Soil Organic Carbon (SOC) Decline Due to Unscientific Fertiliser Use and Climate Change

Soil Organic Carbon (SOC) Latest News

• A six-year-long comprehensive study (2017–2023) by the Indian Council of Agricultural Research (ICAR), and coordinated by the Indian Institute of Soil Science (IISS), Bhopal, has highlighted serious degradation of soil organic carbon (SOC) in India’s arable lands. 
• The study, covering 254,236 soil samples from 620 districts across 29 States, was published in the international journal Land Degradation & Development.

Key Findings of the ICAR Study

• Soil organic carbon (SOC) and soil health:
  • SOC is the foundation of soil chemistry, physics, and biology, influencing fertility and productivity.
  • The study establishes that low organic carbon leads to higher micronutrient deficiency, while higher SOC improves soil quality.
  • Imbalanced fertiliser use and climate change are major causes of SOC depletion.
• Influence of climate and geography (Elevation and temperature):
  • SOC is positively correlated with elevation — higher altitudes (hill regions) show higher organic carbon.
  • SOC is negatively correlated with temperature — hotter regions like Rajasthan and Telangana show lower SOC levels.
  • Rainfall, temperature, and elevation are the three primary natural determinants of SOC concentration.
• Cropping patterns and fertiliser use:
  • Role of cropping systems: Rice-based and pulse-based systems retain higher SOC due to microbial activity enhanced by irrigation. Wheat and coarse-grain systems show lower SOC accumulation.
  • Fertiliser practices: Imbalanced use of urea and phosphorus, especially in Haryana, Punjab, and Western UP, has degraded SOC. States like Bihar, where balanced fertiliser application is practiced, maintain relatively healthier soil carbon levels.
• Development of agri-ecological base map:
  • Scientists developed an agro-ecological base map covering 20 agro-ecological regions to assess SOC variations.
  • The map can guide policy decisions related to land degradation assessment, carbon credit, and sustainable agriculture planning.

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Impact of Climate Change on SOC

• SOC shows a strong negative correlation with rising temperatures, while rainfall variations have minimal impact.
• Declining SOC reduces soil heat absorption and increases surface heat reflection, aggravating greenhouse gas effects.
• Hence, SOC degradation directly links to climate change acceleration and carbon cycle imbalance.

Policy Implications and Recommendations

• Promoting organic carbon sequestration: Identify soils with SOC less than 0.25% and promote organic carbon enrichment through improved cropping systems and irrigation facilities.
• Incentivising carbon credit mechanisms: Introduce carbon credit schemes to reward farmers who sequester higher carbon through sustainable practices.
• Expanding vegetative cover: Encourage perennial plantations and cover crops to maintain soil organic matter and prevent degradation.
• Climate-smart crop management: Develop region-specific crop management practices to mitigate temperature effects and enhance SOC resilience.

Way Forward

• Shift towards balanced fertiliser application, incorporating organic manures and bio-fertilisers.
• Promote integrated nutrient management (INM) and climate-resilient agriculture under national missions like the National Mission for Sustainable Agriculture (NMSA).
• Enhance soil health monitoring through digital soil maps and farmer awareness campaigns.

Conclusion

• The ICAR study serves as a scientific wake-up call for India’s agricultural policy. 
• It establishes that unsustainable fertiliser use and rising temperatures are critically eroding soil organic carbon, the lifeline of soil fertility and climate stability.
• Addressing this requires integrated soil-carbon management, carbon credit incentives, and climate-resilient farming systems — essential for achieving India’s goals of sustainable agriculture and carbon neutrality.

Source: TH