7232780
Pregunta 1
Pregunta
In nature, beneficial mycorrhizae form with the roots of ____.
Respuesta
-
coniferous trees
-
grasses
-
legumes
-
broad leaf trees
-
all of these
Pregunta 2
Pregunta
The second most important biological process on earth is
Respuesta
-
photosynthesis
-
nitrogen volatilization
-
sulfur oxidation
-
nitrification
-
none of the above
Pregunta 3
Pregunta
The site of nutrient transfer between a plant and an ectomycorrhizal fungus is called the _____.
Respuesta
-
arbuscule
-
Hartig net
-
mantle
-
absorptive hyphae
Pregunta 4
Pregunta
Nitrogenase enzyme activity is inhibited by:
Respuesta
-
high oxygen
-
low available C
-
low pH
-
all of these
-
none of these
Pregunta 5
Pregunta
The site of nutrient transfer between a plant and an endomycorrhizal fungus is called the ____.
Respuesta
-
arbuscule
-
Hartig net
-
mantle
-
absorptive hypphate
Pregunta 6
Pregunta
Nitrogen fixing bacteria move through a(n) [blank_start]____[blank_end] to the [blank_start]____[blank_end] which are produced by the plant in the cortical cells, where they reproduce and begin to fix nitrogen.
Respuesta
-
root cortex
-
infection thread
-
stomate
-
nodules
-
stem
Pregunta 7
Pregunta
During symbiotic nitrogen fixation, the plant benefits by:
Respuesta
-
gaining nitrogen
-
gaining carbon
-
getting protection against pathogens
-
the acidification of the root zone
-
none of the above
Pregunta 8
Pregunta
Ectomycorrhizae:
Respuesta
-
penetrate the root cortex cells and produce tree-like structures for nutrient exchange with the plant
-
create a net-like structure between root cortex cells and on the outside of the roots
-
create nodules inside root cells where nutrient exchange with the plant takes place
-
kill the roots and reduce plant nutrient uptake
Pregunta 9
Pregunta
[blank_start]___[blank_end] is produced by the [blank_start]___[blank_end] to maintain [blank_start]___[blank_end] levels of [blank_start]___[blank_end] required for nitrogenase activity.
Respuesta
-
Leghemoglobin
-
Hemoglobin
-
plant
-
bacteria
-
high
-
low
-
carbon dioxide
-
oxygen
Pregunta 10
Pregunta
The main benefit for the plant of having a symbiotic relationship with mycorrhizal fungi is:
Respuesta
-
increased nitrogen availability
-
increased root surface area for nutrient uptake
-
protection against root pathogens
-
increased oxygen in the root for cellular respiration
Pregunta 11
Pregunta
Nitrogen is a component of which essential plant compounds?
Respuesta
-
chlorophyll
-
enzymes
-
DNA
-
all of the above
Pregunta 12
Pregunta
At low soil pH,
Respuesta
-
all nutrients are at deficient levels
-
Ca, Mg, and P are at deficient levels, and Al is at toxic levels
-
Most nutrients tend to be at toxic levels
-
Ca, Mg, and P are at toxic levels, and Al is fixed in insoluble compounds
-
All nutrient elements are at levels that support good plant growth
Pregunta 13
Pregunta
Soils in humid climates tend to acidify [blank_start]___[blank_end] than soils in dry climates because there is [blank_start]___[blank_end] leaching of [blank_start]___[blank_end] cations.
Respuesta
-
faster___
-
slower
-
more
-
less
-
acidic
-
basic
Pregunta 14
Pregunta
Which of the following would not be a liming material?
Respuesta
-
MgCO₃
-
Ca(OH)₂
-
CaSiO₂
-
CaSO₄
-
All of these are lime
Pregunta 15
Pregunta
The type of microorganism that becomes dominant in the final stage of decomposition and breaks down chitin, cellulose, lignins, and waxes is [blank_start]___[blank_end].
Respuesta
-
Fungi
-
protists
-
actinomycetes
-
bacteria
Pregunta 16
Pregunta
Predators that help regulate decomposition rate include:
Respuesta
-
Protists and nematodes
-
Bacteria and fungi
-
Actinomycetes
-
Termites
Pregunta 17
Pregunta
Humus is in which pool of organic matter?
Respuesta
-
active
-
slow
-
rapid
-
passive
Pregunta 18
Pregunta
The humus pool of soil organic matter
Respuesta
-
has a C:N of about 10:1
-
decomposes within 1 to 2 years
-
is very stable
-
decomposes within 5 to 10 years
Pregunta 19
Pregunta
Which of the following statements is true about soil organic matter?
Respuesta
-
It cannot be increased in the soil indefinitely
-
Application to the soil always leads to lots of immediately available nitrogen
-
It breaks down more rapidly is the soil is tilled
-
A and B only
-
A and C only
Pregunta 20
Pregunta
The rate of organic matter decomposition is fastest under which of the following set of conditions?
Respuesta
-
Acid pH, moist soils, warm temperatures, good aeration, residues left on soil surface
-
Alkaline pH, dry soils, cool temperatures, good aeration, residues incorporated into soil
-
Neutral pH, moist soils, warm temperatures, poor aeration, residues left on soil surface
-
Neutral pH, moist soils, warm temperatures, good aeration, residues incorporated
Pregunta 21
Pregunta
Which of the follow C:N ratios will most likely result in a moderate rate of organic matter breakdown with no short term changes in the soil nitrogen?
Respuesta
-
5:1
-
25:1
-
100:1
-
1000:1
Pregunta 22
Pregunta
Long-term tillage tends to reduce the amount of organic matter in a soil because
Respuesta
-
tillage incorporates residues into the soil
-
tillage reduces soil aeration
-
tillage reduces soil erosion
-
tillage reintroduces oxygen into the soil
Pregunta 23
Pregunta
In aerobic respiration by microbes, [blank_start]___[blank_end] is absorbed, and [blank_start]___[blank_end] is released.
Respuesta
-
N₂
-
CO₂
-
O₂
-
O₂
-
N₂
-
CO₂
Pregunta 24
Pregunta
Soil organisms that reproduce rapidly and degrade the simple compounds found in fresh organic matter added to the soil are the ___.
Respuesta
-
fungi
-
rotifers
-
bacteria
-
earthworms
Pregunta 25
Pregunta
An important function of humus is to:
Respuesta
-
help establish and maintain strong granular soil structure
-
hold onto water very tightly so that only soil microorganisms can use it
-
provide large quantities of quickly available plant nutrients
-
provide easily degradable carbon compounds for soil microorganisms
Pregunta 26
Pregunta
Which of the following management practices would most likely be necessary if growing food crops on Spodosols?
Respuesta
-
frequent use of soil tillage and conservation
-
use of erosion control measures such as terracing
-
addition of liming agents
-
supplying water through irrigation
Pregunta 27
Pregunta
Gelisols:
Respuesta
-
are old, deeply weathered soils developed from intrusive volcanic rock
-
contain a permafrost layer within the top 2 meters
-
contain slickensides
-
include all soils with a histic epipedon
-
none of the above
Pregunta 28
Pregunta
Slickensides may be found in:
Respuesta
-
vertisols
-
mollisols
-
andisols
-
oxisols
-
none of the above
Pregunta 29
Pregunta
Andisols:
Respuesta
-
are old, deeply weathered soils developed from intrusive volcanic rock
-
contain slickensides
-
form on unstable landscape positions undergoing erosion and deposition
-
contain a permafrost layer within the top 2 meters
-
none of the above
Pregunta 30
Pregunta
Ultisols:
Respuesta
-
form on unstable landscape positions undergoing erosion and deposition
-
form on old, stable land surfaces in warm humid climates
-
are the most weathered soils
-
contain slickensides
Pregunta 31
Pregunta
The role of soil animals in organic matter decomposition is to:
Respuesta
-
shred and mix fresh organic matter into the soil
-
decompose waxes and lignins
-
feed on bacteria and fungi
Pregunta 32
Pregunta
The organic matter content of a loam soil declined from 5% to 2% as a result of continued cultivation/tillage. This will result in:
Respuesta
-
deterioration of soil structure
-
deterioration of soil texture
-
stabilization of soil structure
-
increase in crop yield
Pregunta 33
Pregunta
The majority of nutrient release occurs during the decomposition of:
Respuesta
-
humus
-
the slow pool of organic matter
-
the active pool of organic matter
-
the passive pool of organic matter
Pregunta 34
Pregunta
The pool of organic matter most impacted by organic matter additions in agriculture is:
Respuesta
-
humus
-
the slow pool
-
the active pool
-
the passive pool
Pregunta 35
Pregunta
The "active" pool usually makes up less than [blank_start]___[blank_end] percent of the total organic matter in a soil.
Respuesta
-
10
-
1
-
0.1
-
0.01
Pregunta 36
Pregunta
Which of the following are characteristics of the majority of microorganisms involved in soil organic matter decomposition?
Respuesta
-
they get C from CO₂ and energy from oxidation of organic compounds
-
they get C and energy from oxidation of organic compounds
-
they get C from CO₂ and energy from oxidation of inorganic compounds
-
none of the above
Pregunta 37
Pregunta
The basic unit of soil classification is the:
Respuesta
-
order
-
great group
-
family
-
series
Pregunta 38
Pregunta
Criteria for grouping soils into orders include:
Respuesta
-
soil forming processes as indicated by the presence or absence of major diagnostic horizons
-
the thickness of major diagnostic horizons
-
soil temperature, mineralogy, and particle size
-
the specific location of the soil
Pregunta 39
Pregunta
The highest level of soil classification is the family.
Respuesta
- True
- False
Pregunta 40
Pregunta
The soil moisture regime that is used in regions where there are cool, moist winters and long, dry summers with drought is called:
Respuesta
-
udic
-
xeric
-
aridic
-
ustic
-
aquic
Pregunta 41
Pregunta
The warmest soil temperature regime is called:
Respuesta
-
thermic
-
frigid
-
mesic
-
cryic
Pregunta 42
Pregunta
The Los Osos soil is classified as an Argixeroll. To what soil Order does it belong?
Respuesta
-
Mollisol
-
Vertisol
-
Gelisol
-
Spodosol
-
Alfisol
Pregunta 43
Pregunta
This soil order commonly forms out of serpentenite parent material and is characterized as having an abundance of smectite clay. It is not good for building on as it swells during wet periods and shrinks during dry periods.
Respuesta
-
Mollisol
-
Aridisol
-
Alfisol
-
Ultisol
-
Vertisol
Pregunta 44
Pregunta
The State Soil of California, San Joaquin, is classified as a Durixeralf. To what soil Order does it belong?
Respuesta
-
Mollisol
-
Vertisol
-
Gelisol
-
Spodosol
-
Alfisol
Pregunta 45
Pregunta
Supposing you want to grow corn, soils of which soil order would be best, based on natural fertility?
Respuesta
-
Mollisol
-
Alfisol
-
Aridisol
-
Entisol
-
Ultisol
Pregunta 46
Pregunta
Which soil order is commonly found on steep backslope landscape positions or in soils where little or no weathering has taken place?
Respuesta
-
Ultisol
-
Entisol
-
Andisol
-
Alfisol
-
Aridisol
Pregunta 47
Pregunta
Soils in this order are commonly sandy in texture, quite acidic and develop primarily under coniferous trees in cool to cold climates:
Respuesta
-
Mollisols
-
Andisols
-
Spodosols
-
Alifisols
-
Ultisols
Pregunta 48
Pregunta
A soil on the dry slopes of the Northern Cascades of California is classified as an Xerept. To what soil Order does it belong?
Respuesta
-
Inceptisol
-
Alfisol
-
Mollisol
-
Ultisol
-
Oxisol
Pregunta 49
Pregunta
Permafrost is:
Respuesta
-
material that remains below 0 degrees Celsius for more than two consecutive years
-
is permanently frozen
-
a surface horizon developed by frost heaving
-
is found in soils in the Order Histosols
-
none of the above
Pregunta 50
Pregunta
Aridisols often contain which of the following horizons?
Respuesta
-
mollic
-
histic
-
albic
-
calcic
-
none of the above
Pregunta 51
Pregunta
Vertisols develop from parent materials rich in [blank_start]___[blank_end]
Respuesta
-
K
-
Ca and Mg
-
Na
-
Na and K
Pregunta 52
Pregunta
Which soil order, containing highly weathered soils composed mainly or iron and aluminum oxide clay, is found in the humid tropics?
Respuesta
-
Histosol
-
Vertisol
-
Ultisol
-
Oxisol
-
none of the above
Pregunta 53
Pregunta
Soils that are commonly sandy in texture, quite acidic and develop primarily under coniferous trees in cool to cold climates often contain which of the following horizons?
Respuesta
-
permafrost
-
argillic
-
albic
-
mollic
-
oxic
Pregunta 54
Pregunta
The most dominant soil forming factor for an Aridisol soil would be [blank_start]___[blank_end]
Respuesta
-
climate
-
parent material
-
time
-
topography
-
vegetation
Pregunta 55
Pregunta
Characteristics of kaolinite clays include:
Respuesta
-
made up of Fe or Al and O, very little net negative charge, positive charge at low pH, low plasticity, stickiness, and water holding
-
significant substitution in the octahedral, layers weakly held together by cations (highly expansible), CEC of 80-120 cmolc/kg
-
significant substitution in the tetrahedra, layers tightly bound (moderately expansible), CEC of 100-180 cmolc/kg
-
significant substitution in the tetrahedra, potassium ions hold clay layers together tightly (non-expansible), CEC of 20-40 cmolc/kg
-
limited isomorphous substitution, layers are H-bonded (non-expansible), CEC of 2-5 cmolc/kg
Pregunta 56
Pregunta
The main cations found on the cation exchange complex at a soil pH between 6 and 7 are:
Respuesta
-
Ca, Al, H
-
Ca, Mg, K
-
K, Al(OH), Mg
-
Al, H, K
Pregunta 57
Pregunta
Which of the following will be readily leached from soils because of the properties it has that influence how tightly they are held on the exchange complex of clay?
Respuesta
-
Al
-
H
-
Ca
-
Na
Pregunta 58
Pregunta
Two major types of soil colloids are:
Respuesta
-
crystalline silicate clays and humus
-
basic cations and humus
-
crystalline silicate clays and quartz sands
-
primary minerals and secondary minerals
-
quartz sands and humus
Pregunta 59
Pregunta
Cation exchange capacity is
Respuesta
-
the amount of exchangeable negatively charged ions per unit weight of dry soil
-
the amount of exchangeable negatively charged and neutral ions per unit weight of soil
-
the amount of exchangeable positively charged ions held per unit weight of dry soil
-
the amount of exchangeable H ions per unit weight of dry soil
Pregunta 60
Pregunta
Which cation would you expect to find tightly held in a soil at pH 4.5?
Respuesta
-
K
-
Ca
-
Na
-
Mg
-
Al
Pregunta 61
Pregunta
The swelling/shrinking tendency of some silicate clay minerals is due primarily to:
Respuesta
-
the presence of cations attracted by the negative charges on the internal surfaces
-
the movement of water molecules in and out of the interlayers of the crystal
-
varying thickness of the film of water covering the external surface of the particles
-
expansion in the width of the interlayers due to movement of larger ions such as K+
-
the high Mg^2+ contents in the octahedral layers
Pregunta 62
Pregunta
The accumulation or loss of what compounds result in the formation of hydric soil indicators?
Respuesta
-
iron, manganese, sulfur, or carbon
-
nitrogen, phosphorus, or potassium
-
iron, carbon, sulfur, or nitrogen
-
iron, manganese, sulfur, or arsenic
Pregunta 63
Pregunta
Which of the follow is not a characteristic of soil colloids?
Respuesta
-
very small size
-
high external surfaces
-
electronegativity charges
-
ability to exchange ions with the soil solution
-
low water holding capacity
Pregunta 64
Pregunta
The criteria required to define wetlands are wetland hydrology, hydric soils, and [blank_start]___[blank_end]
Respuesta
-
water standing on the surface
-
clay subsoils
-
hydrophytic vegetation
Pregunta 65
Pregunta
Conditions required to form hydric soil indicators are elements that reduce, seasonal or permanent water saturation, microorganisms, and [blank_start]___[blank_end]
Respuesta
-
water standing on the surface
-
an organic carbon source
-
hydrophytic vegetation
-
clay subsoils
Pregunta 66
Pregunta
The diffusion rate of oxygen in water is 10,000 times [blank_start]___[blank_end] than in air.
Respuesta
-
faster
-
slower
Pregunta 67
Pregunta
Possible ecological consequences of poor soil aeration include:
Respuesta
-
slow organic matter decomposition
-
release of greenhouse gases into the atmosphere
-
reduced plant photosynthesis
Pregunta 68
Pregunta
A major determinant of the aeration status of soils is:
Respuesta
-
dominant type of clay present
-
pore size and continuity
-
types of wetland plants present
-
presence or absence of carbonates
Pregunta 69
Pregunta
Which type of water includes that which is available to plants?
Respuesta
-
hygroscopic water
-
capillary water
-
gravitational water
-
free water
Pregunta 70
Pregunta
Water moves through soil to plant roots by:
Respuesta
-
capillary flow from high to low water potential
-
hygroscopic flow
-
transpiration
-
capillary flow from low to high water potential
-
gravitational flow
Pregunta 71
Pregunta
Water moves further in finer textured soils because:
Respuesta
-
the granular structure in fine textured soils allows for stronger attraction between water and particles
-
more space between particles causes the bonds of cohesion between water molecules to be stronger
-
there is less space between the particles and the water film is unbroken for longer distances
-
more water is lost by plant transpiration in fine textured soils
Pregunta 72
Pregunta
The bulk of gaseous interchange in soils takes place by:
Respuesta
-
mass flow
-
differences in the pressure of N gas
-
diffusion of individual gases along their concentration gradients
-
moving as dissolved ions in soil water
-
aerobic respiration
Pregunta 73
Pregunta
Clay soils hold more water but have less PAW than loamy soils because:
Respuesta
-
there is less gravitational water in clay
-
plant roots cannot grow as well in clay soils
-
more hygroscopic water is held on clay particles
-
loamy soils have smaller pores
Pregunta 74
Pregunta
Sandy soils have less PAW than loamy soils because:
Respuesta
-
there is less gravitational water in sandy soil
-
plant roots grow better in sandy soils so they use the water faster
-
more hygroscopic water is held on sand particles
-
sandy soils have less surface area
Pregunta 75
Pregunta
Which type of water is not "held" in soils?
Respuesta
-
hygroscopic
-
gravitational
-
capillary
-
water of cohesion
Pregunta 76
Pregunta
Capillarity in soils:
Respuesta
-
involves both adhesion and cohesion
-
is enhanced by the symmetrical nature of the water molecule
-
is independent of the matric potential in soils
-
does not account for unsaturated water movement in soils
Pregunta 77
Pregunta
Which type of bond controls retention and movement of water in soils?
Respuesta
-
capillary
-
covalent
-
pH-dependent
-
hydrogen
Pregunta 78
Pregunta
PAW is highest in soils with the following texture:
Respuesta
-
sand
-
sandy loam
-
silty clay loam
-
clay
Pregunta 79
Pregunta
The electronegative charge on 2:1 type silicate clays is due primarily to:
Respuesta
-
ionization of surface OH groups
-
substitution of one metallic atom for another in the crystal structure
-
extremely small size of the individual colloid particles
-
the effect of pH on the presence of H+ ions in the exchange complex
-
the preponderance of tetrahedron sheets compared to octahedron sheets
Pregunta 80
Pregunta
Formation of granular aggregates is aided by:
Respuesta
-
fungal hyphae
-
fine roots
-
microbial and plant exudates
Pregunta 81
Pregunta
Soils developed from accumulated organic material have which of the following characteristics?
Respuesta
-
flat, high in clay, and fertile
-
coarse, stony, with fast drainage
-
light, porous, and productive
-
clayey and poorly drained
Pregunta 82
Pregunta
Secondary minerals are not found in:
Respuesta
-
metamorphic and sedimentary rocks
-
soils and lacustrine sediments
-
soils and sedimentary rocks
-
igneous rocks and the atmosphere
-
soils and metamorphic rocks
Pregunta 83
Pregunta
Compared to silt, clay-sized particles are characterized by:
Respuesta
-
greater attraction for water
-
greater proportion of primarily minerals
-
less attraction for water
-
less capacity to hold nutrients in plant-available forms
Pregunta 84
Pregunta
Fine sand and smaller particles move parallel to the ground and upward by:
Respuesta
-
Creep
-
Flow
-
Suspension
-
Turbulence
-
Saltation
Pregunta 85
Pregunta
Which of the following would NOT reduce water erosion by controlling soil detachment?
Respuesta
-
barriers
-
stubble mulching
-
conservation tillage
-
cover crops
-
no-till farming practices
Pregunta 86
Pregunta
Causes of soil erosion include:
Respuesta
-
over-harvesting timberland
-
overgrazing rangeland
-
fire
-
poor farming practices
Pregunta 87
Pregunta
Terracing is a means of reducing [blank_start]___[blank_end]
Respuesta
-
soil transport by wind
-
soil detachment
-
soil transport by water
-
soil saltation in wind
Pregunta 88
Pregunta
When water concentrates in small channels as it runs from the soil surface, it is called [blank_start]___[blank_end] erosion.
Respuesta
-
gully
-
wind
-
rill
-
sheet
Pregunta 89
Pregunta
The majority of soil particle movement during wind erosion occurs as:
Respuesta
-
Creep
-
Flow
-
Suspension
-
Turbulence
-
Saltation
Pregunta 90
Pregunta
The total global soil lost through erosion is generally greater from [blank_start]___[blank_end] erosion.
Respuesta
-
gully
-
rill
-
sheet
-
wind
Pregunta 91
Pregunta
Land degradation includes which of the following effects on soil?
Respuesta
-
decline in soil structure
-
reduced microbial biomass
-
salinization
Pregunta 92
Pregunta
Sulfuric acid can be used instead of gypsum to reclaim sodic soils that contain:
Respuesta
-
a high buffering capacity
-
free NaCO₃
-
free CaCO₃
-
a high CEC
Pregunta 93
Pregunta
The exchangeable sodium percentage (ESP):
Respuesta
-
predicts soil pH by indicating the amount of sodium there is in the soil in relation to the H ions on the exchange complex
-
predicts soil CEC by calculating the amount of sodium there is on the exchange complex
-
expresses the ratio of sodium to aluminum in the octahedral sheet of 2:1 clays
-
indicates the hazard of sodium-induced soil dispersion
Pregunta 94
Pregunta
Under what precipitation-to-ET conditions would the most severe soil salinization develop?
Respuesta
-
Ratio of 0.25
-
Ratio of 0.75
-
Ratio of 1.25
-
Ratio of 2.25
Pregunta 95
Pregunta
Your soil begins to disperse and crop yields decline several years after you start irrigating your garden plot. Which of the following would most likely account for this situation?
Respuesta
-
high content of Ca and Mg in the irrigation water
-
high content of Na in the irrigation water
-
excessive drainage of the soil
-
high gypsum content in the soil
Pregunta 96
Pregunta
Sodic soils generally have a poor physical condition. This is most likely due to:
Respuesta
-
low OM content
-
dispersal of the Na saturated soil colloids
-
impact of raindrops on the soil surface
-
precipitation of the Ca and Mg ions as carbonates
-
high content of smectite in the soils
Pregunta 97
Pregunta
Techniques for managing saline soils include:
Respuesta
-
keeping the plant root zone wet during sensitive crop stages
-
adding CaCO₃ to replace the Na on the exchange complex
-
applying excess water to increase leaching
Pregunta 98
Pregunta
Overliming:
Respuesta
-
may occur on coarse-textured soils with low OM
-
may result in NH₃ volatilization if NH₄ is present
-
may result in Fe, Mn, Cu, Zn, P, and B deficiencies
Pregunta 99
Pregunta
The major role of potassium in plants is:
Respuesta
-
as part of the chlorophyll molecule
-
regulating cellular respiration
-
energy storage
-
regulating the opening and closing of stomates
Pregunta 100
Pregunta
Organic forms of P make up about [blank_start]___[blank_end] of total P in the soil.
Respuesta
-
98%
-
50%
-
25%
-
1%
Pregunta 101
Pregunta
Available forms of potassium in the soil usually make up about [blank_start]___[blank_end] of total potassium.
Respuesta
-
95-98%
-
25-50%
-
10%
-
0.1-2%
Pregunta 102
Pregunta
The process of [blank_start]___[blank_end] releases soluble nitrogen as the result of the breakdown of nitrogen-rich organic compounds.
Respuesta
-
nitrification
-
denitrification
-
symbiosis
-
volatilization
-
mineralization
Pregunta 103
Pregunta
[blank_start]___[blank_end] is the process of reduction of NO₃₋ to nitrogen gas by microorganisms under [blank_start]___[blank_end] soil conditions.
Respuesta
-
Nitrification
-
Denitrification
-
Volatilization
-
Mineralization
-
aerobic
-
anaerobic
-
acidic
-
alkaline
Pregunta 104
Pregunta
A pH in the range of [blank_start]___[blank_end] is when phosphorus is most available to plants.
Respuesta
-
3.5-4.5
-
4.5-5.5
-
5.5-7.0
-
7.0-8.0
-
>8.0
Pregunta 105
Pregunta
The highly mobile form of N, which is the main source of N for plants, is:
Respuesta
-
NH₃
-
NH₄
-
NO₃
-
N₂
Pregunta 106
Pregunta
The nutrient most limiting for growing food crops in the world is [blank_start]___[blank_end].
Respuesta
-
phosphorus
-
carbon
-
nitrogen
-
potassium
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