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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
Q

gravimetric approach to measuring soil water

A

weight of a soil sample, oven dry soil sample at 105c. weight loss is water, calculate percent mass.

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26
Q

gravimetric water constant formula

A

(wet weight-oven dry)/oven dry

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27
Q

volumetric

A

theta = w * Bulk Density

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28
Q

evapotranspiration

A

happens most in summer

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29
Q

Irrigation

A

the need for irrigation is closely related to the volume of soil exploited by roots

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30
Q

Irrigation depends on

A

season
time of day
infiltration rate

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31
Q

aeration

A

gets more air into soil, gets rid of co2 and gets o2 in. the more wet the soil, the more co2 trapped in soil.

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32
Q

soil quality

A

based off of plant growth, water supply. It reflects a combination of chemical physical and biological properties.

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33
Q

soil erosion is responsible for how much soil degradation

A

80% erosion by wind and water

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34
Q

geological erosion

A

erosion that takes place without the influence of humans, happens at about the rate soil forms.

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35
Q

human accelerated erosioin

A

humans disturb soil/vegetation. Construction, over grazing

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36
Q

Erosion in arid regions

A

more erosion be less vegetation. Very few intense rain events

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37
Q

Erosion in humid regions

A

lots of vegetation so erosion rates are lower

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38
Q

The major sources of erosion in NC

A

construction, agriculture, and streambank/shoreline erosion

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39
Q

detachment

A

step 1 of the erosion process. Individual particles are loosened from the soil mass

40
Q

transport

A

step 2 of erosion process. Water or wind carries detached particles downslope or downwind.

41
Q

deposition

A

step 3 of erosion process. detached particles are deposited in places of a lower elevation

42
Q

sand erosion potential

A

largest particles so requires higher energy to move

43
Q

sheet erosion

A

uniform movement of water across a surface

44
Q

rill erosion

A

removal of soil by water running through little streamlets 4 inches or so deep. can be fixed easy by tillage

45
Q

gully erosion

A

big ditches caused by erosion

46
Q

bulk density

A

mass oven dry soil/volume
sandy soils have higher bulk density than clayey soils. Organic soils have lowest density

47
Q

porosity

A

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
Q

soil texture

A

distrbution of particles into different size classes.

49
Q

gravel

A

more than 2mm

50
Q

sand

51
Q

silt

A

.05-.002mm

52
Q

clay

A

less than .002mm

53
Q

how do we measure soil texture

A

hydrometer

54
Q

coarse texture soils

A

rapidly drains water, nutrient poor, gritty, low organic matter, like sands

55
Q

fine textured soils

A

water drains slowly, micropores, feels sticky, higher fertility and organic matter than coarse texture.

56
Q

macropores

A

drain water rapidly, sandy soils (cohesion dominant)

57
Q

mesopores

A

water held tighter than force of gravity but not so tight that plants can’t extract water.

58
Q

micropores

A

capillary action (adhesion), tend to retain water well

59
Q

Capillarity

A

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

60
Q

matric potential

A

results from cohesion and adhesion, results in negative potential.

61
Q

gravitational potential

A

positive force.

62
Q

gypsum blocks

A

a method to estimate soil moisture

63
Q

tensiometers

A

a method to estimate soil moisture

64
Q

time domain reflectometry

A

a method to estimate soil moisture

65
Q

3 methods to estimate soil moisture

A

gypsum blocks, tensiometer, time domain reflectometry

66
Q

structureless single grain

A

individual particles, commonly found in sandy c horizon

67
Q

structureless massive

A

no visible structure

68
Q

platy

A

clayey soils, think plates

69
Q

columnar

A

vertical colums

70
Q

prismatic

71
Q

blocky

A

square like blocks w sharp edges, commonly found in subsoils

72
Q

sub angular blocky

A

square blocks w round edges

73
Q

granular

A

cookie crumbs found in a horizons

74
Q

red soil means

A

well drained

75
Q

gray soil means

A

poorly drained (water logged)

76
Q

infiltration

A

how fast water moves through the soil. Sand has fast infiltration,

77
Q

reducing evapotranspiration

A

reduces evaporation by covering soil like mulch.

78
Q

irigation

A

only irrigate to field capacity

79
Q

drainage

A

reduce water filled pore space so some pores can have oxygen that roots need

80
Q

aeration

A

get co2 out of soil and oxygen in

81
Q

o horizon

A

organic material

82
Q

a horizon

A

surface horizon or topsoil

83
Q

b horizon

A

zone of maxium illuviation

84
Q

e horion

A

zone of maximum eluviaion (leached organic matter or clay)

85
Q

c horizon

A

parent material

86
Q

r horizon

A

underlying rock or parent material

87
Q

subordinate usually given to b horizon

88
Q

h

A

humic matter

89
Q

t

A

silicaTe clay

90
Q

w

91
Q

a

A

highly decomposed organic material commonly found in histosols

92
Q

g

A

strong gleying (poorly drained soils)

93
Q

epipedon

A

surface diagnostic horizon

Soil Science (2 decks)

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