The correct option is (a).
Explanation
Plants require a specific pH range for optimal growth. Soil that is either too acidic or too basic hinders nutrient absorption. The process of adjusting soil pH involves neutralization, where basic substances are added to acidic soils and acidic (or acid-releasing) substances are added to basic soils.
Statement-wise Analysis:
- Statement 1 is Correct: The excessive use of chemical fertilizers, particularly nitrogenous fertilizers like ammonium sulphate, leads to the accumulation of acids in the soil. This lowers the soil pH, making it acidic and unsuitable for many crops.
- Statement 2 is Incorrect: Quick lime (Calcium Oxide) and slaked lime (Calcium Hydroxide) are bases. They are used to treat acidic soil by neutralizing the excess acid. They are not used for basic soil, as adding a base to an already basic medium would increase alkalinity.
- Statement 3 is Incorrect: Organic matter (such as compost or manure) releases acids upon decomposition. Therefore, it is used to treat basic soil. The acids released by the organic matter neutralize the basic nature of the soil.
Key Takeaway:
Bases (like quick lime) are used to neutralize acidic soil, while organic matter (which releases acids) is used to neutralize basic soil.