•4 min read
Most aquaponic systems use horizontal grow beds, thereby emulating traditional soil-based practices for growing vegetables. However, over recent years, new vertical farming technologies have evolved which, when linked to the aquaculture part of an aquaponic system, may allow more plants to be grown in comparison to horizontal beds, by using the vertical space that is usually not utilized in production units and greenhouses, and could thus potentially make the systems more productive, especially in urban areas where growing space can be expensive (Palm et al. 2018). This premise would appear to be supported by comparative studies of vertical and horizontal hydroponic systems, which showed significantly greater productivity in vertical systems in terms of ratio of yield to occupied floor area (Liu et al. 2004; Neocleous et al. 2010; Ramírez-Arias et al. 2018; Ramírez‐ Gómez et al. 2012; Touliatos et al. 2016).
However, while optimal use of space is the most commonly cited advantage of vertical aquaponics, this is potentially outweighed by the various disadvantages. Biofouling in an aquaponic system is typical, and vertical systems are particularly susceptible to clogging and reduced flow rates that may starve the plants of water, so routine pressure washing of system components will be needed to avoid this (Patillo 2017). Furthermore, whereas a horizontal flow system only uses electricity to pump water back to the fish tanks, additional pumping is required to lift water to the top of vertical aquaponic systems. Growing plants on horizontal beds has the advantage that natural light is theoretically transmitted from all sides in a free-standing greenhouse without any blockages from other equipment and system components and, where lighting is required, these lighting systems can be readily located immediately above the plants without any interference. However, with vertical aquaponics natural light from above will be greater towards the upper part of the system compared to the bottom, and the vertical elements themselves will block light that is entering the greenhouse. Artificial lighting will therefore be required to compensate for these losses (Khandaker & Kotzen 2018). Careful cost-benefit analyses need to be undertaken, weighing up the benefits of potentially higher yields against the added costs of electricity, before embarking on vertical aquaponics.
There are a lot of different vertical hydroponic system designs which could potentially be combined with a fish production unit. Vertical growing may involve multiple layers of deep water culture, NFT, flood and drain systems, or growing towers that involve aeroponic growing methods, in which the plant roots are suspended in the air and sprayed with nutrient rich water. The design of the system will dictate how many plants can be grown per square metre, and will also influence yields. Numerous studies have shown that root and shoot growth, plant–water relations, nutrient uptake, transpiration and yield are all affected by root restriction in soilless culture. Plants may be more susceptible to growth abnormalities, such as blossom end rot in tomatoes and peppers, and leaf tip burn in lettuce. The smaller the root zone the more intensively the production system needs to be managed to provide a stress-free rhizosphere environment for optimum plant growth (Heller et al. 2015).
Copyright © Partners of the [email protected] Project. [email protected] is an Erasmus+ Strategic Partnership in Higher Education (2017-2020) led by the University of Greenwich, in collaboration with the Zurich University of Applied Sciences (Switzerland), the Technical University of Madrid (Spain), the University of Ljubljana and the Biotechnical Centre Naklo (Slovenia).
Please see the table of contents for more topics.