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Enviromental Science > soil > Flashcards

soil Flashcards

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1
Q

state 9 features of fertile soil

A

water content / soluble materials / air content / dead organic matter / pH / soil biota / soil texture / soil structure / soil depth

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2
Q

why is water content important for fertile soil

A

essential for all organisms living in the soil, including plants, has good water drainage so as to not get waterlogged but retain enough for survival of soil biota

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3
Q

what soluble materials are in fertile soil

A

macronutrients eg nitrogen phosphorous , in ionic form as nitrates and phosphates / micronutrients eg boron, cobalt, copper, iron / toxic ions eg aluminium and heavy metals are absorbed onto the surface of mineral particles so they cant dissolve in water where they could harm soil organisms

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4
Q

why is air content important in soil fertility

A

living organisms in soil and processes that increase fertility are aerobic so well aerated soils are more fertile

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5
Q

why is dead organic matter important to fertile soil

A

they release plant nutrients as it they decompose, increase water retention and provides food for soil biota

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6
Q

what is a good pH for fertile soils

A

ranges from 5.5 - 7, in range for most plants and soil biota

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7
Q

what happens in the soil if the soil is too acidic

A

acidic soils increase leaching of plant nutrients and damage root cell membranes

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8
Q

what happens in the soil if the soil is too alkaline

A

phosphates become insoluble

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9
Q

name 5 living organisms in soil that affect soil fertility

A

detritivores / decomposers / nitrogen-fixing bacteria / nitrifying bacteria / mycorrhizal fungi

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10
Q

how do detritivores affect soil fertility

A

break up dead organic matter and release nutrients into the soil, (earthworms) increase soil drainage and aeration by creating tunnels in the soil

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11
Q

how do decomposers affect soil fertility

A

break down dead organic matter, secrete digestive enzymes to break up dead organic matter and increase its surface area

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12
Q

how do nitrogen-fixing bacteria affect soil fertility

A

convert gaseous nitrogen into ammonium ions

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13
Q

how do nitrifying bacteria affect soil fertility

A

oxidise ammonium ions to nitrite ions and then to nitrate ions

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14
Q

how does mycorrhizal fungi affect soil fertility

A

forms a symbiotic relationship with plant roots and aids phosphate taken up by plants

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15
Q

list 7 features of soil texture

A

drainage rate / capillary action / aeration / nutrient retention / thermal capacity / root penetration / ease of cultivation

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16
Q

what are the 3 types of soil texture

A

clay, sand and silt

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17
Q

compare the drainage rate of sandy and clay soils

A

sandy has larger pore spaces and allows rapid drainage which reduces water content and increases aeration, clay soil is poorly drained

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18
Q

compare the capillary action between sandy and clay soil

A

tiny pore spaces between clay particles allows water underground to rise towards the surface. no capillary rise between sandy soil

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19
Q

compare the aeration between sandy and clay soil

A

pore spaces in well drained sandy soils are filled with air air. clay soils are more likely to be waterlogged with a low aeration rate

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20
Q

compare the nutrient retention between sandy and clay soil

A

nutrient ions adsorb easily to clay particles but not sand particles

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21
Q

compare the thermal capacity between sandy and clay soil

A

high water content of clay soils produce a high thermal capacity so they warm up and cool down slowly. sandy soils have lower thermal capacities so they warm up more rapidly after cold weather

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22
Q

compare the root penetration between sandy and clay soil

A

clay particles are held together by capillary water on the particles surfaces, makes it harder for plant roots to force their way between soil particles. root penetration is easier in sandy soils

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23
Q

compare the ease of cultivation between sandy and clay soil

A

lack of adhesion between particles in sandy soil makes it easier to cultivate than clay soil

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24
Q

how does soil structure affect soil fertility

A

soil particles form peds which affects soil properties and fertility

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25
Q

what are crumb peds

A

small and round peds, good drainage, aeration and easy root penetration so improve soil fertility

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26
Q

what are platy peds

A

large and flat peds, reduce drainage and aeration and minimise root penetration so produce less fertile soils

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27
Q

how does soil depth affect soil fertility

A

deeper soils are less likely to become waterlogged or to dry out rapidly, aid good root anchorage

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28
Q

name 5 human activities that affect soil fertility

A

aeration by ploughing and drainage / soil nutrient levels / irrigation / soil compaction / pH control

29
Q

how does aeration by ploughing and drainage affect soil fertility

A

makes soil more aerobic, increases rate or nitrogen fixation, nitrification, decomposition of dead organic matter

30
Q

how do farmers increase soil nutrient levels

A

adding inorganic fertilisers, organic matter or by supporting natural processes that increase nutrient levels such as bacterial nitrogen fixation

31
Q

how do farmers deplete soil nutrient levels

A

soil erosion, biomass removal, inhibiting natural processes that increase nutrient levels or by increasing leaching of dissolved nutrients

32
Q

how does irrigation affect the soil fertility

A

increases fertility of soil where water is a limiting factor on growth, dissolves nutrients what can be absorbed by plants in ionic form

33
Q

how does soil compaction affect soil fertility

A

excessive use of heavy machinery or high density of livestock can compact the soil, reducing aeration and making waterlogging more likely

34
Q

how does pH control affect soil fertility

A

helps to ensure nutrients are soluble but not too easily leached

35
Q

what are the two types of soil erosion

A

wind erosion and water erosion

36
Q

what is wind erosion

A

dry soils, with low clay content typically, are likely to be loose with little cohesion to hold the soil together, unprotected soil could blow away, can cover crops or land in urban areas

37
Q

name 3 types of water erosion

A

rain splash erosion / surface run off erosion / slumping and landslides

38
Q

what is rain splash erosion

A

soil particles are dislodged by splash of raindrop and soil particles are dispersed in all directions, those going downhill are likely to travel further - causes downhill movement of large amount of soil

39
Q

what is surface runoff erosion

A

when the infiltration capacity of the soil has been exceeded, can occur at heavy or prolonged rainfall or if water is relatively impermeable, more water flows over ground surface

40
Q

what is slumping and landslides

A

soil becomes wet and increased mass and lubrication of water makes downward movement of large amount of soil more likely

41
Q

when do landslides often occur

A

when deep soil on steep slopes becomes less stable following deforestation, roots that held soil together decompose so soil is held together less strongly

42
Q

name factors of vegetation that reduce rate of soil erosion

A

vegetation / vegetation cover and leaf litter / soil organic matter / plant roots / plants

43
Q

how does vegetation reduce rate of soil erosion

A

acts as a natural windbreak, reducing win velocity reduces kinetic energy to carry away soil particles

44
Q

how does vegetation cover and leaf litter reduce rate of soil erosion

A

reduce impact of raindrops on soil surface, soil particles are less likely to be dislodged

45
Q

how does soil organic matter reduce rate of soil erosion

A

helps bind soil particles together eg collodial material humus

46
Q

how do plant roots reduce rate of soil erosion

A

hold soil together

47
Q

how do plants reduce rate of soil erosion

A

increase infiltration of water into the soil, reduces rate of runoff

48
Q

name 6 human activities that increase the rate of soil erosion

A

vegetation removal / ploughing vulnerable soils / overgrazing / reduced soil biota / soil compaction/ cultivating steep slopes

49
Q

how does vegetation removal increase rate of soil erosion

A

removes plants and plant roots and organic soil matter and vegetation cover which protects the soil from soil erosion

50
Q

how does ploughing vulnerable soils increase the rate of soil erosion

A

breaks up the soil structure, exposing particles to erosion by wind or water

51
Q

how does overgrazing increase rate of soil erosion

A

if livestock density is too high = vegetation is eaten faster than it can grow, exposing soil to risk of erosion / disturbance and root damage due to hooves

52
Q

how does a reduced soil biota increase rate of soil erosion

A

living organisms have been removed from the soil, so detritivores cannot break down dead organic matter, release plant nutrients for increased vegetation cover / decomposers aren’t there to produce humus / worms aren’t there to aerate the soil, increase drainage and infiltrate capacity

53
Q

how does soil compaction increase rate of soil erosion

A

gives soil smaller interstitial spaces which reduces infiltration rates so more likely for surface runoff and cause erosion

54
Q

how does cultivating steep slopes increase rate of soil erosion

A

surface run off occurs more rapidly down a steep slope, more kinetic energy and picks up more soil particles

55
Q

name 4 effects of accelerated soil erosion

A

reduced productivity / sedimentation in rivers and reservoirs / increased atmospheric particulates / desertification

56
Q

how is reduced productivity caused by soil erosion

A

when soil erodes normally more fertile top soil is lost which leaves less fertile soil to grow in, causing smaller harvests / shallower soil so root penetration may be more difficult

57
Q

how is sedimentation in rivers and reservoirs caused by soil erosion

A

soil particles carried into rivers may be deposited if water slows sown and has less kinetic energy. sediments in river reduce river flow capacity so more likely to over flow

58
Q

how is increased atmospheric particulates caused by soil erosion

A

wind erosion increases level of atmospheric particulates

59
Q

name 10 ways to reduce soil erosion

A

long term crops / zero-tillage cultivation / contour ploughing / tied ridging / terracing / rows of stones / windbreaks / multicropping / increasing soil organic matter / livestock management

60
Q

how do long term crops help reduce soil erosion

A

limits amount you need to replant them so reduces soil disturbance, reduces erosion rate

61
Q

how does zero-tillage cultivation reduce soil erosion

A

drilling seeds into the ground instead of ploughing, minimises soil disturbance and reduces risk of soil erosion

62
Q

how does contour ploughing reduce soil erosion

A

ploughing contours at 90 degree to the slop reduces erosion as water flow is stopped by ploughed furrows it loses kinetic energy so cant carry soil particles, slower flow rate soil particles are deposited in furrow

63
Q

how does tied ridging reduce soil erosion

A

water is retained in the criss cross intersecting ridges, increasing infiltration and reducing runoff

64
Q

how does terracing reduce soil erosion

A

water flowing over the retaining walls flows quickly but flow slows down when across fields, much of the water infiltrates the soil

65
Q

how does a row of stones reduce soil erosion

A

laid across contours, causes slow runoff and reduces erosion rate

66
Q

how do windbreaks reduce soil erosion

A

growing crops reduces wing erosion, if plants removed soil is exposed. bushes and trees grown around the field

67
Q

how does multicropping reduce soil erosion

A

growing more than one crop at the same rime an reduce wind erosion. harvested and re-sown at different times so always a crop protecting the soil

68
Q

how does increasing organic matter reduce soil erosion

A

organic matter on soil surface protects soil from wind and impact of raindrops, as it decomposes it produces humus to help adhere particles

69
Q

how does livestock management reduce soil erosion

A

stocking density can be controlled to reduce soil damage

Enviromental Science (12 decks)

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