2018 ASHS Annual Conference

The particle density (ρ_s) of a porous medium represents one of its basic physical properties. The ρ_s of coir, peat, perlite, pine bark, and wood fiber were analyzed by gas pycnometer using helium (He), nitrogen (N), and purified air. Gas significantly affected the measured ρ_s of organic substrate components. For example, gas containing high concentrations of N resulted in a lower pine bark ρ_s, 1.08 g/cm³, than He, 1.20 g/cm³. The measured ρ_s of wood, peat, and coir with He were 1.40 g/cm³, 1.44 g/cm³, and 1.49 g/cm³, respectively. Grinding each component increased the measured ρ_s for perlite and pine bark. An increase in ρ_s after grinding suggest that inaccessible voids were present within perlite and pine bark particles. For both perlite and pine bark, the effective ρ_s could be correlated to its particle size distribution. These measurements coupled with the understanding of the potential variability in ρ_s of organic/inorganic substrate components could generate more accurate values of calculated parameters including total porosity and volumetric water content.