Which of the following adds/add nitrogen to the soil?<br/>1. Excretion of urea by animals<br/>2. Burning of coal by man<br/>3. Death of vegetation<br/><br/>Select the correct answer using the codes given below:

1. Excretion of urea by animals — Correct. Urea is a nitrogenous compound; after decomposition in soil, it is converted into ammonia/nitrates and adds nitrogen.

2. Burning of coal by man — Incorrect. Burning coal mainly releases nitrogen oxides to the atmosphere as pollutants; this is not treated as a normal process of adding nitrogen to soil in such questions.

3. Death of vegetation — Correct. Dead plant matter decomposes and returns organic nitrogen to the soil.

Therefore, statements 1 and 3 only are correct.