| Date | November 2019 | Marks available | 2 | Reference code | 19N.2.SL.TZ0.1 |
| Level | Standard Level | Paper | Paper 2 | Time zone | Time zone 0 |
| Command term | Describe | Question number | 1 | Adapted from | N/A |
Question
Figure 1: A typical soil profile
[Source: adapted from WilsonBiggs/Hridith Sudev Nambiar/Wikimedia. File licensed under CC BY-SA 4.0;
https://creativecommons.org/licenses/by-sa/4.0/]
State one transfer of matter occurring within the soil profile.
State one transformation process occurring within the soil profile.
Identify one example of an output to the atmosphere from the soil system.
Describe two characteristics of soil with high primary productivity.
Outline two conservation methods that could be used to reduce soil erosion.
Markscheme
biological mixing by soil animals/earthworms / leaching / seepage / capillary action / drainage / percolation / infiltration / eluviation / absorption of minerals/water by living organisms.
Do not accept INPUTS of matter eg precipitation, leaf litter, parent material, particle deposition or OUTPUTS of matter eg erosion; or TRANSFORMATIONS of matter eg evaporation/weathering.
decomposition;
humus formation/humification of organic matter;
weathering of primary minerals/parent rock;
nutrient cycling/nitrogen fixation/nitrification/denitrification/ammonification;
evaporation;
rusting soil.
Do not accept inputs, outputs or transfers of matter or transformations that do not occur within the soil profile.
Nitrogen (from denitrification) / water (vapour from evaporation) / heat (from radiation/conduction) / soil particles/erosion (from wind) / CO2 (from soil organism respiration) / methane (from anaerobic decomposition).
Do not credit the processes in brackets ... these may give rise to the outputs but are not themselves an output from the soil.
optimum/medium particle size / loam soils / mixed/balanced composition of sand/silt/clay;
allow good drainage/permeability/resist water-logging;
prevent excessive leaching/good water-holding capacity;
provide sufficient air space/porosity for root growth/O2 supply;
contain ample dead organic matter/humus (for decomposers);
healthy/abundant decomposing community/soil organisms;
high availability of minerals/inorganic nutrients;
appropriate pH (6.0–6.8).
Cultivation techniques:
contour ploughing with furrows following the contour lines/at right angles to the slope/to reduce runoff;
terrace farming forms a series of steps in the hillside area/to prevent run-off;
maintaining cover crops/plant roots/stubble/mixed agriculture/agroforestry to hold soil in place between harvesting;
mulching consists of applying organic material over the exposed soil / preventing surface runoff;
buffer strips/vegetative areas by watercourses to reduce run-off/water erosion;
adding soil conditioners/lime/humus/organic material/fertilizers to increase root growth/hold soil together;
wind reduction techniques, eg wind/shelter breaks to prevent wind erosion;
avoid overgrazing/over-cropping/monoculture which degrades soil texture;
zero/minimum tillage reduces soil agitation/potential for erosion;
trickle/drip irrigation reduces run-off causing erosion.
Note: As an ‘outline’ Q, response requires just a little more than just naming a technique eg ‘terrace farming involves creating steps on a hillside’ or ‘terrace farming prevents run-off’ are acceptable ...but ‘terrace farming’ alone is insufficient.
