Marijuana growers spend considerable time and even money delivering the right elements their crops need for growth through specialty fertilizers and supplements. Outdoor crops receive free stuff versus indoor crops -- for example the sun is free and so are oxygen and carbon dioxide.
Indoors, delivering plenty of light while not always cheap, is relatively easy to do. However, in their quest for heavy yields of potent nugs, sometimes indoor growers are missing out on two very important crop feeding nutrients, and that's the invisible ones found in the air: carbon dioxide (CO2) and oxygen (O2).
While keeping a source of fresh air from outside through the crop canopy, especially when the lights are on, does provide some CO2 to your crop, increasing CO2 levels, especially at the right times, can make a big difference in plant health, growth rates and even yields.
But that's one half of the missing equation. Plants live in two different worlds at the same time -- while the green portion of the plant is processing CO2 for energy to grow with light, the lower portion is taking in water and nutrients to balance the equation. Having higher DO (dissolved oxygen) and good ambient O2 levels at the roots do for the plant what CO2 does for the upper portions: it increases growth rates and yields; plants perform at a higher metabolic rate of activity.
Adding CO2 into a relatively healthy growing set-up can typically increase dry harvest weights from 10-25% and shave time off of both the veg and bloom period, creating the opportunity for more harvests per year. Growers also note that when their plants are amped up with higher CO2 levels, insects tend to surface less often and aren't able to gain a foothold to infest as readily. Normal atmospheric CO2 levels are usually around 500 PPM (parts per million), increasing to 800-1800 PPM, especially during veg and peak flowering can make a big difference.
However, you can turbocharge your gains in growth rates and yield potential when you add more O2 at the roots as part of the equation.
The way most growing soils and root systems get their burst of O2 is when watering occurs, or in the case of hydroponics, when a steady flow of nutrient solution washes through the roots.
Following this charge of O2 levels after application, the levels quickly become depleted. From there it is the ambient O2 levels that are helping water and nutrient absorption, and can be be in short supply; slowing progress for growth. Ambient oxygen for roots occurs in the macro and micro pore spaces directly around the roots and in the growing medium.
When there is more air available at the roots in both the solution and through ambient levels, you will see a surge of healthy growth; the difference can be quite noticeable. As a bonus, some growers find they can reduce their fertilizer strengths slightly because plants can take up water and minerals abundantly with increased oxygen levels in the root zone.
Typically, 16 PPM of dissolved oxygen is considered pretty good, and can be accomplished with lots of flow in your solution and some level of aeration.Double these levels can be achieved with specialized equipment. Saturated DO levels can also be used to effectively treat root diseases in hydroponic crops. It has also shown to make plants able to resist powdery mildew up top.
If you like to grow in soil, and don't mind watering more often for better production, simply adding some large sized perlite or grow stones your potting mix will help improve drainage and create more pore space. When roots dry out faster, it means watering more frequently to introduce a dose of dissolved oxygen for better growth and production.