Soil Organic Carbon (SOC)
Context:
A detailed study by the Indian Council of Agricultural Research (ICAR) has found that climate change and the unscientific use of fertilizers are contributing to the degradation of organic carbon in the country's arable areas.
The six-year study used 2,54,236 soil samples from 620 districts across 29 States.
The research highlights that organic carbon is crucial as it covers all aspects of the physics, chemistry, and biology of soil.
What is Soil Organic Carbon (SOC)?
SOC is the main component of soil organic matter (SOM) and is considered a primary indicator of soil quality and health.
SOC comprises carbon derived from plants and animals remains at different stages of decomposition, as well as microbial biomass.
It contains roughly 55-60% carbon by mass.
The soil is a major C reservoir, holding more carbon than the atmosphere and all terrestrial vegetation combined.
SOC directly affects:
Nutrient cycling (especially N, P, and S)
Water-holding capacity
Soil structure and aggregation
Resistance to erosion and degradation
Functions of SOC:
It provides nutrients and habitat for soil organisms.
The decomposition process releases nutrients in the soil.
The ICAR study found that if organic carbon is low, the deficiency of micronutrients is high.
It binds soil particles into aggregates
It improves the soil's physical environment
It also enhances water-holding capacity and aggregate stability.
Improvements in soil health from SOC increase the soil's resilience against intensive practices and extreme climatic events (like drought and heatwaves)
Increasing the quantity of SOC stored in soil is an option for decreasing atmospheric carbon dioxide.
Factors Affecting SOC Levels
Natural Factors:
Temperature:
Organic soil carbon is negatively correlated with temperature.
Regions with very high temperatures (like Rajasthan and Telangana) have low organic carbon content.
Elevation:
Organic carbon is highly correlated with elevation
If the elevation is high, the organic carbon content is high.
Agricultural Practices:
Imbalanced Fertilizers:
The ICAR study found that wherever imbalanced fertilizer application occurred, the organic carbon declined.
This was noted in Haryana, Punjab, and western Uttar Pradesh (here application is skewed towards urea and phosphorus)
Tillage:
Tillage enhances the decomposition rate of organic matter.
This is leading to its reduction.
Burning:
The burning of natural vegetation and crop residues is a common practice for clearing land that degrades SOC.
Monoculture:
Replacing mixed vegetation with the monoculture of crops often leads to rapid mineralization of organic matter.