The nitrogen cycle

2. Agriculture uses these to increase nitrogen levels in soil.
7. Uncultivated land along rivers.
8. This is what happens to the soil when fields are drained.
10. The industrial process for producing ammonia from nitrogen and hydrogen.
14. These reduce soil disturbance during farming.
15. NOx increases the amount of these washed into soil by rain.
16. These are released when biological wastes decompose.

1. A system that uses low-temperature manufacturing processes.
3. Manufactured in the Haber process.
4. This produces organic fertilisers.
5. A way that NOx releases can be reduced.
6. Made from manure, sewage and food production wastes.
9. Minimal use of nitrate fertiliser prevents this happening to aquifers.
11. Reducing these helps combustion processes to be controlled.
12. Soil disturbance increases this.
13. One way the use of nitrate fertilisers impacts on the nitrogen cycle, increasing nitrites and nitrates in water bodies.