WATER CHARACTERIZATION IN GRANULAR MATERIALS (REFEREED)

Six sand samples, four perlite minerals, and three commercial expanded perlites were analyzed in the laboratory to obtain particle size, bulk density, water retention, and saturated hydraulic conductivity.
Two additional fractions (0.5–1 and 0.25–0.5 mm) of each material were obtained and analyzed as well.
Several particle size indexes were used to relate variations in physical properties with particle size.
Water content at -1 kPa and saturated hydraulic conductivity were observed to depend on particle size, while bulk density and water content at -10 kPa did not depend on particle size.
Bulk density and water retention depended on the analyzed material, while saturated hydraulic conductivity did not depend on material.
Water release curves show an increase of water retained at – 10 kPa with increase of internal porosity.
When water release curves are compared within each material for both additional fractions, water retained at -10 kPa increased as well for the coarser fraction of expanded perlite which is not explained by volume of internal porosity alone.
Water retained at -10 kPa may depend on internal pores and on saturation degree achieved.
Several attempts have been reported to correlate hydric properties with particle size for granular and fibrous materials, but, besides specific material properties, variations in internal porosity within the same material due to the lack of uniformity within particle size fractions, may add a new variable to the system.

International Symposium Growing Media and Plant Nutrition in Horticulture

S. Burés, M. Carmen Gago, O. Morales, O. Marfà, F. Xavier Martinez

perlite, sand, physical properties, water retention, particle size, substrates, container media

https://doi.org/10.17660/ActaHortic.1997.450.48