Hydraulic conductivity lies in the
range of 3454e6178 mm/h. It was clear that higher percentage
of perlite and vermiculite in substrate mixes
decreased the weight of substrate and hydraulic conductivity.
In contrary, sand increased the weight of substrate as
well as WHC but decreased AFP. Even though sand enhanced
the weight of substrate, it provides good stability to the
substrate and anchorage for plants. Among the substrate
mixes examined, mix-12 exhibited lowest dry bulk density
(431 kg/m3) as well as highest AFP (19.5%). Even though WHC
of mix-12 was not the highest among the examined mixes,
it was only 3.4% less than that of highest WHC recorded
(mix-8). These values were well above the minimum requirements
for a green roof substrate according to German
FLL (Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau
e.V.) guidelines (FLL, 2002),