APES 4.3 Soil Composition and Properties

Soil Texture

• Soil particles are made of three groups
  • Sand, the biggest particle
  • Silt
  • Clay, the smallest particle
• Most soils are a combination of all three

Water Holding Capacity

• Larger particle sizes allow water to pass through easier (soils with high sand percentages)
• Smaller particle sizes don’t allow water to pass through (high clay percentage)

Measuring Soil Composition

• Soil composition can be determined by percentages

• Knowing the percentage of sand, silt, and clay, can determine the soil type

• The soil triangle is used to determine soil type if you are given the composition

  • It’s not necessary to memorize all the soil combinations or types
  • It is important to know how to use the soil triangle

  

Soil Tests

• There’s a variety of soil assessments
• Chemical
  • Chemicals allow for plants and animals to thrive in soil
  • The addition of fertilizers can increase nutrients: N, P, K
  • Some fertilizers and increased rainfall can also increase acidity
  • Nitrogen (nitrates)
  • Phosphorous (phosphates)
  • pH (acidity)
• Physical
  • Soil composition
  • Determining the amount of sand, silt, and clay will affect percolation and infiltration
  • Percolation is the movement of water into the ground
  • Infiltration is the movement of ions or chemicals trough percolation
  • Water holding capacity
• Biological
  • Soil is not inert
  • Earthworms and other inhabiting organisms
  • Bacteria
  • Archaea
  • Fungi
  • Burrowing animals