Calcium carbonate reduces soil acidity primarily by reacting with and neutralizing the hydrogen ions present in the soil solution.
When calcium carbonate (CaCO₃) is added to wet acidic soil, it undergoes a series of chemical reactions that consume the hydrogen ions (H⁺), which are the main contributors to acidity.
The Chemical Process of Acidity Reduction
According to the provided information, the process unfolds in distinct steps:
- Ionization: In wet acidic soil, calcium carbonate ionises (separates) into calcium and carbonate ions. Calcium (Ca²⁺) is released into the soil, while the carbonate ions (CO₃²⁻) become available to react with acidic components.
- First Reaction: The carbonate ions (CO₃²⁻) are key to neutralizing acidity. The carbonate ions react with hydrogen ions in the soil solution to form bicarbonate ions. This step directly removes hydrogen ions from the soil water.
- Second Reaction: The bicarbonate ions (HCO₃⁻) formed in the previous step continue the neutralization process. The bicarbonate ions react with hydrogen ions in the soil solution to form carbon dioxide and water. This step further consumes hydrogen ions, producing inert substances (CO₂ and H₂O) that do not contribute to acidity.
These reactions effectively lower the concentration of hydrogen ions in the soil solution, thereby increasing the pH and reducing the acidity. Calcium carbonate is a common and effective liming material used in agriculture to improve soil conditions for plant growth in acidic environments.
