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Environmental science > Soil > Flashcards

Soil Flashcards

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1
Q

name the 5 components of soil

A 
mineral skeleton 
water 
air 
biota 
DOM
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2
Q

what is meant by mineral skeleton?

A

particles broken down by weathering of rocks. Proportions of different sized particles = soil texture

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3
Q

why is air important in soil?

A

provides gases for aerobic processes for organisms i.e. decomposition, N2 fixation and nitrification

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4
Q

why is water important in soil?

A

plants need it for various processes i.e. photosynthesis and nutrients can only be absorbed if dissolved in it

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5
Q

why is biota important in soil?

A

responsible for decomposition and aid aeration/draining and nutrient recycling

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6
Q

why is DOM important in soil?

A
  • source of food for some organisms
  • produces humus and releases nutrients
  • humus helps to bind soil together = soil stability
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7
Q

definition of soil fertility

A

the ability of soil to sustain plant growth

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8
Q

Name the 6 factors that influence soil fertility

A 
drainage 
aeration 
thermal capacity 
nutrient levels 
root penetration 
capillary action
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9
Q

name the 3 types of soil particles from largest to smallest

A

sand, silt, clay

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10
Q

what does it mean by soil texture?

A

how big the particles are

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11
Q

Drainage: the _____ the particle, the larger the ____space so drainage is ______. For example _____. This is the opposite for _____ particles like _____.

A
  1. larger
  2. pore
  3. easier
  4. sand
  5. smaller
  6. clay
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12
Q

Thermal capacity: H2O has a ______ thermal capacity (warm/cool ______). ______ retains more H2O so takes _____ to warm/cool. So the ____ H2O the more temp. _____>

A
  1. high
  2. slowly
  3. clay
  4. longer
  5. more
  6. stable
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13
Q

How do soil texture influence aeration?

A

the larger the particle, the larger the pore space = increase aeration/air

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14
Q

which soil texture is the WORST when conserving nutrients and why

A

sand as it has increased drainage due to large particle size so increase leaching

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15
Q

Is clay good at absorbing nutrients?

A

Clay absorbs more nutrients/minerals

- Clay have negative charges = positive charged nutrient ions attach

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16
Q

which soil texture is root penetration easiest in?

A

sandy soils

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17
Q

which soil texture is root penetration hardest in and why?

A

clay - particles held together by capillary H2O on particle surfaces = harder for roots to penetrate between particles

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18
Q

which texture is best at capillary action and why?

A

clay - tiny pores = H2O can rise towards surface

no capillary rise in sandy soils

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19
Q

How does soil biota increase soil fertility? and explain

A
  • detritivores break up DOM (i.e. worms) decomposers break down DOM (i.e. fungi secrete enzymes) = releases nutrients
  • N2 nitrifying bact. = atmospheric N2 to ammonia
  • Nitrifying bact. = oxidise ammonia - nitrite - nitrate
  • mycorrhizal fungi (symbiotic relationship with roots) = increase phosphate uptake
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20
Q

difference between micronutrients and macronutrients with examples

A 
micro = plants need in small amounts i.e. magnesium, cobalt, boron 
macro = need in large amounts i.e. N2, phosphorus, potassium
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21
Q

in fertile soil: _____ ions (i.e. aluminium and _____ metals) are _____ onto surface of particles (usually ___) so does not ______ in ____ where they could harm ____

A
  1. toxic
  2. heavy
  3. absorbed
  4. clay
  5. dissolve
  6. H2O
  7. biota
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22
Q

name the 3 reasons why DOM is important

A
  1. food for biota
  2. releases nutrients i.e. humus
  3. increases H2O retention
23
Q

definition of a ped

A

when soil particles aggregates (clump together) - held together by polysaccharide gum

24
Q

Which is ped is more fertile and why: crumb or platy?

A

crumb: small round particles = good aeration/drainage/easy root penetration
platy: large/flat so decreases those factors

25
Q

for soil fertility which is better: deeper or shallow soils?

A

deeper = less likely to be waterlogged/dry out. Good root drainage.

26
Q

why do soils need high water content but also good drainage?

A
  • ions are dissolved in H2O

- drainage; avoid anaerobic conditions

27
Q

How does the pH influence soil fertility?

A

optimum pH = 5-7
too acidic = cell membrane damage/rapid leaching
too alkali = inhibit nutrient uptake i.e. phosphate becomes insoluble

28
Q

name the 5 human activities that affect soil fertility and briefly explain

A

irrigation: increase fertility = allows stomata to be open + continue gas exchange + H2O dissolves nutrients
use of fertilisers: increase nutrients + support processes like N2 cycle
pH control: ensures nutrients soluble not easily leached
compaction: more compact = less aeration/decrease drainage/harder roots to penetrate
ploughing and drainage: increase aeration = more aerobic processes (i.e. more fixation/nitrification/decomp.)

29
Q

state at least 5 out of the 8 factors that could affect infiltration rate

A

soil moisture, soil texture, soil structure, organic matter content, vegetation cover, soil depth, gradient, intensity of precipitation

30
Q

in soils not been affected by _____ activities the rate of erosion is likely to be the same or ____ that rate of soil ______. Erosion is a problem when it occurs _____ rapidly than soil _______

A
  1. human
  2. less
  3. formation
  4. more
  5. formation
31
Q

all forms of ____ erosion are increased by ______ gradients

A
  1. water

2. steeper

32
Q

Name the 2 types of water erosion

A

rain splash erosion: particles dislodged, move into pore spaces = reducing infiltration

surface runoff erosion: caused by surface runoff (infiltration capacity of soil exceeded), particles dislodged can cause landslides. loss of roots binding from deforestation affect this.

33
Q

describe wind erosion

A

soils are dry/unprotected, wind can carry it away as little cohesion between particles

34
Q

name the 5 ways how vegetation reduces soil erosion

A
  • decrease wind velocity
  • more infiltration = less runoff
  • roots bind the soil
  • organic matter/humus bind soil
  • increased interception (vegetation/leaf litter) = impact of raindrops reduced
    FOR REMOVAL OF VEGETATION IT IS THE OPPOSITE
35
Q

name the 6 activities that can increase soil erosion

A
  1. removal of vegetation: {give general points}
  2. ploughing vulnerable soils: breaks up soil structure = particles exposed
  3. overgrazing: less vege. = increase soil exposure. Hooves = disturbance/root damage
  4. compaction: due to livestock densities/machinery/lack of detritivores. Smaller pores = less infiltration
  5. reduced biota: less nutrients for vege., less humus produced = less adhesion between particles. Less worms: less aeration, less infiltration
  6. cultivating steep slopes: more kinetic energy (carries more particles), disturbing soil
36
Q

Name the 10 methods of reducing soil erosion

A 
long term crops 
terracing 
tied ridging 
rows of stones 
windbreaks 
Zero-tillage cultivation 
contour ploughing 
multicropping 
increasing soil organic matter 
livestock management
37
Q

how does long term crops reduce soil erosion

A

crops used that don’t need to be replanted often = reduces soil disturbance i.e. permanent bush/tree crops (coffee, fruit, tea)

38
Q

Which method to reduce soil erosion for which gradient:
1. Used for a steep slope
2. Used for predominantly flat land
3. Used for a gentle gradient
4. Used for a slope
And explain briefly what each method does

A
  1. terracing: H2O flows over walls quickly, but slows as it goes down = allows H2O to infiltrate
  2. tied ridging: field has criss-cross pattern of intersecting ridges = retains H2O, increases infiltration
  3. rows of stones: rows of stones placed in contours, reduces velocity of runoff = soil deposited behind rocks
  4. contour ploughing: contours made at 90 degrees to slope, kinetic energy lost = soil particles deposited
39
Q

What is zero tillage cultivation?

A

not ploughing/sowing but direct drilling of seeds = reduces soil disturbance

40
Q

How do windbreaks reduce erosion and give examples

A

reduce wind velocity = less soil particles carried away (hedgerows/rows of trees)

41
Q

What is multicropping and how does it reduce erosion

A

growing more than one crop in a field at the same time and harvesting/re-sown at different times. Reduces erosion as: always be vegetation to reduce wind velocity

42
Q

which uses human labour and which uses machinery: strip cropping and multicropping

A 
strip = machinery 
multi = human
43
Q

how does increasing soil organic matter reduce soil erosion

A

DOM on surface (mulch) = protect from wind/impact from raindrops. DOM decomposes produces humus

44
Q

how does livestock management reduce erosion?

A

managing stock density = reduces compaction

managing livestock movement = reducing access to vulnerable soil i.e. riverbanks

45
Q

what does the universal soil erosion loss equation work out? and what is it?

A

rate of erosion (annual soil loss) = RxKxLxSxCxP

46
Q

If you have to rearrange the universal soil erosion loss equation how would you do it?

A

have erosion rate on the top and all the letters on the bottom

47
Q

when in a question and it gives u the erosion rate and tells you that the farming methods have changed i.e. contour ploughing used instead of ploughing or fruit was grown instead of wheat what do you do?

A

erosion rate divided by old method then multiply the whole equation by the new method or change = new erosion rate

48
Q

Name all the symbols in the universal soil erosion loss equation:
1. R 2. K 3. L 4. S 5. C 6. P

A
  1. rainfall erosivity
  2. soil erodibility
  3. slope length factor
  4. slope gradient factor
  5. crop management factor
  6. erosion control factor
49
Q

Name the 5 problems caused by soil erosion

A
  • landslide
  • sedimentation: turbid H2O = blocks out light for photosynthetic organisms. O2 levels drop. Sediments deposited, river more narrow = H2O overspills/flooding
  • reduced productivity : soil has no fertility = lower food produced
  • desertification: when a habitat becomes a desert
  • atmospheric particles: dust clouds/sandstorms reduce light penetration
50
Q

Method for soil water content:

  1. soil sample collected (i.e. _____ sampler or _____)
  2. sample placed in sealed bag (reduce water _____ by ___________)
  3. organisms/large particles _______
  4. sample placed in pre-weighed __________ basin
  5. basin ______ at about 100 for __ hours
  6. basin is ________
  7. stages 5-6 repeated until _______ ______ is reached
  8. calculate ______ content
A
  1. core, auger
  2. loss, evaporation
  3. removed
  4. evaporating
  5. heated, 24
  6. reweighed
  7. constant mass
  8. water
51
Q

what is the equation for % water content?

A

wet soil mass - dry soil mass / wet soil mass X100

52
Q

Method for soil organic matter content:
Steps 1-7 of the soil water content method THEN
8. A ___ soil sample places in ________ crucible which is then _______
9. crucible _______ in a ____ or a bunsen burner
10. crucible is _______
11. stages 9-10 repeated until _______ _____ is reached
12. calculate _____ matter content

A
  1. dry, preweighed, reweighed
  2. heated, furnace
  3. reweighed
  4. constant mass
  5. organic
53
Q

what is the equation for % organic matter content?

A

dry soil mass - burnt soil mass / dry soil mass X100

Environmental science (19 decks)

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