Kratky Method: Non-circulation, non-electric hydroponic system

The Kratky Method of Non-circulation, non-electric hydroponic system was developed by Prof. Kratky from University of Hawaii. It works best for growing lettuce. You only need to fill the hydroponic container once during the grow cycle, when the planting the lettuce. No pump or aeration is needed. The most complete and practical description of the method is available in PDF form here:

Buttercrunch lettuce in Kratky hydroponics at the time of transplant to a net cup:

Lettuce grown with Kratky hydroponics, after 1 month:

Containers for Kratky hydroponics can be made from a variety of sources: Note the 2-inch hole for a net cup in the top cover of the containers, and black spray paint or aluminum foil that blocks the light from entering the water/fertilizer chamber:

The medium placed in the net pots is a mixture of peat and perlite. However, any non-soil growing medium can be used as long as it is sterile.

Prof. Kratky has described 3 non-circulating hydroponic methods for growing lettuce, which do not require electricity, pumps or wicks, with multiple variations. All of the nutrient solution is added prior to planting or transplanting.

- In the simplest system, lettuce is seeded in a tapered plastic net pot filled with growing medium and placed in a darkened, 4-liter plastic bottle filled with nutrient solution with the lower 3-cm-portion of the pot immersed in nutrient solution. Plants are automatically watered, because the entire growing medium in the net pot becomes moistened by capillary action. Plant growth reduces the nutrient solution level, creating an enlarging moist air space. Meanwhile, the root system expands and continues to absorb water and nutrients. Leaf and semi-head lettuce cultivars are usually harvested at about 6 to 7 weeks after seeding.

- A typical expansion of this concept to a commercial scale employs a 14 cm high tank lined with polyethylene sheeting which is filled with nutrient solution and covered with an expanded or extruded polystyrene sheet resting on the
tank frame. Lettuce is planted or transplanted into net pots filled with growing medium and placed in holes in the cover. Lettuce seedlings are initially watered by capillary action, and later, by direct root uptake. The crop is harvested before the nutrient solution becomes exhausted.

- Another modification of this method is a float-support system in long rectangular raceway tanks. Lettuce is planted or transplanted into net pots placed in a sheet of extruded polystyrene. The cover initially floats on the nutrient solution, and then, comes to rest on 2 parallel plastic pipes (10 cm diam) resting on the tank floor as the nutrient solution level recedes due to plant growth. The tank is filled with water immediately prior to harvesting and floating rafts may be easily moved to a harvesting station.

The Kratky method allows you to grow the plants in a static nutrient solution without the need for aeration:

Related products from Amazon:

This is the hydroponic solution (only loaded when planting lettuce) - 2.2 lbs. - MaxiGro - Grow Stimulator - Hydroponic Nutrient Solution - 10-5-14 NPK Ratio - General Hydroponics GH1211, $15 in 2013.

These are the net cups that hold the plants: 100 2-Inch Net Slit Pots for Hydroponic Aeroponic Use, $12 in 2013

You will need a hole saw to make holes for the net cups in the barrier between the outside environment and the hydroponic solution. A 2-Inch Hole Saw should work best for the 2-inch cups. You will also need a mandrel (often sold together with the hole saw) and a standard 3/8 drill.

Dr. Bernard Kratky's American Society for Horticultural Science horticultural talk on non-circulating hydroponics. Graduate of Purdue University and professor in Hawaii, Dr. Kratky's patented methods are known around the world.

Reference articles by B. A. Kratky:

A Suspended Net-Pot, Non-Circulating Hydroponic Method for Commercial Production of Leafy, Romaine, and Semi-Head Lettuce
A Simple Hydroponic Growing Kit for Short-Term Vegetables
A suspended pot, non-circulating hydroponic method
A Capillary, Noncirculating Hydroponic Method for Leaf and Semi-head Lettuce
Growing lettuce by a float-support non-circulating hydroponic method in Hawaii and Pennsylvania
Non-circulating hydroponic methods for growing tomatoes
Non-Circulating Hydroponic Cucumber Production in Plastic Trash Containers
Three non-circulating hydroponic methods for growing lettuce.
Observations on a Noncirculating Hydroponic System for Tomato Production
Plastic-covered rainshelters for vegetable production in the tropics
Growing Hydroponic Cucumbers in a Plastic Trash Container
Small-Scale Lettuce Production with Hydroponics or Aquaponics

More information can be found by searching for "Kratky" here:

Related reading:

Kratky method from "mhpgardener" YouTube channel
Kratky's non-circulating hydroponics - Instructables step-by-step
Frequently Asked Hydroponic Questions & Answers - from "mhpgardener" YouTube channel
From soil gardening to non-circulation hydroponics | Low-tech Urban Farmer
Kratky Method of Hydroponics - Queen D Ranch Gardening
An inexpensive Kratky growing container - TheMrArlington - YouTube
Here is a commercial system modeled after the Kratky method: Viagrow™ Kratky Method Hydroponic System | Atlantis Hydroponics
Floating Lettuce - Hydroponic system saves space and work - Growing Magazine
This looks like one of Prof. Kratky's original articles:
Hydroponic Nutrients For Kratky Method Lettuce - YouTube


Queen D Ranch Gardening said...

Thank you for the link. We appreciate it very much.

We have had spectacular results with Kratky method of non-circulating hydroponics. Our methods differ somewhat from what you outline here. Our media is pretty much anything non-organic. Pea gravel and expanded clay pellets have worked well. Sterilization of the media does not seem to be necessary. We reuse it quite successfully. The nutrient we use is a low nitrogen mix as close to 4-18-38 (masterblend) as we can get if we mix it ourselves. Otherwise we siimply use the 4-18-18 Masterblend water soluble fertilizer.

We have successfully grown and harvested tomatoes, green beans, zucchini, eggplant, Swiss chard and several kinds of lettuce. The growth rate on the Kratky-method plants is astounding. The plants do not get very tall but get very bushy and produce amazingly well.

This type of hydroponics is so easy and produces such great results, we hope that many people enjoy using it. Thank you for spreading the word.

BorealWormer said...

The link to his ASHS HortTalks Presentation now gives a 404 error. If anyone finds the video elsewhere please post a link.

Thank you to the 'Doctor'. Yours is the most complete collection of information about the Kratky method I've found on the web.

ManInVictoria said...

I am wondering about the water to nutrient solution ratio? Could someone give me an example of how much might be needed? Thanks!