Landfarming efficiently recovers marine dredged sediment for pomegranate cultivation

Purpose There is a high quantity of dredged sediments produced every year. Both their landfill disposal and high pollutant concentrations lead to concerns regarding sustainability. The use of dredged sediment in growing media for horticulture is an opportunity to improve its recycling and to reduce the use of non-renewable materials, such as peat. For this purpose, marine sediments, phytoremediated in the framework of the AGRIPORT project (ECO/08/239065), were selected as a substrate component for pomegranate cultivation. Materialandmethods Phytoremediatedsedimentsunderwent3-monthslandfarming,toimprovetheirchemicalandphysical properties and to reduce hydrocarbon concentration. Afterwards, remediated sediment (RS) was mixed with peat (P) in a ratio of 50%. The tested substrates were (v:v) 100% RS (S100), 50% RS and 50% P (S50) and 100% P (S0) as control. Punica granatum L. var. "Mollar de Elche" and "Purple Queen" were selected as target plants. The sediment during the landfarm- ing and the growing media during the plant growth were monitored through physical, chemical, and biological analysis. In addition, the plant performance was evaluated by dry biomass determination. Results and discussion Landfarming decreased electrical conductivity and bulk density as well as increased soluble C and N, reducing hydrocarbon concentration in RS, due to the increase in microbial metabolism. The RS respected the Italian legislation limits for growing media, except for bulk density and organic carbon. The RS + P substrate reached the required legal limits. During plant growth, substrates showed low mineralization, and the increased release of nutrients suggested beneficial changes in the rhizosphere. Higher availability of nutrients was detected in P and a decrease of metal concentrations occurred, as result of the plant uptake. The differences in the substrate properties influenced the pomegranate development with a variety-specific effect. "Purple Queen" increased the dry biomass, while no differences were observed for "Mollar de Elche." Conclusion The use of sediment-based substrates (50% and 100%) for pomegranate cultivation, specifically for the "Mollar de Elche" variety, contributes to reducing peat application in horticulture.