5%

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7
Q

What is the function of S in proteins?

A

Protein folding.

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8
Q

(More/less) weathered soils adsorb sulfate more strongly.

A

More

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9
Q

S mineralization is (positively/negatively) correlated with the abundance of plants.

A

Positively.

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10
Q

In plants, Mg is (mobile/immobile).

A

Mobile

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11
Q

In plants, Ca is (mobile/immobile).

A

Immobile

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12
Q

Step one of N mineralization:

A

Aminization

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13
Q

In soils, K is (mobile/immobile).

A

Mobile.

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14
Q

Where is most S in plants found?

A

Amino acids; ~90%

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15
Q

Under what soil conditions would band placement of P result in the greatest utilization by the plant?

A

Highly buffered soils; banding prevents interactions.

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16
Q

P mineralization occurs at a C:P <____:1.

A

200

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17
Q

What is the difference between single and triple superphosphate?

A

Triple is acidified with sulfuric acid, has less impurities. Single is acidified with phosphoric acid, has more impurities.

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18
Q

S immobilization occurs at a C:S >____:1.

A

400

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19
Q

In legume, N fixation generally accounts for between ____% and ____% of N requirements.

A

50-75%

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20
Q

The most important P fertilizer.

A

Acid treatment P fertilizer: rock phosphate

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21
Q

Sulfate adsorption is increased at (low/high) pH.

A

Low

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22
Q

When pH is lower than 5.5-6, N fixation (increases/decreases).

A

Decreases.

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23
Q

What effect does liming have on K uptake?

A

Ca displaces Al and H, freeing up exchange sites for K. Ca displaces K, improving absorption from solution.

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24
Q

Highly weathered soils (maximize/minimize) P sorption.

A

Maximize; strongly adsorbed to oxides.

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25
Q

The first step of nitrification is carried out by ______.

A

Nitrosomonas

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26
Q

(Singe/triple) superphosphate can cause S deficiencies.

A

Triple; less impurities

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27
Q

S mineralization is (increased/decreased) temperatures below 10C.

A

Decreased

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28
Q

What major differences mark the S cycle in comparison to the N cycle?

A

No S fixation, nitrification, etc…

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29
Q

Anion adsorption is increased when ____ cations are on exchange sites.

A

Divalent

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30
Q

The main P minerals in alkaline and calcareous soils.

A

Calcium phosphates

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31
Q

What is the biggest difference between symbiotic and associative N fixation?

A

Symbiotic N fixation is endophytic (occurring within the plant roots), while associative occurs in the rhizosphere.

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32
Q

N influence on carbohydrate activity:
(High/low) N causes proteins to be formed from carbohydrates, resulting in a more succulent plant.

A

High

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33
Q

Input (quality/quantity) is more important for N availability.

A

Quality

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34
Q

Organic P is concentrated in which soil horizon?

A

A

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35
Q

Why are phosphates used to extract sulfate?

A

Phosphate has a stronger adsorption strength.

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36
Q

The optimal pH for nitrification:

A

8

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37
Q

How does pH affect the form of ammonical N?

A

High pH, more ammonia

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38
Q

The second step of nitrification is carried out by _____.

A

Nitrobacter

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39
Q

At a given level of saturation, (1:1/2:1) clays will supply more Ca.

A

1:1; buffering capacity

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40
Q

At what pH is P availability maximized.

A

6.5

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41
Q

In plants, S is (mobile/immobile).

A

Mobile

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42
Q

N fixation (increases/decreases) soil pH.

A

Decreases

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43
Q

How does the K cycle differ from micronutrient cycles?

A

K fixation

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44
Q

The enzyme complex responsible for N fixation.

A

Nitrogenase

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45
Q

K in organic residues occur mainly as _____.

A

Soluble inorganic K.

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46
Q

____ is the principle dry N source in the world.

A

Urea

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47
Q

Ammonium fixation can occur in ____ clays.

A

2:1

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48
Q

At low pH. P precipitates with ____.

A

Fe and Al.

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49
Q

In soils, Ca is (mobile/immobile).

A

Immobile

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50
Q

______ fix N in symbiosis with nonlegume trees.

A

Frankia

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51
Q

Sulfate (is/is not) easily leached from soil.

A

Is

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52
Q

(T/F) P in soil is lost mainly by leaching.

A

False; erosion

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53
Q

The main pool for soluble P in soil.

A

SOM

54
Q

How does liming an acid soil affect K availability?

A

Displaces H and Al from CEC, freeing up sites for K.

55
Q

T/F: Plants can selectively uptake Ca vs. Mg.

A

False; both move by mass flow and are divalent; Casparian strip cannot differentiate.

56
Q

Adsorption of sulfate is increased in (topsoil/subsoil).

A

Subsoil; more oxides and clay

57
Q

(1:1/2:1) clays generally have more K.

A

2:1; buffering capacity

58
Q

What P fertilizer is often used as a starter fertilizer?

A

Ammonium phosphates

59
Q

Most ammonium in soil is nitrified within ____ weeks.

A

3

60
Q

In plants, N is (mobile/immobile).

A

Mobile

61
Q

N influence on carbohydrate activity:
(High/low) N causes carbohydrates to deposit in the vegetative cells, causing them to thicken.

A

Low

62
Q

What pools of SOM is most important to plant nutrition?

A

The light fraction; active fraction; labile SOM

63
Q

At high pH. P precipitates with ____.

A

Ca

64
Q

At a given level of Ca saturation, (high/low) CEC soils will have greater Ca absorption by plants.

A

Low; buffering capacity

65
Q

What is the added nitrogen interaction?

A

When N fertilizer is applied, less than one half is directly absorbed by plants. Regardless, N uptake roughly equals the amount supplied. This is because microbes uptake the additional fertilizer N, causing them to consume SOC, subsequently releasing SON.

66
Q

Denitrification (increases/decreases) under anaerobic conditions.

A

Increases.

67
Q

(Excessive/deficient) N causes excessive succulence, enhancing diseases, insect damage, and lodging susceptibility.

A

Excessive

68
Q

S mineralization is (positively/negatively) correlated to soil moisture content.

A

Negatively; concentration

69
Q

Calcium uptake is impeded at (low/high) pH.

A

Low; H and Al impede uptake

70
Q

The effect of other cations on Ca uptake.

A

Depressed by other cations.

71
Q

In soils, S is (mobile/immobile).

A

Mobile (except very acid soils).

72
Q

Weathering of parent material generally (increases/decreases) the K content of minerals.

A

Decreases

73
Q

How does Ca on the CEC affect K absorption?

A

Ca displaces K on CEC.

74
Q

In plants, P is (mobile/immobile).

A

Mobile.

75
Q

How does pH affect K availability?

A

Low pH reduces K on CEC.

76
Q

In soil, P is (mobile/immobile).

A

Immobile

77
Q

What is the most commonly used dry Mg fertilizer?

A

Epsom salts.

78
Q

At low pH, what ions impede K uptake?

A

Al and Mn

79
Q

How do divalent cations on the CEC affect P sorption?

A

Increase

80
Q

In soils, Mg is (mobile/immobile).

A

Mobile

81
Q

In soil, NO3 is (mobile/immobile).

A

Mobile

82
Q

Typical N2:N2O produced via denitrification:

A

11:1

83
Q

In plants, K is (mobile/immobile).

A

Mobile.

84
Q

What cation has the greatest potential to leach with nitrate?

A

K

85
Q

How does the biological component of the P cycle compare to the N cycle?

A

Similar

86
Q

(Ammonium/nitrate) improves phosphate uptake.

A

Ammonium

87
Q

What major nutrient enhances P uptake?

A

NH4; increased growth.

88
Q

What effect does gypsum have on K uptake?

A

Ca displaces K on CEC, resulting in higher [K] in solution (more absorption).

89
Q

Ca uptake is (increased/decreased) in the presence of nitrate.

A

Increased.

90
Q

What extractants are mainly used for sulfate?

A

Calcium dihydrogen phosphate and potassium dihydrogen phosphate.

91
Q

Organic N accounts for ____% of total N in soil.

A

95%

92
Q

___% of reactive N produced in Haber-Bosch process and used for animal production enters the human mouth.

A

4%

93
Q

At high pH, what nutrients compete with K for uptake?

A

Ca and Mg.

94
Q

What is the substrate of nitrification?

A

Ammonia!

95
Q

Between ____% and ____% of organic N in mineralized in a growing season.

A

1-4%

96
Q

Naturally occurring P in soils originates from _____.

A

Parent material

97
Q

S mineralization is (positively/negatively) correlated to soil pH.

A

Negatively

98
Q

K is mainly derived from ____.

A

Parent material

99
Q

What is the major difference between the P cycle and N cycle?

A

The abiotic component of the P cycle is highly pH dependent.

100
Q

Sorption of P is stronger in (1:1/2:1) clays.

A

1:1

101
Q

The functions of K are largely related to its ____.

A

Ionic nature; ionic strength of solution in plant cells.

102
Q

Soil carbon storage is maximized under (warm/cool) and (moist/dry) conditions.

A

Cool and moist

103
Q

Ca saturation (increases/decreases) K absorption from soil solution.

A

Increases.

104
Q

Tissue K content is (positively/negatively) correlated to transpiration.

A

Negatively.

105
Q

What is the largest pool of soil S?

A

SOM

106
Q

Nitrification is (more/less) efficient at low pH.

A

Less

107
Q

P immobilization occurs at a C:P>____:1.

A

300

108
Q

K uptake is (greater/less) than Mg uptake.

A

Greater

109
Q

Where is S mainly derived from?

A

Volcanism.

110
Q

K uptake is (positively/negatively) correlated with temperature.

A

Positively

111
Q

The enzyme responsible for mineralization of organic P.

A

Phosphatase

112
Q

Input (quality/quantity) is more important for SOC accumulation.

A

Quantity

113
Q

What is the dominant pool of S in soils.

A

Organic; 94-95%

114
Q

Nitrification is more efficient at (high/low) pH.

A

High; more ammonia, less ammonium

115
Q

Nitrification inhibitors are (more/less) effective than micro-irrigation.

A

Less

116
Q

What is the largest pool of soil N?

A

SOM.

117
Q

Tissue K content is (positively/negatively) correlated to CO2 assimilation.

A

Positively.

118
Q

What is the common K extractant used for arid soil, such as in California?

A

Nitric acid; used for fixed K.

119
Q

What microorganisms are responsible for S oxidation?

A

Sulfur oxidizing bacteria (mostly aerobic).

120
Q

(T/F) Anthropogenic reactive N production is greater than natural production.

A

True

121
Q

(1:1/2:1) clays more strongly adsorb sulfate.

A

1:1

122
Q

Calcium deficiencies are (common/rare).

A

Rare

123
Q

Is symbiotic or associative N fixation more effective?

A

Symbiotic

124
Q

The main form of S that is available to plants.

A

Sulfate.

125
Q

What environmental factors affect S oxidation?

A

Temperature (25-40 C), moisture/aeration (goldilocks zone), and soil pH (wide range, but some microbial species like very low pH).

126
Q

Approximately 50% of N-fixation is carried out by _____.

A

Rhizobia

127
Q

In soil, NH4 is (mobile/immobile).

A

Immobile

128
Q

C:N:P:S in SOM.

A

100:10:1:1

129
Q

What is grass tetany?

A

Magnesium deficiency in ruminants.

130
Q

S mineralization occurs at a C:S <____:1.

A

200

Sustainable Nutrient Management (4 decks)

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