Class 8 Science Notes Chapter 1 (Chapter 1) – Examplar Problems Book

Alright class, let's focus on Chapter 1: Crop Production and Management from your Science Exemplar book. This chapter is fundamental for understanding agriculture, a crucial part of our country's economy, and frequently appears in various government exams. Pay close attention to the details.

Chapter 1: Crop Production and Management - Detailed Notes

1. Introduction

• All living organisms require food for energy, growth, and repair.
• Plants synthesize their own food (autotrophs). Animals, including humans, obtain food from plants or other animals (heterotrophs).
• To provide food for a large population, regular production, proper management, and distribution are necessary.
• Agriculture: The science and practice of farming, including cultivating the soil for growing crops and rearing animals for food and other products.

2. Crops

• Definition: When plants of the same kind are cultivated at one place on a large scale, it is called a crop. (e.g., crop of wheat means all plants grown in a field are wheat).
• Types of Crops based on Season (Important for Exams):
  • Kharif Crops:
    • Sown in: Rainy season (June/July)
    • Harvested in: End of monsoon/Autumn (September/October)
    • Require more water.
    • Examples: Paddy (Rice), Maize, Soyabean, Groundnut, Cotton.
  • Rabi Crops:
    • Sown in: Winter season (October/November)
    • Harvested in: Spring (March/April)
    • Require less water compared to Kharif.
    • Examples: Wheat, Gram, Pea, Mustard, Linseed.
  • (Note: Pulses and vegetables are grown during summer at many places - sometimes called Zaid crops, though not explicitly detailed in basic NCERT)

3. Basic Practices of Crop Production
These activities, undertaken by farmers over a period of time, are called Agricultural Practices.

• a) Preparation of Soil:

  • Purpose: Loosens the soil, allowing roots to penetrate deeper and breathe easily (aeration). Promotes the growth of earthworms and microbes (friends of the farmer) which further enrich the soil with humus. Brings nutrient-rich soil to the top.
  • Processes:
    • Ploughing (or Tilling): The process of loosening and turning the soil.
      • Tools:
        • Plough: Used since ancient times. Made of wood or iron. Drawn by bullocks or other animals. Contains a strong triangular iron strip (ploughshare) and a main wooden part (ploughshaft).
        • Hoe: Simple tool used for removing weeds and loosening soil. Has a long rod (wood/iron) and a strong, broad, bent plate of iron.
        • Cultivator: Driven by a tractor. Saves labour and time.
    • Levelling: Breaking large soil clumps (crumbs) and levelling the field for uniform sowing and irrigation.
      • Tool: Leveller (wood or iron).

• b) Sowing:

  • Definition: Putting seeds into the soil.
  • Key Aspects:
    • Selection of Good Quality Seeds: Healthy, clean seeds of good variety yield more. Farmers select seeds that are disease-free. (Activity: Damaged seeds float on water as they are hollow).
    • Tools:
      • Traditional Tool: Funnel-shaped tool. Seeds are filled into the funnel, pass down through pipes with sharp ends that pierce the soil.
      • Seed Drill: Used with a tractor. Sows seeds uniformly at proper distances and depths. Ensures seeds get covered by soil (protects from birds). Saves time and labour.

• c) Adding Manure and Fertilisers:

  • Purpose: To replenish the soil with nutrients, as continuous cropping makes the soil poor in nutrients. These substances are called manures or fertilisers.

  • Manure:

    • Organic substance obtained from the decomposition of plant or animal wastes (e.g., cow dung, human waste, plant residues).
    • Decomposition is done by microbes.
    • Vermicomposting: Composting using earthworms.
    • Advantages: Enhances water-holding capacity of soil, makes soil porous (improves gas exchange), increases friendly microbes, improves soil texture. Considered environmentally friendly.
    • Disadvantage: Less rich in specific plant nutrients (N, P, K) compared to fertilisers. Bulky to transport and store.

  • Fertilisers:

    • Chemical substances produced in factories, rich in specific nutrients.
    • Examples: Urea, Ammonium Sulphate, Super Phosphate, Potash, NPK (Nitrogen, Phosphorus, Potassium).
    • Advantages: Provide specific nutrients quickly, easy to transport, store, and apply.
    • Disadvantages: Excessive use can reduce soil fertility (changes chemical nature), cause water pollution (eutrophication), does not add humus to the soil.

  • Difference between Manure and Fertiliser (Very Important):

    Feature	Fertiliser	Manure
    Nature	Inorganic salt or Organic compound (Urea)	Natural substance (decomposed organic matter)
    Preparation	Prepared in factories	Prepared in fields (decomposition)
    Humus	Does not provide humus	Provides a lot of humus
    Nutrients	Very rich in specific nutrients (N, P, K)	Relatively less rich in specific plant nutrients
    Environmental	Can cause pollution if used excessively	Generally environment-friendly
    Soil Texture	May degrade over time	Improves soil texture and water retention

  • Other methods to replenish nutrients:

    • Crop Rotation: Growing different crops alternately in the same field (e.g., legumes after wheat). Leguminous plants have Rhizobium bacteria in root nodules which fix atmospheric nitrogen.
    • Fallowing: Leaving the field uncultivated for one or more seasons.

• d) Irrigation:

  • Definition: Supplying water to crops at regular intervals.
  • Importance: Essential for seed germination, absorption of nutrients by roots, protecting crops from frost and hot air currents.
  • Frequency: Varies with crop type, soil type (sandy needs more), and season (summer needs more).
  • Sources: Wells, tube wells, ponds, lakes, rivers, dams, canals.
  • Methods:
    • Traditional Methods: Cheaper but less efficient. Often involve human or animal labour.
      • Moat (Pulley-system)
      • Chain pump
      • Dhekli
      • Rahat (Lever-system)
    • Modern Methods (Water Conservation):
      • Sprinkler System: Useful for uneven land and sandy soil where water is scarce. Perpendicular pipes with rotating nozzles spray water like rain.
      • Drip System: Water falls drop by drop directly near the roots. Best technique for fruit plants, gardens, trees. Water is not wasted at all. Excellent for water-scarce regions.

• e) Protecting from Weeds:

  • Weeds: Undesirable plants that grow naturally along with the crop. They compete with crop plants for water, nutrients, space, and light, affecting crop growth.
  • Weeding: The process of removing weeds. Best done before they produce flowers and seeds.
  • Methods:
    • Manual Removal: Physical removal by uprooting or cutting close to the ground (using Khurpi).
    • Chemical Control (Weedicides): Chemicals sprayed to kill weeds without damaging the crop (e.g., 2,4-D). Sprayed during the vegetative growth of weeds. Caution: Can be harmful to the person spraying; proper precautions needed.

• f) Harvesting:

  • Definition: The cutting of a crop after it matures.
  • Time: Usually takes 3-4 months for a cereal crop to mature.
  • Methods:
    • Manual: Using a Sickle.
    • Mechanical: Using a Harvester machine.
  • Post-Harvest Processes:
    • Threshing: Separating the grain seeds from the chaff (harvested crop). Done manually (beating) or by a machine called a Thresher.
    • Winnowing: Separating grain from husk/chaff with the help of wind. Lighter chaff is blown away.
    • Combine: A machine that performs both harvesting and threshing.

• g) Storage:

  • Importance: Proper storage is crucial to protect grains from moisture, insects, rats, and microorganisms. Freshly harvested grains have more moisture; they need drying before storage.
  • Methods:
    • Small Scale: Dried neem leaves used in homes. Stored in jute bags or metallic bins.
    • Large Scale:
      • Silos: Tall cylindrical structures for storing grains, protected from pests.
      • Granaries: Large warehouses.
      • Chemical treatments are often required to protect large quantities.
  • Key factors for safe storage: Drying (reducing moisture), protection from pests and microorganisms.

4. Food from Animals (Animal Husbandry)

• Besides crops, many people obtain food from animals (milk, eggs, meat).
• Animal Husbandry: Rearing animals on a large scale, providing them with proper food, shelter, and care.

Multiple Choice Questions (MCQs) for Practice:

1. Which of the following is a Rabi crop?
   a) Paddy
   b) Maize
   c) Soyabean
   d) Mustard

2. The agricultural instrument used for loosening and turning the soil, traditionally drawn by bullocks, is called:
   a) Hoe
   b) Plough
   c) Cultivator
   d) Seed Drill

3. Which of the following is NOT an advantage of using manure?
   a) It enhances the water-holding capacity of the soil.
   b) It provides specific plant nutrients like Nitrogen and Phosphorus in very high concentrations.
   c) It improves soil texture and makes it porous.
   d) It increases the number of friendly microbes in the soil.

4. The process of separating grains from the chaff using wind is called:
   a) Threshing
   b) Harvesting
   c) Winnowing
   d) Weeding

5. Which modern irrigation method delivers water drop by drop directly near the roots and is highly efficient in water-scarce areas?
   a) Sprinkler System
   b) Chain Pump
   c) Drip System
   d) Moat System

6. Chemical substances rich in specific nutrients like NPK, produced in factories, are known as:
   a) Manures
   b) Fertilisers
   c) Weedicides
   d) Pesticides

7. Weeds compete with crop plants for:
   a) Water and Nutrients only
   b) Space and Light only
   c) Water, Nutrients, Space, and Light
   d) Only Water

8. Large scale storage of grains is done in:
   a) Jute bags only
   b) Metallic bins only
   c) Silos and Granaries
   d) Underground pits

9. Crop rotation helps in replenishing the soil with nutrients, especially:
   a) Potassium
   b) Phosphorus
   c) Nitrogen
   d) Calcium

10. Kharif crops are typically sown during which season?
    a) Winter (October-November)
    b) Summer (March-April)
    c) Rainy Season (June-July)
    d) Autumn (September-October)

Answer Key for MCQs:

1. d) Mustard
2. b) Plough
3. b) It provides specific plant nutrients like Nitrogen and Phosphorus in very high concentrations. (This is characteristic of fertilisers, not manure)
4. c) Winnowing
5. c) Drip System
6. b) Fertilisers
7. c) Water, Nutrients, Space, and Light
8. c) Silos and Granaries
9. c) Nitrogen (especially if legumes are used in rotation)
10. c) Rainy Season (June-July)

Study these notes carefully. Understand the 'why' behind each agricultural practice. Remember the key differences, examples, and tools. This will build a strong foundation for your exams. Good luck!