How To Combine Organic Growing With Hydroponics

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December 7, 2020

The idea of having an organic hydroponic system might seem like an oxymoron, but it is possible to achieve the terroir of soil growing with the sustainability of hydroponics. Before we find out how this works, it is essential to understand the terms organic and hydroponic.  

What Is Organic?

The legal definition of organic certification varies depending on where you are in the world. As with most things in America, the rules that govern organic certification are less strict than in other developed nations. The USDA states that food crops are organic if they have grown on soil that has not been contaminated with prohibited substances for three years before harvest. 

Prohibited substances include most synthetic fertilizers and pesticides. When a grower uses a manufactured product, it must have third party certification and meet various criteria that ensure human and environmental health. 

organic hydroponic

In Europe and Canada, the rules are much more stringent and encompass the entire cultivation process and its impact on the environment. In the EU, you cannot obtain organic certification if growing in pots or containers rather than in a field. More importantly, they do not allow for the organic certification of soilless hydronic systems like the U.S. has. In general, Canada and the EU have eco-conscious rules in place for the use of precious freshwater in commercial agriculture. They also actively prevent the discharge of waste nutrient solutions into natural waterways by using sustainable irrigation practices. Farmers in the U.S. could learn a thing or two in this regard, especially considering the number of dead zones in natural waterways created by the unchecked discharge of nitrogen fertilizer. American farmers are also the largest consumers of freshwater, leading to wells going dry and land subsidence. 

However, for the sake of this article, “organic” will be defined as a product that is naturally derived and falls under the USDA certification.

What Is Hydroponics? 

Hydroponics means “waterworks” and involves growing plants in media other than soil. Plant food is provided through a nutrient solution, whereas in nature, the earth provides all the food for the plant with water acting as a vehicle. Hydroponics involves growing in different substrates that can be used by themselves or in various mixtures for desired performance. These include Rockwool, perlite, coco, peat, and even aeroponics (growing plants in the air). Deepwater culture, where the roots are suspended in an aerated nutrient solution, is also possible, along with nutrient film technique (NFT), where the plant’s roots grow in a thin stream of moving solution. These systems help save water, as they are mostly recirculating systems, and are extremely clean, spared from the pests and diseases associated with growing in soil. Hydroponic systems allow for a great deal of control in nutrient supply for the plants and allow for higher yield and more crops per year due to the faster growth rates. 

Organic Hydroponics?

In the U.S., there are a few hydroponic growers that are organic certified. They are granted the certification because they use living organic substrates like coconut fiber, peat, and more. The process by which their products are manufactured does not change their functional properties, and no synthetic products are added. Organic hydro growers also use biodynamic nutrient solutions derived from other plants (like compost teas) in addition to refined fish and animal by-products. 

The challenge with these solutions in hydroponic systems is how to deliver them to plants effectively. The simplest is to hand-water pots of organic substrate (other than soil) with a batch of solution mixed at the time of application. At any size farm, it is more challenging to use organic nutrient solutions in drip irrigation systems, as the nutrients can quickly clog a pressure-compensated drip emitter. Most home and small market growers use an open flow irrigation system to allow the solution to pass through the line easily. Unfortunately, this system doesn’t allow for a lot of control, so growers have to use larger volumes of growing media with longer feed times to make up for inconsistencies. Ebb and flow tables are also excellent for using organic nutrients, as there is a reduced risk of equipment failure. Still, more regular observation of the reservoir is required, along with frequent exchanges of nutrient mix to avoid imbalances and potential diseases. 

organic hydroponic

In commercial organic farms, grade pumps maintain pressure-compensated drip systems that deliver water evenly to all the plants. They use nutrient solutions that are refined and filtered. Following every nutrient application through the irrigation system, freshwater is flushed through the lines and drippers to prevent clogs and diseases that can impact quality and yield. When attempting to use organic solutions on a recirculating system, watch for a build-up of ammoniacal nitrogen in the tank. Consider using a biological filter that grows beneficial bacteria to maintain the delicate natural balance. Change the nutrient solution every two weeks.

Aquaponics

Some certified organic hydroponic growers combine aquaculture (AKA fish farming) to provide nutrients to their plants. In these systems, a fish tank is used with a biological filter that maintains naturally-accruing bacteria to break down the fish waste for the plants. Recirculating systems allow the water to flow from the fish tank through mechanical and biological filters to the plants, and then back into the fish tank. It can be challenging to grow with these systems, as you have to keep the fish alive and at a specific size to create enough food for the plants. Also, striking a balance between the plants and fish is not easy. Adding too many supplements or nutrient additives for the plants might hurt or kill the fish. A better idea is to keep the fish and plant systems separate, pulling the wastewater from the fish tank’s biological filters and mixing into the hydroponic nutrient solution. 

Combining the environmental and health benefits of organic growing techniques with the labor and water savings of hydroponics is a great way to grow more food and flowers with fewer inputs. Happy growing!

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Doug Jacobs

Technical Advisor at Grodan
Doug provides expert consulting on proven Precision Growing methods to optimize crop production with Grodan Rockwool growing media and proper irrigation, producing the best quality plants using the least amount of inputs. He has experience with indoor, outdoor, and greenhouse hydroponics, vertical farms, aquaculture, and CEA system design, helping to design farms across North America. Doug showcases his passion and expertise as a feature writer in various national industry publications and as a conference speaker at US events.
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