Recirculating irrigation system

The irrigation system comprised a nutrient bottle, irrigation tubes, a 250 W, stainless steel self-priming pump and electromagnetic valves (Fig. 2a). By controlling the operation of a self-priming pump and an electromagnetic valve at the target RF (Fig. 2a), the times and duration of irrigation for each RF can be set.

The recycle system of irrigation comprised the PVC open box (sub-channel) at the bottom of the RF, a main-channel at the right-bottom of the MF, a temporary storage box below one end of the main channel, and the immiscible pump in the storage box (Fig. 2a). A polyethylene tube was used to drain the excess solution that passed the rhizobox to the main channel through a hole drilled close to one end of the sub-channel (Fig. 2a, see Additional file 1: Figure S1). Then the solution fell into the main-channel and flowed to the storage box, from which it is pumped back to the nutrient bottle.