demonstrations:soil_field_capacity

Soil Field Capacity

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required

Categories: Water and Solubility, Soil and Erosion

Alternative titles: Soil Water Retention

Summary

Different soil types are tested for field capacity by adding water and measuring how much each soil retains after drainage, showing how soil properties affect water holding capacity.

Procedure

  1. Collect several soil samples (e.g., sand, clay, loam, potting soil).
  2. Place filter paper inside a funnel and position the funnel over a flask or beaker.
  3. Add a measured amount of dry soil to the funnel.
  4. Slowly pour water into the soil until it is saturated and water begins to drip through.
  5. Allow the soil to drain until no more water flows from the funnel.
  6. Record the volume of water collected in the flask.
  7. Calculate how much water each soil type retained by subtracting the drained water volume from the amount added.
  8. Compare the field capacity of the different soils.

Soil Water Holding Capacity Determination Practical Experiment - ThomasTKtungnung:


Soil Available Water Capacity Demonstration - WSU CAHNRS:


Variations

  • Test soils mixed with organic matter (e.g., compost) to see how it affects water retention.
  • Use different grain sizes of sand to compare coarse versus fine textures.
  • Investigate how soil compaction changes field capacity.
  • Repeat the experiment with heated or dried soils to observe differences.

Safety Precautions

  • Wash hands after handling soil to avoid exposure to microbes.
  • Ensure glassware is handled carefully to avoid breakage.
  • Clean and properly dispose of soil and filter paper after the experiment.

Questions to Consider

  • Why do different soils hold different amounts of water? (Differences in particle size, porosity, and organic content affect water retention.)
  • Which type of soil would be best for growing crops in dry conditions? (Soils with higher field capacity, such as loam or soils with organic matter, retain more water.)
  • Why is it important for farmers and gardeners to understand soil field capacity? (It helps manage irrigation and prevent overwatering or drought stress.)