How does the imbalance in fertiliser use affect the organic carbon content of soil, and what could be the long-term impact on agriculture?

Imbalance in fertiliser use, especially excessive use of chemical fertilisers and neglect of organic inputs, has a significant impact on the organic carbon content of soil. Soil organic carbon is crucial for maintaining soil fertility, structure, and overall productivity. The decline in soil organic carbon, as highlighted by ICAR studies, is a growing concern for agricultural sustainability in India.

• Reduced Addition of Organic Matter: Over-reliance on chemical fertilisers often leads to reduced use of organic manure, crop residues, and green manures. This lowers the return of organic matter to the soil, resulting in decreased soil organic carbon levels.
• Accelerated Decomposition: Imbalanced fertiliser use can disturb soil microbial activity, sometimes accelerating the decomposition of existing organic matter, which further reduces organic carbon in the soil.
• Soil Structure Degradation: Lack of organic inputs affects the soil’s physical properties, such as aggregation and porosity, making it more prone to erosion and compaction, which in turn hampers organic carbon retention.
• Nutrient Imbalance: Excessive use of nitrogenous fertilisers without adequate phosphorus, potassium, or micronutrients can disrupt soil nutrient cycles, indirectly affecting the buildup and stability of soil organic carbon.
• Impact of Climate Change: Rising temperatures and erratic rainfall patterns, linked to climate change, can further accelerate the loss of soil organic carbon, especially when the soil is already depleted due to poor fertiliser management.

Long-term Impact on Agriculture:

• Declining Soil Fertility: Reduced soil organic carbon lowers the soil’s ability to retain nutrients and water, leading to decreased crop yields over time.
• Increased Input Dependency: Farmers may need to use more chemical fertilisers to maintain yields, raising costs and further degrading soil health.
• Loss of Soil Biodiversity: Low organic carbon harms beneficial soil organisms, affecting nutrient cycling and plant health.
• Reduced Climate Resilience: Soils with low organic carbon are less able to buffer the impacts of drought and floods, making agriculture more vulnerable to climate change.
• Sustainability Threat: Continued decline in soil organic carbon threatens the long-term sustainability and productivity of Indian agriculture.