Agricultural Science — Complete Exercise Solutions
Key Concepts Quick Recap
| Topic | Key Points |
|---|
| Soil texture | Sand (coarse), Silt (medium), Clay (fine); Loam = best for crops |
| Soil pH | Most crops: pH 6-7; acidic soil → lime; alkaline → gypsum |
| NPK | Nitrogen (growth), Phosphorus (roots), Potassium (water regulation) |
| Fertiliser vs Manure | Chemical (quick-release) vs organic (slow-release, improves soil structure) |
| Kharif crops | Grown June-Oct (monsoon); paddy, maize, cotton, groundnut |
| Rabi crops | Grown Oct-March (winter); wheat, barley, gram, mustard |
| Zaid crops | Short duration summer crops; watermelon, cucumber, pumpkin |
| Irrigation efficiency | Drip >90%, Sprinkler ~75%, Flood ~50% |
I. Choose the Best Answer (MCQs)
1. The most fertile type of soil is: (a) Sandy soil (b) Clay soil (c) Loamy soil (d) Silty soil
Answer(c) Loamy soil Loam: mixture of sand, silt, and clay; good water retention, good drainage, adequate aeration, rich in nutrients. Ideal for most crops.
2. Nitrogen fertilisers promote: (a) Root development (b) Fruit setting (c) Vegetative growth (leaves and stems) (d) Water regulation
Answer(c) Vegetative growth (leaves and stems) N is a component of chlorophyll, proteins, and nucleic acids. Promotes lush green growth. Excess N → excessive vegetative growth, poor fruiting.
3. Drip irrigation is preferred in water-scarce areas because: (a) It is cheapest to install (b) It delivers water directly to root zone with minimal evaporation and runoff (c) It can be used only on flat land (d) It requires no electricity
Answer(b) It delivers water directly to root zone with minimal evaporation and runoff Drip irrigation: ~90-95% water use efficiency. Also called micro-irrigation. Ideal for: horticulture crops, vegetables, orchards. Reduces weed growth and foliar disease.
4. Paddy (rice) is a _____ crop: (a) Rabi (b) Kharif (c) Zaid (d) Perennial
Answer(b) Kharif Paddy is a kharif crop grown during June-October (monsoon season). Requires high water and humid conditions. India is the world's second largest producer of rice.
5. Vermicompost is produced by: (a) Chemical decomposition (b) Earthworms decomposing organic matter (c) Burning crop residues (d) Anaerobic fermentation
Answer(b) Earthworms decomposing organic matter Vermicompost: Eisenia fetida (red wiggler worm) decomposes organic waste → nutrient-rich compost. Rich in N, P, K; improves soil structure; eco-friendly alternative to chemical fertilisers.
6. Integrated Pest Management (IPM) involves: (a) Using chemical pesticides only (b) Using biological, chemical, cultural, and physical methods to manage pests economically and ecologically (c) Complete elimination of all pests (d) Using only traditional methods
Answer(b) Using biological, chemical, cultural, and physical methods to manage pests economically and ecologically IPM: minimise pesticide use; use natural predators (biological control), crop rotation (cultural), traps (physical), and chemicals only as last resort; reduces pesticide resistance and environmental harm.
7. Green manure involves: (a) Chemical fertiliser in green bottles (b) Growing leguminous crops and incorporating them into the soil while green (c) Using composted vegetable waste only (d) Animal manure that is green coloured
Answer(b) Growing leguminous crops and incorporating them into the soil while green Green manure crops: Sesbania (Dhaincha), Sunhemp, Cowpea. Legumes fix atmospheric nitrogen → added to soil when ploughed in → improves soil organic matter and nitrogen content.
II. Short Answer Questions
Q1. Distinguish between organic and inorganic (chemical) fertilisers.
Answer
| Feature | Organic Fertilisers | Inorganic (Chemical) Fertilisers |
|---|
| Source | Plant/animal material (compost, FYM, vermicompost) | Synthetic chemicals (urea, DAP, potash) |
| Nutrient content | Low, variable | High, specific (N, P, K % labelled) |
| Release | Slow (improves over time) | Quick (immediate availability) |
| Soil effect | Improves soil structure, microbial life | Can acidify soil; salt build-up if overused |
| Cost | Low (locally available) | Higher |
| Environment | Eco-friendly | Can cause eutrophication if overused |
Q2. What are the major pests and diseases of paddy and their control?
Answer
Pests:
- Stem borer (Scirpophaga incertulas): larvae bore into stem → dead heart, white ear. Control: pheromone traps, Trichogramma (biocontrol), chlorpyrifos.
- Brown planthopper (Nilaparvata lugens): sucks sap → hopperburn. Control: resistant varieties (IR36, Jaya), chemical (imidacloprid).
- Leaf folder (Cnaphalocrocis medinalis): folds leaf, feeds inside. Control: neem-based pesticide.
Diseases:
- Blast (Pyricularia oryzae, fungal): brown diamond-shaped lesions on leaves. Control: carbendazim, resistant varieties.
- Bacterial leaf blight (Xanthomonas oryzae pv. oryzae): water-soaked margins dry and yellow. Control: copper bactericides, resistant varieties.
- Sheath blight (Rhizoctonia solani): lesions on sheath; high humidity. Control: hexaconazole, balanced nitrogen.
Exam Checklist
- Soil texture: sand > silt > clay; loam = best for crops.
- NPK: N (vegetative), P (root), K (water).
- Kharif (June-Oct): paddy, maize, cotton; Rabi (Oct-Mar): wheat, gram, mustard.
- Drip irrigation: 90-95% efficient; best for water-scarce areas.
- IPM: integrate biological, cultural, physical, chemical methods.
- Green manure: legumes ploughed in green → N added to soil.
- Vermicompost: earthworms (Eisenia fetida) decompose organic waste.
