Use of nutrient solution and greywater for aeroponic and hydroponic cultivation of chicory grown on lightweight urban green roof

Green roofs can support urban food production with the additional benefits of being removed from primary urban pollution sources and facilitating a better controlled environment, thus promising, apart from enhanced food security, improved produce quality and sustainability.
Soilless cultivation methods, such as hydroponics and aeroponics, offer an additional level of control that is pertinent to urban agriculture.
The present study used 18 outdoor lysimeters of 2×1 m equipped with load cell sensors simulating building green roof systems (GRS). The lysimeters were used to examine the capacity of hydroponic and aeroponic systems to produce chicory (Cichorium intybus) when irrigated with either nutrient solution or greywater.
Treatments included a) a hydroponic system with bags filled with agricultural perlite as growing medium, b) an aeroponic system using a polystyrene cap as container allowing the unrestricted development and mechanical support of the root system in the air, c) irrigation with modified Hoagland nutrient solution, and d) irrigation with greywater collected from a private house.
Each treatment was replicated 3 times (2 systems × 2 irrigation sources × 3 replications = 12 lysimeters). In each lysimeter, 18 lettuce plants were planted.
Four additional lysimeters served as unplanted irrigated controls and two empty lysimeters simulated a conventional rooftop, totalling 18 lysimeters.
Measurements were performed in 4 central plants within each lysimeter and included plant height and growth index, leaf stomatal conductance, SPAD, leaf fluorescence, pH, and EC of the effluent.
The weight fluctuation of each treatment was determined using weighing lysimeters equipped with load cells in conjunction with real time effluent volume determination using tipping buckets.
Weighing was averaged though a junction box and transmitted using Arduino while tipping bucket data was transmitted through PLC. During the experiment, drainage pH and EC for greywater (8.6-8.8 and 0.6-0.7 dS m^‑1, respectively) and nutrient solution (6.2-6.4 and 1.8 dS m^‑1, respectively) remained within the acceptable range for chicory growth.
SPAD, stomatal conductance and relative chlorophyll fluorescence measurements in the hydroponic treatments were significantly higher than those in the aeroponic treatments, however chicory growth was acceptable only for the fertigated hydroponic treatment (49.9 g plant^‑1) and greywater and aeroponics proved inadequate to support successful cultivation.
While the aeroponic system was not able to support chicory growth under any treatment, it proved extremely lightweight at 5.8-8.3 kg m^‑2 compared to the hydroponic system at 26.1-44.2 kg m^‑2 indicating the need to improve cultivation practice performance to develop successful lightweight GRS.

EHC2024: International Symposium on Urban Horticulture: from Vertical Farming to Planting Design

D. Paradimitriou, P.A. Nektarios, D. Harkoutsis, C. Daskalaki, N. Markakis, T. Manios, I.N. Daliakopoulos

adaptive green roof systems, Mediterranean zone, substrate depth, substrate type, native plant species, deficient irrigation, drought tolerance

https://doi.org/10.17660/ActaHortic.2025.1441.26