SUBSTRATE SATURATION BY VACUUM APLICATION (REFEREED)

The saturation percentage depends on the substrate characteristics (necessary energy) and the used saturation method (applied energy). The saturation method has a direct incidence on the particle density measure for displacement of fluids, and thus on the total porosity, on the water retention curve and on the air volume.

Considering the pores’ accessibility to the air-water exchange, the total volume of the substrates can be classified in three types: easily accessible to the exchange (Type 1), with conditioned accessibility (Type 2) and non accessible volume to water (Type 3). The objective of this paper is to measure the accessible porosity of the substrate through the saturation into vacuum chamber.
The use of the specific volume has several advantages respect to the use of density.

Six substrates have been chosen: fine pine bark, coarse pine bark, granulated slag, slag wool, B6 perlite and Sphagnum peat.
Their physic properties are very diverse.
The independent variable (K) is the ratio between absolute pressure in the vacuum chamber (P1) and the atmospheric pressure (P0), and varies from 0 to 1.

A model of linear answer to the specific volume measured respect to the independent variable (K) is established, in which the independent value is the type 3 volume and the slope the type 2 volume.

The obtained results show the validity of the established linear model, but to determine with trustworthiness the type 2 and 3 volumes is necessary to increase the number of points of the straight, and thus increase the sampling representatives.

International Symposium Growing Media and Plant Nutrition in Horticulture

V. Terés, A.I. Beunza, A. Artetxe

porosity, growing media, specific volume, particle density, methodology, physical properties

https://doi.org/10.17660/ActaHortic.1997.450.47