Improvement in Crop Yields — Long Answer Questions (Class 9 Science, Biology)
Medium Level (Application & Explanation)
Q1. Explain the role of sunlight and photosynthesis in increasing crop yield. How can farmers optimize light for better growth?
Answer:
Sunlight is the main energy source for plants. Through photosynthesis, plants convert light energy, water and carbon dioxide into glucose (food) and oxygen. More photosynthesis means more biomass, healthier plants, and higher yield.
To optimize light:
Choose proper spacing so leaves receive sunlight evenly; avoid overcrowding.
Use row orientation (north–south) for even light during the day.
In orchards or vegetable fields use pruning to allow light penetration into inner canopy.
For greenhouse crops use shade nets or supplemental grow lights when sunlight is insufficient.
Maintain healthy leaf area by managing pests and diseases that reduce photosynthetic surface.
By ensuring good light capture and healthy leaves, farmers improve photosynthesis efficiency, leading to higher and better-quality yields.
Q2. Distinguish between Kharif and Rabi crops with examples, and explain how their seasonal differences affect farming practices.
Answer:
Kharif crops are sown with the onset of the monsoon (June) and harvested in October. Examples: Paddy (rice), maize, soybean, cotton, green gram. They require warm temperatures and abundant rainfall.
Rabi crops are sown after monsoon (November) and harvested in spring (April). Examples: wheat, gram, peas, mustard. They need cool temperatures and good soil moisture from stored rains or irrigation.
Seasonal differences affect practices:
Sowing time is adjusted to rainfall and temperature.
Irrigation is more crucial for Rabi crops, while Kharif relies on rain.
Crop protection timing changes: Kharif may face fungal diseases due to humidity; Rabi can face pests that prefer cooler weather.
Farmers plan seed selection, fertilizers, and irrigation schedules according to these seasonal needs to maximize yield.
Q3. Why is seed selection important for improving crop yield? Describe types of improved seeds and their benefits.
Answer:
Seed selection is crucial because seeds determine the plant’s genetic potential for yield, resistance, and quality. Good seeds give uniform growth, better yields, and stronger disease resistance.
Types of improved seeds:
High Yielding Varieties (HYV): Bred to produce more grain per plant.
Hybrid seeds: Crosses of two parent lines giving hybrid vigour — higher yield and uniformity.
Certified seeds: Tested for purity and germination; ensure reliability.
Disease-resistant varieties: Reduced losses from pests and pathogens.
Benefits:
Faster germination, stronger seedlings, and better response to fertilisers.
Reduced crop failure risk and lower need for chemical control when resistant varieties are used.
Farmers should choose seeds suited to local climate, soil and season and obtain them from authorized sources to realize yield improvements.
Q4. Describe the three major activities—variety improvement, crop production improvement, and crop protection management—and explain how each contributes to higher yields.
Answer:
Variety improvement:
Involves plant breeding to create HYVs, disease-resistant, drought-tolerant, or nutrient-efficient varieties.
Direct effect: higher genetic potential for grain/biomass and resilience to stress.
Crop production improvement:
Includes better agronomic practices: proper land preparation, timely sowing, balanced fertilisation, proper irrigation, and weed control.
Ensures plants get required nutrients, water and space to reach full potential.
Crop protection management:
Prevents loss from pests, diseases, and weeds using integrated approaches.
Protected crops maintain yield and quality; losses can be large without protection.
Together these three reduce gaps between potential and actual yield by improving genetic potential, providing optimal growth conditions, and reducing biotic stress, thus significantly increasing overall crop production.
Q5. Explain why increasing crop production by improving practices is preferable to expanding farmland. Use the example that India increased food grain production four times (1952–2010) with only 25% more land.
Answer:
Expanding farmland often destroys forests, wetlands, and biodiversity, and can cause soil erosion and loss of ecosystem services. Improving production on existing land is environmentally sustainable.
India’s example shows that smart agriculture — better seeds, fertilisers, irrigation, and crop protection — can greatly raise yields per hectare. A fourfold increase with only 25% land growth means farmers produced much more from almost the same area by intensification.
Benefits of intensification:
Protects natural habitats, conserves water and soil.
Raises farmer incomes by increasing productivity rather than land area.
Supports food security without large-scale land conversion.
Thus, scientific improvements and better management are more sustainable and effective for meeting food needs.
High Complexity (Analytical & Scenario-Based)
Q6. A small farmer has 2 hectares in a region with good monsoon rains. Design a cropping plan for one year to maximize yield and sustain soil health. Include crop choices, seasons, and key practices.
Answer:
Plan: Use mixed cropping and crop rotation to spread risk and maintain soil health.
Kharif (June–Oct): Plant paddy in 1 hectare where water holds, and maize + green gram intercropping in 1 hectare. This gives stable income and adds legume benefits.
Post-harvest (Nov–Apr): On paddy field grow wheat or mustard with legume (e.g., chickpea) rotation on the maize field next season.
Key practices:
Use certified seeds and HYVs suited to region.
Apply balanced fertilisers based on soil test; use farmyard manure to improve organic matter.
Adopt proper irrigation (drip where possible) and timely weeding.
Use integrated pest management (IPM) to reduce pesticide use.
Include green manuring or cover crops in fallow periods to add nutrients and prevent erosion.
This plan maximises yield, reduces pest build-up, and sustains soil fertility while providing year-round income.
Q7. Mid-season, a farmer notices yellowing and stunted growth in a wheat crop. Analyze possible causes (water, nutrients, pests, photoperiod) and outline diagnostic steps and corrective measures.
Answer:
Possible causes:
Water stress (too little or waterlogging) causing nutrient uptake problems.
Pest or disease attack (root rot, nematodes or fungal disease).
Incorrect sowing time affecting photoperiod-sensitive growth.
Diagnostic steps:
Check soil moisture and drainage.
Inspect roots and lower stem for rot or pests.
Observe leaves: uniform yellowing suggests N deficiency; specks or lesions suggest disease/pests.
Conduct soil and leaf nutrient test if possible.
Corrective measures:
If water stress: adjust irrigation or improve drainage.
For N deficiency: apply split nitrogen fertiliser as recommended.
For pests/diseases: use appropriate, targeted pesticides after identification; prefer biocontrol where possible.
Ensure timely sowing in next season and use resistant varieties.
Quick, correct diagnosis followed by appropriate action can restore crop health and reduce yield loss.
Q8. Evaluate the roles of irrigation and photoperiod in crop growth. How might changing climate patterns affect these, and what mitigation can farmers use?
Answer:
Irrigation supplies water when rainfall is insufficient; it supports photosynthesis, nutrient uptake, and flowering. Proper irrigation scheduling improves yields and reduces stress.
Photoperiod (length of day) influences flowering and reproductive stages in many crops; some varieties are short‑day or long‑day sensitive. Correct sowing time aligns crop stages with optimal day length.
Climate change impacts:
Erratic rainfall increases reliance on irrigation and can cause droughts or floods.
Changes in temperature and seasonal timing can shift photoperiod-sensitive stages, causing mismatches with ideal growing conditions.
Mitigation strategies:
Adopt water-saving techniques: drip and sprinkler irrigation, rainwater harvesting, and mulching to conserve soil moisture.
Use drought-tolerant and photoperiod-insensitive varieties developed by breeders.
Adjust sowing dates and diversify cropping patterns to spread risk.
Implement climate-smart agriculture: real-time weather advisories and flexible management plans.
These steps help crops cope with altered water availability and changing photoperiod effects.
Q9. Define Integrated Pest Management (IPM) and describe how it can be applied to protect pulse crops with examples. Explain its advantages over heavy pesticide use.
Answer:
Integrated Pest Management (IPM) is a holistic approach combining biological, cultural, mechanical and chemical methods to manage pests in an economic and environmentally friendly way.
Application for pulses (e.g., pigeon pea, moong):
Cultural: crop rotation, timely sowing, removal of volunteer plants to break pest cycles.
Biological: use natural predators (ladybirds, parasitoids) and biopesticides like Bacillus thuringiensis or neem formulations.
Mechanical: handpicking, pheromone traps for pod borer, light...
