H Dr Estelle Kempen Department of Agronomy, Faculty of AgriSciences, Stellenbosch University ydroponics or the technique of growing crops without soil has been around for many years and is employed world-wide mainly for the production of vegetables, cut flowers and ornamental crops. During the last few years there has been renewed interest in hydroponics as a method of increasing food production, specifically in urban and peri-urban areas. As plants are also fertigated and the drained nutrient solution can be re-use it is the perfect solution for a country where water for crop production is increasingly becoming limited. The demand for organic products in South Africa is still growing (Kelly and Metelerkamp 2015). It would therefore seem like a perfect opportunity to produce for the organic market using hydroponics. The question is; can plants in hydroponic systems be certified as organic? According to the FAO organic agriculture can be defined as a system that relies on ecosystem management rather than external agricultural inputs. The environmental and social impacts of the system are considered by eliminating the use of synthetic inputs, including synthetic fertilizers and pesticides and genetically modified seeds. These are substituted with management practices that maintain and increase long-term soil fertility and prevent pest and diseases. According to the International Federation of Organic Agriculture Movements (IFOAM) hydroponic and aeroponic systems are prohibited from organic certification. In most countries therefore hydroponic crops can thus not be certified organic. In the United States the advisory board to the USDA's National Organic Program (NOP) also recommends that potting mixtures devoid of or deficient in organic matter capable of supporting a natural and diverse soil ecology should also be prohibited. However some Figure 1. From Shinohara et al (2016). Tomato growth in a conventional and organic hydroponic system. The growth and quality of tomato plants grown using the organic hydroponics approach with corn steep liquor (CSL) or fish-based soluble (Fish) fertilizer as the nitrogen source, and in a conventional hydroponics system with inorganic fertilizer (conv.).