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OTCO Hydroponic FAQs

Questions and answers regarding organic hydroponic operations


Oregon Tilth Hydroponic Webinar
The following recorded webinar discusses how hydroponic systems work and what Oregon Tilth looks for when evaluating them. The USDA NOP has confirmed the acceptence of hydroponic and aquaponic production under the USDA standards.  What does this all mean and how does the OTCO program verify compliance?  Watch this informational webinar focusing on these unique production methods.

Does the land on which a hydroponic system is constructed need to be free of prohibited materials for 36 months (205.202(b))?
No.  A soil-less system is not required to meet the land history requirements. 

What type of growing media can I use?
Only nonsynthetic growing media is allowed.  Any substance which supports the root system must be nonsynthetic.  Note that rockwool is a prohibited synthetic due to its chemical methods of production (see OMRI, and definition of “Synthetic” in 205.2).  

Are synthetic rafts, floats, tables, containers, gutters, allowed? 
Yes.  Any structure that merely surrounds or supports the plant, and is not a media for the root system, can be synthetic.  This is analogous to a plastic pot or seedling tray in a greenhouse.

What is allowed for pH adjustment?
Only nonsynthetic (natural, mined) or National List synthetic materials are allowed for pH adjustment.  Examples of allowed materials for pH adjustment: citric acid (produced by a non-GMO organism), vinegar, calcium carbonate (oyster shells, etc.).  Examples of prohibited materials: nitric acid, phosphoric acid, potassium hydroxide, calcium hydroxide. 

Is regular water testing required?
No, but the water must not contaminate the organic crop with prohibited substances.

What needs to be in place for an inspection to occur?
The system must be complete with all equipment and ready to begin production, but plants do not need to be growing to be inspected.

Am I allowed to paint the inside of my galvanized tank or other equipment in the growing system?
Yes, but you must show that the paint is not contaminating the organic crop (i.e. leaching or peeling). 

Can I use pressure treated lumber for construction of my building or beds?
Yes, but pressure-treated wood must not contact the water the plant is grown in or the organic crop (205.206(f)).

Can the operation be indoors (i.e. in a house or garage)?
Yes.  There is no requirement in the organic standards that plants be grown outdoors.

Are Fill & Drain (Ebb & Flow) systems allowed?
Yes.  Fill and Drain is a method of water management and is allowed.

Can manure be used in a growing media mix?
Yes, the restriction on manure is the same as applied to any other cropping system (205.203(c)).  If the water or manure touches the organic crop then a 120-day pre-harvest interval is required. 

Can synthetic micronutrients be applied?  What is required to document deficiency?
Synthetic micronutrients can be used in a hydroponic system.  Most hydroponic systems are obviously deficient of micronutrients, however deficiency must still be documented (205.601(j)(6)). Micronutrients which are synthetically chelated are not allowed in organic production [205.601(j)(6)(ii)].

Can I operate a split production system?
Yes, but they must be physically separate and there can be no commingling of water or inputs. Records must be maintained to confirm that contamination and commingling has not occurred.

Does fish food or medicine need to be organic?
No. OTCO considers that fish feed is consumed by the fish and not used by the plants.  All fish feed and medicine inputs are allowed.   However, chemicals which modify the pH of the water, or which can be taken up directly as plant nutrients (potassium hydroxide, phosphoric acid, etc.), are not considered fish food and are therefore not allowed.

Can fish food contain antibiotics?
Yes, provided that antibiotics will not contaminate the organic crop.  Antibiotics may not be administered in the same solution used by the organic crop.  Antibiotics which are solely used for fish production are allowed, as long as it is not intended as a crop production input.

Does an aquaponic system require a pre-harvest interval for fish manure, or testing of water that includes fish excrement?
No.  The NOP definitions in 205.2 states that “Manure” is produced by livestock, and the definition of “Livestock” excludes aquatic animals.  No pre-harvest interval or testing of water is required.  However, the water used for organic production must not contain chemicals (nitrates, etc.), which could contaminate the organic crop.

 For effluent, what are the requirements for the prevention of leaching and/or disposal of excess nutrients?
The operation must manage effluent in a way that does not contribute to the contamination of crops, soil, or water.  This must be included within the operation’s Organic System Plan.

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