Posidonia oceanica based-compost and dredged sediments as a growth substrate for ornamental plants

Sediment-based techno-soil has been recently used as a constituent of peat-free substrates for growing ornamental plants and land reclamation. In recent years, many authors have proposed Posidonia-based compost as a promising nursery growth for food production. The objective of this study was to demonstrate that Posidonia-based compost and decontaminated sediments can be used as constituents of growing-media for ornamental plants. The substrate obtained by mixing Posidonia-based compost and sediment-based techno-soil (70:30, v:v) was compared to a traditional peat substrate in terms of chemical characteristics, but also in relation to plant growth and physiological response, using the ornamental species Viburnum tinus L. Results about chemical (macronutrients) and enzymatic characterization (beta-glucosidase, phosphatase, butyrate esterase and aryl-sulphatase; enzymes link to C, P, S cycle, and to overall microbial activity respectively) of growth media, demonstrated that the substrate was able to sustain the growth of the plants. The performance of the plant growth on Posidonia-based compost and sediments was comparable to the plant growth on the traditional substrate (peat), in terms of stem radial growth. Moreover, the eco-physiological responses of the plants, evaluated by enzyme activities (ascorbate-peroxidase APX, guaiacol peroxidase GPX and superoxide dismutase SOD), and by chlorophyll content and by leaf gas exchanges, demonstrated that the plants were in healthy physiological status, without any hidden stress symptoms. This study represents an important starting point for the endorsement of Posidonia-based compost and sediment-based techno-soil as a constituent of growing media for ornamental plant production. The evidence proved that these organic and mineral wastes can be used for the production of growing media. In addition, this study provides indications that may support the development of the New EU Fertiliser Regulation on the principles of circular economy.