ITALIAN BUCKTHORN RESPONSE TO COMPOST BASED SUBSTRATES

Pot ornamental plants are mostly grown in soilless growing media containing rather expensive peat mixed with an inorganic material. Composted sewage sludge (CSS) could be considered as a much lower priced organic ingredient for pot ornamentals growing media, and simultaneously disposal of these wastes in an environmental-friendly way could be obtained. The objective of the present study was to evaluate the amount of peat that could be replaced by CSS in the commonly used growing medium of Italian buckthorn (Rhamnus alaternus L.) that is to say peat with inert materials. The maturity of the CSS was determined by phytotoxicity measurements. Twelve substrates were obtained by mixing CSS with peat in different proportions in volumes (0, 30, 50, 70) with the addition of inert materials: constant for the 20% (pumice+sand) and differentiated in perlite, almond shells and polystyrene for the 10%. The main physical and chemical characteristics of substrates were measured. Buckthorn high quality plants were obtained when the substitution of peat was of 30% in our experimental conditions, (50% compost and 20% peat). This substratum has chemical-physical characteristics not different from the control (0% compost and 70% peat) normally used for the growing of buckthorn. The most adequate inert material among those tested was almond shells