UPSC CSE Prelims
Sustainable Development Previous Year Questions (PYQs)

Detailed Explanation:

Correct Answer: ✅ Option 1

The 100 Million Farmers (100MF) initiative is a global platform launched by the World Economic Forum to accelerate the transition towards net-zero, nature-positive, and resilient food and water systems. It aims to support farmers in adopting sustainable agricultural practices while improving livelihoods and climate resilience.

✅ Statement I is Correct: The initiative focuses on creating net-zero (carbon), nature-positive, and water-resilient agricultural systems.

✅ Statement II is Correct: It aims to enhance farmer resilience, improve productivity, and promote regenerative agriculture practices.

❌ Option B is Incorrect: This describes organizations promoting organic animal husbandry, not the 100 Million Farmers initiative.

❌ Option C is Incorrect: This refers to a blockchain-based fertilizer trading platform, unrelated to 100 Million Farmers.

❌ Option D is Incorrect: While FPOs improve market access, the primary goal of 100 Million Farmers is sustainable agricultural transformation, not merely forming producer organizations.

Short Notes: 100 Million Farmers Initiative

• Launched by the World Economic Forum (WEF).

• Target: Support 100 million farmers by 2030.

• Promotes regenerative and climate-smart agriculture.

• Focuses on net-zero, nature-positive food systems.

• Enhances soil health, biodiversity, and water efficiency.

• Seeks to improve farmer incomes and resilience.

• Encourages public-private partnerships in agriculture.

• Contributes to global climate and sustainability goals.

Detailed Explanation:

Answer: Option 2 — Only two

This question tests understanding of biofilter functions in Recirculating Aquaculture Systems (RAS). Out of three statements, two are correct regarding waste treatment and ammonia conversion, while the statement about phosphorus is incorrect.

✅ Statement 1 – Correct: Biofilters provide waste treatment by removing uneaten fish feed and organic matter, as beneficial bacteria on biofilter media break down these wastes.

✅ Statement 2 – Correct: Biofilters convert toxic ammonia from fish waste to less harmful nitrate through the nitrification process performed by beneficial bacteria (ammonia → nitrite → nitrate).

❌ Statement 3 – Incorrect: Biofilters do not increase phosphorus levels in water; their primary role is waste removal and ammonia conversion, while phosphorus management is handled through feed formulation and water quality control.

📝 Short Notes: Recirculating Aquaculture System (RAS) and Biofilters

• RAS Definition: A technology for farming fish in tanks where water is filtered and recirculated, minimizing water usage and waste discharge.
• Biofilter Function: Core component of RAS that hosts beneficial bacteria for biological filtration and waste treatment.
• Nitrification Process: Two-step bacterial process where Nitrosomonas bacteria convert ammonia (NH₃) to nitrite (NO₂⁻), then Nitrobacter bacteria convert nitrite to nitrate (NO₃⁻).
• Waste Removal: Biofilters remove solid wastes including uneaten feed, fish feces, and other organic matter through bacterial decomposition.
• Phosphorus Management: Controlled through fish feed formulation, mechanical filtration, and water exchange, not through biofilters.
• Benefits of RAS: Water conservation, reduced environmental impact, disease control, and intensive fish production in limited space.

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

System of Rice Intensification (SRI) is a climate-smart agricultural practice that optimizes resource use through alternate wetting and drying (AWD) of rice fields. This method significantly reduces seed, water, and energy requirements while minimizing methane emissions from paddy fields.

✅ Statement 1 – Correct: SRI requires only 5-8 kg/ha of seeds compared to 60-80 kg/ha in traditional methods, as single younger seedlings are planted with wider spacing.

✅ Statement 2 – Correct: Alternate Wetting and Drying (AWD) prevents continuous flooding, reducing anaerobic conditions that produce methane through methanogenic bacteria, cutting emissions by 30-40%.

✅ Statement 3 – Correct: SRI reduces water requirement by 30-50% through controlled irrigation, directly lowering electricity/fuel consumption for pumping groundwater.

📝 Short Notes: System of Rice Intensification (SRI)

• Origin: Developed in Madagascar in the 1980s by Fr. Henri de Laulanié; promoted globally for sustainable rice cultivation.
• Key Principles: Early, quick, and healthy plant establishment; reduced plant density; improved soil conditions with organic matter; reduced and controlled water application.
• Planting Method: Single seedlings (8-12 days old) transplanted with wide spacing (25×25 cm), unlike traditional clumps of 3-4 seedlings.
• Water Management: Alternate Wetting and Drying (AWD) instead of continuous flooding; fields kept moist but not submerged, saving 25-50% water.
• Environmental Benefits: 30-40% reduction in methane emissions; lower water pollution; reduced energy consumption; enhanced soil health and biodiversity.
• Yield & Economics: 20-50% higher yields with 80-90% less seed requirement; reduces input costs while improving grain quality and farmer income.
• Challenges: Labor-intensive initially; requires knowledge and training; not suitable for all soil types; needs good water control infrastructure.

Detailed Explanation:

Answer: Option 1 — Conveying a false impression that a company's products are eco-friendly and environmentally sound

Greenwashing is a deceptive marketing practice where companies mislead consumers by falsely portraying their products, services, or organizational practices as environmentally friendly when they are not. This involves using misleading labels, imagery, vague claims, or selective disclosure of environmental benefits while hiding negative impacts. The term has become increasingly relevant as consumer demand for sustainable products grows, prompting some companies to exaggerate or fabricate their environmental credentials rather than making genuine improvements.

📝 Short Notes: Greenwashing

• Definition: Misleading marketing that creates a false impression of environmental responsibility or sustainability
• Common Tactics: Vague claims ("eco-friendly", "natural"), misleading labels, irrelevant claims, hidden trade-offs, false certifications, and use of green imagery
• Examples: Companies claiming "carbon neutral" without credible offsets, "biodegradable" plastics that require specific conditions, or highlighting one green feature while ignoring overall environmental harm
• Impact: Undermines genuine sustainability efforts, erodes consumer trust, and diverts attention from companies making real environmental progress
• Regulations: Many countries are developing stricter advertising standards and disclosure requirements to combat greenwashing
• Consumer Protection: Look for third-party certifications (Energy Star, Fair Trade, FSC), detailed data, and transparent reporting to identify genuine environmental claims

Detailed Explanation:

Answer: Option 3 — Creation of mini forests in urban areas

The Miyawaki method is a unique afforestation technique developed by Japanese botanist Dr. Akira Miyawaki that creates dense, multi-layered native forests in small urban spaces. This method enables the growth of forests 10 times faster, 30 times denser, and with 100 times more biodiversity compared to conventional plantation methods, making it ideal for creating mini forests in urban areas.

📝 Short Notes: Miyawaki Method of Urban Afforestation

• Developer: Dr. Akira Miyawaki, Japanese botanist and professor (since 1980); awarded the Blue Planet Prize in 2006
• Principle: Uses native species of plants in multi-layered plantation to replicate natural forest ecosystems
• Key Features: Grows 10x faster, 30x denser, with 100x more biodiversity than conventional methods
• Area Requirement: Can be implemented in areas as small as 20 square meters
• Success Rate: Over 2,000 forests successfully created worldwide using this method
• Advantages: Works irrespective of soil and climatic conditions; requires minimal maintenance after 2-3 years; improves air quality and urban biodiversity
• Indian Context: Adopted in several Indian cities including Bangalore, Mumbai, Delhi, and Chandigarh for urban greening initiatives

Detailed Explanation:

Answer: Option 2 — 1, 2 and 4

This question tests the understanding of differences between permaculture farming and conventional chemical farming. Permaculture emphasizes biodiversity, soil health, and sustainable practices like mulching, while conventional farming relies on monocultures and chemical inputs that can degrade soil quality.

✅ Statement 1 – Correct: Permaculture farming discourages monoculture and promotes polyculture systems with diverse crops, while conventional chemical farming predominantly uses monoculture for efficiency and ease of mechanization.

✅ Statement 2 – Correct: Conventional chemical farming causes soil salinity due to excessive use of synthetic fertilizers and poor irrigation practices, whereas permaculture maintains soil health through organic matter and prevents salinization.

❌ Statement 3 – Incorrect: Permaculture farming can be successfully practiced in semi-arid regions using water harvesting, mulching, and drought-resistant crops; it is not limited by aridity as the statement suggests.

✅ Statement 4 – Correct: Mulching is a core practice in permaculture to conserve moisture, suppress weeds, and improve soil fertility, but it is not essential in conventional chemical farming which relies on herbicides and irrigation.

📝 Short Notes: Permaculture vs Conventional Farming

Detailed Explanation:

Answer: Option 1 — 1, 2 and 3 only

Eco-friendly agricultural practices minimize environmental harm while maintaining productivity. Crop diversification, legume intensification, and precision irrigation using tensiometers all qualify as sustainable practices in the Indian context, whereas vertical farming's high energy demands make it unsuitable.

✅ Statement 1 – Correct: Crop diversification enhances soil health, increases biodiversity, breaks pest cycles, and reduces chemical pesticide dependence.
✅ Statement 2 – Correct: Legume intensification naturally enriches soil through nitrogen fixation via Rhizobium bacteria, reducing synthetic fertilizer requirements.
✅ Statement 3 – Correct: Tensiometers measure soil moisture tension, enabling precision irrigation that conserves water and prevents nutrient leaching from over-watering.
❌ Statement 4 – Incorrect: Vertical farming in India is not eco-friendly due to its heavy reliance on artificial lighting and climate control systems powered predominantly by fossil fuel-based electricity, creating a large carbon footprint.

📝 Short Notes: Eco-Friendly Agricultural Practices

• Crop Diversification: Growing multiple crop species in rotation or together; improves soil fertility, pest control, and resilience to climate variability.
• Legume Intensification: Increased cultivation of pulses/legumes (e.g., lentils, chickpeas) that fix atmospheric nitrogen naturally, reducing chemical fertilizer use.
• Precision Irrigation: Use of tools like tensiometers, drip irrigation, and soil moisture sensors to optimize water use and prevent wastage.
• Organic Farming: Avoids synthetic chemicals; uses compost, green manure, and biopesticides.
• Agroforestry: Integrating trees with crops/livestock; enhances carbon sequestration and biodiversity.
• Conservation Tillage: Minimal soil disturbance practices like zero-tillage that preserve soil structure and organic matter.
• Integrated Pest Management (IPM): Combines biological, cultural, and mechanical pest control methods to minimize pesticide use.
• Green Manuring: Growing and plowing back green crops (like Sesbania, Dhaincha) to enrich soil organic content.

Detailed Explanation:

Answer: Option 3 — 1, 3 and 4 only

Fertigation is the technique of applying fertilizers through irrigation systems, allowing precise nutrient delivery to the root zone. This method enables control over irrigation water pH, increases nutrient availability to plants, and reduces nutrient leaching, but cannot be used for water-insoluble fertilizers like rock phosphate.

✅ Statement 1 – Correct: Fertigation allows control of irrigation water alkalinity/pH by adjusting it to optimal levels for nutrient absorption.
❌ Statement 2 – Incorrect: Rock phosphate is not water-soluble and cannot be efficiently applied through fertigation systems, which require water-soluble fertilizers.
✅ Statement 3 – Correct: Fertigation delivers nutrients directly to the root zone, significantly increasing nutrient availability and uptake efficiency.
✅ Statement 4 – Correct: Precise nutrient application through fertigation reduces excess fertilizer use and minimizes nutrient leaching into groundwater.

📝 Short Notes: Fertigation

• Definition: Application of fertilizers through irrigation systems (drip, sprinkler) directly to the crop root zone.
• Water-soluble fertilizers used: Urea, potassium nitrate, calcium nitrate, mono-ammonium phosphate (MAP), di-ammonium phosphate (DAP).
• Key advantages: Uniform nutrient distribution, higher nutrient use efficiency (30-50% savings), labor reduction, timely nutrient supply.
• pH management: Allows adjustment of irrigation water pH through acid injection (phosphoric acid, sulfuric acid) to optimize nutrient availability.
• Reduced leaching: Controlled application prevents over-fertilization and groundwater contamination.
• Limitations: Requires soluble fertilizers, initial setup cost, technical knowledge, and regular maintenance of irrigation system.

Detailed Explanation:

Answer: Option 1 — 1, 2, 5 and 6 only

India's National Policy on Biofuels (2018) permits the use of surplus food grains, damaged grains, starch-rich crops like cassava, and sugar-rich crops like sugar beet for ethanol production. Oil-seed crops and protein-rich pulses like groundnut seeds and horse gram are not included as feedstock for biofuels to avoid competition with edible oil and food supply.

✅ Statement 1 – Correct: Cassava is a starchy root crop explicitly allowed as feedstock for ethanol production under the policy.
✅ Statement 2 – Correct: Damaged wheat grains (surplus or non-edible) can be diverted for biofuel production to prevent wastage.
❌ Statement 3 – Incorrect: Groundnut seeds are oil-seeds and not permitted for biofuel production to avoid competition with edible oil markets.
❌ Statement 4 – Incorrect: Horse gram is a pulse (protein-rich crop) and is not included in the biofuel feedstock list.
✅ Statement 5 – Correct: Rotten potatoes (damaged/surplus tubers) can be used for biofuel production as waste utilization.
✅ Statement 6 – Correct: Sugar beet is a sugar-rich crop approved for ethanol production under the policy.

📝 Short Notes: National Policy on Biofuels 2018

• First Generation (1G) Biofuels: Produced from sugars, starch, vegetable oils – includes bioethanol and biodiesel.
• Second Generation (2G) Biofuels: Produced from non-food biomass like agricultural residues, forest waste, municipal solid waste.
• Allowed Feedstock for Ethanol: Sugarcane, sugar beet, cassava, damaged food grains, surplus food grains, sweet sorghum.
• Allowed Feedstock for Biodiesel: Non-edible oilseeds (Jatropha, Karanja, Mahua, etc.), used cooking oil, animal fat.
• Not Allowed: Edible oil-seeds (groundnut, soybean, sunflower), pulses and protein-rich crops to avoid food security concerns.
• Ethanol Blending Target: 20% by 2025 (E20) for petrol blending.
• Indicative Biodiesel Blending Target: 5% by 2030.

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

Zero tillage is a conservation agriculture practice where seeds are sown directly into untilled soil, leaving crop residues on the field. This method offers multiple environmental and economic benefits including reduced labor costs, improved soil health, and enhanced carbon storage.

✅ Statement 1 – Correct: Zero tillage allows wheat sowing directly into fields with previous crop residue (like rice stubble) intact, eliminating the need for burning, which reduces air pollution and preserves soil nutrients.
✅ Statement 2 – Correct: Direct seeding of paddy (DSR - Direct Seeded Rice) in wet soil is possible under zero tillage, bypassing the traditional nursery-transplanting method, saving water, labor, and time.
✅ Statement 3 – Correct: By leaving crop residues undisturbed and minimizing soil disturbance, zero tillage enhances organic matter retention and carbon sequestration in soil, mitigating climate change.

📝 Short Notes: Zero Tillage/Conservation Agriculture

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

Biochar is a carbon-rich, porous material produced through pyrolysis of biomass. It serves multiple functions in agriculture by improving soil structure, supporting beneficial microorganisms, and enhancing water retention. All three statements correctly describe the agricultural uses of biochar.

✅ Statement 1 – Correct: Biochar can be used as a component of growing media in vertical farming systems, where it improves substrate structure and nutrient retention.
✅ Statement 2 – Correct: The porous structure and chemical properties of biochar create favorable conditions for nitrogen-fixing microorganisms, enhancing biological nitrogen fixation in the soil.
✅ Statement 3 – Correct: Due to its high porosity and large surface area, biochar can absorb and retain significant amounts of water, making it available to plants over extended periods.

📝 Short Notes: Biochar in Agriculture

• Definition: Biochar is a stable, carbon-rich solid obtained from the pyrolysis (thermal decomposition in absence of oxygen) of biomass.
• Soil Amendment: Improves soil structure, porosity, and cation exchange capacity (CEC), leading to better nutrient retention.
• Water Retention: Its porous nature can hold 2-5 times its weight in water, reducing irrigation requirements.
• Microbial Habitat: Provides surface area and micro-habitats for beneficial soil microorganisms, including nitrogen-fixing bacteria.
• Carbon Sequestration: Stores carbon in soil for hundreds to thousands of years, contributing to climate change mitigation.
• Nutrient Management: Reduces nutrient leaching, improves fertilizer efficiency, and can adsorb contaminants.
• Applications: Used in conventional farming, vertical farming, container gardening, and soil remediation projects.

Detailed Explanation:

Answer: Option 4 — 2, 4 and 5

Conservation Agriculture is based on three core principles: minimum soil disturbance (minimum/no tillage), permanent soil cover (using crop residues or mulches), and crop diversification (through rotations and intercropping). Options 2, 4, and 5 directly align with these principles, while options 1 and 3 are not recognized components of Conservation Agriculture.

✅ Statement 2 – Correct: Minimum tillage is a fundamental principle of Conservation Agriculture that reduces soil disturbance and erosion.
❌ Statement 1 – Incorrect: While crop diversification is encouraged, avoiding monoculture is not explicitly defined as a Conservation Agriculture practice.
❌ Statement 3 – Incorrect: Conservation Agriculture does not exclude plantation crops; these can be cultivated using conservation practices.
✅ Statement 4 – Correct: Maintaining permanent soil cover using crop residues is a core principle of Conservation Agriculture.
✅ Statement 5 – Correct: Crop rotations and sequencing are essential for crop diversification under Conservation Agriculture.

📝 Short Notes: Conservation Agriculture

• Definition: A sustainable farming system based on three interlinked principles that enhance agricultural productivity while protecting the environment.
• Three Core Principles:
  • Minimum Soil Disturbance: No-till or minimum tillage farming reduces soil erosion and improves soil structure.
  • Permanent Soil Cover: Use of crop residues, mulches, or cover crops to protect soil from erosion and maintain moisture.
  • Crop Diversification: Crop rotations, intercropping, and crop sequencing to improve soil fertility and break pest cycles.
• Benefits: Reduces soil erosion, improves water retention, enhances soil organic matter, reduces input costs, and increases resilience to climate variability.
• FAO Support: The Food and Agriculture Organization (FAO) actively promotes Conservation Agriculture globally as a climate-smart practice.
• Application in India: Particularly relevant in water-stressed regions and areas with declining soil health; promoted through various government schemes.

Detailed Explanation:

Answer: Option 3 — 1 and 3 only

Water conservation in agriculture involves practices that reduce water loss through evaporation, improve soil water retention, and enhance infiltration. Reduced or zero tillage and leaving crop residue on fields are effective water conservation techniques, while gypsum application primarily improves soil structure rather than directly conserving water.

✅ Statement 1 – Correct: Reduced or zero tillage minimizes soil disturbance, creating a more compact surface that reduces evaporation and allows better water infiltration and retention in the soil.

❌ Statement 2 – Incorrect: Gypsum (calcium sulfate) is a soil amendment that improves soil structure and reduces sodicity, but it does not directly contribute to water conservation; it may even increase leaching in some cases.

✅ Statement 3 – Correct: Crop residue left on the field acts as mulch, reducing soil evaporation, suppressing weeds, preventing erosion, and maintaining soil moisture for longer periods.

Detailed Explanation:

Answer: Option 2 — 2 only

❌ Statement 1 – Incorrect: GIAHS does not focus on providing modern technology or training in modern farming methods to enhance productivity. Its goal is to conserve and support traditional agricultural systems and indigenous knowledge, not to replace them with modern intensive practices.

✅ Statement 2 – Correct: The core objective of GIAHS is to identify, safeguard and promote traditional agricultural systems that demonstrate sustainable practices, conserve agricultural biodiversity, preserve traditional landscapes, and protect the indigenous knowledge systems of local communities. It recognizes these systems as living, evolving heritage.

❌ Statement 3 – Incorrect: GIAHS designation does not automatically confer Geographical Indication (GI) status to agricultural products. GI is a separate intellectual property right granted under different legal frameworks and criteria. While some GIAHS products may independently qualify for GI, it is not an inherent feature of the GIAHS initiative.

Detailed Explanation:

Answer: Option 3 — 1 and 3 only

✅ Statement 1 – Correct: Drip irrigation delivers water directly to the root zone of plants, keeping the soil surface relatively dry. Since weeds require moist topsoil to germinate and grow, restricting surface water availability significantly reduces weed proliferation compared to flood or sprinkler irrigation methods.

❌ Statement 2 – Incorrect: Drip irrigation does not directly reduce soil salinity. In fact, because water is applied in small quantities at specific points, salts can accumulate at the edges of the wetted zone. While proper management practices (like periodic leaching) can help control salinity, drip irrigation itself is not a method for reducing existing soil salinity.

✅ Statement 3 – Correct: By releasing water slowly and directly at the root zone, drip irrigation minimizes surface runoff and water flow across the soil surface. This controlled water application prevents the washing away of topsoil, thereby reducing soil erosion and preserving soil structure and fertility.