UPSC Prelims 2015 Question:

What can be the impact of excessive/inappropriate use of nitrogenous fertilizers 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 groundwater can occur.
   
   

Select the correct answer using the codes given below.

Explanation:

• Proliferation of nitrogen-fixing microorganisms in soil doesn't have any direct relationship with Nitrogenous Fertilizers. Also, as the plants are provided the required nitrogen by such fertilizers, there is hardly any requirement of the symbiotic relationship with the plant for nitrogen fixation. In such conditions, it is difficult for the nitrogen fixers to survive without symbiosis, thus, the microorganisms would not further proliferate in the soils.  So, statement 1 is not correct.
  
  
• The use of fertilizers, particularly those containing nitrogen, has frequently been blamed for soil acidity. Acidity is produced in the soil when ammonium-containing materials are converted to nitrate. The soil becomes more acidic as more ammoniacal nitrogen fertilizer is applied. So, statement 2 is correct.
  
  
• Once nitrogen fertilizers are applied to agricultural systems, the fertilizers are absorbed directly by plants or converted into various other forms through the oxidation process. Excess nitrogen is lost in ionic or gaseous form through leaching, volatilization, and denitrification. If nitrate is not absorbed by plant roots, it is carried away by runoff or leaches into the soil along with water. So, statement 3 is correct.
  
  

Therefore, option (3) is the correct answer.

Subject: Geography| Agriculture and Allied Sectors(geo)