Particle density of substrate components measured by gas pycnometer

The particle density (ρ_s) of a porous medium represents one of its basic physical properties.
Understanding the ρ_s of a substrate allows for the most accurate calculation of total porosity (TP). However, there are difficulties in determining the ρ_s of organic compounds with traditional liquid pycnometer procedures.
Direct ρ_s measurements were conducted on five substrate components (coir, peat, pine bark, perlite, and wood) using a helium gas pycnometer.
This method resulted in consisted ρ_s measurements with low deviations.
Coir yielded the highest ρ_s of the five materials at 1.47 g cm^‑3. Peat and wood had similar ρ_s at 1.41 and 1.38 g cm^‑3, respectively.
Of the organic materials, pine bark yielded the lowest measured ρ_s at 1.29 g cm^‑3. Perlite yielded the lowest ρ_s at 0.67 g cm^‑3. Differences observed between particle density-derived TP and saturation method-derived TP could provide valuable insights with respect to substrate water capture and retention.
Due to compounding errors with increasing bulk density, use of a single, “generic” ρ_s value for a component or a mix of materials to determine TP should be avoided.
Further measurements of particle density should be made across a wider range of organic and inorganic components to reduce our reliance upon inconsistent techniques and unreferenced values.

XXX International Horticultural Congress IHC2018: II International Symposium on Soilless Culture and VIII International Symposium on Seed, Transplant and Stand Establishment of Horticultural Crops

P.C. Bartley, A. Amoozegar, W.C. Fonteno, B.E. Jackson

porous medium, helium gas pycnometer, saturation method

https://doi.org/10.17660/ActaHortic.2020.1273.3