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. Statement 1 is correct. Animals excrete nitrogenous waste, primarily as urea (in mammals) or uric acid. When deposited on soil, microorganisms decompose these compounds, releasing nitrogen (initially as ammonia) which can then be converted into forms usable by plants, thus adding nitrogen to the soil. 2. Statement 2 is incorrect. The burning of coal releases nitrogen oxides (NOx) into the atmosphere, contributing to air pollution and acid rain. While acid rain can deposit atmospheric nitrogen onto the soil, the act of burning coal itself is not considered a direct process of adding usable nitrogen to the soil for fertility purposes; it is primarily an atmospheric emission source. 3. Statement 3 is correct. Vegetation contains organic nitrogen in proteins, nucleic acids, etc. Upon the death of vegetation, decomposition by microorganisms (bacteria and fungi) breaks down the organic matter. This process, called mineralization, releases inorganic nitrogen compounds (like ammonium) into the soil, making nitrogen available for uptake by living plants. 4. Therefore, the excretion of urea by animals and the death of vegetation are processes that add nitrogen to the soil.