Which of the following adds/add nitrogen to the soil? 1. Excretion o

Which of the following adds/add nitrogen to the soil?

  • 1. Excretion of urea by animals
  • 2. Burning of coal by man
  • 3. Death of vegetation

Select the correct answer using the codes given below.

1 only
2 only
1 and 3 only
1, 2 and 3
This question was previously asked in
UPSC IAS – 2013
Statements 1, 2, and 3 all describe processes that add nitrogen to the soil.
1. Excretion of urea by animals: Urea is a nitrogen-rich organic compound. When animals excrete urea onto the soil, decomposers convert it into inorganic forms like ammonium, which plants can absorb. This is a direct addition of nitrogen to the soil through the nitrogen cycle.
2. Burning of coal by man: Combustion of fossil fuels like coal releases nitrogen oxides (NOx) into the atmosphere. These atmospheric nitrogen compounds can be deposited onto the soil through dry deposition (particles) or wet deposition (acid rain). This process, known as atmospheric nitrogen deposition, adds nitrogen to ecosystems, including soil.
3. Death of vegetation: When plants and other organisms die, their organic matter is decomposed by microorganisms in the soil. This process, called mineralization, breaks down organic nitrogen compounds into inorganic forms (like ammonium), making nitrogen available in the soil for uptake by plants. This is a crucial part of the nitrogen cycle.
Nitrogen is a vital nutrient for plant growth. Nitrogen is added to the soil through various natural processes (like biological nitrogen fixation, atmospheric deposition, decomposition) and human activities (like application of fertilizers, burning fossil fuels leading to deposition). While decomposition and biological fixation are primary natural inputs, anthropogenic activities have significantly altered the global nitrogen cycle, increasing deposition rates in many areas.