Summer and hydroponics
By Noucetta Kehdi – GHE
Summer, especially when it is a hot one, may be a difficult season for hydroponics growers. Every year we receive a stack of
questions from clients asking what to do during the hot days, when one is growing hydroponically?
This is an important question, knowing that a successful hydroponics operation relies on good oxygenation of the root mass, and that oxygenation and temperature are closely linked… Indeed, hydroponics is a growing method that relies upon a dynamic flow of water saturated with oxygen. But the higher the temperature, the less oxygen will remain in your solution and in summer, when outside – and room – temperatures climb up to 30 and 40°C, then it is time to start worrying. With high temperature and little oxygen, your roots will start to deteriorate, and soon pathogens will develop. These are the basic conditions for insects and fungi to thrive on weakened individuals with no or hardly any defenses left. If you are not careful, or if you don’t know how to do it, you may loose some plants or even a whole crop.
So what do you do in summer?
If you are very rich, or if you live in a country where electricity is very cheap (or free like in a few petrol producing countries), you can hook your grow room to the air conditioning! That’s an excellent climate control!
But in Europe electricity is still an expensive resource, and you may have to find a more affordable alternative. Water chillers may seem to be an option. They are easily available in pet shops where they are sold to keep aquarium waters at the right temperatures. We tested them ourselves and found them non-efficient in the case of flowing water. The drop in temperature you obtain is hardly noticeable because water, while circulating, will keep picking up the surrounding warm air. To be really efficient, you must buy a very big model, which uses so much energy that you are still better off with the expensive, but way more efficient, air conditioner.
Don’t panic yet! If there are no easy or affordable ways to avoid heat, there are a few useful “tricks” to be applied:
• First of all, it is important to know which are the temperature limits your plant can bare, as different plants will require different life environments. For most of them the ideal will fluctuate between 20 to 25° C. If you are using indoor hydroponics in summer, it is good to know that although unhappy and weakened, most plants will survive in hotter conditions, and you can allow your room to go up to 30 or 32°C – but with care and attention.
• Choose a highly oxygenated growing system. The higher the oxygenation, the better are your chances to keep a good temperature to oxygen ratio.
• Use a biofilter. This allows you to add extra oxygen in your water while purifying it from most pathogens.
• In slower systems, you may add an air stone or a stronger pump, to increase your oxygen content a little more.
• It is a good idea to start the new crop with reverse light cycles: shut your lights during the day and put them on only at night, to take advantage of the cooler air.
• During that period you must take regular care of your plants.
• Keep your environment as clean as possible.
• Of course install 24/24 hour ventilation. If possible bring the air in from the northern face of your building, or better still when available, bring it up from the cellar. As much as you can, keep humidity level as high as possible, trying to reach 75 or 80%.
• Add micro organisms like Trichoderma harzianum. In a biofiter when working with bare roots, or directly into the substrate when working with pure coconut fibre or clay pellet and coconut mixes.
• Keep a good eye on the roots. Use silicate powder to prevent fungi infestation. Important: do not add silicate powder in presence of micro organisms. They are not compatible.
• Of course, check for pests. Don’t allow the smallest spider mite or aphid. If a plant looks bad, check the roots; when it is sick don’t keep it.
• Check the pH level every day and try to keep it as stable as possible. Don’t overdo it though. It is better to let your pH drift between 5.5 and 6.5 than add unneeded acids. All tests show that plants will continue thriving with a wide spectrum of pH.
• Keep your EC low to avoid too much salt intake: indeed, as it is hot and they transpire a lot, your plants will be drinking and absorbing as much mineral salts as there are in the nutritive solution.
• Use a salts cleaning solution regularly, and change your water every 10 days to every second week at least.
• At the end of the cycle, if your crop looks weakened, use a «forcing solution» to make sure your plants will release all their potential before dying.
This may seem a lot to do, and indeed it is. But for a dedicated grower, most of the time it is a pleasure, especially when the harvest is plentiful! If you follow these few suggestions summer should become less of a problem in no time. Professional growers who keep their grow rooms running during the summer obtain beautiful crops.
But when the summer is really too hot like in Andalusia, Sicily, or Greece, then our general advice is: shut your operation and wait for more beneficial days. In the meantime, you can of course take a holiday or do anything else you wish to do. Before going anywhere, take advantage of this window in time to thoroughly clean your growing area and your systems, and get them ready for the next cycle:
• To avoid throwing away too much water and nutrients, choose a day when your nutritive solution is very low in the system, and stop your pump. Empty your reservoir. (Don’t throw the solution, but dilute it with tap water, check its pH, and give it to your potted plants, they’ll look great in no time!)
• Take apart your growing system and wash all parts. Unclog each sprayer, tubing, connector, etc. Clean the pump. Rinse your system thoroughly. If you had a disease or any kind of pest in your room this is the best time to disinfect your system. You may use Chlorox water or pH Down in very acidic dilutions (pH 3.0). If you use Chlorox, don’t forget to rinse very well.
• Separate the root mass from the substrate. Depending on the substrate you use, you can wash it and use it again. Some, like clay pellets and coconut fibre, can be used several crops in a row, and then may be recycled and disposed of in the soil. They will help lighten it and enrich it.
If using rockwool, it is important to look for the best way to dispose of it because it is not biodegradable and represents an environmental problem. Wash your substrate as well as possible and let it dry.
For clay pellets, especially if you are working in Aero-hydroponics and you don’t have much, boil them on the kitchen stove.
• Once your system and instruments are clean, wash your growing area to leave it dirt and disease-free, and let it rest until September, when the cooler days start coming back. You still can, in the meantime, and if you have an enclosed space small enough to easily control your temperature and humidity, prepare the cuttings or sprout the seeds for your next crop!
For more info please visit www.eurohydro.com, or contact firstname.lastname@example.org. For hydroponics micro farms, also visit www.hydroponicmicrofarm.com