3.3. Properties of the growing media
Table 4 shows the physical and physico-chemical characteristics
of the substrates, in comparison with the values of the ideal substrate,
according to Abad et al. (2001) and Noguera et al. (2003).
These properties were statistically affected by the origin and percentage
of compost in the substrates, as observed by Zhang et al.
(2013). The bulk density (BD) of the substrate increased when the
percentage of compost augmented in the mixture; the values of this
parameter for the mixtures with 50 and 75% of compost were superior
to the ideal substrate. Other authors have also found an increase
in the BD of the substrate with increasing compost
proportion in the substrate (Hernandez-Apaolaza et al., 2005 ;
Bustamante et al., 2008b). As the percentage of compost in the
substrate increased, the total pore space (TPS), aeration capacity
(AC) and shrinkage decreased, whereas the total water holding
capacity (TWHC) increased. In all the substrates with compost, the
TPS values were lower than for the ideal substrate. All the growing
media studied had low AC, which was dependent on the type of
compost: the growing media with greatest values were peat and