IB ESS HL 5.1 Soil Questions

Practise IB ESS HL 5.1 by tracing soil-system flows, classifying soil texture and using property evidence to explain productivity and fertility.

Exam points

Explain soil as an open ecosystem using storages, flows, biotic and abiotic components, and their interactions.
Build flow diagrams linking soil to the atmosphere, lithosphere and organisms; trace matter through water, carbon or nitrogen cycles.
Distinguish soil inputs/outputs from transfers/transformations using weathering, decomposition, leaching and plant uptake.
Classify soil texture from sand, silt and clay proportions; compare sandy, clay and loam effects on plant productivity.
Use nutrient, organic-matter, pH, texture and organism evidence to explain soil fertility and primary productivity.
Explain how over-irrigation changes fertility through salinization, nutrient loss, waterlogging and reduced nutrient cycling.

Covered syllabus points

5.1.1—Soil as dynamic system 5.1.2—Soil composition 5.1.3—Soil profiles and horizons 5.1.4—Soil system inputs 5.1.5—Soil system outputs 5.1.6—Soil transfers 5.1.7—Soil transformations 5.1.8—Soil flow diagrams 5.1.9—Soil foundation role 5.1.10—Soil and biodiversity 5.1.11—Soil in element recycling 5.1.12—Soil texture 5.1.13—Texture affects productivity 5.1.14—Soil carbon role 5.1.15 (HL)—Soil classification 5.1.16 (HL)—Soil horizons 5.1.17 (HL)—A horizon (topsoil)5.1.18 (HL)—Soil formation factors 5.1.19 (HL)—Sand, silt, clay differences 5.1.20 (HL)—Soil property analysis 5.1.21 (HL)—Carbon release from soils

[Maximum number: 4]

Outline how soil can be viewed as an ecosystem.

Like an ecosystem, soil is an open system with inputs and outputs;
(inputs of) eg water / $\mathrm{O}_{2}$ (and outputs of) eg $\mathrm{CO}_{2}$ / nitrogen; ...and storages and flows/processes;
(storages of) eg nitrates/water (and flows of) eg leaching/decomposition;
like an ecosystem, soil is a community of living/biotic and abiotic elements;
(biotic) eg bacteria/fungi/earthworms (and abiotic) eg clay/sand/silt/water/heat; ...with the many complex interactions/interrelationships/eg mineral cycling/leguminous plants;
interacts with/supports other systems/eg vegetation growth, animal movement/burrowing/human development;

Award marks as above for identifying relevant common features, and also for giving examples (provided it is clear what is being exemplified).

[Maximum number: 1]

Explain how the production of cash crops (such as pineapples) may have an environmental impact on:

soil

[Maximum number: 9]

Soil quality is important for global food production systems.

(a)

Figure:Soil texture triangle

[ 1 ]

(b)

Describe how the addition of sand to a silty clay loam could alter its characteristics for healthy plant growth.

[ 2 ]

Positive effects:
it will increase drainage / prevent water-logging;
it will increase infiltration/permeability / reduce loss of water through run-off;
it will increase porosity/air spaces/reduce soil compaction providing more $\mathrm{O}_{2}$ to roots;
it would allow for increased flow/availability of nutrients;
it will promote detritivore/decomposer/mycorrhizal/microbial communities;
it will allow for easier root penetration;
Negative effects:
it will reduce water-holding capacity so less water for plants;
it will increase possibility of leaching, reducing minerals for plants;
it will reduce stability of soil giving less anchorage to plants;

Award [1] for each correct answer, up to [2 max].
Although question implies positive effects on soil, credit can be given for negative effects as long as candidates make this clear as in MPs given above.

(c)

Figure:Horizons in a typical soil profile

[ 4 ]

(i)

Draw a flow diagram to show the flows of leaching and decomposition associated with the mineral storage in the "A" horizon in the soil-profile diagram shown above.

[ 2 ]

(ii)

Identify one other input to the mineral storage in the "A" horizon.

[ 1 ]

(iii)

Identify one other output from the mineral storage in the "A" horizon.

[ 1 ]

(d)

Outline why leaving arable farmland fallow (unused) between growing seasons could lead to soil degradation.

[ 2 ]

All question bank results loaded

Covered syllabus points

Question 1

Question 2

Question 3

Question (a)

Question (b)

Question (c)

Question (i)

Question (ii)

Question (iii)

Question (d)