Consider the following statements: I. Agricultural soils release nitrogen oxides into environment. II. Cattle release ammonia into environment. III. Poultry industry releases reactive nitrogen compounds into environment. Which of the statements given above is/are correct?

All three statements are correct, so the answer is D. The core concept is reactive nitrogen (Nr), meaning nitrogen in forms other than inert N2, such as NOx, NH3, N2O and nitrates. Human activity has roughly doubled the flow of Nr into the biosphere, mainly because of the Haber-Bosch process for fertiliser.

• Statement 1 is correct. Soils emit NOx (and N2O) through nitrification and denitrification of nitrogen from fertilisers, manure and crop residues. Nitrogen fertiliser use is the biggest driver.
• Statement 2 is correct. Cattle excrete urea in urine and nitrogen compounds in dung. Urea breaks down into ammonia, so livestock is a major source of NH3, especially in intensive dairy and feedlot systems.
• Statement 3 is correct. Poultry litter is rich in uric acid and nitrogen, which volatilises as ammonia. Large poultry operations are a notable point source of reactive nitrogen.

Mains angle: this links to GS-3 environment (nitrogen cycle, air pollution, eutrophication, particulate matter formation) and to fertiliser policy, including neem-coated urea and nano-urea.

Trap: aspirants often reject statement 1 thinking soils only absorb nitrogen, or assume livestock emit only methane and skip ammonia. Agriculture is the largest source of atmospheric ammonia globally.