State the soil texture that has the following composition: 20 % clay; 55 % silt; 25 % sand.

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

Draw a flow diagram to show the flows of leaching and decomposition associated with the mineral storage in the “A” horizon in Figure 2(b).

Identify one other input to the mineral storage in the “A” horizon in Figure 2(b).

Identify one other output from the mineral storage in the “A” horizon in Figure 2(b).

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

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 O₂ 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.

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.

Award [1] for each correctly labelled flow with arrows in the right direction.

leaching/mineral flow/eluviation through from O horizon;
nitrogen fixation (ie of N diffusing in from atmosphere);
addition of inorganic/nitrate/phosphate fertilizer;
capillary flow up from B horizon;

Do not credit use of simply “fertilizers” or organic fertilizer/compost etc as this would be an input from decomposition. Do not credit “water” as an input.

uptake of minerals by plants;
soil erosion;
denitrification;
human activities of mining/soil extraction;
immobilization/microbial conversion of inorganic to organic.

Do not credit cropping/deforestation (as in themselves they are a loss of biomass, not mineral storage). Do not credit drainage/percolation (synonymous with leaching).
Award [1] for correct answer, up to [1 max].

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.

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

A great majority could apply the soil texture triangle to identify a soil type.

Majority of candidates could identify at least one relevant impact of adding sand …incorrect responses were generally due to being too vague e.g. “make it better for plant growth/more like loam”.

Majority of candidates produced very confused, erroneous or ambiguous responses. All the question required was one storage/box labelled “minerals in A horizon” and two flows/arrows labelled respectively “leaching” and “decomposition” connecting to that box. Whereas, responses included sketches of soil profiles, unattached/unlabelled arrows, paragraphs of text, sequences of soil activities etc.

Again, probably due to candidate’s ambiguous perception of the storage identified, this question produced mostly invalid responses.

A good proportion of candidates were able to score at least one of the available marks but often responses were too vague e.g. identifying “soil erosion” “loss of nutrients” but not outlining “why” these were connected to disuse.