Of all the hydroponic growing media you can use water is cheap and the easiest to obtain. Water can be filtered, typically with an RO machine, and sterilized with UV or Ozone to create a clean and consistent substrate tailored to your growing requirements. Many hydroponic growers already understand the virtues of using, and more importantly reusing, water in hydroponic systems. So, why not go the whole hog, throw away your rock wool/soil/coco/clay pebbles and use water culture?!

What is Water Culture?

Deep water culture (DWC) – At its essence, a DWC system is made up of a container, lid and net pot. The container holds the nutrient solution (typically 2.5–4 gallons (10–15 liters)) and the lid supports a single plant growing in a net pot. Roots grow out the net pot and into the nutrient solution held in the container below. In the container, an air stone bubbles away to agitate the solution and keep dissolved oxygen levels high—essential in any DWC system. Shallow water culture (SWC) is based on the same principle but, yes you’ve guessed it, uses a lower volume of water.

Single vs. Recirculating

Single stand-alone systems are fairly cheap to buy and even more popular for DIY enthusiasts. Modular DWC systems, in which many containers are connected to a central reservoir, create an active system where the nutrient solution is able to cycle from the reservoir around all the pots, arriving back at the reservoir. Each has inherent issues. Stand-alone systems can be inconvenient to work with, while recirculating systems can spread problematic root diseases very quickly. The key is to operate the chosen water culture system properly, and you’ll be sure to get explosive results. Once you play around with DWC, you’ll most likely wish your system was modular and recirculating.

Q: Ok, lets start with the basics; what types of nutrients and additives work in DWC?

A: In my experience, pure synthetics of the highest solubility tend to work best. Especially formulations with well-balanced mineral ratios as well as being balanced on a molecular level. This tends to translate to a more pH stable nutrient solution that stays viable for longer periods of time.

Q: Where do you stand when it comes to Beneficial Biology in DWC systems?

A: There’s a bit of a fork in the road philosophically when it comes to“bennies” or no “bennies”. In my experiences both tend to work but I lean towards more of a sterile aqueous root zone. It is possible to use a more carbon-based substrate for a plant’s root crown cultivation. It’s this beneficial habitat that could harbor and allow colonization of a plant’s mutualistic organisms. The solution itself has little potential for colonization of anything other than bacteria, which while useful, don’t offer the benefits of fungi’s, which share a more direct relationship with the roots themselves.

Q: Are there any specific pH and EC requirements you recommend?

A: Depending on the nutrient, working with a pH between 5.5–6.5 works fine. If you want to be more specific 6.0–6.3 for veg, and 5.7–5.9 for flower. It’s in these pH ranges that the minerals most needed for the respective plant cycles are most available. With regards to EC, I generally recommend 50–75% of a nutrient manufacturers directed dosage for best results. Remember that lower EC can result in a higher intake of water into a plant’s tissue, which in turn speeds plant metabolism and increases nutrient transport.

Q: How often should growers change-out the nutrient solution? Are there signs they should look out for?

A: Depending on the type of nutrients, a 14–21 day change out schedule is typical. When plants are growing vigorously they can turn the nutrients over several times in that time frame. This is essentially “changing the nutes” by displacement from the top-off reservoir. If the nutes begin to fluctuate in pH or become murky, or if plants begin reducing nutrient usage this is usually a good time to purge the reservoir and mix a fresh batch.

Q: What is the ideal water temperature for DWC systems?

A: We’ve observed that no matter the ambient air temperature, plant roots tend to do best at 62–68°F (17–20°C). Above 72°F (21°C) the solutions dissolved oxygen (DO) holding potential quickly diminishes and below 60°F (16°C) plants tend to slow their metabolism in response to what is perceived as changing seasons. This said, growers could aid in fruit/flower ripening by reducing water temps toward the end of the reproductive cycle. Being able to dial in each zone of the plant (Leaf/Root) specifically often leads to an amplification of plant productivity.

Q: Speaking about DO, what is the best practice for monitoring and maintaining DO levels?

A: Keep nutrients cool and ppm’s at a modest level to ensure good DO saturation. Surface aeration and the implementation of air pumps and diffusers is an easy way to keep the solution agitated and moving. Manual as well as digital meters can be useful for those more meticulous souls. If you go digital buy high end as the budget meters (which still run several hundred dollars) are typically unreliable instruments in a pretty plastic housing.

Q: Can you run through your recommendations for propagating plants destined for DWC?

A: Establishing cuttings with an aeroponic cloner using 1/8th strength nutrients is ideal, preferably under mixed spectrum T-5 lighting. Propagating bare root plants suits DWC best. This offers an easier transition to water culture given there is no wicking substrate (rock wool, Sure To Grow) to hold excess moisture too close to the root crown.

Q: Is there an ideal water level to be maintained in the reservoir?

A: Start with the bare root submersed to the base of the rooted stalk, being sure to not submerse the stem or stalk tissue so as to avoid water logging. If using a wicking substrate, ensure the cube is approx. 1“ above water line; this may necessitate hand watering for a few days before the roots hit the water.

Q: What are the potentialities for plant steering using water level / amount of root zone exposed to the air?

A: With water as their growing media, growers can tailor nutrient solution parameters more specifically. Provoking plant responses such as essential oil production, fruiting and flowering are better manipulated when the substrate can be dialed in. For example, higher exposure of the root zone to atmospheric oxygen can help trigger a plant to increase oil production as a means to conserve water, and can also apply mild root stresses that are often interpreted by the plant as reproductive cues. While higher water levels can cause plants to focus more energy on vegetative production, particularly fan leaves, which in turn speeds transpiration and photosynthetic potential.

Q: Are there any specific pests or pitfalls DWC growers should watch out for?

A: Root diseases no doubt, Pythium, Fusarium, etc. These types of problems are most evident in water culture given the roots high profile, but are also typically found in most hydro methods currently practiced. In our experiences we’ve observed that once the variable causing the problem is removed (warm water, too high an EC, sludging inputs, etc.), it’s completely likely the plants will recover. In other words, root disease is not a death sentence, but a symptom of a problem needing to be addressed.

Q: I have heard from a few DWC growers that veg times can be significantly reduced, is this true?

A: Growers will need to make that call, but when dialed-in there is no faster way to grow plants—hydroponically or otherwise. A well-hydrated plant typically grows more quickly which will inevitably create shorter veg times and still achieve a premeditated harvestable plant size.

Q: Is DWC suitable for longer-term plants, such as donor plants? Commercially DWC is only used for lettuce and short-cycle plants, not for annuals.

A: Water culture is still a relatively new hydroponics method. Though first introduced in the 1930s by professor Gericke at UC Berkley, using water as a primary growth medium is still seen as somewhat impractical by commercial farmers. Due to the need to keep water conditions cool, it’s caused the bottom line to operate large-scale water culture facilities to be cost prohibitive.

Though with the recent improvements in cooling technology and increased efficiencies, I think we are likely to see a move toward water culture as a viable alternative to the current carbon substrate-based approaches presently being used for the growth of annual vegetables.

Especially as farmers discover the reduced volume of fertilizer inputs and the conservation of precious water that are key to water culture’s allure. This is an exciting time for water culture as what has been considered a black art is now emerging as a legitimate means of cultivating a variety of crops.

DESIGNING A HYBRID AERO-FOG-SWC SYSTEM

This system irrigates each plant in three different ways, yet it’s blissfully simple. It’s essentially a modular re-circulating system which incorporates: shallow water culture (SWC) aeroponics misters and aeroponic foggers.

Each plant gets the VIP treatment, basking in a 20 gallon Rubbermaid container! Wow! There are 70 plant containers in total. They are all joined together via ¾” tubing. Nutrient solution is pumped from an underground 55 gallon reservoir with a 1546 gallon per hour pump to the middle of each container. Within each container there’s a large ¾” flexible PVC irrigation ring with 3 x 180° misting nozzles ready to rumble. When the misters are on, the container gets filled with small droplets of nutrient solution, the droplets that don’t get absorbed by the roots fall to fill the bottom of the containers. As the container fills past 2.5 gallons, the solution reaches an overflow tube, from here it returns through ¾” PVC pipe back to the main reservoir.

After running a few tests Devin adjusted the return pipe to the reservoir to make it a more direct return. The foggers are set to spray for almost 7 minutes on and off for 4 minutes. This timing is deliberately adjusted so that sometimes there is only fog, sometimes fog and sprinklers, and sometimes sprinklers half the time and fog half the time. The timers are set so that different watering techniques are activated at different times in different combinations. The logic is the plant won’t get too used to anything and it also allows the root zone to dry a little, encouraging the root hairs to go in search for food. This makes the roots very tenacious, white, and strong.

As soon as the solution returns back to the 55 gallon from the overflow the system kicks back on. The return takes almost 4 minutes. When spraying the roots, the solution comes from the 55 gal reservoir, and it takes just 7 minutes to empty the 55 gal. This is the maximum watering duration that Devin feels he can achieve without getting a bigger reservoir.

In the bottom of each container is a 4” air stone, these are connected to 4 x 750psi air compressors to infuse the 2.5 gallons of nutrient solution with oxygen rich bubbles. Sounds just like an interesting re-circulating system right? Well here is the secret to this high yielding system…

Each container has an aeroponic fogger floating just under the surface of the nutrient solution. Each fogger has three disks. These foggers are on a 5 minute on, 5 minute off cycle to create an extremely fine mist or ‘fog’ with a particle size of 3-5 microns! Such a fine fog of nutrient solution creates supercharged roots with an abundance of fine root hairs. These root hairs can take up water and nutrients at a rapid rate creating explosive plant growth. This technique of utilizing ultra sonic foggers to deliver a nutrient fog to the roots has been recently dubbed ‘Fogponics’, although officially it falls under the banner of aeroponic cultivation.

AEROPONIC FOGGERS

Aeroponic foggers come in various shapes and sizes but all utilize the same technology. They work by sending ultrasonic frequencies to ceramic disks which sit just below the surface of the water. These ultrasonic frequencies vibrate the disk which oscillates the water above creating an ultra fine fog. This fog has such a small particle size that it feels dry to the touch yet it can easily penetrate roots without totally saturating them.

CHALLENGES

1) Foggers

The main drawback of using most foggers with nutrient solutions is they can become clogged very quickly with nutrient precipitate. Even using foggers in hard water alone can cause a quick build up of lime scale, let alone adding mineral salts to the mix, so how does this extreme aeroponic system get around this?

Through trial and error and with some help from Ryan Clout at Sunflower Supply and the online garden forums, these crazy cats found a solution. Devin located a company online selling Teflon coated disks that are longer lasting and keep residues from building up on the disk surface. This drastically prolongs the life of the foggers reducing the need for constant cleaning and frequent replacements.

As mentioned previously, the foggers need to be just below the surface of the water in order to emit the ultra-fine fog. To enable the water level in the container to rise and fall while still allowing the fogger work it became clear that the fogger would have to float. So armed with a tiny budget and a trip to the dollar store, the floats for the foggers were created from play snorkels and net cups for only a dollar for each fogger!

2) Solution Temperature

While in operation, the foggers generate a significant amount of heat that gets soaked up into the nutrient solution. Even with the solution circulating from a large reservoir around all the containers, the temperature of the solution in the bottom of the containers was quickly rising to beyond 75°F. Ideally the nutrient solution should be around 65°F for optimal levels of dissolved oxygen and nutrient uptake. This was a tough nut to crack. The way forward was to cool the nutrient solution and, being and inventive bunch of growers, they decided to make their very own homemade water chiller.

Using an old freezer (2ftx2ftx4ft) as the cooling chamber the crew drilled two ¾” holes through the casing, one near the top and one near the bottom. The cooling mechanism was created by constructing a coil made from 25ft of aluminum tubing. This fitted perfectly into a five gallon bucket which had a drilled hole at the top and bottom. This allowed the ends of the coil to come through. Then, they fed a ½” hose into each of the holes in the freezer, used silicone to seal the holes, and connected them to the coil lines. After making sure the hose and coil were watertight, they used non-toxic propylene glycol antifreeze to fill the five gallon bucket and popped a lid on it.

This homemade chiller is located next to the underground 55 gallon reservoir with the upper ½” hose connected to a pump in the bottom of the reservoir and the lower hose draining the chilled solution back into to the reservoir. This constant flow of nutrient solution being pushed through the chiller created a constant nutrient solution temperature in the reservoir of 60°F, with the containers stabilizing at 70°F, keeping the heat emitted by the foggers under control.

3) Environment

Being in the heart of Southern Oregon, air temperature during summer is also an issue for this aeroponic set-up. The roots are particularly susceptible to extremes in temperature as there is no growing media to act as insulation. On a nice sunny day, an outside temperature of 75°F can easily create up to 100°F in the greenhouse and that’s with the 24 inch ventilation fan and both 24 inch passive shutter inlets open! To keep temperature down on hot days a 25,000 BTU air conditioner was incorporated. It also doubles up as a heater for those cold nights in winter.

SYSTEM ENHANCEMENT

The secret to the system is the hybridizing of SWC, aero-sprayers, and the ultra fine fog creating by the foggers. Studies in the late 90s by NASA have shown that solely using ultra sonic foggers to feed plant roots creates a disproportionate amount of root hair with significantly less lateral root growth, making ‘fogponics’ less suitable for prolonged plant growth – i.e. bringing plants to full maturity. By combining the two aeroponic techniques of fogging and misting upper root zone and utilizing SWC to supply water, dissolved oxygen and nutrients to the lower branching roots, they have achieved the best of both worlds.

One key aspect of this hybrid system that Devin is keen on maintaining is a high beneficial microbe count, particularly predatory nematodes, in the growing media and nutrient solution. The beneficial nematodes are an excellent predator of fungus and bacteria, which Devin is sure will help keep the system clean.

To provide a good home for the microbes to hang out and breed, they have come up with a media mix for the net pots of 5 parts Hydroton to 1 part ‘loose fill’ Sure To Grow. Devin and the crew feel that this mix provides them with the ideal surface area for the microbes to stay happy.

To inoculate the system with tons of beneficial microbes they brew their very own worm compost tea!

DEVIN’S WORM COMPOST TEA

Step 1: To 16 gallons of reverse osmosis water, add 1 fluid oz (28.5ml) of fulvic acid and 1 oz of brewers’ yeast (used for home brewing beer and wine).

Step 2: Add 2.1 fluid oz (60ml) of Humboldt Honey Hydro ES to provide food and energy for the microbes.

Step 3: Add 4 teaspoons (20ml) of Cutting Edge Solutions’ calcium carbonate, the microbes to love it!

Step 4: Take 15” x 23”brew craft fine screen mesh bag and add 2.5 pounds of worm castings.

Step 5: Add and air stone (attached to an air pump) to the mix.

Step 6: Steep the worm casting bag in to solution for 72 hours.

Step 7: Remove the bag, give it a few squeezes and let the solution brew for another 12 hours.

Step 8: Prepare the nutrient solution, Devin uses Cutting Edge 3 part formula.

Step 9: Add the 16 gallons of fresh worm tea to 300 gallons of nutrient solution.

Using this technique the crew manage to brew a full 16 gallons for $15! With this fresh brew of beneficial microbes Devin says you can’t add too much. They even spray the mix on the plants in vegetative growth stage which they have found works best neat or at a minimum dose of 1 part tea to 5 parts water.

Using a plant viable form of calcium carbonate really works wonders. Microbes like to have some kind of nutritional buffer, whether it’s a little bit of potassium or even phosphorus, they just need some kind of mineral to feed off. Devin noticed that his nematode population is 10-15% higher when he used calcium carbonate. He used Cutting Edge Solutions’ calcium carbonate – once you open it you really must use within eight weeks, otherwise it can get susceptible to mold.

Using this concentrated homemade worm-tea the growers find they only need to use ½ to ¾ strength nutrient solution! The main reason is that the worm-tea contains a huge population of predatory nematodes and protozoa (single celled organisms that are found across several kingdoms). They are non algal, and non fungal (such as amoebaes, ciliates, and flagellates) and are the number one predators to bacteria and fungi alike. These little worm-like parasites are nasty little buggers. They are heterotrophic which means they cannot produce their own food. Instead they hunt bacteria and fungi while remaining harmless to you and your plants. They locate and shred apart the fungal mycelia and bodies of bacterial organisms which then provide plant available nutrients and minerals to the root system. It’s a beautiful circle!

Freshly brewed, actively-aerated compost tea and compost tea brewing machines with ready-to-use brewing kits are also available from several companies.

We recommend you check out:

• Vermi-T from Vermicrop Organics
• Progress Earth
• Nature Technologies International
• Bountea

To complete the beneficial microbe mix, they add other beneficial liquid additives. These include Canna’s Cannazyme and Botanicare’s Aquashield. Also, check out Sub Culture B from General Hydroponics.

Every two weeks they change out the nutrient solution for a fresh batch. To empty the system all they need to do is open up three taps – this allows the solution to run out through pipe work onto an outdoor vegetable plot, putting even the ‘waste’ nutrient to good use. To fill the whole system they prepare a 300 gallon reservoir which pumps the fresh solution to each container.

Devin has extensive hydroponic experience with flood and drain tables, drain to waste systems, Deep Water Culture, aeroponics, soilless and soil yet finds this hybrid shallow water culture/aeroponic/fogponic system the most sanitary, easier to clean with the least amount of nutritional and pest problems.

To provide support for the plants they use tomato cages fitted into the exterior of the net pots. This offers great support and allows the branches to be trained out, which in turn enables the plant access to more light, better support, more growth and more fruit!!!!

The assemblage of all these high yielding methods with a few tweaks has provided Devin and his crew an affordable homemade system that that they can literally (and physically) grow trees in!

WHAT DO YOU THINK OF THIS

SYSTEM? ARE THESE GUYS DESTINED FOR GREATNESS OR WHAT?

Special thanks to Ryan at Sunflower Supplies (www.sunflowersupplies.com) for his help with the ultrasonic foggers!

A glass jar, sprouting cubes, some foam scraps, a little yarn, an airstone, and an airpump. Add water and seeds to start your own. Simple enough for anyone to try, complex enough to show the basic principles of a larger system. Alas, this is the end of the raft. The cotton yarn gave out. So if you try it, keep that in mind and use a man-made fiber.

However all is not lost. These two radish sprouts (Ray and Kevin) and everything but the raft will be joining us again for Crocheted Hydroponics: Part 2.

Peace, love, and puka shells,
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