Q14. Which of the following bacteria is associated with the formation of root nodules of leguminous plants?
[RRB NTPC CBT-I (24 July 2021, Shift 2)]
(A) Clostridium
(B) Escherichia
(C) Rhizobium
(D) Salmonella
Answer: (C) Rhizobium
Explanation: Rhizobium bacteria form a symbiotic association with legumes such as peas and beans. They inhabit root nodules and convert atmospheric nitrogen into plant-usable compounds. This natural nitrogen fixation improves soil fertility and helps decrease the requirement for external nitrogen fertilisers.
Q13. What do the letters NPK on a fertilizer pack indicate?
[RRB NTPC CBT-I (4 March 2021, Shift 2)]
(A) Nitric acid, Phosphorus, Potassium
(B) Nitrogen, Phosphoric acid, Potassium
(C) Nitrogen, Potassium, Phosphors
(D) Nitrogen, Phosphorus, Potassium
Answer: (D) Nitrogen, Phosphorus, Potassium
Explanation: N, P and K denote nitrogen, phosphorus and potassium, the three primary fertiliser nutrients. Nitrogen supports leafy growth, phosphorus assists roots and energy transfer, and potassium regulates water balance and enzymes. Fertiliser grades express their concentrations using the N–P₂O₅–K₂O convention.
Q12. Artificial fertilizers were first created during the _______ century.
[RRB NTPC CBT-I (9 January 2021, Shift 1)]
(A) 19th
(B) 16th
(C) 18th
(D) 17th
Answer: (A) 19th
Explanation: The nineteenth century saw major advances in agricultural chemistry, including manufactured superphosphate fertilisers. Early industrial fertiliser production predated the twentieth-century Haber–Bosch ammonia process. These innovations helped agriculture move beyond exclusive reliance on manure and naturally occurring nutrient deposits.
Q11. With reference to chemical fertilizers in India, consider the following statements:
1. At present, the retail price of chemical fertilizers is market-driven and not administered by the Government.
2. Ammonia, which is an input of urea, is produced from natural gas.
3. Sulphur, which is a raw material for phosphoric acid fertilizer, is a by-product of oil refineries.
Which of the statements given above is/are correct?
[UPSC CSE Prelims GS Paper I (2020)]
(A) 1 only
(B) 2 and 3 only
(C) 2 only
(D) 1, 2 and 3
Answer: (B) 2 and 3 only
Explanation: Urea pricing in India is administered rather than fully market-driven, so statement 1 is incorrect. Natural gas provides hydrogen for ammonia synthesis, and sulphur recovered from petroleum refining is used to make sulphuric acid for phosphatic fertiliser production. Thus, statements 2 and 3 hold.
Q10. Which one is a fertilizer?
[WBCS Prelims (2020)]
(A) Nâ‚‚
(B) Oâ‚‚
(C) Pâ‚„
(D) NaNO₃
Answer: (D) NaNO₃
Explanation: Sodium nitrate, NaNO₃, also called Chile saltpetre, is a nitrate-based nitrogen fertiliser. Plants readily absorb nitrogen in nitrate form. Molecular nitrogen in air is not directly usable by most plants, while oxygen and elemental phosphorus are not conventional fertilisers.
Q9. Which of the following is not a raw-material for fertilizer industry?
[MPPSC State Service GS (2020)]
(A) Naphtha
(B) Gypsum
(C) Sulphur
(D) Caustic soda
Answer: (D) Caustic soda
Explanation: Naphtha can provide feedstock for ammonia manufacture, sulphur is used to make sulphuric acid for phosphate processing, and gypsum has agricultural amendment uses. Caustic soda is principally used in soap, paper, aluminium and other industries, rather than as a standard fertiliser raw material.
Q8. How much amount of urea will be required for supplying 1 kg of nitrogen?
[UPPSC BEO (16 August 2020)]
(A) 2.0 kg
(B) 2.2 kg
(C) 2.5 kg
(D) 2.7 kg
Answer: (B) 2.2 kg
Explanation: Commercial urea contains about 46% nitrogen by mass. To supply one kilogram of nitrogen, divide 1 by 0.46, giving approximately 2.17 kilograms. Rounded to one decimal place, the required quantity is 2.2 kilograms of urea.
Q7. Which of the following fertilizers has more nitrogen content?
[WBCS Prelims (2019)]
(A) Urea
(B) Ammonium nitrate
(C) Potassium nitrate
(D) Ammonium phosphate
Answer: (A) Urea
Explanation: Urea has approximately 46% nitrogen by mass, higher than the nitrogen fractions of the other listed fertilisers. Its chemical formula is CO(NHâ‚‚)â‚‚. High nitrogen concentration makes it economical to transport and apply, although efficient use requires appropriate management.
Q6. Grey revolution is related to ______.
[RRB Group D (28 September 2018, Shift 2)]
(A) Leather
(B) Silk
(C) Fish
(D) Fertilizers
Answer: (D) Fertilizers
Explanation: The term Grey Revolution is conventionally associated in competitive-exam terminology with increased fertiliser production. Other colour-coded revolutions denote different sectors, such as the White Revolution for milk and the Blue Revolution for fisheries. Such terms are general-knowledge associations rather than formal chemical classifications.
Q5. Why does the Government of India promote the use of ‘Neem-coated Urea’ in agriculture?
[UPSC CSE Prelims GS Paper I (2016)]
(A) Release of neem oil in the soil increases nitrogen fixation by soil microorganisms.
(B) Neem coating slows down the rate of dissolution of urea in the soil.
(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.
Answer: (B) Neem coating slows down the rate of dissolution of urea in the soil.
Explanation: Neem coating slows nitrogen release and inhibits processes that rapidly convert urea nitrogen into easily lost forms. This can improve nitrogen-use efficiency and limit diversion of subsidised urea. It does not eliminate nitrous oxide emissions or turn urea into a weedicide.
