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Soil Science > Exam > Flashcards

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1
Q

bulk density

A

weight of oven dry soil/ volume of soil

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2
Q

water that plants uptake and release back into atmosphere

A

transpiration

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3
Q

cohesion

A

the attraction of water molecules for each other due to primary h bonding

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4
Q

adhesion

A

the attraction of water molecules for solid surfaces, think a meniscus. also h bonding

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5
Q

hydrophobic

A

water resistant

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6
Q

capalarrity

A

the movement of water up a wick made of hydrophilic solid materials

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7
Q

hydrophilic

A

water loving, adhesion and cohesion forces cause water to cling to surfaces

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8
Q

osmotic potential

A

water moves toward higher concentration of salts or organics to reach equilibrium. Using energy to move (negative force)

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9
Q

saturation

A

all voids are filled w water and there is no air in the soil 0kpa

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10
Q

filed capacity

A

water content of soil after drained 24-48 hours. Macropores are filled w air

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11
Q

permanent wilting point

A

point at which plants cannot remove water. plant wilts beyond recovery. -1500kpa

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12
Q

gravitational water

A

water between saturation and field capacity is gravitational water

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13
Q

plant available water

A

water between field capacity and permanent wilting point, plant availible water is water that will relinquish to the plant. Held is mesopores

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14
Q

unavailable water

A

water between permanent wilting point and oven dry is unavailable water. Held in micropores

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15
Q

Wet soils

A

water loosely held. Energy status is relatively high

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16
Q

Dry soils

A

water is held tightly by the soil solids. energy status is much lower

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17
Q

time domain reflectometry

A

nondestructive methods for measuring soil by using radar to transmit signals into soil and analyzing the reflected results.

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18
Q

clay soils

A

high water holding capacity

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19
Q

sandy soils

A

low water holding capacity

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20
Q

wilting point is characterized by

A

the amount of water tightly held to soil particles

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21
Q

what pore size is plant available water held in

A

mesopores

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22
Q

how is soil water content estimated

A

tensiometer

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23
Q

soil water potential

A

the energy status of the soul water in terms of bars, atms, or kpas

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24
Q

soil water content

A

the amount of water in the soil can be reported as weight or volume.

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25
gravimetric approach to measuring soil water
weight of a soil sample, oven dry soil sample at 105c. weight loss is water, calculate percent mass.
26
gravimetric water constant formula
(wet weight-oven dry)/oven dry
27
volumetric
theta = w * Bulk Density
28
evapotranspiration
happens most in summer
29
Irrigation
the need for irrigation is closely related to the volume of soil exploited by roots
30
Irrigation depends on
season time of day infiltration rate
31
aeration
gets more air into soil, gets rid of co2 and gets o2 in. the more wet the soil, the more co2 trapped in soil.
32
soil quality
based off of plant growth, water supply. It reflects a combination of chemical physical and biological properties.
33
soil erosion is responsible for how much soil degradation
80% erosion by wind and water
34
geological erosion
erosion that takes place without the influence of humans, happens at about the rate soil forms.
35
human accelerated erosioin
humans disturb soil/vegetation. Construction, over grazing
36
Erosion in arid regions
more erosion be less vegetation. Very few intense rain events
37
Erosion in humid regions
lots of vegetation so erosion rates are lower
38
The major sources of erosion in NC
construction, agriculture, and streambank/shoreline erosion
39
detachment
step 1 of the erosion process. Individual particles are loosened from the soil mass
40
transport
step 2 of erosion process. Water or wind carries detached particles downslope or downwind.
41
deposition
step 3 of erosion process. detached particles are deposited in places of a lower elevation
42
sand erosion potential
largest particles so requires higher energy to move
43
sheet erosion
uniform movement of water across a surface
44
rill erosion
removal of soil by water running through little streamlets 4 inches or so deep. can be fixed easy by tillage
45
gully erosion
big ditches caused by erosion
46
bulk density
mass oven dry soil/volume sandy soils have higher bulk density than clayey soils. Organic soils have lowest density
47
porosity
total pore space that holds air or water. Porosity increases as bulk density decreases. Improve porosity by adding organic matter. Clay soils have more pore space than sandy soils
48
soil texture
distrbution of particles into different size classes.
49
gravel
more than 2mm
50
sand
2-.05mm
51
silt
.05-.002mm
52
clay
less than .002mm
53
how do we measure soil texture
hydrometer
54
coarse texture soils
rapidly drains water, nutrient poor, gritty, low organic matter, like sands
55
fine textured soils
water drains slowly, micropores, feels sticky, higher fertility and organic matter than coarse texture.
56
macropores
drain water rapidly, sandy soils (cohesion dominant)
57
mesopores
water held tighter than force of gravity but not so tight that plants can't extract water.
58
micropores
capillary action (adhesion), tend to retain water well
59
Capillarity
the movement of water up a wick made of hydrophilic solid materials.
60
matric potential
results from cohesion and adhesion, results in negative potential.
61
gravitational potential
positive force.
62
gypsum blocks
a method to estimate soil moisture
63
tensiometers
a method to estimate soil moisture
64
time domain reflectometry
a method to estimate soil moisture
65
3 methods to estimate soil moisture
gypsum blocks, tensiometer, time domain reflectometry
66
structureless single grain
individual particles, commonly found in sandy c horizon
67
structureless massive
no visible structure
68
platy
clayey soils, think plates
69
columnar
vertical colums
70
prismatic
71
blocky
square like blocks w sharp edges, commonly found in subsoils
72
sub angular blocky
square blocks w round edges
73
granular
cookie crumbs found in a horizons
74
red soil means
well drained
75
gray soil means
poorly drained (water logged)
76
infiltration
how fast water moves through the soil. Sand has fast infiltration,
77
reducing evapotranspiration
reduces evaporation by covering soil like mulch.
78
irigation
only irrigate to field capacity
79
drainage
reduce water filled pore space so some pores can have oxygen that roots need
80
aeration
get co2 out of soil and oxygen in
81
o horizon
organic material
82
a horizon
surface horizon or topsoil
83
b horizon
zone of maxium illuviation
84
e horion
zone of maximum eluviaion (leached organic matter or clay)
85
c horizon
parent material
86
r horizon
underlying rock or parent material
87
subordinate usually given to b horizon
88
h
humic matter
89
t
silicaTe clay
90
w
weak
91
a
highly decomposed organic material commonly found in histosols
92
g
strong gleying (poorly drained soils)
93
epipedon
surface diagnostic horizon
94
95

Soil Science (2 decks)

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