Agriculture

• To learn life skills and acquire knowledge to pursue a career in agriculture
• Soil formation

  Formed by the weathering or breakdown of rock on the upper layers of the solid mass of earth
• Soil water is usually found in the pores between soil particles
• Soil science

  • Branch of agriculture that studies soil as a natural resource on the surface of the earth
• Soil science branches

  1. Soil formation (soil genesis)

  2. Classification (pedology) and mapping

  3. Physical properties of soil (soil physics)

  4. Chemical and fertility properties of soil (soil chemistry)

  5. Biological life in the soil (soil biology and biochemistry)
• Soil is the unconsolidated mineral or organic material on the immediate surface of the earth that serves as a natural medium for the growth of land plants
• Soil solution is the resulting liquid when soluble materials are dissolved in soil water
• Components of soil

  • Water (25% by volume)
  • Air (25% by volume)
  • Organic matter (5% by volume)
  • Mineral matter (45% by volume)
• Factors influencing soil formation

  • Living organisms
  • Climate
  • Type of parent material
  • Time that the parent material undergoes weathering
  • Topography
• When water is removed from soil, it shrinks in volume, becomes hard, and cracks appear
• Microorganisms


  Organisms that are so small they cannot be seen with the unaided eye and require microscopes to be seen
• Microorganisms in the soil

  • Bacteria, algae, nematodes, protozoa, some types of fungus, viruses
• The term fauna collectively refers to all the animal life in a place or region; flora collectively refers to all the plant life in a particular region
• Macroorganisms


  Large organisms that can be seen with the unaided eye
• Organisms in the soil

  • Macroorganisms
  • Microorganisms
• Mineral matter is also called inorganic matter and is made up of particles of rocks and minerals
• Soil texture and soil structure are important physical properties of the soil
• Large organisms in the soil

  • Earthworms, insects, plant roots, plant stems, millipedes, centipedes, snails, slugs, snakes, rodents, spiders, mites
• Soil solution is involved in food manufacture through photosynthesis, where water and carbon dioxide are used to form carbohydrates in the presence of light and chlorophyll
• Soil air contains oxygen, carbon dioxide, and nitrogen
• Soil colour is another physical property of the soil
• Soil mineral matter

  Major source of all inorganic plant food or nutrients, provides physical support for the soil
• Soils rich in organic matter are usually dark in color
• Functions of organic matter

  • Source of essential plant nutrients including nitrogen, phosphorus, and sulfur
  • Improves soil structure
  • Main source of carbon and energy for many microscopic soil organisms (heterotrophic microorganisms)
• Photosynthesis

  Water and carbon dioxide are used in the presence of light and chlorophyll to form the energy-giving food called carbohydrate
• When water goes into the soil


  It drives out the soil air
• The higher the amount of water in the soil

  The smaller the amount of air; the smaller the amount of water in the soil, the greater the amount of soil air
• Organic matter

  Comes from plants and animal remains, such as leaves, stems, and roots in various stages of decay
• Soil air (especially nitrogen) is used by nitrogen-fixing bacteria in plants


  To enhance the production of protein in plant parts like leaves, stems, fruits, and seeds
• Soil air

  Composed of several gases, including oxygen, carbon dioxide, and nitrogen
• Humus


  The fraction of soil organic matter which remains after the major portions of added plant and animal residues have decomposed
• To score 20 Distinction and NO Fails in 2014/201 GRADE 9 AGRICULTURE
• Functions of organic matter when placed on the soil surface as mulch

  • Protects the soil by reducing erosion
  • Improves soil structure
  • Reduces soil temperature
  • Does not allow weeds to grow under the mulch
  • Reduces the force or impact of raindrops on the soil
  • Absorbs and retains water, increases the amount of water that filters into the soil
  • Improves soil habitat for living things such as earthworms, insects, plant roots, and underground stems
• Soils with little or no organic matter are light in color
• When water is removed from the soil

  More air enters the soil
• Macronutrients


  Nutrients required in large amounts by plants for their growth and development
• Macronutrients

  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
  • Phosphorus
  • Potassium
  • Magnesium
  • Calcium
  • Chlorine
  • Sulfer
• Soil texture test flow chart

  Follow one arrow at a time: Sand -> Can you make a ball? -> Sandy loam -> Begin here -> Is the soil gritty? -> Yes -> Silty loam -> Is the soil sticky? -> Can you make a circle? -> Yes -> Clay loam -> Is the circle without cracks? -> Yes -> Clay
• The soil is a storehouse for water which plants use to cool themselves; plant nutrients also move into plants in the form of dissolved materials
• Essential Nutrient elements in plants must fulfill specific conditions to be regarded as essential