As a control, a row of 29 boxes in a hydroponic
system was installed, holding 1.2 m3 LECA
(Fig. 2). Tap water was pumped from a separate
0.3 m3 water reservoir at a rate of 5 m3 h1
, and fertilizer [19] was applied two or three times a
week to maintain a fertilizer concentration with
an electrical conductivity of 2.5 mS cm1