| heal.abstract |
To reduce water consumption and construction weight of green roofs, the synergistic effect of the type and depth of substrate layer and irrigation frequency was investigated on the growth performances of six xerophytic, aromatic Mediterranean species, Helichrysum italicum Roth., H. orientale L., Origanum majorana L., O. dictamnus L., Santolina chamaecyparissus L., Artemisia absinthium L. Rooted cuttings were planted in plastic boxes, with a green roof infrastructure (substrate moisture retention and protection of the insulation, drainage element and filter sheet), placed in a fully exposed second floor roof at the Agricultural University of Athens. Two types of substrate were used, peat: soil: perlite (2:3:5, v/v) and marc compost: soil: perlite (2:3:5, v/v) as well as two substrate depths, 7.5 (shallow) and 15 cm (deep). Two irrigation frequencies, sparse (every 5 or 7 d in shallow and deep substrate respectively) and normal (every 3 or 5 d in shallow and deep substrate respectively) were investigated for the substrates. Increased contents in macro elements especially P and K were recorded in the compost substrate, while substrates differed slightly in physical properties. The use of compost and the deep substrate gave plants with higher dry weight of the aerial part in all species except for O. dictamnus; the latter grew better in low depth peat substrate with sparse irrigation. A remarkable result was that low depth compost substrate with sparse irrigation resulted in similar or even superior growth in all species, except for O. dictamnus, than high depth peat substrate with normal irrigation. So the replacement of peat by marc compost helps to reduce the water needs of plants, as well as the depth of the substrate layer, thus reducing the weight of the construction of a green roof. © ISHS 2013. |
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