Growing in Water or Soil

By Rupert Jannasch

A nutrient film feeds hydroponically grown plants

A novel trend may be emerging in organic agriculture - crop production without soil. It is curious because organic food production has, without exception, always been dependent on fertile soil. Certification standards provide detailed guidelines on how to protect, conserve and build soil. Biological soil processes are essential to converting organic fertilizers into forms useable by plants. How is it that soil-less culture using nutrients dissolved in water - the system known as hydroponics - is considered organic?

In an 8000 ft² greenhouse near Westport between Kingston and Ottawa, organic herbs and gourmet greens are thriving in what may be Canada's first certified "organic, hydroponic" greenhouse. In March, 2003, Ray Cooper and his partner Gerrie Baker, planted their first basil seedlings in a mixture of peat, perlite (expanded volcanic rock) and compost. Ten days later the seedlings were transplanted into perlite beds on sloped, plywood tables.

Nutrient solution is pumped from a 900 gallon tank to the raised end of each bed. Instead of top watering, the plant roots are drenched in a nutrient solution film that flows slowly down the table. The key element, says Gerrie "is that plants receive as much air as water - that's where the perlite helps."

The nutrient flow is determined by an electronic device that measures accumulated sunlight. The goal is to supply just enough nutrient's to match the rate of energy capture, or photosynthesis, from the sun. This has two advantages. When nutrients are delivered in tune with the plant's needs, waste is eliminated. Unused solution is recycled through the main tank via an ultra violet filter which kills algae and bacteria. Secondly, a well-tailored fertilizer regime should produce fast growing and robust plants resistant to pests and disease.

The main fertilizer is made from ingredients such as fish meal, composted seabird guano, soybean extract, potassium carbonate and raw sugar cane extract. Its N-P-K analysis is 3-1.5-4. Leaf tissue analysis is used as basis for detecting any deficiencies of micronutrients such as zinc, copper or iron. These elements can be mixed in the solution, as can a concentrated nitrogen fertilizer (16:0:0 N-P-K) if needed to balance the mixture. All the fertilizers are approved by Organic Crop Producers and Processors (OCCP), the organic certifier for Ray and Gerrie's.

Nutrient solutions are not new to organic agriculture. For example, fish emulsion and seaweed extracts are commonly used for soil-based transplant production in greenhouse culture. The fungi and bacteria in compost teas can help ward off plant diseases. It is unusual, however, for liquid fertilizers to be the sole source of nutrients in organic systems.

Populations of beneficial and harmful organisms are highly regulated in hydroponic greenhouses. On one hand, biological control using active nematodes such as Steinermenia feltaie against fungus gnats represents the leading edge in organic pest management. The widespread use of bleach, however, to maintain sterile conditions and prevent plant disease, illustrates that hydroponic greenhouses are artificial environments that do not operate under normal cycles of growth and decay.

Gerrie Baker believes customers are eager to buy her products because they appreciate the taste, cleanliness and uniformity of hydroponic crops.

"I'd like to see a marriage of hydroponics and organic for the benefit of the customer," she says. "They get a superior product. The nutrition and the aesthetics is in the food because it is being produced organically, but in an insect and fungus-free environment."

Not everyone in the organic community may share Gerrie Baker's enthusiasm. In fact, the question of soil-less, organic culture has stirred debate since the 1940s. Currently, the Certified Organic Organizations of British Columbia and Demeter exclude hydroponics from organic certification altogether. The National Organic Program in the United States has not yet taken a position on the matter.

At issue is whether organic production should be regulated as a process based on well defined principles of organic agriculture, or, whether organic certification can hinge on compliance with an approved materials list. Organic hydroponics appears to have the green light not so much because it resembles established models of organic crop production, but because substances prohibited in organic agriculture are not used.

Does this matter? Maybe not, but it could lead to at least one large question of credibility. Consider that soil-less culture has many merits, two of them being efficient nutrient use and a low risk of soil and water pollution. In this case, why not allow conventional fertilizers in "organic hydroponics?" Fertilizers will not disrupt soil processes because, unlike field conditions, there is no plant/soil interaction to disrupt. Pollution is not a threat because hydroponic operations produce little waste. Although organic standards clearly prohibit the use of artificial fertilizers, the rules make little sense in the case of hydroponics.

Sooner or later, as hydroponics catches on - and it definitely will - powerful interests will push for permitting artificial fertilizers in "organic hydroponics." Opening this can of worms may well decide if organic farmers continue to work by the maxim, 'feed the soil or the plant.'

Rupert Jannasch, M.Sc., P.Ag. is a consultant for the Organic Agriculture Centre of Canada. Please send comments or questions by phone to 902-893-7256 or by email to oacc@nsac.ca.

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