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Environmental Science > Soil > Flashcards

Soil Flashcards

1
Q

What is soil fertility?

A

The ability of soil to sustain plant growth

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2
Q

What are the main features to check soil fertility?

A

Water content, soluble materials, air content, dead organic matter, pH, soil biota and soil texture

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3
Q

Why is water content important?

A

Ensures survival of biota and plant nutrient are absorbed dissolved in ionic form

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4
Q

What macronutrients are found in fertile soils?

A

Nitrates, phosphates and potassium ions

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5
Q

What micronutrients are also found in fertile soils?

A

Boron, cobalt, copper, iron, manganese and magnesium

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6
Q

What happens to toxic ions in fertile soils?

A

They adsorb onto the surface of mineral particles, usually clay, so they cannot dissolve in water where they may cause harm to organisms

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7
Q

What is hygroscopic water?

A

Water held on the surface of mineral particles by adhesion- this cannot be absorbed by plants

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8
Q

How does air content affect soil fertility?

A

Many processes and living organisms are aerobic so aerated soils are more likely to be fertile

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9
Q

How does dead organic matter content impact soil fertility?

A

High content will release plant nutrients as it decomposes increasing the fertility of the soil, it also increases water retention and provides food for soil biota

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10
Q

What is the typical pH of fertile soils?

A

5.5-7 (the range of tolerance for most plants and soil biota)

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11
Q

How do acidic soils affect fertility?

A

Increase leaching of plant nutrients and damage root cell membranes

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12
Q

How do alkaline conditions affect the fertility of the soil?

A

Phosphates may become insoluble

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13
Q

What are some essential soil biota?

A

Detritivores, decomposers, nitrogen fixing bacteria, nitrifying bacteria and mycorrhizal fungi

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14
Q

What are some examples of detritivores?

A

Beetle larvae, millipedes, woodlice and slugs

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15
Q

What do detritivores do?

A

Break up dead organic matter and release nutrients into the soil

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16
Q

How do worms aid soil fertility?

A

They are detritivores that also increase soil drainage and aeration by creating tunnels in the soil

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17
Q

What are some decomposer examples?

A

Bacteria and fungi

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18
Q

What do decomposers do?

A

Hydrolyse dead organic matter

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19
Q

What’s the difference between decomposers and detritivores?

A

Decomposers secrete digestive enzymes and rely on detritivores to physically break up the DOM and increase it’s surface area

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20
Q

How does nitrogen-fixing bacteria aid soil fertility?

A

Converts gaseous nitrogen into ammonium ions

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21
Q

How does nitrifying bacteria aid soil fertility?

A

Oxidise ammonium ions to nitrite ions then to nitrate ions

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22
Q

How does mycorrhizal fungi aid soil fertility?

A

Form symbiotic relationships with plant roots and aid phosphate uptake by the plants

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23
Q

What are the three soil particles types?

A

Clay, Silt and Sand

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24
Q

What’s the smallest and largest soil particle?

A

Clay is the smallest, then silt and sand is the largest

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25
Q

Whats the standard ratio of soil texture in loam soils?

A

40:40:20 (clay)

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26
Q

How is soil texture determined?

A

The proportions of the different size categories of mineral particles present in the soils

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27
Q

What are some feature of sandy soils?

A

Large pore spaces, no capillary water, cannot adsorb nutrient ions easily, low thermal capacity (less water) so warm rapidly, root penetration easier, lack of adhesion

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28
Q

What are some features of clay soils?

A

Poorly drained, allows capillary rise of water, more likely be water logged with low aeration, nutrient ions adsorb easily, high thermal capacity, poor root penetration and high adhesion

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29
Q

What are peds?

A

Aggregates of soil particles

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30
Q

How are soil particles bound together?

A

Polysaccharide gums (produced by decomposition), fungal hyphae, roots, action of soil biota and hygroscopic clay particles

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31
Q

What are the two different types of peds?

A

Platy and crumb

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32
Q

What are the features of crumb peds?

A

Small and round

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33
Q

How do crumb peds improve soil fertility?

A

Produce good drainage, aeration and easy root penetration

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34
Q

What are the features of platy peds?

A

Large and flat

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35
Q

How do platy peds reduce soil fertility?

A

Reduce drainage, aeration and root penetration

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36
Q

How does soil depth affect soil fertility?

A

Deeper soils are less likely to become waterlogged or to dry out rapidly, they can also aid good root anchorage

37
Q

What human activities can affect soil fertility?

A

Ploughing, drainage, inorganic fertilisers, organic matter addition, irrigation, soil compaction

38
Q

How can farmers aerate soils?

A

Ploughing and drainage

39
Q

How does ploughing and drainage affect soil fertility?

A

Increases the rate of nitrogen fixation, nitrification and decomposition of dead organic matter

40
Q

How can farmers deplete soil nutrient levels?

A

Soil erosion, biomass removal, inhibiting natural processes

41
Q

How does irrigation help plants?

A

Increases water levels to keep stomata open and allow gas exchange and dissolves ions for the plant

42
Q

How do farmers contribute to soil compaction?

A

Excessive use of heavy machinery or high livestock densities

43
Q

How does soil compaction affect soil fertility?

A

Reduces aeration and makes waterlogging more likely

44
Q

How does pH control affect soil fertility?

A

Ensures nutrients are soluble but not too easily leached

45
Q

What is soil erosion?

A

The removal of soil particles by wind or water

46
Q

When are soils likely to be loose with little cohesion?

A

When they are dry or with low clay content

47
Q

How can soil deposition after erosion be a problem?

A

Cover crops or land in urban areas

48
Q

What are the three types of water erosion?

A

Rain splash erosion, surface runoff erosion and slumping and landslides

49
Q

What is rain splash erosion?

A

When soil particles are dislodged by the splash of a raindrop and dispersed in all directions

50
Q

What are the dangers of rain splash erosion?

A

Over time, it can cause downhill movement of large amount of soils

51
Q

What is surface runoff erosion?

A

Caused by the surface runoff when the soil infiltration capacity has been reached

52
Q

When does surface runoff erosion occur?

A

In times of heavy or prolonged rainfall or if the soil is relatively impermeable

53
Q

How do slumps and landslides occur?

A

When soil on slopes becomes wet the increased mass and lubrication of the water makes the movement of large amounts of soil more likely

54
Q

When do slumping and landslides occur?

A

Deep soil on steep slopes becomes less stable following deforestation

55
Q

How does vegetation reduce soil erosion rates?

A

Natural windbreak, cover from rain, organic matter binds soil together, roots hold soil together, increase infiltration capacity

56
Q

How does vegetation act as a natural windbreak reduce soil erosion?

A

Reduces wind velocity and therefore the kinetic energy to carry away soil particles

57
Q

What is humus?

A

The decaying organic matter within soil

58
Q

What human activities increase the rate of soil erosion?

A

Vegetation removal, ploughing vulnerable soils, overgrazing, reduced soil biota, soil compaction and cultivating steep slopes

59
Q

How does overgrazing contribute to soil erosion?

A

Removal of vegetation by livestock, increases the exposure of the soil and the risk of erosion, the disturbance and root damage by hooves increase the risk of erosion

60
Q

How can soil biota be reduced?

A

Ploughing, removing organic matter and agrochemical

61
Q

How do soil biota reduce soil erosion?

A

Break down organic matter to release nutrients for plant cover, humus produced creates adhesion and worms aerate the soil

62
Q

How does soil compaction occur?

A

Heavy machinery use, high livestock density and reduction in detritivores

63
Q

How does the cultivation of steeper slopes increase soil erosion rates?

A

The surface runoff flows more rapidly so it has more kinetic energy to pick up and carry soil particles

64
Q

What is accelerated soil erosion?

A

The natural equilibrium between formation and erosion is broken and the erosion rate is exceeding

65
Q

What are the effects of accelerated soil erosion?

A

Reduced productivity, sedimentation in rivers and reservoirs , increased atmospheric particulates and desertification

66
Q

How does soil erosion reduce productivity?

A

When erosion occurs it is often the most fertile topsoil that is lost, remaining soil is less fertile and the erosion may leave shallower soils which make root penetration more difficult

67
Q

How does soil erosion lead to sedimentation in rivers and reservoirs?

A

Soil particles carried into water are deposited if the water slows down and has less kinetic energy

68
Q

How does soil sedimentation negatively impact the river?

A

Reduces flow capacity so the river is more likely to overflow and cause flooding following heavy rain

69
Q

What health problems can an increase is atmospheric particulates cause?

A

Worsen problems such as asthma

70
Q

How does soil erosion contribute to desertification?

A

Important part of the combination of processes that cause the expansion of deserts, it makes it more difficult for vegetation to grow so more erosion occurs and less rainfall

71
Q

What are some methods of reducing soil erosion?

A

Long-term crops, zero-tillage cultivation, contour ploughing, tied ridging, terracing, row of stones, windbreaks, multi-cropping, increase soil organic matter and livestock management

72
Q

How does plantation of long-term crops reduce soil erosion?

A

Reduces soil disturbance

73
Q

What are some long-term crops?

A

Permanent grassland or bush and tree crops such as fruit, tea, coffee and cotton

74
Q

What is a method of zero-tillage cultivation?

A

Direct drilling of seeds rather than ploughing or sowing

75
Q

What is contour ploughing?

A

Ploughing at 90° rather than vertical on slopes

76
Q

How does contour ploughing reduce soil erosion?

A

Reduces velocity of surface runoff and therefore kinetic energy so the soil particles are less likely to be carried away

77
Q

What is tied ridging?

A

Used on land that is almost flat, the field is divided with a criss-cross of intersecting ridges

78
Q

How does tied ridging reduce soil erosion?

A

The ridges retain water when it rains, increasing infiltration and decreasing runoff

79
Q

What is terracing?

A

Creation of narrow fields with the soil held in place by retaining walls built along the contours on sloping land

80
Q

How does terracing reduce soil erosion?

A

Water flowing over the walls flows quickly, but it slows down as it flows across the fields, much of the water infiltrates the soil

81
Q

How do rows of stones reduce the soil erosion?

A

Can slow runoff and reduce the erosion rate, any disturbed soil is deposited behind the stone rows

82
Q

What are some examples of windbreaks?

A

Hedgerows or rows of trees

83
Q

When are windbreaks needed?

A

When the crops are removed for harvest and the soil is exposed

84
Q

How effective are hedgerows at reducing soil erosion?

A

Reduce wind velocity for a distance up to 30 times its height

85
Q

How does multi-cropping reduce soil erosion?

A

Reduce exposure to wind erosion if they are harvested an re-sown at different times

86
Q

When does multi-cropping work easiest?

A

When the farming uses human labour rather than machinery as machinery uses ‘strip cropping’ which is most effective at 90°

87
Q

How does mulch reduce soil erosion?

A

Protects the soil from wind ad the impact of rain drops

88
Q

What is the USLE?

A

Universal Soil Loss Equation

89
Q

What factors determine the rate of soil erosion?

A

Rainfall erosivity factor, Soil erodibility factor, Slope length, Slope gradient, Cropping management and Erosion control

Environmental Science (22 decks)

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