There is a long-standing debate as to whether soilless hydroponic systems can ever be completely organic. For the most part, this debate is the result of disputed ideas about what organics actually means. Even in the commercial horticultural world, things are not clear-cut when it comes to what is and what isn’t considered organic.
In many parts of the world, certified-organic systems must have soil as the cornerstone of their production. In the United States, certain types of hydroponic systems can become organically certified without the use of soil.
While the reasoning behind whether or not hydroponics is organic is still under debate, hobby growers need not bother with the large-scale logic. Instead, they should decide what organics means to them and follow techniques to fulfill their own ideologies.
For some growers, producing organic and natural crops from an indoor garden simply means avoiding the use of toxic chemicals such as synthetic pesticides, fungicides and sterilization agents. These types of growers choose to focus more on natural approaches while fully embracing hydroponic methods.
For others, growing organically means incorporating the use of organic nutrients combined with beneficial microbial populations similar to the methods used by soil-based organic producers. Unfortunately, it’s not just a simple case of switching from traditional, fertilizer-salt-based nutrients to organic ones since many early hydroponic systems were never designed to be used with organic compounds and many growers have run into major issues when trying this.
Traditional hydroponic nutrients are made from fertilizers such as calcium nitrate, potassium nitrate, monopotassium phosphate, iron chelate and many others that, when dissolved into water, dissociate into ions ready for immediate uptake by plants. This is what allows for such rapid and balanced plant growth.
The plants never have to starve or wait for nutrient ions to become available. However, calcium nitrate and many others used in traditional hydroponic systems are not considered organic, but synthetic or man-made, and are not part of an organic system.
Replacing highly effective and carefully calculated fertilizer salts with organic nutrient sources is not easy. Manufacturers of hydroponic fertilizer products go to great lengths to get the ideal parts per million of each nutrient ion in their products so plants grow as fast and balanced as possible.
With organic nutrient sources, it’s impossible to be so precise, so mineral deficiencies within organic hydroponic systems are often an issue. Also, organic nutrients contain a great deal of carbon, which non-organic nutrient products do not provide. This carbon is an ideal source of food for microbes in the nutrient solution and root zone, feeding both beneficial and pathogenic fungi and bacteria.
If unwanted microbes begin feeding on the carbon from organic nutrient sources, things can get a little toxic, creating slimy nutrient solutions, anaerobic root conditions, diseases and even plant die back. To avoid these problems, organic growers just starting out should begin slowly and with systems known to have a better success rate.
Among the most successful systems for organic hydroponics are aquaponic systems. If the system is run with the correct fish-to-plant ratio and a good rate of mineralization carried out by specific bacteria, aquaponics is one of the easiest approaches to organics.
Novice growers should start with low-nutrient-demanding crops, such as lettuce, salad greens and fresh herbs, and gradually build up to fruiting plants as the system matures and higher rates of mineralization occur. Even though aquaponic systems provide good levels of nutrient ions from fish waste, high-nutrient-demanding crops may still need a little supplementation, especially extra trace elements from time to time.