Identify in the spaces provided the missing flows and storages labelled 1–4 within the diagram.

Overgrazing may lead to soil degradation. Identify one impact that overgrazing may have on a named flow and a named storage within the nitrogen cycle.

(i) Impact on flow:

(ii) Impact on storage:

Identify two ways in which humans can restore soils degraded by overgrazing

Explain how the use of non-biodegradable pesticides on farmland may affect the human food chain.

For 3 - do not accept lightning or the Haber process.
Award [1] for two or three correct responses and [2] for four correct responses.

[2 max]

Impact on flow: [1 max]
less plants available for feeding;
reduce of flow into dead organic matter;
Do not accept ‘plants absorb less nitrogen’.

Impact on storage: [1 max]
less nitrogen stored within plants;
less nitrogen within dead organic matter /soil;
less nitrogen within animal store;
more nitrogen in the atmosphere;

[2 max]

addition of fertilizers/soil conditioners;
planting leguminous plants (e.g. clover);
wind reduction techniques/wind breaks/shelter belts/strip cultivation/crop rotation;
cultivation techniques/terracing/contour ploughing;
forestation/re-afforestion;
agroforestry/forest farming;

Do not credit ‘leave land fallow/empty of animals’ or only ‘plant grass’.
Accept any other reasonable response.

[2 max]

movement of non-biodegradable material in food chain;
potential to biomagnify;
potential to bio-accumulate/bio-concentrate;

Accept any other reasonable response.

[2 max]

Few candidates achieved both marks for this question. Most achieved either 0 or 1 mark with a number of students not attempting the question. Popular correct responses included (1) consumers and (4) decomposition and few were able to correctly identify (2) as nitrates/nitrites or (3) as nitrogen fixation.

Many candidates struggled with these two questions. For b(i) responses often focused on nitrogen store instead of impact on flow and for b(ii) often stated ‘an increase in nitrogen within soils’ instead of the converse or ‘nitrogen in plants’ which was too vague.

The majority of candidates gained some marks for this question.

Most candidates performed well on this question with many achieving full marks.