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Step-by-step answers for all textbook questions in this chapter
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This page covers all exercise questions from Samacheer Kalvi 8th Science Chapter 7 — Crop Production and Management. Work through each section in order: start with MCQs to test recall, then move to short and detailed answers for deeper understanding. The Common Mistakes and Exam Checklist at the end help you identify gaps before your exam.
Key Concepts
| Term | Definition |
|---|---|
| Ploughing | The process of loosening and turning the soil to improve aeration, nutrient mixing, and root penetration before sowing. |
| Sowing | Placing seeds in the soil at the correct depth and spacing to ensure proper germination and crop growth. |
| Irrigation | Supplying water to crops at regular intervals through traditional or modern methods to maintain adequate soil moisture. |
| Weeding | Removing unwanted plants (weeds) that compete with the main crop for nutrients, water, sunlight, and space. |
| Harvesting | Cutting and gathering mature crops from the field using manual tools (sickle) or machines (combine harvester). |
| Manure | Organic substance derived from decomposed animal and plant waste that improves soil texture and adds nutrients. |
| Fertilizer | Inorganic chemical compounds (e.g., NPK) that supply specific nutrients to plants but do not improve soil texture. |
| Crop Rotation | Planting different crops in the same field in a defined order to maintain soil fertility and disrupt pest cycles. |
| Kharif | Crops sown during the southwest monsoon (June–July) and harvested in September–October; e.g., paddy, maize. |
| Rabi | Crops sown in winter (October–November) and harvested in March–April; e.g., wheat, gram, mustard. |
| Panchakavya | An organic growth promoter made from five cow products — milk, curd, ghee, dung, and urine. |
| Bio-pesticide | Biological agents such as Bacillus thuringiensis that control insects and pests without harming the environment. |
I. Choose the Best Answer (MCQs)
Q1. The process of placing seeds in the soil is called
- (a) Ploughing (b) Sowing (c) Transplantation (d) Harvesting
Q2. Organism that controls insects and pests of plant crops is
- (a) Bio-pesticides (b) Weedicides (c) Fertilizers (d) Manure
Q3. The method in which water flows over the soil surface and allows it to infiltrate is
- (a) Drip irrigation (b) Surface irrigation (c) Sprinkler system (d) None of the above
Q4. Effective microorganisms preparation is not used in
- (a) Seed treatment (b) Seedling treatment (c) Soil treatment (d) Compost treatment
Q5. Which of the following is not present in Panchakavya?
- (a) Milk (b) Curd (c) Ghee (d) Sugar
Additional MCQs
Q6. Ornamental crop is
- (a) Paddy (b) Wheat (c) Euphorbia (d) Sugarcane
Q7. Lichen is a
- (a) Bio-fertilizer (b) Bio-indicator (c) Bio-pesticide (d) Bio-predator
Q8. Neem is a good
- (a) Insect repellant (b) Bio-fertilizer (c) Bio-predator (d) Weedicide
Q9. Royal Botanical Garden is located at
- (a) Chennai (b) Mumbai (c) Kolkata (d) Delhi
Q10. Method of sowing seeds by hand is called
- (a) Broadcasting (b) Dibbling (c) Transplanting (d) Drilling
Q11. Which irrigation method delivers water directly to the root zone through a network of pipes and emitters?
- (a) Surface irrigation (b) Sprinkler system (c) Drip irrigation (d) Chain pump
Q12. Levelling the soil after ploughing is important because it
- (a) Increases soil erosion (b) Prevents uniform distribution of water (c) Ensures uniform distribution of water and prevents waterlogging (d) Reduces soil fertility
II. Fill in the Blanks
1. The process of actively growing seedling from one place and planting in the main field is Transplantation. 2. A plant growing where it is not wanted is called a Weed. 3. Chemicals used for killing weeds are called Herbicides. 4. Seed that transfers its unique characteristics to descendants is called Heirloom seed. 5. Centers that serve as the ultimate link between ICAR and farmers are Krishi Vigyan Kendra. 6. Several popular high yielding varieties developed by IARI (Indian Agricultural Research Institute). 7. Kharif crops are sown during June-July (southwest monsoon). 8. Rabi crops are harvested during March-April. 9. The process of loosening and turning the soil is called Ploughing/Tilling. 10. Supplying water to crops at regular intervals is called Irrigation.
III. True or False
IV. Match the Following
| Column A | Column B | Answer |
|---|---|---|
| Bio-pesticide | (a) Neem Leaves | (b) Bacillus thuringiensis |
| Bio-predator | (b) Bacillus thuringiensis | (c) Controls white flies |
| Bio-fertilizer | (c) Controls white flies | (d) Improves soil fertility |
| Bio-indicator | (d) Improves soil fertility | (e) Quality of environment |
| Bio-repellant | (e) Quality of environment | (a) Neem Leaves |
V. Short Answers
Q1. What is ploughing? Answer: Ploughing (or tilling) is the process of loosening and turning the soil to facilitate nutrient availability in the root zone. It aerates the soil, helps mix nutrients, and allows roots to penetrate deeper. Ploughing also uproots weeds and exposes pests to sunlight, reducing their population before the crop is sown. The process is typically carried out using a plough drawn by animals or a tractor.
Q2. What are the methods of sowing? Answer: 1. Broadcasting — Scattering seeds by hand over the field. This method is simple but results in uneven distribution of seeds. 2. Seed drill — Using a machine to place seeds at uniform depth and spacing. This is the most efficient method as it ensures proper seed placement and covers them with soil. 3. Dibbling — Placing seeds in holes made at specific intervals using a dibbler or pointed stick. This method is commonly used for larger seeds and in small-scale farming.
Q3. What is foliar spray? Answer: Foliar spray is the method of feeding plants by applying liquid fertilizer directly to the leaves. The nutrients are absorbed through the stomata and epidermis, providing quick nutrition to the plant. This method is especially useful when the soil is deficient in certain micronutrients, as the leaves absorb nutrients faster than roots. It is commonly used for micronutrient supplementation and pest control applications.
Q4. What is Krishi Vigyan Kendra? Answer: Krishi Vigyan Kendra (KVK) is a farm science centre that serves as the ultimate link between ICAR (Indian Council of Agricultural Research) and farmers. It tests new agricultural technologies at the local level and advises farmers on weather conditions, market pricing, and best cultivation practices. KVKs also conduct training programmes, demonstrations, and awareness camps to help farmers adopt modern and sustainable farming techniques.
Q5. What is a bio-indicator? Answer: A bio-indicator is a species whose status reveals the qualitative status of the environment. For example, lichens indicate air quality — their presence means the air is clean; their absence suggests pollution. Bio-indicators are valuable because they respond to environmental changes more quickly than physical or chemical measurements, giving early warning signals about ecosystem health. Frogs, certain fish species, and lichens are commonly studied bio-indicators.
Q6. What is weeding? Answer: Weeding is the removal of undesirable plants (weeds) that compete with the main crop for nutrients, water, sunlight, and space. Methods include manual pulling, tilling, and using herbicides. Timely weeding is critical because unchecked weed growth can significantly reduce crop yield — sometimes by 20–40%. Farmers typically weed during the early growth stages of the crop, when competition for resources is most intense.
Q7. What is crop rotation? Answer: Crop rotation is the practice of planting different crops in the same field in a defined order (e.g., legumes followed by cereals). It helps maintain soil fertility, as legumes fix nitrogen in the soil, and prevents pest and disease buildup. Rotating crops also reduces the reliance on chemical fertilizers, since different crops have different nutrient requirements. Over successive seasons, this practice leads to healthier soil and more sustainable agricultural yields.
Q8. What is green manure? Answer: Green manure refers to plants like Sun hemp or guar that are grown and then ploughed into the soil before sowing the main crop. As they decompose, they enrich the soil with nitrogen and phosphorus, improving fertility and organic matter. Green manure crops also help suppress weed growth during the off-season and prevent soil erosion by covering the soil surface. This practice is a sustainable alternative to chemical fertilizers and improves overall soil health.
VI. Detailed Answers
Q1. Explain the various agricultural practices involved in crop production. Answer: Crop production involves a sequence of well-defined agricultural practices, each essential for achieving a good yield:
1. Soil Preparation: Ploughing loosens and aerates the soil, levelling ensures uniform water distribution, and manuring adds organic matter. Proper soil preparation creates an ideal seedbed for germination.
2. Sowing: Seeds are placed in the soil at the right depth and spacing through broadcasting, seed drill, or dibbling. The choice of method depends on the crop type, field size, and available resources. A seed drill is the most efficient method as it ensures uniform depth and spacing.
3. Adding Manure and Fertilizers: Nutrients are supplied through organic manure (cow dung, compost, green manure) or inorganic fertilizers (NPK, urea). Manure improves soil texture and water retention, while fertilizers provide specific nutrients quickly.
4. Irrigation: Water is supplied at regular intervals through traditional methods (moat, chain pump, dhekli, rahat) or modern methods (sprinkler, drip system). Adequate irrigation ensures continuous crop growth, especially during dry spells.
5. Weeding: Unwanted plants that compete with crops are removed manually, through tilling, or using weedicides. Timely weeding prevents yield reduction caused by resource competition.
6. Harvesting: Mature crops are cut and gathered manually using a sickle or mechanically using a combine harvester. Harvesting at the right time ensures maximum grain quality and yield.
7. Threshing and Winnowing: Grains are separated from the chaff through threshing (beating or using machines) and winnowing (using wind to separate lighter chaff from heavier grain).
8. Storage: Grains are stored in silos, granaries, or cold storage to protect them from pests, moisture, and fungal growth. Proper storage prevents post-harvest losses that can be as high as 10–15%.
Q2. Explain the different methods of irrigation. Answer: Irrigation is the process of supplying water to crops at regular intervals, and the method chosen depends on the terrain, water availability, and crop type.
Traditional Methods: 1. Moat (Pulley system): Water is drawn from wells using a pulley and rope. This is a labour-intensive method suitable for small fields, where a farmer manually pulls water up from a well. 2. Chain Pump: A chain with attached buckets lifts water from a well or water source in a continuous loop. It is more efficient than the moat for deeper water tables but still requires manual or animal power. 3. Dhekli: A lever-based system that uses a counterweight to lift water. A long wooden beam is pivoted on a post, with a bucket on one end and a counterweight on the other, making it easier to draw water. 4. Rahat (Persian Wheel): An animal-powered wheel with buckets attached lifts water from a well continuously. This method can irrigate larger areas compared to manual methods.
Modern Methods: 1. Sprinkler System: Water is sprayed through rotating nozzles, simulating rainfall. This method is suitable for uneven land and sandy soil where surface irrigation is inefficient. It minimizes water wastage and ensures even distribution. 2. Drip System: Water is delivered directly to plant roots through a network of pipes and emitters. This is the most water-efficient method, ideal for fruit crops, vegetables, and areas with water scarcity. It reduces evaporation and ensures each plant receives the exact amount of water needed.
Modern methods are generally more efficient than traditional ones, reducing water usage by 30–60% and improving crop yields through precise water delivery.
Q3. Explain weed control methods. Answer: Weeds are unwanted plants that compete with crops for nutrients, water, sunlight, and space. Controlling them is essential for maintaining crop productivity.
1. Mechanical method: Pulling weeds by hand or using tools like khurpi and trowel. This is the simplest method and is effective for small fields, though it is labour-intensive.
2. Tillage: Ploughing before sowing uproots weeds and buries them in the soil, where they decompose. This method is effective as a preventive measure before the crop is planted.
3. Crop Rotation: Alternating different crops disrupts the life cycle of weeds specific to one crop. For example, rotating cereals with legumes prevents weed species adapted to a single crop from dominating.
4. Summer Tillage: Ploughing during summer exposes weed seeds to intense heat, killing them before the next sowing season. This is particularly effective in tropical climates.
5. Biological method: Using bio-agents like insects or fungi that selectively attack weeds. For example, the cochineal insect is used to control prickly pear weed. This method is eco-friendly and targets specific weed species.
6. Chemical method: Applying weedicides (herbicides) like 2,4-D that kill broadleaf weeds without harming the crop. Chemical control is fast and effective for large fields but must be used carefully to avoid environmental harm.
7. Integrated Weed Management: Combining multiple methods — mechanical, biological, and chemical — for effective and sustainable weed control. This approach reduces reliance on any single method and minimizes negative impacts on the environment.
Additional Detailed Answers
Q4. What are Kharif and Rabi crops?
| Feature | Kharif Crops | Rabi Crops |
|---|---|---|
| Sowing season | June-July (monsoon) | October-November |
| Harvesting season | September-October | March-April |
| Examples | Paddy, maize, soybean, groundnut | Wheat, gram, pea, mustard, linseed |
| Water requirement | High (rain-fed) | Moderate (irrigation needed) |
Kharif crops depend heavily on the southwest monsoon and require warm, wet conditions for growth. Rabi crops thrive in cool winter weather and need less water, relying more on irrigation and stored soil moisture. Understanding the distinction between these two crop categories is essential for planning sowing schedules, irrigation strategies, and nutrient management throughout the agricultural year.
Q5. What is Panchakavya? Answer: Panchakavya is an organic growth promoter made from five cow products: milk, curd, ghee, cow dung, and cow urine. It is mixed in specific proportions and used to enhance crop growth and yield naturally. It acts as a bio-fertilizer and bio-pesticide. Panchakavya enriches the soil with beneficial microorganisms, improves soil fertility over time, and boosts the plant's natural immunity against diseases. It is widely recommended in organic farming as a sustainable alternative to chemical inputs, and it can be applied as a foliar spray or soil drench at various stages of crop growth.
Q6. What are heirloom seeds? Answer: Heirloom seeds are seeds that have been passed down through generations and transfer their unique characteristics to descendants. They preserve genetic diversity and traditional crop varieties. Unlike hybrid seeds, heirloom seeds can be saved from each harvest and replanted the next season, maintaining the same traits year after year. This makes them invaluable for food security and biodiversity conservation. Many heirloom varieties are also better adapted to local climate and soil conditions, having been selected over generations for resilience in specific regions.
Q7. What are seed banks? Answer: Seed banks are facilities that store seeds of various crop varieties to preserve genetic diversity. They serve as a backup against crop extinction and ensure availability of diverse seeds for future cultivation. Seeds in a bank are kept under controlled temperature and humidity conditions to maintain viability for decades or even centuries. The Svalbard Global Seed Vault in Norway is the world's largest seed bank, storing millions of seed samples from around the world. In India, the National Bureau of Plant Genetic Resources (NBPGR) maintains seed collections to safeguard indigenous crop varieties and support agricultural research.
Common Mistakes
- Confusing manure with fertilizer: Manure is organic (animal/plant waste) and improves soil texture; fertilizers are inorganic chemicals providing specific nutrients.
- Confusing bio-pesticides with bio-fertilizers: Bio-pesticides control pests (Bacillus thuringiensis); bio-fertilizers improve soil fertility (Rhizobium).
- Mixing up Kharif and Rabi seasons: Kharif crops are sown in monsoon (June-July); Rabi crops are sown in winter (October-November).
- Saying broadcasting is the best sowing method: Seed drill is more efficient — it ensures uniform depth, spacing, and covers seeds with soil.
- Confusing weedicides with pesticides: Weedicides kill weeds; pesticides kill insects and pests.
- Mixing up drip and sprinkler irrigation: Drip delivers water to roots; sprinkler sprays water like rain over the field.
- ❌ Thinking ploughing is only done after sowing — ✅ Ploughing is always done before sowing to prepare the seedbed. If soil is ploughed after sowing, it would uproot or damage the germinating seeds.
- ❌ Believing all weeds should be killed with chemicals — ✅ Integrated weed management combining mechanical, biological, and chemical methods is more sustainable. Overusing herbicides harms soil health and beneficial organisms, and can lead to herbicide-resistant weed species over time.
Exam Checklist
- [ ] Can you list all steps of crop production in order?
- [ ] Can you explain the difference between Kharif and Rabi crops with examples?
- [ ] Can you compare traditional and modern irrigation methods?
- [ ] Can you define crop rotation and explain its benefits?
- [ ] Can you explain the difference between manure and fertilizer?
- [ ] Can you list and explain weed control methods?
- [ ] Can you define Panchakavya and list its ingredients?
- [ ] Can you explain what bio-pesticides, bio-fertilizers, and bio-indicators are?
- [ ] Can you define heirloom seeds and seed banks?
- [ ] Can you explain the role of Krishi Vigyan Kendra?
- [ ] Can you describe why levelling is important after ploughing?
- [ ] Can you distinguish between the drip system and sprinkler system, including which crops each is best suited for?