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Environmental Science > Soils > Flashcards

Soils Flashcards

1
Q

Why is soil important?

A

agriculture
supports biodiversity
habitat for some organisms
site of chemical reaction
supports plants for climate regulation

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2
Q

What does soil fertility mean?

A

the ability of soil to sustain plant growth

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3
Q

Components of soil: minerals - sand

A

mixture of small pieces of different rocks or minerals

particles = round

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4
Q

Components of soil: minerals - silt

A

fine sand/clay carried by running water and deposited as a sediment

larger than clay, smaller than sand

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5
Q

Components of soil: minerals - clay

A

grained earth

flat and platey

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6
Q

Components of soil: DOM

A

decomposition - cycling of nutrients

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7
Q

Components of soil: soil biota

A

micro-organisms, spiders, insects, earthworms

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8
Q

Components of soil: missing two

A

water and air

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9
Q

Features of soil which affect soil fertility and productivity: water content

A

essential for all organisms
good soils allow good drainage, but retain enough for soil biota
dissolves nutrients

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10
Q

Features of soil which affect soil fertility and productivity: soluble materials (micro/macro nutrients and metal ions)

A

macro - phosphorus, nitrogen, potassium
micro - boron, cobalt, copper, iron, manganese, magnesium

shortage of nutrients limits plant growth

harmful metals adsorb onto surface of clay particles

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11
Q

Features of soil which affect soil fertility and productivity: air content

A

most processes = aerobic
well aerated = more fertile
aerobic = faster decomposition

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12
Q

Features of soil which affect soil fertility and productivity: DOM

A

more DOM = fertile soils
binds soils
increases nutrients, water retention and food for soil biota

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13
Q

Features of soil which affect soil fertility and productivity: pH

A

fertile soils = 5.5-7
acidic soils = increased leaching and damage to root cell membranes
alkaline soils = phosphates are insoluble

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14
Q

Features of soil which affect soil fertility and productivity: soil biota

A

detritivores break down DOM and release nutrients
decomposers break down DOM and secrete digestive enzymes
nitrogen fixing bacteria
nitrifying bacteria
mycorrhizal fungi

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15
Q

Features of soil which affect soil fertility and productivity: soil texture

A

controlled by different mineral particles
clay = small
silt = medium
sand = small

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16
Q

Features of soil which affect soil fertility and productivity: soil structure

A

soil particles from aggregates (peds)

crumb peds = small and round = good drainage/aeration/root penetration

platy peds = large and flat = decreases drainage/aeration/root penetration

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17
Q

Features of soil which affect soil fertility and productivity: soil depth

A

deeper soil s= dry out rapidly

root anchorage

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18
Q

How particle size affects soil properties: drainage

A

large and spherical = better drainage

quicker in sand than clay soils

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19
Q

How particle size affects soil properties: water content and capillary action

A

more water drawn up in clay soils as water content is higher

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20
Q

How particle size affects soil properties: aeration

A

higher in sandy soils as more porous

21
Q

How particle size affects soil properties: nutrient levels

A

higher in clay as more water available so more nutrients dissolved

some able to adsorb to clay particles

22
Q

How particle size affects soil properties: thermal capacity

A

higher water content = higher thermal capacity

23
Q

How particle size affects soil properties: root penetration

A

higher in sandy soils

24
Q

How particle size affects soil properties: ease of cultivation

A

higher in sandy soils

25
Q

Soil Analysis: soil texture - sedimentation method

A

handful of soil in tray
rub sample through fingers to separate
remove obvious pieces of organic particles and any large chunks
half fill cylinder with soil
fill rest of cylinder with water
invert repeatedly to mix and suspend
leave for at least a week
use graduations to determine % of sand, silt, clay
use soil triangle to determine soil type

26
Q

Soil Analysis: soil texture - soil sieve method

A

stack of sieves = different sizes
1st = stones, sticks, gravel
2nd = sand
3rd = silt
4th = clay
collect total mass of each to work out percentage

only works if soil is dry and separated

27
Q

Soil Analysis: water content

A

weigh crucible
add soil and reweight
place in oven at 100 degrees for 24hrs
weigh crucible and dry soil
determine mass of water lost
work out % mass of water in original sample

28
Q

how do you know if all the water has evaporated?

A

heat until constant mass

29
Q

Soil Analysis: soil air

A

add 250ml of soil to 500ml beaker
add 250ml of water and stir
record new vol
work out % air = loss of expected volume/ original vol of soil

30
Q

Soil Analysis: organic matter

A

weigh empty crucible
add dry soil and reweigh
determine mass of soil
place in oven at 450 degrees and leave overnight
weight soil and crucible again
determine loss of mass
work out %

31
Q

When determining organic matter content, why should the oven temp be kept below 550 degrees?

A

to not break down sand, silt, clay

difficult to distinguish between mass lost due to DOM and mass lost due to minerals

32
Q

Soil Analysis: soil pH - universal indicator

A

add 2.5cm3 of soil to test tube
add 1cm3 of BaSO4 (speeds up settling)
add 3.5cm3 distilled water
add 10 drops universal indicator
bung test tube and shake
leave for 15 minutes
use colour card to determine pH

33
Q

Soil Analysis: soil pH - universal indicator paper

A

same test tube set up as universal indicator
dip paper into settled solution

34
Q

Soil Analysis: soil pH - pH probe

A

calibrate using buffer solution
take readings at equal depths

35
Q

Soil Analysis: soil organisms - random sampling

A

suitable for large areas

uses a quadrat - place using randomly selected co-ordinates

36
Q

Soil Analysis: soil organisms - soil flooding (using irritant)

A

suitable for extracting worms

flood area of soil in a quadrat, often using irritant (e.g. mustard powder)
worms come to surface and are counted

37
Q

Limitations of soil flooding

A

worms may die
worms may move sideways
irritant may not percolate deep enough

38
Q

Soil Analysis: soil organisms - soil pit extraction

A

dig out area of quadrat to an agreed depth
hand sort worms out of soil

39
Q

Limitations of soil pit extraction

A

worms may move sideways
small worms may be missed

40
Q

Human activities affecting soil fertility: aeration by ploughing and drainage

A

makes soils more aerobic
increases rate of nitrogen fixation, nitrification and decomposition of DOM

41
Q

Human activities affecting soil fertility: increasing and decreasing soil nutrient levels

A

increasing = inorganic fertilisers, organic matter, support natural processes (e.g. nitrogen fixation)

decreasing = erosion, biomass removal, increased leaching

42
Q

Human activities affecting soil fertility: irrigation

A

increases soil fertility where water is the limiting factor - allows plants to keep stomata open

dissolves nutrients that can be absorbed as ions

43
Q

Human activities affecting soil fertility: soil compaction

A

caused by excessive use of heavy machinery

reduces aeration and increases chance of waterlogging

44
Q

Human activities affecting soil fertility: controlling pH

A

ensures nutrients are soluble but not too easily leached

crushed limestone increases pH

digging in sulphur decreases pH

45
Q

Types of soil erosion: wind

A

picks up soil particles and moves them

most likely to happen to dry/sandy soils

46
Q

Types of soil erosion: water

A

rain splash erosion

surface runoff erosion

slumping and landslides

47
Q

Ways in which vegetation reduces soil erosion

A

root binding

48
Q
A

Environmental Science (27 decks)

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