Class 8 Science Notes Chapter 1 (Crop Production and Management) – Science Book

If you're preparing for any exams, here’s a structured and easy-to-understand guide to Chapter 1: Crop Production and Management from the NCERT Class 8 Science textbook, for exam preparation.

Chapter 1: Crop Production and Management

1. Introduction

• Need for Food: All living organisms require food for energy, growth, repair, and carrying out various life processes.
• Source of Food: Green plants synthesize their own food (autotrophs). Animals, including humans, obtain food from plants or other animals (heterotrophs).
• Agriculture: The science and practice of farming, including cultivation of the soil for growing crops and rearing animals to provide food, wool, and other products.
• Crop: When plants of the same kind are cultivated at one place on a large scale, it is called a crop. Examples: Crop of wheat means all plants grown in a field are that of wheat.

2. Types of Crops

Based on the season in which they are grown, crops in India are broadly classified into two types:

• Kharif Crops:
  • Sown in: Rainy season (Generally June-July).
  • Harvested in: End of monsoon season (September-October).
  • Require: More water, warm weather.
  • Examples: Paddy (Rice), Maize, Soyabean, Groundnut, Cotton.
• Rabi Crops:
  • Sown in: Winter season (Generally October-November).
  • Harvested in: Spring season (March-April).
  • Require: Less water, cold weather.
  • Examples: Wheat, Gram (Chana), Pea, Mustard, Linseed.
• (Note: Pulses and vegetables are grown during summer at many places - sometimes referred to as Zaid crops, though less emphasized in this chapter).

3. Basic Practices of Crop Production (Agricultural Practices)

These are the sequential activities undertaken by farmers over a period of time for crop cultivation.

• Step 1: Preparation of Soil

  • Importance: First step; crucial for root penetration, aeration (allows roots to breathe easily), growth of earthworms and microbes (friends of the farmer, aid decomposition and humus formation), brings nutrient-rich soil to the top.
  • Process:
    • Ploughing (or Tilling): Loosening and turning the soil.
    • Tools:
      • Plough: Ancient tool made of wood or iron, drawn by bullocks or other animals. Contains ploughshare (triangular iron strip) and ploughshaft (main wooden part).
      • Hoe: Simple tool used for removing weeds and loosening soil. Has a long rod of wood/iron and a bent plate of iron fixed to one end.
      • Cultivator: Tractor-driven ploughing tool. Saves labour and time.
    • Levelling: Breaking large soil clumps (crumbs) and levelling the field using a leveller. Important for uniform sowing and irrigation.
    • Manuring: Sometimes manure is added before ploughing to ensure proper mixing.

• Step 2: Sowing

  • Importance: Process of putting seeds into the soil. Selection of good quality, clean, healthy seeds of a good variety is crucial for high yield.
  • Seed Selection: Damaged seeds become hollow and lighter. They float on water – a simple test to separate good seeds.
  • Tools:
    • Traditional Tool: Funnel-shaped tool. Seeds 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 after sowing (prevents bird damage). Saves time and labour.
  • Key Considerations: Appropriate distance between seeds (avoids overcrowding, allows sufficient sunlight, nutrients, water) and correct depth (protects from birds, ensures germination).

• Step 3: Adding Manure and Fertilisers

  • Importance: Supplying essential nutrients to the soil for healthy plant growth. Continuous cropping depletes soil nutrients.

  • Manure:

    • Organic substance obtained from the decomposition of plant or animal wastes (e.g., cow dung, vegetable peels).
    • Decomposed by microbes.
    • Advantages: Enhances water holding capacity of soil, makes soil porous (improves gas exchange), increases number of friendly microbes, improves soil texture. Considered better for long-term soil health.
    • Types: Farm Yard Manure (FYM), Compost, Vermicompost (compost prepared using earthworms).

  • 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 handle and apply.
    • Disadvantages: Excessive use can reduce soil fertility, cause water pollution (eutrophication), harm soil microbes.

  • Difference between Manure and Fertiliser: (Crucial for exams)

    Feature	Manure	Fertiliser
    Nature	Natural, organic substance	Man-made, inorganic salt or organic compound
    Preparation	Prepared in fields/pits (decomposition)	Prepared in factories
    Humus	Provides a lot of humus to the soil	Does not provide any humus
    Nutrients	Relatively less rich in specific nutrients	Very rich in specific nutrients (N, P, K)
    Effect on Soil	Improves texture & water holding capacity	May degrade soil structure over time
    Pollution	Generally non-polluting	Can cause water pollution

  • Other Methods of Replenishment:

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

• Step 4: Irrigation

  • Importance: Supplying water to crops at regular intervals. Essential for seed germination, absorption of nutrients by roots, transport of nutrients within the plant, protection from frost and hot air currents.
  • Sources: Wells, tube wells, ponds, lakes, rivers, dams, canals.
  • Methods:
    • Traditional Methods: Cheaper but less efficient; often involve manual labour or animal power. Water wastage is higher.
      • Moat (Pulley-system)
      • Chain Pump
      • Dhekli (Lever system)
      • Rahat (Lever system using animal power)
    • Modern Methods: Conserve water, more efficient.
      • Sprinkler System: Useful for uneven land and sandy soil where water availability is less. Water sprinkled like rain through rotating nozzles on perpendicular pipes.
      • Drip System: Water falls drop by drop directly near the roots. Best technique for water-scarce regions. Ideal for fruit plants, gardens, trees. No water wastage.

• Step 5: Protecting from Weeds

  • Weeds: Undesirable plants that grow naturally along with the crop. Examples: Xanthium, Parthenium.
  • Harm: Compete with crop plants for water, nutrients, space, and light, thus affecting crop growth and yield. Some may be poisonous or interfere with harvesting.
  • Weeding: The process of removing weeds.
  • Methods:
    • Tilling/Ploughing: Before sowing, tilling uproots and kills weeds.
    • Manual Removal: Physical removal by uprooting or cutting close to the ground using hands or tools like khurpi. Best done before weeds produce flowers and seeds.
    • Chemical Control (Weedicides): Chemicals sprayed in fields to kill weeds without damaging crops. Example: 2,4-D (2,4-Dichlorophenoxyacetic acid). Diluted with water and sprayed during the vegetative growth of weeds (before flowering). Caution: Can be harmful to farmers' health; protective measures needed during spraying.

• Step 6: Harvesting

  • Definition: The cutting of the crop after it matures.
  • Time: Usually takes 3-4 months for a cereal crop to mature.
  • Methods:
    • Manual: Using a sickle.
    • Mechanical: Using a machine called a Harvester.
  • Post-Harvest Processes:
    • Threshing: Separating the grain seeds from the chaff (husk/stalk). Done manually by striking against a hard surface or by a machine called a Thresher.
    • Combine: A large machine that performs harvesting and threshing simultaneously.
    • Winnowing: Separating lighter chaff/husk particles from heavier grain seeds using wind or a winnowing machine. (Often done by small farmers).

• Step 7: Storage

  • Importance: Protecting harvested grains from moisture, insects, rats, and microorganisms for future use or sale. Freshly harvested grains have high moisture content, favouring spoilage.
  • Process:
    • Drying: Grains are properly dried in the sun to reduce moisture content.
    • Storage Structures:
      • Small Scale: Jute bags, metallic bins.
      • Large Scale: Silos (tall cylindrical structures) and Granaries (large warehouses) are used to protect from pests like rats and insects.
    • Protection Methods:
      • Dried neem leaves (used at home).
      • Specific chemical treatments (fumigation) in large godowns.

4. Food from Animals (Animal Husbandry)

• Many people living in coastal areas consume fish as a major part of their diet.
• Similar to crop production, animals reared at home or on a farm need proper food, shelter, and care.
• Animal Husbandry: Rearing animals on a large scale for food (milk, meat, eggs) and other products.

Key Terms for Revision:

• Agriculture, Crop, Kharif, Rabi, Ploughing, Tilling, Levelling, Manure, Fertiliser, NPK, Crop Rotation, Rhizobium, Irrigation, Sprinkler System, Drip System, Weeds, Weeding, Weedicides (e.g., 2,4-D), Harvesting, Threshing, Winnowing, Storage, Silos, Granaries, Animal Husbandry, Plough, Hoe, Cultivator, Seed Drill, Sickle, Harvester, Combine.

Exam Focus Points:

• Definitions of all key terms.
• Differences between Kharif and Rabi crops (season, examples).
• Differences between Manure and Fertilisers (composition, source, effect on soil, humus content).
• Sequence and purpose of Agricultural Practices.
• Tools used in each practice and their specific functions (e.g., Seed Drill advantages, Cultivator function).
• Modern vs. Traditional Irrigation methods (names, advantages/disadvantages, suitability).
• Methods of weed control.
• Importance and methods of storage.
• Role of Rhizobium bacteria and legumes in nitrogen fixation/crop rotation.
• Definition of Animal Husbandry.

This comprehensive structure covers the essential points from the chapter relevant for competitive exams, emphasizing definitions, differences, processes, and key examples as per the NCERT Class 8 syllabus.