1.Biochar can be used as a part of the growing medium in vertical farming.
2.When biochar is a part of the growing medium, it promotes the growth of nitrogen-fixing microorganisms.
3.When biochar is a part of the growing medium, it enables the growing medium to retain water for longer time.
Which of the statements given above is/are correct?
Answer & explanation▾
Answer: (d) 1, 2 and 3
All three statements are correct: biochar, the porous charcoal made by heating plant waste without oxygen, can be mixed into growing media, it supports biological nitrogen fixation, and it helps the medium hold water for longer.
✓1.Biochar is a stable, porous carbon material that can be blended into potting and soil-less growing mixes, which is how vertical farms grow plants; UPSC's key accepts this use.
✓2.The IPCC lists enhanced biological nitrogen fixation among the effects of adding biochar to soil, along with lower nitrogen losses and less fertiliser need.
✓3.The IPCC notes that applying biochar enhances soil water-holding capacity, which raises resilience to drought.
Remember · Biochar (pyrolysed plant waste) locks up carbon and improves soil: more water held, more nitrogen fixed, less fertiliser needed.
Sources
IPCC Special Report on Climate Change and Land, Chapter 4: Land Degradation ↗“Additional climate benefits of biochar can arise through: reduced nitrogen fertiliser requirements, due to reduced losses of nitrogen through leaching and/or volatilisation (Singh et al. 2010 1434 ) and enhanced biological nitrogen fixation (Van Zwieten et al. 2015 1435 ) … application of compost or biochar that enhances soil water-holding capacity, so increases resilience to drought.”
Question and answer: UPSC's official GS Paper I (2020, Series A) —
paper ↗ · answer key ↗.
Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·
What is/are the advantage/advantages of zero tillage in agriculture?
1.Sowing of wheat is possible without burning the residue of previous crop.
2.Without the need for nursery of rice saplings, direct planting of paddy seeds in the wet soil is possible.
3.Carbon sequestration in the soil is possible.
Select the correct answer using the code given below:
Answer & explanation▾
Answer: (d) 1, 2 and 3
Why not the tempting option · UPSC's key is (d). Statement 3 says carbon sequestration 'is possible', which is the standard claim for no-till with residue retention — FAO's own account is that such systems accumulate more carbon in the soil and turn it into a net sink; the IPCC's caution that the evidence for net sequestration from no-till alone is not compelling qualifies the size of the gain, not the possibility. Statements 1 and 2 describe zero-till wheat sown through paddy stubble and no-till direct-seeded rice, both established practices. In the exam, read 'is possible' as a soft claim: one documented mechanism is enough.
Zero tillage means sowing the next crop directly into undisturbed soil without ploughing. All three are its advantages: wheat can be sown straight through paddy stubble without burning it, paddy can be direct-seeded without raising a nursery, and the undisturbed, residue-covered soil accumulates organic carbon.
✓1.Zero-till drills such as the Happy Seeder sow wheat straight through paddy stubble, so the residue need not be burnt; the Government promotes them for in-situ crop residue management in Punjab, Haryana, Uttar Pradesh and Delhi.
✓2.Direct seeding of rice into unpuddled, untilled soil skips the nursery and transplanting; trials in the Indo-Gangetic Plains found yields equal to puddled transplanting with 35–40 per cent less irrigation water.
✓3.Leaving the soil unploughed with residue on the surface slows the breakdown of organic matter; FAO notes that systems based on high residue addition and no tillage accumulate more carbon in the soil than plough-based tillage, turning the soil into a net carbon sink. It also cuts erosion and nutrient loss.
Remember · Zero tillage means sowing without ploughing: it lets farmers skip stubble burning and the rice nursery, cuts soil erosion, and builds up carbon in the soil.
FAO, Conservation Agriculture: Benefits of CA ↗“Systems, based on high crop residue addition and no tillage, accumulate more carbon in the soil, compared to the loss into the atmosphere resulting from plough-based tillage.”
With reference to pulse production in India, consider the following statements:
1.Black gram can be cultivated as both kharif and rabi crop.
2.Green-gram alone accounts for nearly half of pulse production.
3.In the last three decades, while the production of kharif pulses has increased, the production of rabi pulses has decreased.
Which of the statements given above is/are correct?
Answer & explanation▾
Answer: (a) 1 only
Only statement 1 is correct: black gram (urad) is sown in both the kharif and rabi seasons. Green gram (moong) gives only about a tenth of India's pulses, and rabi pulses have not shrunk; they now make up the larger share of production.
✓1.Government crop statistics list urad separately for the kharif and the rabi season, so it is grown in both.
✗2.ICAR-IIPR says mungbean (green gram) accounts for 10% of India's pulse production; it is gram (chickpea), at about 10.4 of 23.4 million tonnes, that comes close to half.
✗3.Rabi pulses have not decreased: in the 2016-17 to 2020-21 average, rabi pulses gave 14.69 million tonnes against 8.73 million tonnes from kharif pulses.
Remember · Gram (chickpea) is about 45% of India's pulses; moong is about 10% and urad about 11%; rabi pulses give the larger share.
Question and answer: UPSC's official GS Paper I (2020, Series A) —
paper ↗ · answer key ↗.
Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·
“The crop is subtropical in nature. A hard frost is injurious to it. It requires at least 210 frost-free days and 50 to 100 centimeters of rainfall for its growth. A light well-drained soil capable of retaining moisture is ideally suited for the cultivation of the crop.” Which one of the following is that crop?
Answer & explanation▾
Answer: (a) Cotton
The clue that decides it is '210 frost-free days': NCERT gives this requirement for cotton, a kharif crop that needs high temperature, light rainfall and bright sunshine and dislikes frost.
✓(a)Cotton needs high temperature, light rainfall or irrigation, 210 frost-free days and bright sunshine, and takes 6 to 8 months to mature.
✗(b)Jute needs high temperature and well-drained fertile flood-plain soil renewed every year, and is grown in West Bengal, Bihar and Assam; there is no 210-day frost-free rule.
✗(c)Sugarcane wants hot, humid weather at 21°C to 27°C with 75 to 100 cm of rainfall, and needs irrigation where rainfall is low.
✗(d)Tea needs warm, moist, frost-free weather and deep, humus-rich, well-drained soil, and is a plantation crop of humid hill and plain areas.
Remember · '210 frost-free days' is cotton's signature requirement; also high temperature, light rain and bright sunshine.
NCERT Class 10 · Contemporary India – II, Chapter 4“It requires high temperature, light rainfall or irrigation, 210 frost-free days and bright sun-shine for its growth. It is a kharif crop and requires 6 to 8 months to mature.”
NCERT Class 10 · Contemporary India – II, Chapter 4“It grows well in hot and humid climate with a temperature of 21°C to 27°C and an annual rainfall between 75cm. and 100cm. Irrigation is required in the regions of low rainfall.”
Question and answer: UPSC's official GS Paper I (2020, Series A) —
paper ↗ · answer key ↗.
Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·
With reference to the current trends in the cultivation of sugarcane in India, consider the following statements:
1.A substantial saving in seed material is made when ‘bud chip settlings’ are raised in a nursery and transplanted in the main field.
2.When direct planting of setts is done, the germination percentage is better with single-budded setts as compared to setts with many buds.
3.If bad weather conditions prevail when setts are directly planted, single-budded setts have better survival as compared to large setts.
4.Sugarcane can be cultivated using settlings prepared from tissue culture.
Which of the statements given above is/are correct?
Answer & explanation▾
Answer: (c) 1 and 4 only
Statements 1 and 4 are correct: bud-chip nursery seedlings save a lot of seed cane, and tissue-culture plantlets can be used to raise sugarcane. Statements 2 and 3 are wrong because single-budded setts are the weaker option, with poorer germination and survival than larger setts.
✓1.ICAR-SBI says sugarcane needs nearly 7.5 to 10 tonnes of seed cane per hectare and calls planting of pre-germinated settlings the best answer for seed multiplication. In the bud-chip method only a bud with a small piece of stem is cut and raised in a nursery, so far less seed cane is needed.
✗2.Setts with several buds germinate better than single-budded setts, because the extra buds and reserves give a better chance of sprouting.
✗3.In bad weather, larger setts survive better, since they hold more food and moisture; single-budded setts are the more fragile.
✓4.ICAR-SBI produces virus-free tissue-culture seedlings of sugarcane and supplies them to sugar factories and farmers, so sugarcane can be raised from such seedlings.
Remember · Sugarcane seed saving: bud-chip and tissue-culture settlings use far less seed cane; single-budded direct planting is riskier than multi-budded setts.
Question and answer: UPSC's official GS Paper I (2020, Series A) —
paper ↗ · answer key ↗.
Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·
In the context of India, which of the following is/are considered to be practice(s) of eco-friendly agriculture?
1.Crop diversification
2.Legume intensification
3.Tensiometer use
4.Vertical farming
Select the correct answer using the code given below:
Answer & explanation▾
Answer: (a) 1, 2 and 3 only
Crop diversification, legume intensification and tensiometer use are eco-friendly practices: they cut risk and chemical inputs and save water. Vertical farming, a factory-like indoor system, is not counted among India's eco-friendly farming practices.
✓1.Diversification means changing the cropping pattern and adding other activities. The Centre's Crop Diversification Programme shifts water-guzzling paddy to pulses, oilseeds and other crops, and restores soil fertility through leguminous crops.
✓2.ICAR's review calls legumes in cropping systems a pathway to sustainable production, because they fix nitrogen and improve soil fertility while cutting water use and pest pressure.
✓3.A tensiometer measures soil matric potential, which ICAR research uses to schedule irrigation by the soil's need instead of a fixed interval, so water is not wasted.
✗4.Vertical farming is a high-technology indoor system whose benefits the IPCC calls unproven so far, so it is not treated as an established eco-friendly practice in India.
Remember · Eco-friendly farming: diversify crops, put legumes in rotation, irrigate by soil-moisture readings (tensiometer); vertical farming is not on this list.
NCERT Class 11 · Indian Economic Development, Chapter 5“Diversification includes two aspects - one relates to change in cropping pattern and the other relates to a shift of workforce from agriculture to other allied activities”
Question and answer: UPSC's official GS Paper I (2020, Series A) —
paper ↗ · answer key ↗.
Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·
What are the advantages of fertigation in agriculture?
1.Controlling the alkalinity of irrigation water is possible.
2.Efficient application of Rock Phosphate and all other phosphatic fertilizers is possible.
3.Increased availability of nutrients to plants is possible.
4.Reduction in the leaching of chemical nutrients is possible.
Select the correct answer using the code given below:
Answer & explanation▾
Answer: (c) 1, 3 and 4 only
Fertigation, applying water-soluble fertiliser through the drip irrigation water, makes nutrients more available near the roots and cuts losses by leaching, and acid injection can lower the alkalinity of irrigation water. It cannot be used for rock phosphate or other phosphatic fertilisers that do not dissolve.
✓1.Acidifying fertilisers such as phosphoric acid injected with the water lower the pH of alkaline irrigation water; this is a recognised benefit, and UPSC's key treats it as correct.
✗2.Phosphate fertilisers tend to precipitate in irrigation water; the Tamil Nadu Agricultural University guide says super phosphate must be avoided, and only soluble forms such as phosphoric acid or mono-ammonium phosphate suit fertigation. Rock phosphate does not dissolve.
✓3.The Centre's Per Drop More Crop scheme promotes fertigation to improve nutrient application efficiency, because fertiliser is delivered with irrigation water straight to the root zone, so more of it reaches the plant.
✓4.Small, frequent doses given near the roots are absorbed quickly, so less fertiliser is lost by leaching.
Remember · Fertigation = fertiliser through drip water: soluble fertilisers only, more nutrient use efficiency, less leaching; no rock phosphate.
Sources
PIB, Ministry of Agriculture & Farmers Welfare: Per Drop More Crop (PDMC) and fertigation ↗“The scheme also promotes fertigation to improve nutrient application efficiency and prioritizes water-scarce and groundwater-stressed regions. Fertigation is the process of applying fertilizers with irrigation water directly to the region where most of the plant’s roots develop.”
Fertigation, TNAU Agritech Portal (Tamil Nadu Agricultural University) ↗ · reference work“Application of super phosphorus through fertigation must be avoided as it makes precipitation of phosphate salts. … Nutrients and water are supplied near the active root zone through fertigation which results in greater absorption by the crops.”
Question and answer: UPSC's official GS Paper I (2020, Series A) —
paper ↗ · answer key ↗.
Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·