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Science: Class 8 — Chapter 1: Crop Production and Management

1.0 Introduction to Crop Production and Management
1.1 Agricultural Practices
1.1.1 Cropping Patterns
  • Kharif Crops:
    • Sowing Season: Rainy season (June to September).
    • Examples: Paddy, maize, soyabean, groundnut, cotton.
  • Rabi Crops:
    • Sowing Season: Winter season (October to March).
    • Examples: Wheat, gram, pea, mustard, linseed.
  • Summer Crops: Pulses and vegetables are grown during summer at many places.
1.2 Basic Practices of Crop Production
1.3 Preparation of Soil
1.3.1 Agricultural Implements for Soil Preparation
  • Purpose: To break soil clumps for better yield before sowing.
  • Main Tools: Plough, Hoe, and Cultivator.
1.3.1.1 Plough
  • Historical Use: Used since ancient times for tilling, adding fertilisers, removing weeds, and turning soil.
  • Construction: Made of wood (traditional) or iron, drawn by animals (bulls, horses, camels).
  • Components:
    • Ploughshare: Strong triangular iron strip.
    • Ploughshaft: Long log of wood, main part.
    • Handle: At one end of the shaft.
    • Beam: Attached to the other end of the shaft, placed on animals' necks.
  • Modern Trend: Indigenous wooden ploughs are being replaced by iron ploughs.
1.3.1.2 Hoe
  • Function: Simple tool used for removing weeds and loosening the soil.
  • Construction: Long rod of wood or iron with a strong, broad, bent iron plate fixed at one end, acting like a blade.
  • Operation: Pulled by animals.
1.3.1.3 Cultivator
  • Modern Ploughing: Done by tractor-driven cultivators.
  • Advantages: Saves labour and time.
1.4 Sowing
1.4.1 Selection of Seeds Process
  • Method: Damaged seeds become hollow and lighter, hence float on water.
  • Benefit: Good method for separating good, healthy seeds from damaged ones.
1.4.2 Tools Used for Sowing Seeds
1.4.2.1 Traditional Tool
  • Shape: Like a funnel.
  • Mechanism: Seeds filled into the funnel pass down through two or three pipes with sharp ends, which pierce the soil to place seeds.
1.4.2.2 Seed Drill
  • Modern Use: Used for sowing with tractors.
  • Advantages: Sows seeds uniformly at equal distance and depth, ensures seeds are covered by soil, and protects them from birds.
  • Efficiency: Saves time and labour.
1.4.3 Seedling Transplantation and Spacing
  • Nursery Growth: Seeds of some plants (e.g., paddy, forest plants, flowering plants) are first grown in nurseries.
  • Transplantation: Seedlings are manually transplanted to the field when grown.
  • Appropriate Spacing: Necessary to prevent overcrowding of plants.
  • Benefits of Spacing: Ensures sufficient sunlight, nutrients, and water from the soil.
  • Overcrowding Prevention: A few plants may need to be removed to prevent it.
1.5 Adding Manure and Fertilisers
1.5.1 Manure
  • Nature: Organic substance.
  • Origin: Obtained from the decomposition of plant or animal wastes (e.g., cattle dung).
  • Preparation: Farmers dump waste in pits; microorganisms cause decomposition.
  • Vermicomposting: A method of making compost using earthworms.
  • Advantages of Manure (Organic):
    • Enhances soil's water-holding capacity.
    • Makes soil porous, easing gas exchange.
    • Increases friendly microbes.
    • Improves soil texture.
    • Provides a lot of humus to the soil.
    • Relatively less rich in specific plant nutrients compared to fertilisers.
    • Can be prepared in the fields.
1.5.2 Fertilisers
  • Nature: Chemicals rich in a particular nutrient.
  • Production: Produced in factories (man-made inorganic salts).
  • Examples: Urea, ammonium sulphate, super phosphate, potash, NPK (Nitrogen, Phosphorus, Potassium).
  • Benefits: Help farmers get better yield of crops (wheat, paddy, maize).
  • Disadvantages of Excessive Use:
    • Makes soil less fertile.
    • Source of water pollution.
1.5.3 Soil Nutrient Replenishment Methods
  • Substituting Fertilisers: Use organic manure or leave fields uncultivated (fallow) between crops.
  • Crop Rotation: Growing different crops alternately.
    • Example: Northern Indian farmers grew legumes (fodder) in one season and wheat in the next, replenishing soil nitrogen.
    • Rhizobium Bacteria: Present in root nodules of leguminous plants, fix atmospheric nitrogen.
1.5.4 Differences between Fertiliser and Manure
  • Fertiliser:
    • Man-made inorganic salt.
    • Prepared in factories.
    • Does not provide any humus to the soil.
    • Very rich in plant nutrients (N, P, K).
  • Manure:
    • Natural substance from decomposition of cattle dung and plant residues.
    • Can be prepared in the fields.
    • Provides a lot of humus to the soil.
    • Relatively less rich in plant nutrients.
1.6 Irrigation
1.6.1 Sources of Irrigation
  • Natural Sources: Wells, tubewells, ponds, lakes, rivers, dams, and canals.
1.6.2 Traditional Methods of Irrigation
  • Mechanism: Water lifted from sources using cattle or human labour.
  • Characteristics: Cheaper but less efficient.
  • Types:
    • Moat (pulley-system).
    • Chain Pump.
    • Dhekli.
    • Rahat (Lever system).
  • Pumps: Commonly used for lifting water, run by diesel, biogas, electricity, and solar energy.
1.6.3 Modern Methods of Irrigation (Water-Economical)
  • Purpose: To use water economically.
  • Main Methods: Sprinkler System and Drip System.
1.6.3.1 Sprinkler System
  • Usefulness: More useful on uneven land where water is insufficient.
  • Mechanism: Perpendicular pipes with rotating nozzles join main pipeline; water under pressure sprinkles like rain.
  • Applications: Lawns, coffee plantations, and several other crops.
1.6.3.2 Drip System
  • Mechanism: Water falls drop by drop directly near the roots.
  • Best Technique For: Watering fruit plants, gardens, and trees.
  • Advantage: No water wasted; a boon in regions with poor water availability.
1.7 Protection from Weeds
1.7.1 Weed Control Methods
  • Tilling: Before sowing, helps uproot and kill weeds, which then dry and mix with soil.
  • Timing: Best time for removal is before weeds produce flowers and seeds.
  • Manual Removal: Physical uprooting or cutting close to the ground using tools like a khurpi.
  • Seed Drill Use: Can also be used to uproot weeds.
  • Weedicides: Chemicals (e.g., 2,4-D) sprayed in fields to kill weeds without damaging crops.
  • Weedicide Application: Diluted with water and sprayed with a sprayer.
  • Safety Precautions: Farmers should cover their nose and mouth during spraying due to potential health effects.
1.8 Harvesting
1.8.1 Threshing and Winnowing
  • Threshing Definition: Separation of grain seeds from the chaff in harvested crops.
  • Combine Machine: A machine that acts as both a harvester and a thresher.
  • Stubble Burning Concerns: Leftover stubs are sometimes burned, causing pollution and potential fire hazards to crops.
  • Winnowing: Farmers with small land holdings separate grain and chaff by winnowing.
1.8.2 Harvest Festivals
  • Significance: A period of great joy and happiness, celebrating the efforts that bore fruit.
  • Examples in India: Pongal, Baisakhi, Holi, Diwali, Nabanya, and Bihu.
1.9 Storage
1.10 Food from Animals
Key Learnings and Keywords