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Five and a half years ago Ben Derdundat posted this on this forum.
***Saturation Levels Of Dissolved Oxygen In Relation To Water Temperature*** https://www.thcfarmer.com/community/threads/saturation-levels-of-dissolved-oxygen-in-relation-to-water-temperature.23805/
“The purpose of chilling the water in an Under Current system or any system for that matter is not only to keep the root zone healthy and free from disease, it is also done so to help increase the saturation level of dissolved oxygen that is in your nutrient solution. The whole point of the Under Current and DWC is to have large amounts of dissolved oxygen in the nutrient solution. This is what causes the plants to be able to assimilate nutrients faster and have such rapid cell growth.”
UCMENOW said, “.....keep your DO high as possible and your PPM's only as high as necessary to meet your plants nutritional needs.”
Lost posted this expert opinion,
Recirculation Basics – Part 3
By Urban Garden Magazine ⋅ April 24, 2010 ⋅ Email This Post ⋅ Print This Post ⋅ Post a comment
Filed Under air circulation, air-flow, airflow, CO2, humidity, Issue 10, Michael Christian, oxygen, temperature, ventilation http://urbangardenmagazine.com/2010/04/hydroponic-recirculation-basics-part-3/
What all Hydroponic Growers Need To Know About Nutrient Recirculation
As we’ve learned in part 1 and part 2, in order to grow successfully in a hydroponic system, there are certain basics that always need to be kept in check: otherwise, plant performance inevitably suffers. After covering source water, nutrient and pH, world-renowned hydroponics expert Michael Christan breaks down the final ingredients of a healthy indoor growing environment: oxygen, light, temperature, humidity, air circulation and CO2.
Photos courtesy of AmHydro.
The 5 basics of recirculation and plant performance:
1. Pure source water
2. Balanced nutrient ions/anions (EC)
3. Optimum pH
4. Plentiful oxygen availability
5. Optimum light/temp/humidity/air circulation/CO2
The Importance of Oxygen
It’s obvious that loose, friable soil with organic matter and thriving microbes grows plants much better than tight, clay soil devoid of organic matter. The primary missing ingredient in the latter is air (oxygen) availability.
The air we breathe is composed of gasses: 78% nitrogen (N2), 21% oxygen (02), 0.9% argon (Ar) and 0.03% carbon dioxide (CO2). The one we’re focusing on in this article is oxygen. The action of microbes on organic matter in a loose soil produces air pockets as organic matter is mineralized. These oxygen pockets are crucial to the survival and rapid colonization of healthy microbial populations. When the organic matter in the soil is fully consumed by the microbes and plants have consumed all the minerals, oxygen becomes depleted and, if more organic matter is not reapplied, plant performance slows and pathogenic (anaerobic) microbes can colonize. This condition is best avoided.
In media-based recirculating systems, the O2 is in the media: e.g. rockwool, perlite, grow rocks. Plentiful air space is available even after water is drained from the media. Roots thrive in O2-rich pockets. They are able to produce prolific root systems and plentiful root hairs to increase surface area to better absorb available ions. This is the best reason for using media with porosity. Of course, flood and drain systems suck fresh air into the media when it drains, which is why it’s such a great irrigation system.
In water-based recirculating systems, NFT, DFT and Aeroponics, O2 availability is intrinsic to the design of the system. NFT is a flat-bottomed tube with a shallow nutrient stream moving slowly, keeping root hairs moist and absorbing O2 (see “NFT Gro-Tanks,” UGM009). Aeroponics is misting droplets of water, increasing the surface area many-fold for roots to grow prolific root hairs for ion absorption. It supersaturates the solution with O2. DFT uses air pumps and water temp to keep roots bubbled with 02 and oxygen rich.
The heart of a media-based or water-based recirculating system is the nutrient reservoir. This too requires oxygenation, especially when water temperatures rise. The use of air pumps and air stones on smaller reservoirs and pump-powered eductors (venturis) on larger reservoirs make a big difference in pathogen suppression (nasty fungi and bacteria don’t like O2). This agitation drives ethylene gas from the solution and increases the longevity of the nutrient. Be sure that, if there are reservoir lids, there’s room for air exchange with ambient air in the room or greenhouse. Many commercial growers use fresh outside air in their eductors to keep the nutrient solution optimum.
Dissolved Oxygen (DO) can be measured to determine solubility of oxygen in fresh water. Fresh water at 72°F (22°C) has a DO of 8.7 ppm; at 82°F (28°C) it drops to 8.1 ppm. Salt solutions are lower. As a rule of thumb, every increase of 1ppm in DO is equivalent to an 11°F (12°C) temp drop. The cooler the temp, the higher the DO. You don’t want cold water on plant roots, though. You want 72°F (22°C) water at your roots for most plants.
When we measured DO in our greenhouse reservoirs, we found that a 74°F (23°C) nutrient tank at an EC of 2 had a DO of 6.3 ppm (low because of salts and sitting still). When we turned on an eductor (venturi), which we do in ALL reservoirs, we received a reading of 7.6 ppm. BIG difference. That’s an increase of 1.3 ppm without changing temperature.
Then we add an in-line Mazzei injector in between the tank and the feeder pipe, which raises DO to 8.3 ppm. By the time the water had run down the NFT channel and 18 plants had their way with the O2, with some off-gassing occurring, there was an 8.1 ppm DO left in the nutrient solution going back to the reservoir. That’s what we’re after! Plants thrive at those DO levels. Makes ALL the difference.
Be careful: as water temperatures of salt solutions increase, you must mitigate by adding O2 in the reservoir as well as directly on the roots. If you can’t get the DO level up by mechanical means, then you will most likely require a water chiller, which is expensive but sometimes imperative. If you cannot bring water temps down or increase DO in the nutrient solution, your next action will be disease suppression or inoculating roots with beneficials to out-compete the pathogens that thrive in high temp, low DO water. If you do get a DO meter, get a good one. We use an Extech Model 407510.
[Be aware of using water chillers and cold water: Hydrozone Bennies are Bacillus amyloliquefaciens. Bacillus amyloliquefaciens are gram positive rods with peritrichous flagella allowing motility. The cells often appear as long chains unlike many other Bacillus species that form as single cells. The optimal temperature for cellular growth is between 30 and 40 degrees Celsius. Similar to other Bacillus species, B. amyloliquefaciens forms endospores allowing survival for a long period of time. Endospores appear centrally in the cells which do not have a swollen appearance. These beneficials thrive in warm/hot environments and fail to thrive well in cold environments, they love 30 - 40 C = 84 - 104F. They fail to thrive well in 65F – 68F environments. That is 19F – 36F colder than they like, figure that one out.
So here we are years down the road from this post and very little has changed or improved here. What do you think happens in the root zone and submerged roots when you have plenty of air and cold water but your oxygen is low in your RDWC/DWC?
Do you really like treating fungal diseases (root rot)… because if you cannot prevent the disease you will most probably catch the disease. So what is your preference, preventing fungal disease or treating disease? In America and the rest of the world... you will treat chemicals, teas and dips or you may prevent it if you like because you only have these 2 choices.]
***Saturation Levels Of Dissolved Oxygen In Relation To Water Temperature*** https://www.thcfarmer.com/community/threads/saturation-levels-of-dissolved-oxygen-in-relation-to-water-temperature.23805/
“The purpose of chilling the water in an Under Current system or any system for that matter is not only to keep the root zone healthy and free from disease, it is also done so to help increase the saturation level of dissolved oxygen that is in your nutrient solution. The whole point of the Under Current and DWC is to have large amounts of dissolved oxygen in the nutrient solution. This is what causes the plants to be able to assimilate nutrients faster and have such rapid cell growth.”
UCMENOW said, “.....keep your DO high as possible and your PPM's only as high as necessary to meet your plants nutritional needs.”
Lost posted this expert opinion,
Recirculation Basics – Part 3
By Urban Garden Magazine ⋅ April 24, 2010 ⋅ Email This Post ⋅ Print This Post ⋅ Post a comment
Filed Under air circulation, air-flow, airflow, CO2, humidity, Issue 10, Michael Christian, oxygen, temperature, ventilation http://urbangardenmagazine.com/2010/04/hydroponic-recirculation-basics-part-3/
What all Hydroponic Growers Need To Know About Nutrient Recirculation
As we’ve learned in part 1 and part 2, in order to grow successfully in a hydroponic system, there are certain basics that always need to be kept in check: otherwise, plant performance inevitably suffers. After covering source water, nutrient and pH, world-renowned hydroponics expert Michael Christan breaks down the final ingredients of a healthy indoor growing environment: oxygen, light, temperature, humidity, air circulation and CO2.
Photos courtesy of AmHydro.
The 5 basics of recirculation and plant performance:
1. Pure source water
2. Balanced nutrient ions/anions (EC)
3. Optimum pH
4. Plentiful oxygen availability
5. Optimum light/temp/humidity/air circulation/CO2
The Importance of Oxygen
It’s obvious that loose, friable soil with organic matter and thriving microbes grows plants much better than tight, clay soil devoid of organic matter. The primary missing ingredient in the latter is air (oxygen) availability.
The air we breathe is composed of gasses: 78% nitrogen (N2), 21% oxygen (02), 0.9% argon (Ar) and 0.03% carbon dioxide (CO2). The one we’re focusing on in this article is oxygen. The action of microbes on organic matter in a loose soil produces air pockets as organic matter is mineralized. These oxygen pockets are crucial to the survival and rapid colonization of healthy microbial populations. When the organic matter in the soil is fully consumed by the microbes and plants have consumed all the minerals, oxygen becomes depleted and, if more organic matter is not reapplied, plant performance slows and pathogenic (anaerobic) microbes can colonize. This condition is best avoided.
In media-based recirculating systems, the O2 is in the media: e.g. rockwool, perlite, grow rocks. Plentiful air space is available even after water is drained from the media. Roots thrive in O2-rich pockets. They are able to produce prolific root systems and plentiful root hairs to increase surface area to better absorb available ions. This is the best reason for using media with porosity. Of course, flood and drain systems suck fresh air into the media when it drains, which is why it’s such a great irrigation system.
In water-based recirculating systems, NFT, DFT and Aeroponics, O2 availability is intrinsic to the design of the system. NFT is a flat-bottomed tube with a shallow nutrient stream moving slowly, keeping root hairs moist and absorbing O2 (see “NFT Gro-Tanks,” UGM009). Aeroponics is misting droplets of water, increasing the surface area many-fold for roots to grow prolific root hairs for ion absorption. It supersaturates the solution with O2. DFT uses air pumps and water temp to keep roots bubbled with 02 and oxygen rich.
The heart of a media-based or water-based recirculating system is the nutrient reservoir. This too requires oxygenation, especially when water temperatures rise. The use of air pumps and air stones on smaller reservoirs and pump-powered eductors (venturis) on larger reservoirs make a big difference in pathogen suppression (nasty fungi and bacteria don’t like O2). This agitation drives ethylene gas from the solution and increases the longevity of the nutrient. Be sure that, if there are reservoir lids, there’s room for air exchange with ambient air in the room or greenhouse. Many commercial growers use fresh outside air in their eductors to keep the nutrient solution optimum.
Dissolved Oxygen (DO) can be measured to determine solubility of oxygen in fresh water. Fresh water at 72°F (22°C) has a DO of 8.7 ppm; at 82°F (28°C) it drops to 8.1 ppm. Salt solutions are lower. As a rule of thumb, every increase of 1ppm in DO is equivalent to an 11°F (12°C) temp drop. The cooler the temp, the higher the DO. You don’t want cold water on plant roots, though. You want 72°F (22°C) water at your roots for most plants.
When we measured DO in our greenhouse reservoirs, we found that a 74°F (23°C) nutrient tank at an EC of 2 had a DO of 6.3 ppm (low because of salts and sitting still). When we turned on an eductor (venturi), which we do in ALL reservoirs, we received a reading of 7.6 ppm. BIG difference. That’s an increase of 1.3 ppm without changing temperature.
Then we add an in-line Mazzei injector in between the tank and the feeder pipe, which raises DO to 8.3 ppm. By the time the water had run down the NFT channel and 18 plants had their way with the O2, with some off-gassing occurring, there was an 8.1 ppm DO left in the nutrient solution going back to the reservoir. That’s what we’re after! Plants thrive at those DO levels. Makes ALL the difference.
Be careful: as water temperatures of salt solutions increase, you must mitigate by adding O2 in the reservoir as well as directly on the roots. If you can’t get the DO level up by mechanical means, then you will most likely require a water chiller, which is expensive but sometimes imperative. If you cannot bring water temps down or increase DO in the nutrient solution, your next action will be disease suppression or inoculating roots with beneficials to out-compete the pathogens that thrive in high temp, low DO water. If you do get a DO meter, get a good one. We use an Extech Model 407510.
[Be aware of using water chillers and cold water: Hydrozone Bennies are Bacillus amyloliquefaciens. Bacillus amyloliquefaciens are gram positive rods with peritrichous flagella allowing motility. The cells often appear as long chains unlike many other Bacillus species that form as single cells. The optimal temperature for cellular growth is between 30 and 40 degrees Celsius. Similar to other Bacillus species, B. amyloliquefaciens forms endospores allowing survival for a long period of time. Endospores appear centrally in the cells which do not have a swollen appearance. These beneficials thrive in warm/hot environments and fail to thrive well in cold environments, they love 30 - 40 C = 84 - 104F. They fail to thrive well in 65F – 68F environments. That is 19F – 36F colder than they like, figure that one out.
So here we are years down the road from this post and very little has changed or improved here. What do you think happens in the root zone and submerged roots when you have plenty of air and cold water but your oxygen is low in your RDWC/DWC?
Do you really like treating fungal diseases (root rot)… because if you cannot prevent the disease you will most probably catch the disease. So what is your preference, preventing fungal disease or treating disease? In America and the rest of the world... you will treat chemicals, teas and dips or you may prevent it if you like because you only have these 2 choices.]
