Environmental Science: Farm Emissions, Erosion and Carbon Accounting
Farm–environment interactions
Flooded paddy soil is anaerobic and emits methane; fertilized soils release nitrous oxide; residue burning releases particulates and carbon dioxide. Assam's specific pressures are Brahmaputra bank erosion and flooding, hill deforestation, shifting cultivation, loss of beels and human–wildlife conflict around protected areas.
Concepts to hold firmly
- Global warming potential (100-year): CH4 ≈ 28, N2O ≈ 265 times CO2.
- Carbon sequestration through soil organic matter, agroforestry and reduced tillage.
- Erosion types: sheet, rill, gully; the universal soil loss equation combines rainfall, soil, slope, cover and management factors.
- Waste hierarchy: reduce, reuse, recycle.
- Environmental impact assessment precedes large projects.
Worked example
Carbon stock of the 0–30 cm layer, bulk density 1.3 g/cm³, soil organic carbon 0.6 per cent. Soil mass/ha = 10,000 m² × 0.30 m × 1,300 kg/m³ = 3.9 × 10^6 kg. Carbon = 0.006 × 3.9 × 10^6 = 23,400 kg ≈ 23.4 t C/ha. Raising SOC to 0.8 per cent stores about 31.2 t C/ha - roughly 8 t more carbon per hectare. That is why organic matter management is a climate tool, not just a fertility practice.
Traps that cost marks
- Naming CO2 as the main greenhouse gas of flooded rice - it is methane.
- Multiplying SOC percentage by soil volume instead of soil mass.
- Treating compost application and residue burning as equivalent practices.
- Confusing sheet erosion with gully erosion.