Posidonia-Based Compost and Dredged Sediment in Growing Media Improve Tolerance and Nutrient Uptake in Ornamental Plants

Because of the high costs and environmental impacts of peat and chemical fertilizers, thesearch for sustainable alternatives is increasing. Posidonia-based compost (C) has been widely testedas a growing media, while the combination with decontaminated dredged sediments (S) has onlyrecently been studied. Moreover, little information is available on the relationship between plantsand growing media. In this work, the suitability of growing media (CS) composed of 100% C, 70%C + 30% S and 30% C + 70% S were investigated compared to peat, for ornamental plants (Elaeagnusmacrophylla, Photinia fraseri and Viburnum tinus). Plant growth, physiological, nutritional andantioxidant responses were also investigated. The CS were compliant with current legislation ongrowing media. The Cu (+60%; +70%), Mg (+11%; +23%) and Ca (+66%; +72%) concentrations werehigher in CS with 30% and 70% of S, respectively, than peat. The plants growing in CS had lowerantioxidant activities than those on peat, suggesting a better plant tolerance to abiotic stress. Inconclusion, the use of CS growing media, especially those with 30% and 70% of S, can be a valuablestrategy to replace peat and reduce the application of fertilizers.