Environmental Science and Sustainable Agriculture
Environmental Science and Sustainable Agriculture
This domain tests pollution, natural resource conservation, organic farming, integrated nutrient management and climate-smart practices. Questions often ask for the environmental reason behind a farm practice.
Core rules
- Sustainable agriculture aims at stable productivity while protecting soil, water and biodiversity. Practices include crop rotation, cover crops, mulching, reduced tillage, integrated nutrient management and integrated pest management.
- Eutrophication is nutrient enrichment of water, especially by nitrogen and phosphorus, causing algal growth and oxygen depletion. Greenhouse gases from agriculture include methane from flooded rice and ruminants, and nitrous oxide from nitrogen fertilizers.
- Organic manure improves soil organic matter and structure but releases nutrients slowly. Compost should be mature; a high C:N ratio can temporarily tie up nitrogen.
- Soil erosion is reduced by vegetative cover, contour barriers, terracing and avoiding excessive tillage.
Worked example
Ten tonnes of farmyard manure contains 0.5% N. Total N applied = 10,000 kg x 0.005 = 50 kg N. If 30% is available in the first season, available N = 15 kg. Urea equivalent = 15/0.46 = 32.6 kg urea. The reasoning shows that fresh manure is not equivalent to its total nutrient content because mineralization is gradual.
Traps
Organic does not mean nutrient-free or automatically higher-yielding. Do not ignore slow nutrient release from manure. Eutrophication is caused by nutrient enrichment, not only by pesticides. Methane is not the same as nitrous oxide. Mulching conserves moisture but may affect soil temperature.