Why does the Government of India promote the use of 'Neem-coated Urea' in agriculture?

(a) Release of Neem oil in the soil increases nitrogen fixation by the soil microorganisms
(b) Neem coating slows down the rate of dissolution of urea in the soil ✓ UPSC's answer
(c) Nitrous oxide, which is a greenhouse gas, is not at all released into atmosphere by crop fields
(d) It is a combination of a weedicide and a fertilizer for particular crops

Why the answer is (b)

• Neem oil contains compounds that inhibit nitrifying bacteria, so a neem coating slows the conversion and dissolution of urea in the soil, releasing nitrogen gradually — option (b).

• This raises nitrogen-use efficiency, cuts urea consumption by 10–15%, reduces leaching and nitrous-oxide emissions, and curbs diversion of subsidised urea to industry; 100% neem coating was mandated in 2015.

• It does not increase nitrogen fixation (a), completely stop N2O (c) or act as a weedicide (d).

• Hence option (b).

Why the other options are wrong

(a) Release of Neem oil in the soil increases nitrogen fixation by the soil microorganisms: Neem coating does not boost microbial nitrogen fixation.
(c) Nitrous oxide, which is a greenhouse gas, is not at all released into atmosphere by crop…: N2O emissions are reduced, not eliminated.
(d) It is a combination of a weedicide and a fertilizer for particular crops: It is not a weedicide.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2016, held on 7 August 2016. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.