Composted Amendment Affects Soil Quality and Hedges Performance in the Mediterranean Urban Landscape

The influence of increasing rates (0, 15, 30, and 45%) of composted sewage sludge (CSS) in the plantation hole on both urban soil properties and three native Mediterranean woody hedge growth was monitored over a two-year period after establishment. The results indicate that the urban soil physical characteristics were positively influenced by the compost: the highest CSS rate showed an increase in both moisture and infiltration values. The chemical properties of the amended soils were also directly affected by the CSS rate, but the compost effect on organic matter, N and K contents decreased over time. At the end of the trial, the hedge grown on the 30% CSS rate showed significantly higher dry weight values compared to the 45% CSS. The growth response to the compost rates of the three species was not similar: mock privet presented hedges with higher dry weight value than the Mediterranean buckthorn mean value, whereas the lowest ones were found in Tarentum myrtle. Phillyrea, in our experimental conditions, developed regularly not being stressed by the presence of high pH values (45% compost rate); it encourages, in the the Mediterranea basin, sustainable landscaping and xerogardening. The results proved that, compared to urban non amended soils, the amended ones are more suitable to the hedge growth; therefore, a plan of hedge establishment based on the use of composted sludge as amendment for sclerophyllous could be feasible and, what is more, helpful to mitigate the environmental impact of organic waste disposal.