Continuing

• Agriculture


  Cultivating crops and planting things in the soil
• Soil


  The top layer of the Earth's surface, also called dirt
• Soil is fundamental to the growth of plants
• Plants can be grown in water, but they don't get 100% of the required nutrients, so artificial fertilizers are often used
• Composition of soil


  • Organic matter
  • Minerals
  • Gases like nitrogen
  • Liquids like water
  • Organisms
• Mineral particles


  Combination of rock fragments and other inorganic substances, e.g. sand, silt, clay
• Organic content


  Mixture of living things (plants, animals, microorganisms) and dead plant remains
• Air in soil


  Air enters soil by diffusion and fills the pores between soil particles
• Water in soil


  Water enters soil through precipitation or irrigation and moves up to plant roots
• Typical composition of cultivated soil: 25% air, 45% minerals, 25% water, 5% organic matter
• Proportion of soil components depends on soil type
• Sandy soil


  • Light, warm, dry, acidic, low in nutrients
• Clay soil


  • Heavy, high in nutrients, remains wet in winter and dry in summer
• Silt soil


  • Light, moisture retentive, high fertility
• Peat soil


  • High in organic matter, retains a large amount of moisture
• Chalk soil


  • Highly alkaline due to calcium carbonate
• Loam soil


  Mixture of sand, silt and clay to avoid negative effects of each type
• Soil composition depends on weathering, erosion, climate, and mineral particle size
• Weathering


  1. Physical weathering by frost, heat, water, wind

  2. Chemical weathering by acid rain, reactions

  3. Biological weathering by plant roots, organisms
• Soil particle types by size

  • Sand (2-0.02mm)
  • Silt (0.02-0.002mm)
  • Clay (less than 0.002mm)
• Soil properties for plant growth

  • Availability of important nutrients (N, P, K)
  • Ability to hold roots firmly
  • Ability to supply water and oxygen to roots
• NPK


  Nitrogen, phosphorus, and potassium - essential plant nutrients
• Organic content producers


  • Earthworms
  • Fungi
  • Bacteria
• Benefits of high organic matter in soil

  • Increased water holding capacity
  • Less irrigation required
• Organic content producers


  Bacteria and other organisms that work on organic matter to convert it
• Organic content producers


  • Bacteria
  • Other organisms
• Humus


  The nutrient-rich soil created by the breakdown of organic matter
• High organic matter in soil

  Positive effects:
• Positive effects of high organic matter in soil

  • Increases water holding capacity
  • Increases air space
  • Increases number of decomposer tunnels and burrows
• 1% increase in organic matter can increase available soil water by 20,000 gallons per acre
• pH


  A scale that measures the acidity or basicity of a substance
• Ideal soil pH for plant growth is 7 (neutral)
• Soil pH


  Depends on parent rock type and water pH flowing into the area
• Soil pH


  Affects nutrient uptake by plants
• Acidic soil


  Soil with a pH lower than 7
• Signs of nutrient deficiency in plants

  • Nitrogen deficiency: Slow growth, yellowing of oldest leaves
  • Potassium deficiency: Poor fruit/seed quality, leaf edges turn brown
  • Sulfur deficiency: Yellowing of youngest leaves
  • Calcium deficiency: Poor fruit storage, tissue depth
  • Magnesium deficiency: Yellowing between leaf veins, early leaf fall
  • Iron deficiency: Yellowing between leaf veins, affects youngest leaves first
  • Copper deficiency: Leaves become dark green, twisted and withered
  • Zinc deficiency: Leaves show poor development, very small size
  • Boron deficiency: Leaves misshapen and malformed, hard areas in fruits
• Agriculture


  The cultivation of animals, plants and fungi for food and other products used to sustain human life
• Factors affecting agriculture


  • Climate
  • Culture
  • Technology
  • Economics
• Types of agriculture


  • Arable (growing crops)
  • Pastoral (raising livestock)
  • Mixed (both crops and livestock)
• Subsistence agriculture


  Growing food crops to meet the needs of the farmer and their family, with little surplus for sale