Class 11 Agricultural Science — Exercise Solutions
Key Concepts Quick Recap
| Concept | Details |
|---|
| Soil texture | Sand (coarse) + Silt (medium) + Clay (fine); Loam = ideal balance |
| NPK | N: leaf growth; P: root and flower; K: fruit and disease resistance |
| Kharif crops | June-Nov: rice, cotton, maize, groundnut |
| Rabi crops | Oct-Apr: wheat, barley, mustard, gram |
| Irrigation types | Drip (~90-95% efficient), sprinkler (~75-80%), furrow (~50-60%) |
| Organic farming | No synthetic pesticides/fertilisers; compost, green manure, crop rotation |
I. Choose the Best Answer (MCQs)
1. The most fertile soil type in India is: (a) Laterite (b) Red soil (c) Alluvial soil (d) Desert soil
Answer(c) Alluvial soil Alluvial soil: deposited by rivers (Ganga, Brahmaputra, Indus plains). Rich in minerals; high fertility; supports wheat, rice, sugarcane, maize. Covers about 43% of total land area of India. Two types: Khadar (newer, more fertile) and Bhangar (older, slightly less fertile).
2. Which nutrient is most essential for vegetative (leaf) growth of plants? (a) Phosphorus (b) Potassium (c) Nitrogen (d) Calcium
Answer(c) Nitrogen Nitrogen (N): essential component of amino acids, proteins, chlorophyll, and nucleic acids. Promotes vegetative growth, green colour. Deficiency: chlorosis (yellowing of leaves), stunted growth. Main N fertilisers: Urea (46% N), Ammonium Sulphate, DAP. Phosphorus: roots, flowers, seeds. Potassium: fruit quality, disease resistance.
3. The most efficient method of irrigation is: (a) Flood irrigation (b) Furrow irrigation (c) Drip irrigation (d) Sprinkler irrigation
Answer(c) Drip irrigation Drip (trickle) irrigation: water delivered directly to root zone through emitters; 90-95% efficiency (minimal evaporation and runoff). Ideal for fruit trees, vegetables in arid regions. Sprinkler: 75-80% efficient. Flood: 40-50% efficient. Drip also reduces weed growth (dry areas between plants).
4. Green manure is: (a) Chemical fertiliser coloured green (b) Crop residue + compost (c) Green leafy crops ploughed into soil while still green to add organic matter (d) Animal dung used as fertiliser
Answer(c) Green leafy crops ploughed into soil while still green to add organic matter Green manure crops: Sesbania (Dhaincha), sun hemp, cowpea. These are grown and ploughed back into soil before flowering → decompose → add organic matter + fix atmospheric nitrogen (legumes). Cost-effective; improves soil structure.
5. Crop rotation is practised because: (a) It increases cost of production (b) Different crops have different nutrient needs, preventing soil nutrient depletion; legumes fix nitrogen (c) It is a legal requirement (d) It helps only rice production
Answer(b) Different crops have different nutrient needs, preventing soil nutrient depletion; legumes fix nitrogen Crop rotation: alternating crops on the same field each season. Benefits: prevents nutrient depletion, breaks pest/disease cycles, legume rotation adds nitrogen (via Rhizobium symbiosis), improves soil organic matter.
6. Integrated Pest Management (IPM) involves: (a) Using only chemical pesticides (b) Combination of biological, cultural, mechanical and judicious chemical control (c) Eliminating all pests completely (d) Abandoning crop production
Answer(b) Combination of biological, cultural, mechanical and judicious chemical control IPM: uses all available pest control tactics in combination; minimises economic and environmental impact. Biological control: natural predators (ladybird for aphids), parasitoids, Bt (Bacillus thuringiensis). Cultural: crop rotation, resistant varieties, intercropping. Mechanical: traps, barriers. Chemical: as last resort.
7. Urea contains what percentage of nitrogen? (a) 16% (b) 26% (c) 36% (d) 46%
Answer(d) 46% Urea (CO(NH₂)₂): highest N content (46%) among common fertilisers. Most widely used nitrogenous fertiliser in India. Converted to ammonium in soil (urease enzyme). Other N fertilisers: DAP (18% N, 46% P₂O₅), Ammonium Sulphate (21% N).
II. Short Answer Questions
Q1. Explain the types of fertilisers and their importance.
Answer
Fertilisers supply nutrients that soil may lack. Types:
Nitrogenous fertilisers: Provide nitrogen. Urea (46% N), Ammonium Sulphate (21% N), Calcium Ammonium Nitrate. Promotes vegetative growth. Applied at sowing and top-dressed during growth.
Phosphatic fertilisers: Provide phosphorus. Single Superphosphate (SSP, 16% P₂O₅), Triple Superphosphate, DAP. Promotes root development, flowering, seed formation.
Potassic fertilisers: Provide potassium. Muriate of Potash (MoP, 60% K₂O), Sulphate of Potash. Promotes fruit quality, disease resistance, water regulation.
Complex fertilisers: Contain two or more nutrients. DAP (18:46:0), NPK mixtures. Reduce labour of applying separate fertilisers.
Organic fertilisers (manures): FYM (farmyard manure), compost, green manure. Improve soil structure, microbial activity; slowly released nutrients.
Balanced fertilisation (following soil testing recommendations) prevents deficiency and over-application.
Q2. What is the importance of crop rotation with an example?
Answer
Crop rotation: growing different crops on same field in sequential seasons.
Benefits: 1. Nutrient management: Legumes (pulses) fix atmospheric nitrogen via Rhizobium bacteria in root nodules → reduce N fertiliser need for next crop. 2. Pest and disease control: Specific pests/pathogens associated with one crop cannot build up if host crop is changed each season. 3. Weed management: Different crops suppress different weeds; breaks weed cycles. 4. Soil structure: Different root systems improve soil aeration and water infiltration. 5. Economic: Income diversification; reduces input cost.
Example (common rotation in India):
- Year 1 (Kharif): Rice
- Year 1 (Rabi): Wheat
- Year 2 (Kharif): Maize
- Year 2 (Rabi): Gram (chickpea — legume, fixes N)
- Year 3 (Kharif): Rice
Exam Checklist
- Alluvial soil: most fertile; Indo-Gangetic plains.
- N: vegetative growth; P: roots/flowers; K: fruit/disease resistance.
- Urea: 46% N; most common fertiliser.
- Kharif: June-Nov (rice, cotton, maize); Rabi: Oct-Apr (wheat, barley, mustard).
- Drip irrigation: 90-95% efficient; most water-saving.
- Green manure: plough green crop into soil.
- IPM: biological + cultural + mechanical + chemical (last resort).
- Crop rotation: prevents nutrient depletion; legumes fix N.
