The attention for the replacement of peat in growing substrates is increasing due to its
environmental and economic advantages. The aim of the present work was to evaluate the impact
of peat substitution by new type olive mill pomace and its compost on the vegetative activity of
potted olive trees. A new type of humid pomace (hP) derived from an innovative two phase
extraction system and its derived compost (C-hP) are used as total or partial (50% vol/vol)
replacement of peat in olive growing substrate. The main chemical characteristics (moisture,
water extractable organic carbon, total nitrogen, C/N ratio and electrical conductivity) of the hP
and C-hP were measured. In order to evaluate the effects of the peat substitution on the plants
vegetative activity, measurements of mortality, plant height, leaf net photosynthesis and plant
growth (through final destructive measurements) were carried out. The use of hP resulted in a
significant increase of the salinity of the substrate. The water extractable organic carbon
concentration was higher in all substrates where peat was ewplaced and in particular when C-hP
was used. The total replacement of peat with hP caused 100% mortality of the plants while C-hP
can substitute peat up to 50% without causing a significative reduction of the final plant growth
