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HOW DOES DEEP WATER CULTURE WORKS?
Deep water culture (DWC) is unlike almost all of the other commonly utilized hydroponic methods and practices. In most hydro systems, water is flowing around the plants’ roots either constantly or in cycles, such as in an ebb and flood system. In DWC, the plant roots are constantly submerged in a sufficient volume of well-aerated, nutrient-rich water.
Some Vertical farming systems even include animal production, but this is not that common a practice. In these setups, fowl (usually chickens) or pigs are raised on the floor level and plant crops are raised on higher levels. Other systems involving animals raise freshwater fish such as tilapia, striped bass, and trout. Crustaceans and mollusks like crayfish, mussels, and shrimp are grown in other systems. Rabbits raised for meat, may become another animal that can be incorporated into the indoor farming landscape of vertical farms.
The key here is that the water must be constantly oxygenated. Oxygen must be continually pumped into the water solution to be available to the roots. In conventional horticulture (grown in soil), roots get their oxygen from the porosity, or spaces between the soil particles. In DWC, they have to get it all from the water. Unlike in traditional soil culture, the plants must get all of their nutrients as well, from the water that they are submerged in.
Benefits of DWC
There are several benefits of growing your plants in a DWC system. First, is its ease of setup (see more on that below). DWC systems can be as simple or as complicated to construct as your desire and your budget allow. They can be as basic as a five-gallon bucket and an air pump if that is all that you want to start with. In addition to not being as expensive to setup, the ongoing costs are generally less in a DWC system. There is no soil to buy with every new grow, which can of course add up very quickly. There is also little to no nutrient waste which also cuts down costs.
They require less maintenance than other hydroponic systems too. As long as the water volume is sufficient to maintain a stable pH and EC, there is less management of the nutrient solution. This is of course providing that both are monitored regularly. This simplicity also translates to lower costs for both setup and on-going maintenance as well, depending on the size and complexity of the system. While not recommended, plants in a healthy, well-balance DWC system can be left unattended for several days before suffering any noticeable side-effects if any part of the system should fail. This is in contrast to an ebb and flood system that fails, which would generally result in total crop loss if left unattended for multiple days.
What may be the most important benefit to a DWC system are the crop yields. Plants grow faster (two to three times faster in some cases) in a DWC system than with traditional cultivation approaches. This translates to larger plants, reaching harvestable size sooner and providing bigger yields. Depending on the type of plant grown, this can also mean more harvests per year compared to other growing methods.
How to Build a Deep Water Culture System
The good news about building a Deep Water Culture system is that it is one of the easiest hydroponic setups out there. All of the needed components are easily obtainable to get started. It is important though to first identify the location. Basements and other locations that tend to stay cool are ideal for setup of DWC systems. Then you can assemble or acquire the needed parts to put together your system.
First step is to obtain a container to set everything up into. This can be anything from a five-gallon bucket to a large tank. Whatever the container is, make sure it is a color that does not allow light to penetrate. Ensure that there are not cracks as well. If you are not obtaining a new container for this, make sure that whatever container you have is thoroughly sterilized before using to kill any potentially harmful bacteria or pathogens. It is tempting to re-purpose an old fish tank for this, and it can be done, but it must be covered in a material to block out any light.
Next, you will need small pots or baskets for your plants to grow in and media for the roots to grow through. While there are several options, the most common media for DWC systems is clay pebbles in individual mesh pots. These need to fit into holes in the container lid, a floating piece of foam, or some setup where they can remain in place and the root system can remain constantly submerged.
The oxygenating components will then need to be gathered. Generally, most DWC system setups include a pump for air and an aerator for the water, such as an air stone or the like. The air pump will need to be sized accordingly to the volume of water. To determine how big of a pump, a good estimate that for each gallon of water in the system, the pump should be able to move one liter of water per minute. So, a 5-gallon system should have an air pump of at least 5 liters per minute. A 1-liter per minute is approximately 16 gallons per hour. The appropriate pump size for a 5-gallon DWC system is at least 80 gallons per hour. Then of course you will need the appropriate tubing for the pump and the air stone or oxygenator. Then you should have monitoring equipment on hand.
The very minimum monitoring tools you should have are a thermometer, a pH meter, and an EC meter. You can get good and reliable combination pH and EC meters, or they can be obtained separately. This will allow you to measure the water temperature and pH and the available nutrient levels in your water solution. These are critical to know to effectively manage your system.
Managing Your DWC System
In order to reap all of the benefits of a DWC, and enjoy the lower levels of maintenance needed, you must do regular monitoring of the system. This includes temperature, pH, EC, O2, and whole system monitoring. As mentioned, water temperatures must not be allowed above 22 C (72 F) and preferably kept in the range of 16- 20 C (60 - 68 F). If the ambient room temperature is held at that temperature and there is not a heat producing light source above your DWC system, then this should be fairly easy to keep in check. If, however you are using HPS lighting or anything other than LEDs, this will need to be checked more often and your DWC system may need a chiller added to it to keep the water temperatures in check.
There are some other methods to keep the water temperature down if your system will ever be at risk of higher temperatures and a chiller is not an option. Ventilation of the growing room is critical if warm air should build up. Exhaust fans are a must if rising air temperatures will threaten your water temperature. Using higher volume containers will also help as the higher the water volume, the longer it will take to increase in temperature. You can also add insulation to your growing containers to try and maintain the temperature. Painting the containers white can also be a solution of they are absorbing too much heat from their environment.
Keeping the appropriate temperature in your DWC system is so important to make sure your plants stay healthy. When the water is in the optimal range, your plants can absorb the levels of oxygen and nutrients needed. If the water temperature is too high, then the dissolved oxygen levels drop, even if the water is being aerated continually. This has the effect of choking your plant roots, resulting in a dying plant. Oxygen levels are generally “in check” in a DWC system so long as the water is continually aerated, and the temperatures are held within the ideal range. Conversely, if the water temperatures are not high enough, your plants will transition their growth patterns, “thinking” that the seasons are changing and pushing them towards dormancy or death.
Just as it is important to keep the water temperature of your system within an optimal range, so too is it necessary to keep your water within an ideal pH range. In a Deep Water Culture system, the ideal range for pH is generally accepted to be between 5.5 and 6.5. Some variation may be needed depending on which particular crop you are growing, but more often than not, this is the range to obtain and maintain. The higher end of this range (6.0 – 6.4) should be expected during the vegetative phase of your plant production and the lower end (5.6-5.9) during the flowering phase. If these ranges do not occur on their own, it is necessary to adjust the pH levels accordingly.
Nutrient levels are equally important to monitor. An advantage to soil culture, is that soil is a great buffer for excessive EC levels; there is no such buffer in a DWC system. If the EC or TDS levels are too high, then it is time to act and dilute the water or change it out and flush the plant roots entirely. Some growers avoid this by keeping a sterile system (more on that below). Proper EC levels will help your plants to absorb water. This keeps the plant’s metabolic rate active which in turn keeps the plant cycling through nutrients the way it is supposed to.
It is necessary to know both pH and EC levels in real time. You can have the ideal pH, meaning that nutrients are able to be absorbed by the plant at optimal levels, but that is meaningless if the nutrients are not present in those levels. On the other side of that scenario, you could have the perfect blend and amount of nutrients in your DWC system, but if the pH is too high or too low, your plants will not be able to make use of them. Keeping optimum pH and EC levels will ensure that the needed minerals and nutrients are both available and usable at the times needed during various stages of plant development.
A wholistic check of your DWC system is needed routinely as well. This includes inspecting the aeration equipment to make sure there is no blockage and checking all of the hoses and supply lines. Check the container your plants are in for cracks which can become leaks over time letting light in and/or water out. You will need to assess when its time to change the water as well. This is as much art as science. Some growers just keep adding what is needed to the existing stock from crop to crop, others change it out entirely between crops and start anew each time (suggested by most as the best practice). Still others will completely swap out the water more frequently at different phases of plant growth. Each grower will have to find the “rhythm” that works best with their particular system that works best with their corps in their growing environment. At the end of the day, so long as the plants have what they need in the levels that they will thrive on, the rest is just “fussing” and fine tuning.
Things to Keep in Mind about DWC Systems
Deep Water Culture systems are a great and easy way to grow crops without continual maintenance. They are not however, right for all growers in all situations and that should be considered before jumping right in.
Deep Water Culture systems are not always ideal for hot climates. Because the water must be kept on the cooler side, this is obviously more challenging for warmer environments. This is why a cool basement or below grade room is ideal.
There can be a learning curve that is typically steeper on small scale systems. This is because fluctuation in pH, EC and temperature is more likely to occur in a smaller system, or at least more likely to happen quicker with lower water volumes. These fluctuate during different periods of plant growth, and the smaller the system, the more impact these physiological changes between plant phases will affect the various levels. Also, human error is amplified on smaller scale systems. If you put too much nutrient solution into a large system, it is easier to dilute and correct. If not caught early on in a small system, all of the plants could be damaged because of the lower buffer levels in smaller systems. Simply put, small mistakes in a smaller system, can be more detrimental to your plants than the same small mistake in a larger system.
Root rot can occur if regular temperature monitoring is not performed. To avoid this, some growers opt for a sterile DWC system. This takes a higher level of diligence than a regular DWC, so is not necessarily the best option for the casual or hobby grower. The nutrient and pH levels are much more predicable in a sterile system. Pathogens and diseases are also in general avoided, but so are beneficial bacteria unable to grow.
In a sterile DWC system, there is regular and frequent sanitation of the water reservoir as well as the growing media (usually clay pebbles). Larger air stones or aerators are used in sterile systems as well as oversized pumps. These stronger pumps create an environment that is not conducive for bacteria to develop or survive. These are more apt for larger scale systems managed by more experienced growers because of the additional maintenance as compared to a standard DWC system.
To find a complete system or all of the parts you need for a successful Deep Water Culture system, visit Hydrotek Hydroponics at hydrotekhydroponics.com. There you will find all of the tools you need for anything for a small, single plant system, to large, commercial cultivation enterprises. From pumps to RO systems and fittings to supply lines, they have all of components you need to be successful with your DWC system. Check out their line of monitoring equipment as well to take full advantage of all of the benefits of a Deep Water Culture system.