Substitution of peat in the cultivation of two shrub species used for ecological restoration and recovery of degraded green areas

Environmental restoration and recovery of abandoned and degraded urban areas require cares in the choice and cultivation of plants, which must show high adaptability to stressful conditions after transplanting. For these species, standard cultivation methods are often adopted in intensive nursery production. While more sustainable methods of cultivation are required, little is known about the possibility of replacing peat in the growing media. In this work, a one-year cultivation cycle was carried out with two species: Viburnum lantana L., a native deciduous shrub, and Viburnum rhytidophyllum Hemsl. Six different substrates were tested: 1) peat:pumice 70:30 v v-1, as a control; 2) coconut coir dust:pumice 70:30 v v-1; 3) coconut coir dust:green compost 55:45 v v-1; 4) coconut coir dust:stabilized wood fibre 60:40 v v-1; 5) green compost:stabilized wood fibre 30:70 v v-1; 6) coconut coir dust:green compost:stabilized wood fibre 40:30:30 v v-1. Growing performance was assessed by measuring plant height, collar diameter, biomass accumulation, leaf area, SPAD index, and leaf fluorescence. In addition, only for V. lantana L., leaf gas exchange was measured. V. rhytidophyllum Hemsl. and V. lantana L. grown in peat-free substrates showed comparable, or even significantly higher, values for the measured traits in comparison to the control treatment. Similar results were recorded for SPAD index and net photosynthesis for V. lantana L., while no significant differences were found in the measurement of photosystem efficiency, leaf transpiration, stomatal conductance and internal CO2 concentration. Results suggested that V. rhytidophyllum Hemsl. and V. lantana L. can be cultivated in professional nurseries on growing media that are more sustainable and environmentally friendly than peat.