What can be the impact of excessive/inappropriate use of nitrogenous fertilisers in agriculture?

1. Proliferation of nitrogen-fixing microorganisms in soil can occur.
2. Increase in the acidity of soil can take place.
3. Leaching of nitrate to the ground-water can occur.

Select the correct answer using the code given below:

1. 1 and 3 only
2. 2 only
3. 2 and 3 only
4. 1, 2 and 3

Explanation

Impact 1 is incorrect

• Excessive use of nitrogenous fertilisers (like urea) reduces the need for biological nitrogen fixation. As a result, the activity and population of nitrogen-fixing microorganisms (e.g., Rhizobium) may decline, not proliferate.

Impacts 2 and 3 are correct

• Nitrogenous fertilisers can release acidic compounds as they break down in the soil, leading to increased soil acidity.
• Nitrates are highly soluble and can easily leach into groundwater, leading to contamination and problems such as eutrophication and health hazards.

Answer: (c) 2 and 3 only; Difficulty Level: Medium