LE3 Flashcards
(155 cards)
1
Q
Soil microorganisms play a very important role in the ff
A
- Soil health
- Ecosystem functions
- Plant nutrition and growth promotion
2
Q
Activities of Soil Microorganisms
A
- Decomposition of organic compounds
- Transformation of nutrients such as Nitrogen and Sulfur
- Pesticide degradation
3
Q
The compound that is resistant to microbial action
A
Humus
4
Q
TRUE OR FALSE
Anaerobic decomposition is very -fast- and may result in the accumulation of organic matter
A
FALSE
very slow
5
Q
Factors affecting SOM decomposition
A
- Aeration
- Soil temperature
- Soil moisture
- Soil pH
- Soil texture
- C/N ratio of organic material
6
Q
TRUE OR FALSE
Fungi is -unaffected- by pH level
A
TRUE
7
Q
At what soil pH are bacteria and actinomycetes inhibited?
A
pH 5.5
8
Q
It is a convenient tool for predicting the rate of decomposition
A
Carbon/Nitrogen ratio
9
Q
It is the optimum C/N ratio of organic materials for faster decomposition
A
20:1
10
Q
It is the reduction of atmospheric nitrogen gas to ammonia
A
Nitrogen Fixation
11
Q
Process that makes N available for assimilation by plants
A
Nitrogen Fixation
12
Q
What is the nitrogen-fixing bacteria that can convert atmospheric nitrogen into useable form of ammonium?
A
Rhizobium
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
14
Q
What are the factors that influence the rates of mineralization?
A
- temperature
- moisture
- aeration
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
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
17
Q
It is the process by which microorganisms convert ammonium to nitrate to obtain energy
A
Nitrification
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
19
Q
TRUE OR FALSE
The nitrifying bacteria are -anaerobic-
A
FALSE
Aerobic
20
Q
Soil microbial activity that can significantly increase soil acidity due to the production of H+ ions
A
Nitrification
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
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
23
Q
Bacteria responsible for denitrification belong to the ff genera
A
- Pseudomonas
- Clostridium
- Bacillus
- Paraccoccus
24
Q
Under aerobic environment, sulfur may be oxidized by ___________ to SO4 with a release of energy
A
Thiobacillus thiooxidans
25
Under anaerobic conditions, sulfate may be reduced by what bacteria?
**Desulfovibrio desulfuricans**
26
It is the end product of sulfur transformations and emanates the characteristic offensive odor of flooded soils
**H2S**
Hydrogen sulfide
27
Processes involved in the inactivation of pesticides in the soil
- **Detoxification**
- **Conjugation**
- **Degradation**
28
It is the conversion of the pesticide molecule to a non-toxic compound
**Detoxification**
29
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
**Conjugation**
30
It is the breaking down/transformation of a complex substrate into simpler products leading finally to mineralization
**Degradation**
31
It is the single most important method by which pesticides are completely removed from soils
**Biochemical degradation of pesticides by microorganism**
32
TRUE OR FALSE
The organophosphate insecticides, such as parathion, are degraded quite -rapidly- in soils by a variety of organisms
**TRUE**
33
Creatures that spend all part of their lives in the soil environment
**Soil organisms**
34
Roles of soil organisms
- **maintaining fertility, structure, drainage and aeration of soil**
- **decomposition**
- **conversion of nutrients into plant-available forms**
35
It is the mix of species present
**Species diversity**
36
It is the capacity to use a wide variety of substrates and provide a range of ecosystem services of function
**Functional diversity**
37
The species diversity and functional diversity of the soil are influenced primarily by the ______________________
**amount and quality of available food**
38
What are the classifications of soil organisms?
- **based on size**
- **based on metabolism**
- **based on ecological function**
- **based on hierarchy of organisms in the soil food web**
39
Classification of soil organism based on size with a range of 20mm upward
**megafauna**
40
Classification of soil organisms based on size with a range of 2 to 20mm
**macrofauna**
41
Classification based on size with a range of 100 micrometers to 2mm
**mesofauna**
42
Classification of soil organisms based on size with a range of 1 to 100 micrometers
**microfauna and microflora**
43
These are the primary producers and organisms that obtain their C mainly from CO2
**autotrophs**
44
Autotrophs that obtain energy from sunlight
**Photoautotrophs**
45
Autotrophs that obtain energy from or oxidation of various elements
**chemautotrophs**
46
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
**Heterotrophs**
47
Organisms that subsist on living plants
**herbivores**
48
Organisms that subsist on dead plant debris
**detritivores**
49
Organisms that consume animals
**predators**
50
Organisms that live off but do not consume other organisms
**parasites**
51
These are known as the “cows” of the soil and these tackle easy to decompose materials like green yard waste and manure
**soil bacteria**
52
These are known as the “goats” of the soil that consumes the tougher, hard to decompose materials like straw, pine needles, bark and wood
**fungi**
53
In the third level of the soil food web, these are highly mobile organisms that feed on bacteria and on each other
**Protozoa**
54
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
**microarthropods**
55
These are the ingested soil expelled by earthworms
**globular casts**
56
What are the major groups of soil microorganisms?
- **bacteria**
- **fungi**
- **actinomycetes**
- **algae**
57
These are prokaryotic, single-celled, microscopic oganisms that is considered the most important in terms of their effect on soil properties
**bacteria**
58
Classifications of bacteria
- **based on morphology**
- **based on nutritional requirements**
59
Groupings of bacteria based on oxygen requirement
- **aerobic**
- **anaerobic**
- **facultative**
- **microaerophiles**
- **aerotolerant**
60
Bacteria group that prefers aerobic respiration but is capable of switching to anaerobic if oxygen is absent
**facultative**
61
Bacteria group that needs low concentration of oxygen
**microaerophiles**
62
Bacteria group that doesnt need oxygen but is not poisoned by oxygen
**aerotolerant**
63
Bacteria groupings based on pH for optimum growth
- **acidophiles (below neutral)**
- **neutrophiles (neutral)**
- **alkaliphiles (alkaline)**
64
Bacteria grouping based on temperature for optimum activity
- **mesophilic (20-45C)**
- **thermophilic (45-85C)**
- **psychrophilic/cryophilic (-20-10C)**
- **hyperthermophilic (115C)**
65
Functional groups of bacteria in the soil
- **decomposers**
- **mutualists**
- **pathogens**
- **lithotrophs/chemautotrophs**
66
Microscopic cells that usually grow as long threads or strands called hyphae
**fungi**
67
Fungi are __________
**aerobic and heterotrophic**
68
It is a symbiotic association composed of a fungus and roots of a vascular plant
**mycorrhiza**
69
TRUE OR FALSE
Mycorrhizal plants are often more resistant to diseases
**TRUE**
70
It is an intermediate between bacteria and fungi; unicellular and do not have distinct cell wall like bacteria
**actinomycetes**
71
It is important in the degradation of organic materials in the soil including lignin
**actinomycetes**
72
It is present in most of the soils where moisture and sunlight are available; aerobic and photoautotrophic
**algae**
73
Four main classes of algae
- **cyanophyta (blue-green)**
- **chlorophyta (grass-green)**
- **xanthophyta (yellow-green)**
- **bacillariophyta (golden-brown)**
74
Specialized cells that are possesed by some blue green algae which is the site of nitrogen fixation
**heterocyst**
75
It is the capacity of a soil to provide essential chemical elements in adequate quantities and proportions for the growth of specified plants
**soil fertility**
76
It is the capacity of a soil for producing a specified plant or sequence of plants under a specified system of management
**soil productivity**
77
Other factors that make a soil productive
- **moisture**
- **aeration**
- **absence of pests and diseases**
- **presence of micro-organisms that support plant growth**
- **management practices**
- **large amount of topsoil**
78
How many nutrient elements are considered essential for plant growth
**18**
79
The essential nutrient elements are derived from :
- **organic matter**
- **minerals**
- **air**
- **water**
80
What is the major source of N?
**organic matter**
81
What are the major sources of P?
- **acid soluble P**
- **calcium phosphate**
- **aluminum phosphate**
- **iron phosphate**
82
Nutrient element that are found in minerals like feldspars and micas
**potassium**
83
Nutrient element that are found in minerals like gypsum and pyrite
**sulfur**
84
It is among the most abundant of micronutrients
**iron**
85
TRUE OR FALSE
Kaolinite clays exchange Ca2+ more readily at a much lower %BS
**TRUE**
86
What are the mechanisms of nutrient uptake?
- **root interception**
- **mass flow**
- **diffusion**
87
What are the most active points of nutrient uptake?
**root hairs**
88
A concept that states plant growth is constrained by the essential element that is most limiting
**Justus von Liebig’s Law of Minimum**
89
Any organic or inorganic material or compound which can supply one or more of the essential nutrients needed by plants for normal growth
**fertilizers**
90
It is the guaranteed minimum analysis of the plant nutrient in terms of N, P, K percentage
**fertilizer grade**
91
It is the relative proportion of each of the primary nutrients in a fertilizer material
**fertilizer ratio**
92
Any substance added to fertilizer materials to provide bulk, prevent caking or serve some purpose other than providing essential plant nutrients
**filler**
93
Classification of fertilizers
- **organic**
- **inorganic**
94
Common approaches used to determine fertilizer needs
- **nutrient hunger signs on growing crops**
- **plant analysis**
- **soil tests**
- **fertilizer trials**
95
The Rs in the proper use of fertilizers
**right type, right time, right place, right amount, right method**
96
It is the loss of soil through the action of water, wind, or gravity
**soil erosion**
97
TRUE OR FALSE
75% of the Philippines’ croplands are vulnerable to erosion
**TRUE**
98
On-site impacts of soil erosion
- **reduction in soil depth**
- **structure deterioration**
- **nutrient loss**
- **decline in soil fertility**
- **loss of production**
- **decline in soil biota**
99
What are the general types of soil erosion?
- **geological erosion**
- **accelerated erosion**
100
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
**geological erosion**
101
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
**accelerated erosion**
102
The process of soil erosion
**detachment, transport, deposition**
103
It is the most important detachment agent
**rainfall**
104
It is a step in the soil erosion process that occurs when sufficient energy is no longer available to transport the particles
**deposition**
105
Three important effects of raindrop impact
- **it detaches the soil**
- **it destroys granulation**
- **its splash, under certain conditions, causes an appreciable transportation of soil**
106
Kinds of soil erosion by water
- **sheet erosion**
- **rill erosion**
- **gully erosion**
107
It is the removal of a fairly uniform layer of soil from the land surface by runoff water
**sheet erosion**
108
It occurs mainly on cultivated soils wherein numerous small channels of only several centimeters in depth are formed
**rill erosion**
109
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
**gully erosion**
110
For rainfall, it is a function of intensity, duration, mass of raindrop, diameter of raindrop, and velocity of raindrop
**erosivity**
111
TRUE OR FALSE
Fine particles are resistant to detachment because of their cohesiveness
TRUE
112
It is the function of slope length and slope steepness
**slope**
113
TRUE OR FALSE
As slope steepness increases, soil loss rate also rises at an increasing rate
**TRUE**
114
It is the greatest deterrent to soil erosion
**plant cover**
115
It reduces vegatation cover due to tillage, burning, overgrazing, mining, logging and road construction
**human activities**
116
It is the most widely-used to tool to estimate soil erosion
**Universal Soil Loss Equation (USLE)**
117
The soil erodibility factor K can be approximated from a ____________
**nomograph**
118
What are the methods of soil conservation?
- **control of soil erosion**
- **maintenance of soil fertility and productivity**
- **avoidance of soil toxicities**
119
It is the single most effective measure in reducing erosion
**surface covers**
120
These are temporary vegetative cover of fast growing annuals
**cover crops**
121
These are perennials or regenerating annuals specifically established to protect soil from erosive agents
**ground cover**
122
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
**mulching**
123
It is the use of coconets to protect the slopes
**geotextiles**
124
These are constructed along the contour of the land at defined intervals, to intercept and/or divert runoff
**physical barriers**
125
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
**bench terracing**
126
These are fence-like structures made up of rocks and/or stones piled along the contour of sloping lands
**contour rockwalls**
127
These are embankments of stones, grasses, or compacted soil which are constructed along the contour to slow down surface runoff and trap eroded soil
**contour bounds**
128
These are ipil-ipil stems bundled into rows across the slope and staked to form low barriers
**pole barriers/contour fences**
129
These are hedges of leguminous trees or shrubs or grasses grown on the contour at a defined interval
**contour hedgerows**
130
These are naturally occurring vegetation like grasses and herbs that are left in narrow strips to serve as barriers
**natural vegetative strips**
131
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
**contour composting**
132
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
**diversion canals**
133
These are holes that are dug immediately along water channels
**contour canals**
134
These are channels constructed across the slope to catch upslope runoff and divert it safely to a nearby gully, waterway/river
**grassed waterways**
135
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
**check dams**
136
These are small canals dug along the contour line
**soil traps**
137
It is the practice of sowing crops directly into the residue of the previous crop without cultivation
**zero tillage**
138
It is the practice of sowing crops on lightly cultivated soil
**minimum tillage**
139
It is the practice of plowing, harrowing, and furrowing along the contour of the land
**contour plowing**
140
It is a method that forms multi-layered canopy that reduces rainfall velocity
**multi-storey agroforestry system**
141
The soil classification system used by the Philippines
**USDA Soil Taxonomy**
142
Soil order with formative element **alf**
**Afisols**
143
Soil order with formative element **and**
**Andisols**
144
Soil order with formative element **id**
**Aridisols**
145
Soil order with formative element **ent**
**Entisols**
146
Soil order with formative element **el**
**Gelisols**
147
Soil order with formative element **ist**
**Histosols**
148
Soil order with formative element **ept**
**Inceptisols**
149
Soil order with formative element **oll**
**Mollisols**
150
Soil order with formative element **ox**
**Oxisols**
151
Soil order with formative element **od**
**Spodosols**
152
Soil order with formative element **ult**
**Ultisols**
153
Soil order with formative element **ert**
**Vertisols**
154
How many soil orders are there?
**12**
155
Three soil orders that are not found in the Philippines
**Gelisols, aridisols and spodosols**
