CHAPTER 3 agriculture and the environment

CHAPTER 3: AGRICULTURE AND THE ENVIRONMENT

UNIT 3.1: The Soil

1. What is Soil?

  • Definition: Soil is a habitat for plants and organisms, composed of various components.

  • Components: Four main components:

    • Mineral Particles: Comprised of rock fragments and inorganic items.

    • Organic Content: Mixture of living organisms and their remains.

    • Air: Held in the pores between soil particles.

    • Water: Also held in soil pores, available for plant uptake.

  • Variability: Proportions depend on the soil type, management, climatic conditions, and particle size.

2. Components Origin

  • Weathering and Erosion: Particles formed from the breakdown of parent rock.

  • Weathering Forms:

    • Physical Weathering: Caused by frost, heat, water, and wind.

    • Chemical Weathering: Involves reactions like carbonic acid formation.

    • Biological Weathering: Caused by plant root growth and animal movement.

3. Particle Size Classification

  • Types:

    • Sand: 2.0 mm - 0.02 mm; gritty, with large pores allowing easy movement of water and air.

    • Silt: 0.02 mm - 0.002 mm; silky texture.

    • Clay: < 0.002 mm; small particles, limits water drainage, sticky when wet.

UNIT 3.2: Soils for Plant Growth

1. Factors for Successful Plant Growth

  • Requires:

    • Availability of mineral nutrients.

    • Anchorage for roots.

    • Supply of water and oxygen.

2. Mineral Ions

  • Plants require essential minerals such as nitrogen, phosphorus, and potassium for growth.

  • Ions are taken up through roots, facilitated by electric charges.

3. Soil pH

  • Importance of Soil pH: Influences nutrient uptake and plant health. Different plants have preferred pH levels.

4. Soil Organic Content

  • Composed of living organisms and decomposers like earthworms, fungi, and bacteria that recycle nutrients.

UNIT 3.3: Agriculture

1. Definition

  • Agriculture: Cultivation of animals, plants, and fungi for food and other products.

2. Types of Agriculture

  • Subsistence vs. Commercial:

    • Subsistence: Focused on family needs, minimal surplus.

    • Commercial: Focused on selling for profit.

  • Arable vs. Pastoral:

    • Arable: Crop production.

    • Pastoral: Livestock production.

UNIT 3.4: Increasing Agricultural Yields

1. Challenges of Population Growth

  • Increased demand for food with rising population.

2. Techniques for Improving Crop Yields

  • Crop Rotation: Change type of crops each year to maintain soil health.

  • Fertilizers: Essential for plant growth; must be used correctly to avoid environmental damage.

  • Organic vs. Inorganic Fertilizers: Organic improves soil structure; inorganic is easier to apply.

UNIT 3.5: The Impact of Agriculture on People and the Environment

1. Risks of Pesticide Overuse

  • Resistance development in pests; unintended harm to beneficial insects and ecosystems.

2. Misuse of Fertilizers

  • Issues like eutrophication and soil toxicity due to over-application.

3. Waste in Agriculture

  • Overproduction and Mechanization: Can lead to economic waste and environmental impacts.

UNIT 3.6: Causes and Impacts of Soil Erosion

1. Causes of Soil Erosion

  • Removal of vegetation, over-cultivation, overgrazing, and water/wind erosion.

2. Impacts of Soil Erosion

  • Loss of topsoil, habitat destruction, reduced water quality, and desertification.

UNIT 3.7: Managing Soil Erosion

1. Techniques for Erosion Control

  • Terracing: Flat areas to slow water runoff.

  • Contour Ploughing: Follows land contour to prevent runoff.

  • Maintaining Vegetation Cover: Using legumes and planting trees.

UNIT 3.8: Sustainable Agriculture

1. Aims of Sustainable Agriculture

  • Efficient use of resources, supporting ecosystems, economic sustainability for farmers.

2. Practices for Sustainability

  • Organic fertilizers, managed grazing, pest-resistant crops, irrigation management, and hydroponics.what hh