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.).