Nitrogen cycle in soil

Statement 1 is correct - urea excretion by animals adds nitrogen to soil through animal waste, which breaks down and contributes nitrogen compounds to soil. Statement 2 is incorrect - burning of coal by man releases nitrogen oxides into the atmosphere but does not directly add nitrogen to soil; it may cause acid rain instead. Statement 3 is correct - death of vegetation adds organic matter containing nitrogen to soil; as dead plant material decomposes, nitrogen is returned to the soil. Therefore, statements 1 and 3 are correct. > Animal urea and dead plants both return nitrogen to soil. Coal burning releases NOx to air, not to soil. Answer: (c).