NCSU Horticulture Substrates Lab Hydration Index

Step 1

  • Test mix is spread on tray to air dry
  • Moisture content should be about 15%
    • Tests should not be run on samples with moisture below 10% or above 20%
  • This drying process can take 2-5 days in the lab
Hydration Step 1
Hydration Step 2

Step 2

  • 200 ml of sample is placed into a tube and firmed to a consistent bulk density
  • Four replicate samples are used for each test

Step 3

  • 200 ml of distilled water is poured through the sample
  • Water is poured slowly so as to minimize disturbance
  • Effluent is collected in a beaker placed below the sample

Hydration Step 3
Hydration Step 4

Step 4

  • After a few minutes, the collected water is measured in a graduated cylinder, recorded, and discarded
  • A fresh 200 ml of water is introduced to the surface and effluent measured again
  • This pourthru cycle is performed a total of 10 times

Step 5

  • After 10 pourthrus, the height of the sample in the cylinder is recorded.
  • The sample is then removed, and weighed.
  • The wet sample is dried at 105 C until all water is removed (24+ hours).

Hydration Step 5
Hydration Step 6

Step 6

  • Each Pourthru is plotted with the amount of water retained at each pourthru.
  • A curve of the hydration of the sample shows the relative ease or difficulty of wetting

Test Results | Test Equipment


Maintained by Bill Fonteno

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