Effect of sediment-based growing media on cut flower production of calla lily

Recently published research findings from EU projects have provided scientific evidence of the potential reuse of remediated dredged sediments in agriculture. Given that bottom sediments might be polluted by organic and inorganic contaminants, remediated sediments could better be recycled as an ingredient of soilless growing media for no-food crops, such as flowers and ornamental plants. Hence, the use of peat, which has a high environmental impact, could be reduced. In the present study, phytoremediated and landfarmed sediment was reused as plant substrates for the cultivation of calla lily for cut flower production. Three different substrate mixtures were tested, combining different proportions of the remediated sediment (0, 25 and 50%) with a standard peat-based substrate. Calla rhizomes were planted in 30 L pots containing the chosen mixtures. The experiment set-up was performed under greenhouse conditions, and three different water regimes were applied. Before and at the end of the plant cycle, the substrates were characterized by a number of physical, chemical and biochemical parameters. Calla vegetative growth and productivity in terms of leaf stem and leaf blade length, number of flowers, flower length, color of flower spathe and flower senescence were monitored during the plant life cycle. Physiological parameters such as fluorescence of chlorophyll, nutrients and heavy metal concentrations in leaves were analyzed as well. Significant differences were observed among the tested growing media and water regimes for all considered growth and productive parameters. Plants grown on a mixture containing 50% remediated sediment under high water supply exhibited more significant plant development and higher cut flower production and vase life quality. These results demonstrated that the treated sediment might be used as a partial substitute for peat for the production of calla lily cut flowers.