Efficiencies in Open and Closed Hydroponics System

Understanding Hydroponics Systems

The word hydroponics originates from two Greek words ‘hydro’ meaning water and ‘ponos’ meaning labor.

Hydroponics systems by design are made for mineral nutrient solution management.

The success of a hydroponic system relies on the composition of the nutrient solution, which contains all the essential mineral elements necessary for optimal plant growth and development.

Presently, hydroponics systems are commonly used for high-value crop production, since they produce better marketable quality (Maboko et al., 2011) and higher yields compared to conventional agriculture.

Classifying Hydroponics: Open vs. Closed Systems

Hydroponics systems may be classified into two categories - recirculating and non-recirculating. In non-recirculating (open) hydroponics systems, the nutrient solution is single-use. Each irrigation event involves a supply of freshly mixed nutrient solution to the root zone or substrate (Maboko et al., 2011). Once the substrate is saturated or the nutrient solution passes through the root zone it is discarded into a drainage tank as waste. Therefore, irrigation runoff management in open hydroponics systems is essential to reduce negative environmental impacts.

In stark contrast, recirculating hydroponic systems also called closed-loop hydroponics systems, recycle nutrient solution leachate after passing through the substrate or the rootzone.

Innovative Hydroponics: Tower Garden Greens in a Portable Closed-Loop Recurculating Aeroponics Vertical Farm (Photo courtesy: Chad Fischl)

The environmental impact of hydroponics is significantly influenced by the system's design, with closed-loop recirculating systems offering up to 35% higher water use efficiency (WUE) compared to their non-recirculating systems (Fayezizadeh et al., 2021). Published research has reported that non-recirculating hydroponic systems may require up to 75% more nutrients during the crop lifecycle compared with closed-loop recirculating hydroponics systems (Méndez-Cifuentes et al., 2020).

Overcoming Limitations of Hydroponics Systems

On the contrary, advanced operational efficiencies of recirculating hydroponics systems come with several limitations, including high initial investment cost, greater energy demands, vulnerability to power outage due to water and air pump utilization, and specialized knowledge requirements for operation and maintenance (Domingues et al., 2012; Hashida et al., 2014). Maintaining balanced mineral nutrition in closed-loop hydroponics systems is much more challenging and requires continuous nutrient solution monitoring. Out-of-balance closed-loop hydroponic solutions may result in certain nutrients becoming deficient or accumulating to toxic levels. Hence, leading to nutritional imbalances and death of the plant in more extreme cases.

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Further Reading:

Domingues, D.S., Takahashi, H.W., Camara, C.A., and Nixdorf, S.L. (2012) Automated system developed to control pH and concentration of nutrient solution evaluated in hydroponic lettuce production. Comput. Electron. Agric. 84: 53–61. doi:10.1016/j.compag.2012.02.006.

Fayezizadeh, M.R., Ansari, N.A.Z., Albaji, M., and Khaleghi, E. (2021) Effects of hydroponic systems on yield, water productivity and stomatal gas exchange of greenhouse tomato cultivars. Agric. Water Manag. 258: 107171. doi:10.1016/j.agwat.2021.107171.

Hashida, S.N., Johkan, M., Kitazaki, K., Shoji, K., Goto, F., and Yoshihara, T. (2014) Management of nitrogen fertilizer application, rather than functional gene abundance, governs nitrous oxide fluxes in hydroponics with rock wool. Plant Soil, 374(1): 715–725. doi:10.1007/s11104-013-1917-4.

Maboko, M.M., Du Plooy, C.P., and Bertling, I. (2011) Comparative performance of tomato cultivars cultivated in two hydroponic production systems. S. Afr. J. Plant Soil 28(2): 97–102. doi:10.1080/02571862.2011.10640019.

Méndez-Cifuentes, A., Valdez-Aguilar, L.A., Cadena-Zapata, M., González-Fuentes, J.A., Hernández-Maruri, J.A., and Alvarado-Camarillo, D. (2020) Water and fertilizer use efficiency in subirrigated containerized tomato. Water, 12(5): 1313. doi:10.3390/w12051313.