Environmental Science and Sustainable Agriculture
Environmental Science and Sustainable Agriculture
This domain tests ecosystem processes, pollution, climate change, greenhouse gases, soil degradation and farming practices that sustain productivity without depleting resources.
Core rules and concepts
- Ecosystems cycle carbon, nitrogen, phosphorus and water. Decomposition, nitrification and denitrification are microbial processes in the nitrogen cycle.
- Greenhouse gases include CO2, methane (CH4) and nitrous oxide (N2O). Global warming potential converts them to CO2-equivalent (CO2e).
- Eutrophication follows excess nitrogen and phosphorus in water; soil erosion, salinity and waterlogging degrade farmland.
- Sustainable practices include crop rotation, organic matter addition, conservation tillage, integrated pest management, efficient irrigation and agro-biodiversity.
- Organic farming avoids synthetic inputs but still requires nutrient balance and pest management; it is not automatically higher-yielding.
Worked example
Using a 100-year global warming potential of 298 for N2O, 2 kg N2O equals 2 × 298 = 596 kg CO2e. Reason: CO2e expresses the climate impact of different gases on a common scale. If a newer assessment factor such as 273 is specified, the answer changes, so the factor used must be stated.
Traps that cost marks
Treating CO2e as the same as CO2; ignoring methane from livestock and flooded rice; assuming organic produce is always environmentally superior; confusing eutrophication with salinisation; forgetting that conservation tillage may require different weed management.