NCSU Horticulture Substrates Lab Diagnostic Services
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Types of Tests
| Costs | Sample Submission | Shipping Instructions | More Information

Types of Tests

HSL provides a diagnostic service primarily for physical properties of substrates, substrate components, composts, barks, and urban soils. The following physical property tests are available:

  • The NCSU Porometerwill provide measurements of Total Pore Space (% by volume), Air Space, Water Holding Capacity, Bulk Density, and Percent Moisture Content. These measurements provide data suitable for the preparation of registration documents, such as the Horticultural Growing Media Registration Document for the Georgia Department of Agriculture.
  • The Hydration Indextest provides a measure of wettability for substrates or components.
  • The Hydraulic Conductivity test (in cm/hr) provides a measure of percolation/infiltration under saturated conditions.
  • The15 bar test is a measure of water (% volume) remaining at -15 bars tension (1.5 MPa) which is often considered a measure of water unavailable for plant growth.
  • Particle size distributionis done on dry samples with 12 screens, ranging from 0.5 inch down to pan.
  • HSL will also provide pH andelectrical conductivitydeterminations on test samples. We use a 1:2 substrate:water extraction.

The length of time usually required to analyze samples is 5 to 7 working days.


Pricing structure as of February 1, 2008 is as follows:


Cost per Sample



Hydration Index


15 Bar


Hydraulic Conductivity


Particle Size




Electrical Conductivity


Sample Submission

Samples submitted should be representative of the bulk components/substrates. If variability within a material is suspected, several subsamples should be taken and submitted separately.

Five quarts of a material are necessary for each Porometer test. Four to five quarts will be needed for each Hydration Index. Tests for 15 bar and hydraulic conductivity will require an additional 5-quart sample. one to two quarts are needed for each Electrical Conductivity and pH (pH and EC can be done on the same sample).

All materials should be packaged separately and securely; strong plastic bags inside sturdy cardboard boxes work best.

Each bag or container must be clearly marked with sample name and company.

Ship samples to:

Horticultural Substrates Laboratory
North Carolina State University
21 Kilgore Hall
Raleigh, NC 27695-7609

For more information contact:

Dr. William C. Fonteno
Horticultural Substrates Laboratory
North Carolina State University
152 Kilgore Hall, Box 7609
Raleigh, NC 27695-7609
Phone: (919) 515-5368
FAX: (919) 513-3192


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