Oxygen — who doesn't need it? But, does a cannabis plant need oxygen?
Yes, cannabis plants do need oxygen to thrive.
However, it's not so simple. You don't need to get oxygen cylinders to make your plants happy.
But, first, how important is oxygen? Many growers often overlook oxygen's importance in growing cannabis — who wants to think about the air when you are already feeding your plant boosters and what not?
The truth is, oxygen is one of the crucial components of your plant's health and growth, especially if you want big, bushy nugs.
As a cannabis grower, your goal must be to try everything that offers maximum satisfaction to your plants.
You will understand the importance of oxygen and how your plants can benefit from it as you read on.
But wait, doesn't the air around you already have enough oxygen? Yes, our atmosphere has around 21% oxygen — that's enough for most growers — but if you want to take your cultivation to the next level, you need to give more oxygen to your plant.
There are two ways you can do this:
- Improving the air circulation, so your plant has fresh air to breathe.
- Increasing the oxygen levels in the root zone by aerating the medium or using dissolved oxygen (DO).
The first method improves air exchange between the plant and the atmosphere, while the latter makes the roots grow faster with dense root hair, enhancing nutrient and water uptake. Ultimately, the plant will produce more yield. Thus, oxygen, especially when you're growing hydroponic cannabis, can increase yields.
Learn why your cannabis plant needs oxygen and how you can make it reach your plant in this article.
Respiration
Like other plants, cannabis also breathes. Without respiration, the plant will struggle to survive and die. However, oxygen isn't as critical as other components like, say, water for cannabis since the atmosphere contains lots of oxygen.
This means that there's no necessity to supplement more oxygen above the roots or ground level. Cannabis, like other plants, also releases oxygen during photosynthesis. However, it needs oxygen below the roots.
Suffice it to say that cannabis doesn't need oxygen as much as humans. But, they need a well-ventilated environment to grow healthy. During aerobic respiration, cannabis plants use leaves, roots, and stems, and oxygen serves as an oxidizer.
Aerobic respiration occurs throughout the day, but it's ramped up at night due to a lack of photosynthesis. For photosynthesis, the cannabis roots absorb water while the leaves absorb CO2. Then, the plant uses sunlight to convert the CO2 and water to release oxygen back into the air.
As you can understand by now, photosynthesis involves many processes. And without sunlight at night, the cannabis plant increases its photorespiration activity. This is one of the reasons why you need to manipulate the temperatures at night and keep it low.
Now, you've heard that CO2 helps the plants grow healthy, and rightly so. However, there's no necessity to inject oxygen above the root level to assist cannabis. Instead, you can increase the oxygen levels below to ensure the plants are happy.
So, how important is it to improve oxygen below the ground level?
It's extremely important that the soil or water and roots have enough oxygen. If you use soil, it's even more critical to keep it oxygenated. Why? Because the soil is full of microbes that also need oxygen to survive. When you grow plants in soil, the plants grow healthy and absorb nutrients because of the microorganisms, so it's essential to keep them happy.
In addition, the soil should be porous to let the plants breathe freely. You can make your own mix by adding perlite or purchasing loose soil.
In short, it's essential to keep the plant stomas clean so the plant can breathe. Stomas are pores through which the plant breathes CO2 and releases oxygen into the atmosphere. You can keep the stomas clean by washing them with water. Outdoors, it's not a problem as nature takes care of it. Indoors, however, you can spray the leaves, including the undersides, to ensure it's all clean and prevent clogging.
How Does the Cannabis Plant Use Oxygen?
The roots of the cannabis plant absorb oxygen from the soil. If the plant is growing in water, it takes dissolved oxygen present in the water. Lack of oxygen will expose the roots to many pathogens that can destroy the plant.
Remember that cool water has more oxygen than warm water. Therefore, you can maintain the water temperature between 70°F to 73°F as much as possible to ensure the plants have plenty of oxygen. For example, you can use a water cooler to keep the water cool. The point is to maintain a cool temperature in your reservoir even if the environment around is hot. We will discuss many methods of increasing oxygen in subsequent sections below.
How to Improve Air Circulation for Cannabis?
If you're growing outdoors, you don't have to worry much about this because of the natural air circulation. However, you can take additional measures to keep the grow room well oxygenated for indoor plants.
To aid air circulation for an indoor plant, you must focus on three factors:
- Keep the stomas clean so the leaves can respire efficiently — you can do this by simply spraying some water on the underside of the leaves frequently. Don't overdo it, as you'll end up overwatering. Just a quick spray once in 7-10 days must be enough.
- Good air circulation, so there is always fresh air for the plant to breathe.
- And the consistent exchange of air between the plant and grow room air.
You must ensure an even distribution of air throughout the grow room for proper plant growth. Stagnant air can be bad for the plant, leading to slower growth and even mold infestation in your culture.
This is a balancing act — the air must not be too moist or too dry.
Improving Air Circulation in the Grow Room
To accomplish the goal of keeping the grow room environment not too moist or not too dry, you can invest in various equipment, such as the following:
- Carbon filters that scrub the air of the signature cannabis odor
- Intake fans to pull fresh air into the grow room
- Exhaust fans to push out the air
- Ventilation ducts to aid air exchange
- Fans (ceiling, clip, and oscillating fan) to circulate the air and avoid warm zones in the grow room
- Acoustic box to reduce the sound of fans
- Humidifier or dehumidifier to control the relative humidity in the grow room
- Thermohydrometer to measure the grow room's humidity and temperature levels
Improve the grow room's air circulation to optimize your plant's respiration, so it can grow big and develop bushy buds.
How to Increase Oxygen Levels in the Root Zone?
Air circulation is crucial, but your plant also absorbs oxygen via the roots. So, there is a better way to feed your plant more oxygen to grow healthy and tall. You can increase the oxygen levels in the root zone in two ways:
- Improve the grow medium's air retention
- Infuse more oxygen into the water
When your plant transpires, it exhales oxygen and water vapor via the stomas, which helps the plant stay cool, maintain cell osmotic pressure, and allow a steady uptake of nutrients and water at the root level.
So, when the roots are well-oxygenated, they can more efficiently absorb nutrients as oxygen enhances their metabolic energy. In addition, higher oxygen levels in the root zone lead to a greater root mass with dense root hair, leading to even more nutrient and water uptake.
On the other hand, a lack of oxygen in the root zone hampers nutrient and water uptake, which further reduces your plant's growth, photosynthesis process, and glucose transferring abilities.
In severe cases, it can even lead to heat stress and wilting and the production of ethylene, which can cause a risk of disease and cell collapse. In short, it can create many problems for your plant.
Here are the ways you can improve oxygenation of the root zone.
Aerating the Soil
The easiest method is to mix aerating products to your soil, like perlite, hydroton, or coco coir. These products improve the soil's ability to retain oxygen.
An added benefit of aerated soil is that it needs the soil to be watered more frequently, which lets you implement a better feeding routine.
If you want to aerate your soil to improve its oxygen retention, mix four parts of soil with one part aerating product to create a potting mix that drains fast while retaining enough oxygen.
This is just a general guideline — follow the manufacturer's recommendation for the exact ratio.
How to Increase Oxygen Levels in the Water?
Dissolved oxygen is described as the level of oxygen saturation in water. The higher the oxygen levels in the water, the better off your plant roots will be. But, not every water source suits all plants. For example, you can't grow cannabis in stagnant water. Why? Because there's a lack of oxygen.
On the other hand, flowing water is perfect for most plants since it contains ample oxygen. For instance, imagine a river flowing from one place to another. It comes in contact with air and traps molecular oxygen as it travels. Stagnant water also comes in contact with air, but the oxygen levels deplete and invite pathogens that thrive in anaerobic conditions. This is why you see water in a glass turning bad if it sits in one place for a long time.
Here are some of the benefits of using DO for cannabis:
- Many growers report that dissolved oxygen (DO) helped them decrease their feeding costs by 15%.
- Growers have also reported an average increase in yield by 11%.
- DO allows your plant's roots to grow bigger with dense root hair, which improves the roots' water and nutrient uptake, leading to a healthier, bigger plant.
- DO also protects your plant from root rot caused by anaerobic bacteria.
- Roots that don't get enough oxygen substitute it with other compounds that produce ethylene. This compound increases your plant's risk of systemic diseases and cell damage.
- DO also prevents calcium deficiency as it helps the roots absorb calcium more efficiently.
Improving water's DO levels is a no-brainer, and here are a few ways you can do that.
How to Circulate Water or Increase Oxygen in the Water
The levels of oxygen increase as the water circulation increase. Thus, you should aim to prevent stagnant water and increase circulation as much as possible.
An air pump or submersible pump will provide just enough circulation to keep your system going. The turbulence it creates is perfect to increase oxygen as the water gets in contact with the air around and exchanges the CO2 present in it for oxygen.
Many growers use hydrogen peroxide to kill harmful pathogens lurking in the soil and water. The added advantage is that it increases oxygen as well. However, you need to be careful and dilute it properly. You will find various concentrations of H2O2 (3%, 5%, 10%), so you can pick up anything and dilute it further to increase oxygen.
For example, 10% H2O2 should be diluted at a 1:200 ratio (hydrogen peroxide: water), whereas a 3% H2O2 will require a 1:5 dilution with water. So, you can take 1 part of H2O2 and mix it with 5 parts of water.
You can add hydrogen peroxide to both soil and water at the same rate. When irrigating plants in soil, add it to the water. For hydroponic plants, add it to your main reservoir.
So, how does H2O2 increase oxygen? Hydrogen peroxide is nothing but water and an extra oxygen atom. Due to its unstable nature, it can jump and mix with other molecules, and it burns pathogens when it comes in contact with them.
Since the oxygen atom is unstable, it can combine with another oxygen molecule and create O2. The remaining H2 is water, and the O2 will be available for roots. Therefore, you can add H202 twice every week for good benefits. However, do not overdo this as it can build up toxicity and harm the plants. Using it once a month may temporarily increase the oxygen levels.
Concentrated H2O2 can burn you, so use it only after diluting it.
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Add a Stirring Pump to Your Hydro System
If you're growing your cannabis plant in a hydroponic system, you can add a stirring pump at the bottom of the reservoir.
The pump will turn at the bottom, mixing the nutrient solution on a timed or continuous cycle. This turning mixes oxygen into the water and keeps the DO levels stabilized.
This device works on a similar principle of how the ocean's water keeps moving thanks to the currents.
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Use a Molecular Oxygen Infusion System
Another effective method to raise the DO levels in your water is by using molecular oxygen infusion.
Essentially, this system increases the DO levels in the water without producing too many bubbles (like a bubbler) or using too much energy.
A molecular oxygen infusion device contains a fiber module cluster made from mass transfer fiber. This fiber of 1 cubic foot has a surface area of 7,500 square feet. Each of these fibers is loaded with pure oxygen.
Additionally, the fiber has tiny pores, so no bubbles pass into the water — only oxygen does.
Thanks to this large surface area, the fiber enhances the interface between oxygen and water. So, when the water passes through the canister, which contains oxygen, the oxygen starts dissolving in the water.
Thanks to an efficient oxygen infusion, the DO stays stable in the water for longer, even when you spray water on the growing medium.
Thus, a molecular oxygen infusion system is perhaps the most effective and economical way to increase DO levels in the water. The system is so efficient that its oxygen infusion levels are similar to laboratories — it helps you supersaturate the water with oxygen, depending on your plant's growth stage and preferences.
Another effective method is to infuse ozone with water since ozone is nothing but a molecule that contains three oxygen atoms. Ozone is easier to infuse in water as it is 12.5x more soluble than oxygen.
However, you need to invest in an ozone generator and a treatment system to handle high ozone concentrations without any leaks. This is because even a minor leak can be harmful to you, your pet, and your plant.
You must also ensure that the system can maintain the DO levels in the water. Otherwise, ozone-based DO will be displaced from water within 5 to 10 minutes.
Methods That May Not Be as Effective
We have mentioned three ways to offer more oxygen to the roots, and they are pretty effective. On the other hand, other methods may not be as effective, such as:
Bubbler is perhaps the most popular way of oxygenating water, wherein air is injected into the water using air stones.
While this does work in increasing the DO levels in the water, it is not efficient. The difference is not enough in the long run. Also, according to Henry's Law, these bubbles only work to infuse water with oxygen when the concentration, temperature, and pressure are correct.
The Venturi system is another method to oxygenate the water, but even this is relatively ineffective. A venturi system uses the Bernoulli principle, where the air is injected into the water using a high-velocity pipe — just like a carburetor.
This system does work in increasing the water's DO levels, but you will need a solid understanding of engineering to calculate the baseline figures for the best performance. The reason this system is ineffective is that it is time and labor-intensive.
Another reason why this system may be ineffective for you is if you set the pump too deep in the reservoir. The deeper you set the pump, the less the venturi effect will occur as the system starts suffering from air column pressure.
How Much Oxygen is Needed?
In regular tap water, the dissolved oxygen levels are around 5 to 9 ppm, but scientists say the plants only benefit from DO once the ppm levels rise over 12.
According to the University of Minnesota, plants absorb nutrients and water more effectively at a DO ppm of 18 to 25.
However, according to Charlie Hayes, owner of Advanced Treatment Technologies, the benefits of DO peak at 40 to 45 ppm in the root zone.
So, aim to at least have a DO ppm of 25. The higher, the better — as long as it is under 45 ppm.
What Should the Water's Temperature Be?
A crucial aspect of increasing DO levels and oxygenating the roots is the water's temperature. So, you must maintain the right temperature for the roots to thrive.
This is because roots' ability to absorb nutrients and water depends on the temperature. If the temperature is under 60°F, the metabolic activity of the roots decreases, and if it is over 75°F, the risk of root rot increases.
Hence, you must maintain a water temperature between 62 to 66°F.
Additionally, the DO levels also depend on the temperature. For example, fully oxygenated water can hold up to 9 ppm of DO at 66 to 68°F but only 7.5 ppm at 86°F. So, it makes sense to use water around the 65 degrees Fahrenheit mark.
Summary: How to Increase Oxygen for Healthy Cannabis Plants?
Yes, your cannabis plant does need oxygen to thrive, and there's enough of it in the environment for healthy growth. However, advanced growers know that higher oxygen levels can be a game-changer for cultivation, especially dissolved oxygen.
While the investments into the DO systems may not make sense, they are worth it if you want to cultivate cannabis commercially. Otherwise, simply caring for your plant and providing it with the right grow environment should be enough for healthy growth and terrific yield.
