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Agronomy QUESTION #2107
Question 1
Soil organic carbon (SOC) sequestration through agricultural management contributes to climate change mitigation because:
  • SOC increases soil pH, which directly reduces methane emissions from paddy soils
  • Increasing SOC stocks through reduced tillage, organic amendments, cover crops, and biochar additions removes CO₂ from the atmosphere and stores it in stable soil organic matter pools — partially offsetting agricultural GHG emissions while also improving soil health and productivity✔️
  • SOC sequestration is exclusively achieved through afforestation and has no relevance to cropland management
  • Higher SOC concentrations accelerate denitrification, converting harmful \(NO_3^-\) to inert \(N_2\)
Correct Answer Explanation
Agricultural soils have lost 50–70% of their original SOC through tillage, erosion, and oxidation. Conservation tillage, organic matter additions, cover cropping, and biochar can rebuild SOC stocks. Each 1% increase in SOC in the top 30 cm represents ~25 t CO₂-equivalent per hectare sequestered. The '4 per 1000' initiative proposes 0.4% annual SOC increase globally to offset anthropogenic CO₂ emissions — highlighting cropland SOC management as a climate mitigation strategy.