Table A1.

Liquid or solution culture techniques further subdivided into circulating (closed) and non-circulating (open) techniques. GM, growth medium.

Technique	Description	Advantages	Disadvantages
Circulating methods (closed systems)	Nutrient solution pumped through plant root system, collecting and reusing excess solution.
NFT [23,31,43,110]	Plants in channels with nutrient solution flowing past roots driven by a slight gradient. Often in substrate-filled net pots.	- low initial costs - reusability of nutrient solution - low probability of blockages	- control of nutrient concentrations and pH required - difficult for species with short roots - power/pump failures
DFT [23,31,43,167]	Growing directly in nutrient solution. Often in substrate-filled net pots.	- efficient water and nutrient use - water-loving and fast-growing plants - can be organic	- take care regarding sufficient oxygenation - risk of diseases, etc.
Ebb and flow system [23,31,168,169]	Plants placed directly in growing trays often filled with medium. Nutrient solution periodically floods planting chamber and returns to reservoir.	- water-loving plants - energy-efficient - easily scalable	- high demand for reservoir capacities and nutrient medium - risk of anoxia - power/pump failures
Drip system [23,31,33,43,170]	Substrate in which roots are supplied with nutrient solution via drip emitter, often periodically.	- simple installation - efficient water and nutrient use and easy control	- drip lines/emitters susceptible to blockages - control of nutrient concentrations and pH required - power/pump failures
Wick system [23,43,171]	Capillary action feeds plants via synthetic fibers such as nylon. Often with absorbent medium.	- suitable for indoor, small or single plants such as herbs and spices - passive; no electricity needed	- requires a lot of water
Aeroponic [28,166,172]	Roots hang in air surrounded by sufficient oxygen and wetted with aerosol of nutrient solution distributed by atomizers.	- excellent aeration - reusability of nutrient solution - absence of GM - water-saving - low risk of diseases - high productivity - vertical usability	- maintenance effort - atomizers may clog - cleaning of root chambers - high initial costs - power/pump failures - control of nutrient concentrations and pH required
Aquaponic [28,77,95]	Combining hydroponic culture of plants with aquaculture of fish in closed water cycle and nitrifying bacteria.	- efficient water and nutrient use - no fertilizers required	- maintenance effort - risk of algae growth - risk of diseases, etc. - power/pump failures - sufficient oxygenation
Non-circulating methods	Nutrient solution is replaced when nutrient concentration decreases or pH and EC change.
Root dipping technique [173]	Pots closely spaced submerged in nutrient solution.	- inexpensive - little maintenance - passive; no electricity needed - good aeration	- less efficient water and nutrient use - risk of diseases, etc.
Floating technique [27]	Plants in small pots are fixed to Styrofoam sheet (or light plate) and float on nutrient solution.	- inexpensive - little maintenance - passive; no electricity needed	- less efficient water and nutrient use - risk of diseases, etc. - artificial aeration
Capillary action technique [174]	Plant pots with holes at bottom and inert medium placed in shallow containers. Nutrient solution reaches medium by capillary action.	- suitable for ornamental, flower and indoor plants	- aeration depending on medium