Hydroponics and Organic Production

Hydroponic production continues to be one of the most debated areas within U.S. organic agriculture. While hydroponics is not explicitly defined or prohibited in the National Organic Program (NOP) regulations, USDA has clarified that hydroponic and container-based systems may be certified organic, provided they comply with the same core principles and production requirements that apply to all organic crop operations.

What the NOP Does (and Does Not) Say About Hydroponics

The NOP regulations (7 CFR Part 205) do not contain the words hydroponics, aquaponics, aeroponics, or soilless production. As a result, certification decisions rely on how hydroponic systems are evaluated against existing organic crop standards, including:

Soil fertility and crop nutrient management
Natural resource conservation
Prohibited substance restrictions
Organic system plan (OSP) documentation
Reliance on biological and ecological processes

To help address this gap, USDA convened the Hydroponic and Aquaponic Task Force, which issued its Final Report in 2016. While the report is not regulation, it provides the most detailed federal guidance on how hydroponics should be interpreted within the organic framework.

Key Guidance from the 2016 Hydroponic Task Force Report

One of the most important conclusions of the Task Force is that existing NOP regulations do not fully address container-based or hydroponic production, and that additional standards would be necessary if these systems are to be certified consistently.

“If certification includes crops grown in containers, it will require additional standards to cover the practices that are not covered by existing regulations.”

The report identifies the central challenge of hydroponics in organic production:

How to ensure that container-grown plants receive most of their fertility from natural processes of the soil or compost-based media, rather than from continuous liquid feeding.

Proposed Fertility Limitations (Task Force Recommendations)

To preserve the biological foundation of organic production, the Task Force suggested the following interpretive limits:

No more than 50% of a crop’s required fertility should be added after planting
No more than 20% of fertility should be supplied through liquid fertilizers after planting
For perennial crops, these limits should apply on an annual basis

These thresholds were proposed to prevent hydroponic systems from functioning as nutrient-solution delivery systems rather than biologically active growing systems.

Notably, the report references similar approaches used by IFOAM EU, which also limits post-planting fertility inputs to preserve soil-based nutrition, even in greenhouse and intensive systems.

Growing Media Volume Matters

The Task Force also highlighted research by Dr. Martine Dorais (Laval University / Agassiz Research and Development Centre), which demonstrated that:

When crops are grown in 100–180 liters of soil per square meter
Fertility can be supplied by biological activity in the growing medium
No liquid fertilization is required

This finding reinforces a key organic principle: fertility should be driven primarily by microbial processes, mineralization, and organic matter cycling, not constant external feeding.

The Task Force further recommended that the entire growing area, including paths between rows, be considered part of the production area. While this interpretation stretches the literal language of the Organic Foods Production Act (OFPA), it better reflects the intent of organic land stewardship.

What Else Can We Interpret from the NOP for Hydroponics?

Even without hydroponics-specific rules, several existing NOP provisions clearly shape how hydroponic systems must be designed and managed.

1. Soil Fertility and Crop Nutrient Management (7 CFR §205.203)

Although hydroponics may not use in-ground soil, the regulation requires that fertility be managed through:

Tillage and cultivation practices
Crop residues
Manure and compost
Cover crops
Biological activity

For hydroponic and container systems, this implies:

Compost-based or biologically active media
Nutrient cycling within the system
Clear limits on reliance on soluble fertilizers

eCFR :: 7 CFR Part 205 Subpart C -- Organic Production and Handling Requirements

A producer may manage crop nutrients and soil fertility to maintain or improve soil organic matter content in a manner that does not contribute to contamination of crops, soil, or water by plant nutrients, pathogenic organisms, heavy metals, or residues of prohibited substances by applying:

(1) A crop nutrient or soil amendment included on the National List of synthetic substances allowed for use in organic crop production;

(2) A mined substance of low solubility;

(3) A mined substance of high solubility: Provided, That, the substance is used in compliance with the conditions established on the National List of nonsynthetic materials prohibited for crop production;

(4) Ash obtained from the burning of a plant or animal material, except as prohibited in paragraph (e) of this section: Provided, That, the material burned has not been treated or combined with a prohibited substance or the ash is not included on the National List of nonsynthetic substances prohibited for use in organic crop production; and

(5) A plant or animal material that has been chemically altered by a manufacturing process: Provided, That, the material is included on the National List of synthetic substances allowed for use in organic crop production established in § 205.601.

(e) The producer must not use:

(1) Any fertilizer or composted plant and animal material that contains a synthetic substance not included on the National List of synthetic substances allowed for use in organic crop production;

(2) Sewage sludge (biosolids) as defined in 40 CFR part 503; and

(3) Burning as a means of disposal for crop residues produced on the operation: Except, That, burning may be used to suppress the spread of disease or to stimulate seed germination.

2. Natural Resource Conservation (7 CFR §205.200)

Organic operations must maintain or improve:

Soil quality
Water quality
Ecosystem health

For hydroponics, this affects:

Nutrient runoff and discharge
Water reuse and efficiency
Salt accumulation
Waste nutrient streams

Systems that function as closed-loop, biologically buffered environments are more consistent with this requirement than open nutrient-solution systems.

3. Prohibited Substances and Material Inputs (§205.105, §205.601)

Hydroponic systems must:

Use only allowed fertilizers and inputs
Avoid synthetic chelates, acids, or stabilizers not permitted under the NOP
Ensure nutrients are not functioning as a replacement for biological fertility

eCFR :: 7 CFR 205.105 -- Allowed and prohibited substances, methods, and ingredients in organic production and handling.

Allowed synthetics as crop or soil amendments

Aquatic plant extracts (other than hydrolyzed)
– Extraction process limited to potassium hydroxide or sodium hydroxide
– Solvent amount limited to the minimum necessary for extraction
Elemental sulfur
Humic acids
– From naturally occurring deposits
– Water and alkali extracts only
Lignin sulfonate
– Chelating agent
– Dust suppressant
Magnesium oxide
– For use only to control the viscosity of a clay suspension agent for humates
Magnesium sulfate
– Allowed with a documented soil deficiency
Micronutrients
– Not to be used as a defoliant, herbicide, or desiccant
– Those made from nitrates or chlorides are not allowed
– Micronutrient deficiency must be documented by soil or tissue testing or another documented and verifiable method approved by the certifying agent
- Soluble boron products
- Sulfates, carbonates, oxides, or silicates of zinc, copper, iron, manganese, molybdenum, selenium, and cobalt
Liquid fish products
– May be pH adjusted with sulfuric, citric, or phosphoric acid
– Acid use limited to the minimum required to lower pH to 3.5
Vitamins C and E
Squid byproducts
– From food waste processing only
– May be pH adjusted with sulfuric, citric, or phosphoric acid
– Acid use limited to the minimum required to lower pH to 3.5
Sulfurous acid (CAS # 7782-99-2)
– For on-farm generation of the substance
– Must use 99% purity elemental sulfur per paragraph (j)(2) of this section

As algicides, disinfectants, and sanitizers, including irrigation system cleaning systems

Alcohols
- Ethanol
- Isopropanol
Chlorine materials
– For pre-harvest use, residual chlorine levels in water in direct crop contact, or in water from cleaning irrigation systems applied to soil, must not exceed the maximum residual disinfectant limit under the Safe Drinking Water Act
– Exception: chlorine products may be used in edible sprout production according to EPA label directions
- Calcium hypochlorite
- Chlorine dioxide
- Hypochlorous acid (generated from electrolyzed water)
- Potassium hypochlorite (for use in irrigation water)
- Sodium hypochlorite
Copper sulfate
– For use as an algicide in aquatic rice systems only
– Limited to one application per field during any 24-month period
– Application rates must not increase baseline soil copper levels over a timeframe agreed upon by the producer and the accredited certifying agent
Hydrogen peroxide
Ozone gas
– For use as an irrigation system cleaner only
Peracetic acid
– For disinfecting equipment, seed, and asexually propagated planting material
– Also permitted in hydrogen peroxide formulations allowed under §205.601(a)
– Maximum concentration: 6%, as indicated on the pesticide product label
Soap-based algicides / demossers
Sodium carbonate peroxyhydrate (CAS #15630-89-4)
– Federal law restricts use in food crop production to approved food uses identified on the product label

As crop disease control.

Aqueous potassium silicate (CAS #-1312-76-1)—the silica, used in the manufacture of potassium silicate, must be sourced from naturally occurring sand.

Coppers, fixed—copper hydroxide, copper oxide, copper oxychloride, includes products exempted from EPA tolerance, Provided, That, copper-based materials must be used in a manner that minimizes accumulation in the soil and shall not be used as herbicides.

Copper sulfate—Substance must be used in a manner that minimizes accumulation of copper in the soil.

Hydrated lime.

(5) Hydrogen peroxide.

Lime sulfur.

Oils, horticultural, narrow range oils as dormant, suffocating, and summer oils.

Peracetic acid—for use to control fire blight bacteria. Also permitted in hydrogen peroxide formulations as allowed in § 205.601(i) at concentration of no more than 6% as indicated on the pesticide product label.

Potassium bicarbonate.

Elemental sulfur.
Polyoxin D zinc salt.

As insecticides (including acaricides or mite control).

Ammonium carbonate—for use as bait in insect traps only, no direct contact with crop or soil.

Aqueous potassium silicate (CAS #-1312-76-1)—the silica, used in the manufacture of potassium silicate, must be sourced from naturally occurring sand.
Boric acid—structural pest control, no direct contact with organic food or crops.
Copper sulfate—for use as tadpole shrimp control in aquatic rice production, is limited to one application per field during any 24-month period. Application rates are limited to levels which do not increase baseline soil test values for copper over a timeframe agreed upon by the producer and accredited certifying agent.

Elemental sulfur.

Lime sulfur—including calcium polysulfide.

Oils, horticultural—narrow range oils as dormant, suffocating, and summer oils.

Soaps, insecticidal.

Sticky traps/barriers.

Sucrose octanoate esters (CAS #s—42922-74-7; 58064-47-4)—in accordance with approved labeling.

As insect management.

Pheromones.

Allowed synthetics as synthetic inert ingredients as classified by the Environmental Protection Agency (EPA), for use with nonsynthetic substances or synthetic substances listed in this section and used as an active pesticide ingredient in accordance with any limitations on the use of such substances.

EPA List 4—Inerts of Minimal Concern.

(2) EPA List 3—Inerts of unknown toxicity—for use only in passive pheromone dispensers

Production aids.

(1) Microcrystalline cheesewax (CAS #'s 64742-42-3, 8009-03-08, and 8002-74-2)—for use in log grown mushroom production. Must be made without either ethylene-propylene co-polymer or synthetic colors.

(2) Paper-based crop planting aids as defined in § 205.2. Virgin or recycled paper without glossy paper or colored inks.

4. Organic System Plan (OSP) Accountability

Hydroponic producers must clearly document:

Growing media composition
Source of fertility before and after planting
Percentage of nutrition supplied via liquid feeding
How biological activity is maintained
How the system aligns with organic principles

Hydroponics may be eligible for organic certification under the current NOP framework but only when it is managed as organic crop production, not as a nutrient-delivery technology.

The strongest interpretation of the NOP suggests that organic hydroponic systems should: