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AGRI 51 > LE3 > Flashcards

LE3 Flashcards

1
Q

Soil microorganisms play a very important role in the ff

A
  • Soil health
  • Ecosystem functions
  • Plant nutrition and growth promotion
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2
Q

Activities of Soil Microorganisms

A
  • Decomposition of organic compounds
  • Transformation of nutrients such as Nitrogen and Sulfur
  • Pesticide degradation
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3
Q

The compound that is resistant to microbial action

A

Humus

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4
Q

TRUE OR FALSE

Anaerobic decomposition is very -fast- and may result in the accumulation of organic matter

A

FALSE

very slow

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5
Q

Factors affecting SOM decomposition

A
  • Aeration
  • Soil temperature
  • Soil moisture
  • Soil pH
  • Soil texture
  • C/N ratio of organic material
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6
Q

TRUE OR FALSE

Fungi is -unaffected- by pH level

A

TRUE

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7
Q

At what soil pH are bacteria and actinomycetes inhibited?

A

pH 5.5

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8
Q

It is a convenient tool for predicting the rate of decomposition

A

Carbon/Nitrogen ratio

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9
Q

It is the optimum C/N ratio of organic materials for faster decomposition

A

20:1

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10
Q

It is the reduction of atmospheric nitrogen gas to ammonia

A

Nitrogen Fixation

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11
Q

Process that makes N available for assimilation by plants

A

Nitrogen Fixation

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12
Q

What is the nitrogen-fixing bacteria that can convert atmospheric nitrogen into useable form of ammonium?

A

Rhizobium

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13
Q

In mineralization/ammonification/decay, what are the fates of NH4+?

A
  • fixed by clay minerals
  • lost by soil erosion
  • used by plants
  • volatilization
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14
Q

What are the factors that influence the rates of mineralization?

A
  • temperature
  • moisture
  • aeration
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15
Q

It is the process in which nitrate and ammonium are taken up by soil organisms and therefore become unavailable to crops

A

Immobilization

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16
Q

TRUE OR FALSE

Incorporation of materials with a high carbon to nitrogen ratio will -increase- biological activity and cause a greater demand for N, and thus result in N immobilization

A

TRUE

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17
Q

It is the process by which microorganisms convert ammonium to nitrate to obtain energy

A

Nitrification

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18
Q

TRUE OR FALSE

Nitrification is most rapid when soil is warm and moist and well-aerated, but is virtually halted below 5 degrees celsius and above 50 degrees celsius

A

TRUE

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19
Q

TRUE OR FALSE

The nitrifying bacteria are -anaerobic-

A

FALSE

Aerobic

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20
Q

Soil microbial activity that can significantly increase soil acidity due to the production of H+ ions

A

Nitrification

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21
Q

A process where N is lost through the conversion of nitrate to gaseous forms of N such as nitric oxide, nitrous oxide and dinitrogen gas

A

Denitrifiction

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22
Q

It is common in poorly-drained soils and occurs when the soil is saturated, and the bacteria uses nitrate as an oxygen source

A

Denitrification

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23
Q

Bacteria responsible for denitrification belong to the ff genera

A
  • Pseudomonas
  • Clostridium
  • Bacillus
  • Paraccoccus
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24
Q

Under aerobic environment, sulfur may be oxidized by ___________ to SO4 with a release of energy

A

Thiobacillus thiooxidans

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25
Q

Under anaerobic conditions, sulfate may be reduced by what bacteria?

A

Desulfovibrio desulfuricans

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26
Q

It is the end product of sulfur transformations and emanates the characteristic offensive odor of flooded soils

A

H2S
Hydrogen sulfide

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27
Q

Processes involved in the inactivation of pesticides in the soil

A
  • Detoxification
  • Conjugation
  • Degradation
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28
Q

It is the conversion of the pesticide molecule to a non-toxic compound

A

Detoxification

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29
Q

A process by which an organism make the substrate more complex by combining the pesticide with cell metabolites; addition of amino acid, organic acid or methyl crown to the substrate

A

Conjugation

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30
Q

It is the breaking down/transformation of a complex substrate into simpler products leading finally to mineralization

A

Degradation

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31
Q

It is the single most important method by which pesticides are completely removed from soils

A

Biochemical degradation of pesticides by microorganism

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32
Q

TRUE OR FALSE

The organophosphate insecticides, such as parathion, are degraded quite -rapidly- in soils by a variety of organisms

A

TRUE

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33
Q

Creatures that spend all part of their lives in the soil environment

A

Soil organisms

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34
Q

Roles of soil organisms

A
  • maintaining fertility, structure, drainage and aeration of soil
  • decomposition
  • conversion of nutrients into plant-available forms
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35
Q

It is the mix of species present

A

Species diversity

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36
Q

It is the capacity to use a wide variety of substrates and provide a range of ecosystem services of function

A

Functional diversity

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37
Q

The species diversity and functional diversity of the soil are influenced primarily by the ______________________

A

amount and quality of available food

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38
Q

What are the classifications of soil organisms?

A
  • based on size
  • based on metabolism
  • based on ecological function
  • based on hierarchy of organisms in the soil food web
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39
Q

Classification of soil organism based on size with a range of 20mm upward

A

megafauna

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40
Q

Classification of soil organisms based on size with a range of 2 to 20mm

A

macrofauna

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41
Q

Classification based on size with a range of 100 micrometers to 2mm

A

mesofauna

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42
Q

Classification of soil organisms based on size with a range of 1 to 100 micrometers

A

microfauna and microflora

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43
Q

These are the primary producers and organisms that obtain their C mainly from CO2

A

autotrophs

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44
Q

Autotrophs that obtain energy from sunlight

A

Photoautotrophs

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45
Q

Autotrophs that obtain energy from or oxidation of various elements

A

chemautotrophs

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46
Q

Organisms that are incapable of making their own food from light or organic compounds that’s why they feed on organisms or remains of other organisms to get their necessary energy to survive

A

Heterotrophs

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47
Q

Organisms that subsist on living plants

A

herbivores

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48
Q

Organisms that subsist on dead plant debris

A

detritivores

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49
Q

Organisms that consume animals

A

predators

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50
Q

Organisms that live off but do not consume other organisms

A

parasites

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51
Q

These are known as the “cows” of the soil and these tackle easy to decompose materials like green yard waste and manure

A

soil bacteria

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52
Q

These are known as the “goats” of the soil that consumes the tougher, hard to decompose materials like straw, pine needles, bark and wood

A

fungi

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53
Q

In the third level of the soil food web, these are highly mobile organisms that feed on bacteria and on each other

A

Protozoa

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54
Q

In the third level of the soil food web, these organisms feed on fungi and plant-feeding nematodes; they chew fresh organic material into smaller pieces for easier decomposition

A

microarthropods

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55
Q

These are the ingested soil expelled by earthworms

A

globular casts

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56
Q

What are the major groups of soil microorganisms?

A
  • bacteria
  • fungi
  • actinomycetes
  • algae
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57
Q

These are prokaryotic, single-celled, microscopic oganisms that is considered the most important in terms of their effect on soil properties

A

bacteria

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58
Q

Classifications of bacteria

A
  • based on morphology
  • based on nutritional requirements
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59
Q

Groupings of bacteria based on oxygen requirement

A
  • aerobic
  • anaerobic
  • facultative
  • microaerophiles
  • aerotolerant
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60
Q

Bacteria group that prefers aerobic respiration but is capable of switching to anaerobic if oxygen is absent

A

facultative

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61
Q

Bacteria group that needs low concentration of oxygen

A

microaerophiles

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62
Q

Bacteria group that doesnt need oxygen but is not poisoned by oxygen

A

aerotolerant

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63
Q

Bacteria groupings based on pH for optimum growth

A
  • acidophiles (below neutral)
  • neutrophiles (neutral)
  • alkaliphiles (alkaline)
64
Q

Bacteria grouping based on temperature for optimum activity

A
  • mesophilic (20-45C)
  • thermophilic (45-85C)
  • psychrophilic/cryophilic (-20-10C)
  • hyperthermophilic (115C)
65
Q

Functional groups of bacteria in the soil

A
  • decomposers
  • mutualists
  • pathogens
  • lithotrophs/chemautotrophs
66
Q

Microscopic cells that usually grow as long threads or strands called hyphae

A

fungi

67
Q

Fungi are __________

A

aerobic and heterotrophic

68
Q

It is a symbiotic association composed of a fungus and roots of a vascular plant

A

mycorrhiza

69
Q

TRUE OR FALSE

Mycorrhizal plants are often more resistant to diseases

A

TRUE

70
Q

It is an intermediate between bacteria and fungi; unicellular and do not have distinct cell wall like bacteria

A

actinomycetes

71
Q

It is important in the degradation of organic materials in the soil including lignin

A

actinomycetes

72
Q

It is present in most of the soils where moisture and sunlight are available; aerobic and photoautotrophic

A

algae

73
Q

Four main classes of algae

A
  • cyanophyta (blue-green)
  • chlorophyta (grass-green)
  • xanthophyta (yellow-green)
  • bacillariophyta (golden-brown)
74
Q

Specialized cells that are possesed by some blue green algae which is the site of nitrogen fixation

A

heterocyst

75
Q

It is the capacity of a soil to provide essential chemical elements in adequate quantities and proportions for the growth of specified plants

A

soil fertility

76
Q

It is the capacity of a soil for producing a specified plant or sequence of plants under a specified system of management

A

soil productivity

77
Q

Other factors that make a soil productive

A
  • moisture
  • aeration
  • absence of pests and diseases
  • presence of micro-organisms that support plant growth
  • management practices
  • large amount of topsoil
78
Q

How many nutrient elements are considered essential for plant growth

A

18

79
Q

The essential nutrient elements are derived from :

A
  • organic matter
  • minerals
  • air
  • water
80
Q

What is the major source of N?

A

organic matter

81
Q

What are the major sources of P?

A
  • acid soluble P
  • calcium phosphate
  • aluminum phosphate
  • iron phosphate
82
Q

Nutrient element that are found in minerals like feldspars and micas

A

potassium

83
Q

Nutrient element that are found in minerals like gypsum and pyrite

A

sulfur

84
Q

It is among the most abundant of micronutrients

A

iron

85
Q

TRUE OR FALSE

Kaolinite clays exchange Ca2+ more readily at a much lower %BS

A

TRUE

86
Q

What are the mechanisms of nutrient uptake?

A
  • root interception
  • mass flow
  • diffusion
87
Q

What are the most active points of nutrient uptake?

A

root hairs

88
Q

A concept that states plant growth is constrained by the essential element that is most limiting

A

Justus von Liebig’s Law of Minimum

89
Q

Any organic or inorganic material or compound which can supply one or more of the essential nutrients needed by plants for normal growth

A

fertilizers

90
Q

It is the guaranteed minimum analysis of the plant nutrient in terms of N, P, K percentage

A

fertilizer grade

91
Q

It is the relative proportion of each of the primary nutrients in a fertilizer material

A

fertilizer ratio

92
Q

Any substance added to fertilizer materials to provide bulk, prevent caking or serve some purpose other than providing essential plant nutrients

A

filler

93
Q

Classification of fertilizers

A
  • organic
  • inorganic
94
Q

Common approaches used to determine fertilizer needs

A
  • nutrient hunger signs on growing crops
  • plant analysis
  • soil tests
  • fertilizer trials
95
Q

The Rs in the proper use of fertilizers

A

right type, right time, right place, right amount, right method

96
Q

It is the loss of soil through the action of water, wind, or gravity

A

soil erosion

97
Q

TRUE OR FALSE

75% of the Philippines’ croplands are vulnerable to erosion

A

TRUE

98
Q

On-site impacts of soil erosion

A
  • reduction in soil depth
  • structure deterioration
  • nutrient loss
  • decline in soil fertility
  • loss of production
  • decline in soil biota
99
Q

What are the general types of soil erosion?

A
  • geological erosion
  • accelerated erosion
100
Q

A type of soil erosion that is described as wearing away of the earth’s surface by water or other natural agents under natural environmental conditions of climate, vegetation and so on; undisturbed by man

A

geological erosion

101
Q

A type of soil erosion that is much more rapid than normal, natural, geological erosion; primarily a result of the activities of humans or, in some cases, animals

A

accelerated erosion

102
Q

The process of soil erosion

A

detachment, transport, deposition

103
Q

It is the most important detachment agent

A

rainfall

104
Q

It is a step in the soil erosion process that occurs when sufficient energy is no longer available to transport the particles

A

deposition

105
Q

Three important effects of raindrop impact

A
  • it detaches the soil
  • it destroys granulation
  • its splash, under certain conditions, causes an appreciable transportation of soil
106
Q

Kinds of soil erosion by water

A
  • sheet erosion
  • rill erosion
  • gully erosion
107
Q

It is the removal of a fairly uniform layer of soil from the land surface by runoff water

A

sheet erosion

108
Q

It occurs mainly on cultivated soils wherein numerous small channels of only several centimeters in depth are formed

A

rill erosion

109
Q

It is a kind of soil erosion wherein water accumulates in narrow channels and, over short periods, removes the soil from this narrow area to considerable depths

A

gully erosion

110
Q

For rainfall, it is a function of intensity, duration, mass of raindrop, diameter of raindrop, and velocity of raindrop

A

erosivity

111
Q

TRUE OR FALSE

Fine particles are resistant to detachment because of their cohesiveness

A

TRUE

112
Q

It is the function of slope length and slope steepness

A

slope

113
Q

TRUE OR FALSE

As slope steepness increases, soil loss rate also rises at an increasing rate

A

TRUE

114
Q

It is the greatest deterrent to soil erosion

A

plant cover

115
Q

It reduces vegatation cover due to tillage, burning, overgrazing, mining, logging and road construction

A

human activities

116
Q

It is the most widely-used to tool to estimate soil erosion

A

Universal Soil Loss Equation (USLE)

117
Q

The soil erodibility factor K can be approximated from a ____________

A

nomograph

118
Q

What are the methods of soil conservation?

A
  • control of soil erosion
  • maintenance of soil fertility and productivity
  • avoidance of soil toxicities
119
Q

It is the single most effective measure in reducing erosion

A

surface covers

120
Q

These are temporary vegetative cover of fast growing annuals

A

cover crops

121
Q

These are perennials or regenerating annuals specifically established to protect soil from erosive agents

A

ground cover

122
Q

It is the practice of spreading plant residues/other organic materials on the ground between crop rows or round tree trunks to protect the bare soil

A

mulching

123
Q

It is the use of coconets to protect the slopes

A

geotextiles

124
Q

These are constructed along the contour of the land at defined intervals, to intercept and/or divert runoff

A

physical barriers

125
Q

It is a method where slope is converted into series of level to nearly level steps running across the slope supported by steep risers with horizontal cultivated area on the step

A

bench terracing

126
Q

These are fence-like structures made up of rocks and/or stones piled along the contour of sloping lands

A

contour rockwalls

127
Q

These are embankments of stones, grasses, or compacted soil which are constructed along the contour to slow down surface runoff and trap eroded soil

A

contour bounds

128
Q

These are ipil-ipil stems bundled into rows across the slope and staked to form low barriers

A

pole barriers/contour fences

129
Q

These are hedges of leguminous trees or shrubs or grasses grown on the contour at a defined interval

A

contour hedgerows

130
Q

These are naturally occurring vegetation like grasses and herbs that are left in narrow strips to serve as barriers

A

natural vegetative strips

131
Q

These are banks or barrier trashes and/or earth that are constructed across the slope of the land to check surface runoff and soil erosion

A

contour composting

132
Q

These are natural/artificial drainage channel along the steepest slope, in the valley or along the boundaries of the upland farm used to accomodate runoff

A

diversion canals

133
Q

These are holes that are dug immediately along water channels

A

contour canals

134
Q

These are channels constructed across the slope to catch upslope runoff and divert it safely to a nearby gully, waterway/river

A

grassed waterways

135
Q

These are obstruction walls across the bottom of a gully which reduce the velocity of the runoff and prevent the deepening or widening of the gullies

A

check dams

136
Q

These are small canals dug along the contour line

A

soil traps

137
Q

It is the practice of sowing crops directly into the residue of the previous crop without cultivation

A

zero tillage

138
Q

It is the practice of sowing crops on lightly cultivated soil

A

minimum tillage

139
Q

It is the practice of plowing, harrowing, and furrowing along the contour of the land

A

contour plowing

140
Q

It is a method that forms multi-layered canopy that reduces rainfall velocity

A

multi-storey agroforestry system

141
Q

The soil classification system used by the Philippines

A

USDA Soil Taxonomy

142
Q

Soil order with formative element alf

A

Afisols

143
Q

Soil order with formative element and

A

Andisols

144
Q

Soil order with formative element id

A

Aridisols

145
Q

Soil order with formative element ent

A

Entisols

146
Q

Soil order with formative element el

A

Gelisols

147
Q

Soil order with formative element ist

A

Histosols

148
Q

Soil order with formative element ept

A

Inceptisols

149
Q

Soil order with formative element oll

A

Mollisols

150
Q

Soil order with formative element ox

A

Oxisols

151
Q

Soil order with formative element od

A

Spodosols

152
Q

Soil order with formative element ult

A

Ultisols

153
Q

Soil order with formative element ert

A

Vertisols

154
Q

How many soil orders are there?

A

12

155
Q

Three soil orders that are not found in the Philippines

A

Gelisols, aridisols and spodosols

AGRI 51 (2 decks)

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