Characterization and Use of Olive Mill Waste Compost as Peat Surrogate in Substrate for Cultivation of Photinia Potted Plants: Assessment of Growth Performance and In Vitro Suppressiveness

Starting from polluting waste, such as those produced by the olive oil industry, composting is able to produce stable organic materials that can be suggested as peat surrogate in the preparation of growth media for potted plants. In this work stable and mature olive mill waste compost (OMWC) was produced by using a simplified novel static composting procedure conducted in gas permeable bags. In order to predict its nutritional and suppressive potential, physico-chemical and biological characteristics of OMWC were investigated as well as its performance when used instead of peat in the preparation of growth media for Photinia fraseri cv. Red Robin potted plants. The innovative composting technique showed to be fully comparable to conventional methods of aerobic composting and able to convert OMWs into well-humified, stable, mature and rich in nutrients amendment. OMWC was colonized by different fungal species belonging to the genus Aspergillus and Penicillium that showed an appreciable suppressive potential against Sclerotinia sclerotiorum and Phytophthora cactorum. OMWC also resulted suitable for nursery cultivation of P. fraseri, showing the best performance when used at 33 and 66% peat substitution rate. The recycling method proposed represents a virtuous and low cost model for proper and successful management of olive mill waste.