Earthworms

• Importance of earthworms

  • detritovores - decompose dead organic matter that adds nutrients to the soil, increasing fertility so increasing yield of food
  • Aeration - create tunnels which increases air in the soil, increasing aerobic processes in the nitrogen cycle
  • Increase infiltration - decrease surface runoff, erosion and flooding
• Ways to measure Earthworm abundance:

  1. Pit extraction
  2. Soil flood
• Pit extraction:

  1. dig up and remove a set volume of soil e.g. 1m3
  2. Count the number of earthworms in the sample
  3. Times up to estimate the total number of earthworms in the whole field
• Soil Flood:

  Earthworms aerobically respire so must come to the surface to breathe if the ground is flooded

  1. Clear the area because you may not be able to see the earthworms and objects may intercept the water
  2. Quadrats - 1m by 1m - to measure the area
  3. Flood the area with an irritant e.g. mustard in water

  • saturating the area so there is no surface runoff
  • flood the whole surrounding area so the worms don't go to the side.

  1. Collect earthworms in the quadrat to count, measure size, length or mass, or work out species
• Soil Flood Limitations

  • Sampling
  • need large number of samples to spot anomalies in results
  • Sample over the seasons or throughout the year
  • Worms might drown
  • Water might not percolate deep enough
  • worms might not surface
  • surrounding area is not flooded/earthworms travel sideways and are missed