IB ESS SL 5.1 Soil Question Bank

State the soil texture that has the following composition: 20 % clay; 55 % silt; 25 % sand.
silt loam;
NB if candidate names more than one soil type, examiners should only assess the first one listed (even if the first is wrong and a later one is correct).

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 increase 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;

Marking guidance:

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.

roots no longer hold soil in place/stabilize soil; soil surface uncovered/more exposed to wind/water erosion;
uninterrupted rainfall/percolation will increase leaching of minerals; greater evaporation may lead to salinization; reduction/change in soil fauna/microbes;
lack of veg cover may lead to greater evaporation/drying out of soil;

Marking guidance:

Award [1] for each correct answer, up to [2 max].