Once everything’s installed and ready to go, you’ll need to know exactly how to use CO2. Well, it’s used in the flowering period from the 21 st day onwards, once the buds start to take shape and are slowly popping up at the tips of all of the branches. You’ll need to change your air filtration so that the extractor only works for around 15 minutes an hour because if it’s left on it will get rid of all of the CO2 and all of the effort will have been for nothing. You can use another timer to program the CO2 controller so that it doesn’t turn on when the extractor is on. CO2 should only be administered when the lights are on, as the extraction should be on constantly when the lights are off.
If you notice your plants get weak or yellowish at any moment, or worse, then stop using CO2 immediately and try and find out what’s going wrong. Either too much CO2 is accumulating or we’re giving them too little and it’s too warm. Make sure you follow the parameters exactly or using it can actually do more harm than good. If done properly, your harvest will be ready a few days earlier and you’ll get a higher yield.
CO2 increases your plants cell walls and multiplies them rapidly, but make sure that you fertilize them also as they’ll end up light and pretty down looking if they get a lot of CO2 but not any nutrition. They’ll also need a slightly higher heat than usual, around 28-32ºC so that the water in the leaves can evaporate slightly faster and the plants can absorb the nutrients straight away. Basically, we want the plants to absorb the nutrients but get rid of the water fast. You’ll need a dehumidifier to lower the ambient humidity to normal levels, because once the temp is raised and your plants begin evaporating water, humidity levels will raise a lot.
If you have any questions feel free to leave a comment.
You can use any way of dispensing CO2, connected to a CO2 controller that will shut off the flow of CO2 once it reaches a certain level, and open it again once it gets too low. If all you have is a normal CO2 meter, you can still control the CO2 levels by opening and closing a solenoid valve using a timer. (Solenoid valves are valves that are opened and closed with an electromagnetic charge). Whichever kind of system you use, you must know the exact PPM (parts per million) of CO2 in your grow room.
Here’s a guide on what you should do and the strength of the CO2 in your grow room from the 21 st day of flowering onwards. EC levels apply if you’re growing in hydro or aeroponics. If you want to measure them in soil you’ll need to measure the water that comes out from the bottom of the flowerpot once you’ve watered; if more is needed you can add it in the next watering, and if it’s too high then the next watering should just be water on its own.
If you don’t use CO2 in the right way you could end up with yellowing plants, or long stretched out plants with hardly any buds. You’re going to need to know what you’re doing to implement CO2 correctly. There are many systems that can be used to get more CO2 into your crop; beginner systems that are used as a little extra boost and don’t require much care, and then professional systems that measure the PPM of CO2 that there is in the atmosphere. Professional systems are obviously much more effective and efficient than beginner ones, but they also require more work and attention.
CO2 needs to be introduced into your room through a silicone tube, with one outlet per plant near the bottom of the trunk. You can also use a 2m tube to go around the grow area with holes facing the center, towards the plants.
- Day 21 of flowering: Begin with 800 PPM, and keep it at that when the extractor isn’t on. When watering, you’ll need to raise the EC every time to raise the CO2 levels. For this first week you’ll need about 1.7 EC using normal irrigation water.
- Day 24 of flowering: Raise the CO2 to 850 PPM, and the EC to 1.8.
- Day 27 of flowering: CO2 to 900 PPM and EC to 1.9
- Day 29 of flowering: From this day onwards you’ll need to increase both CO2 and EC every two days. 950 PPM and 2.0 EC.
- Day 31 of flowering: 1000 PPM and 2.1 EC.
- Day 33 of flowering: 1050 PPM and 2.2 EC
- Day 35 of flowering: 1100 PPM and 2.3 EC
- Day 37 of flowering: 1150 PPM and 2.4 EC
- Day 39 of flowering: 1200 PPM and 2.5 EC. From this day onwards, increase levels every day.
- Day 40 of flowering: 1250 PPM and 2.6 EC
- Day 41 of flowering: 1300 PPM and 2.7 EC
- Day 42 of flowering: 1350 PPM and 2.8 EC
- Day 43 of flowering: 1400 PPM and 2.9 EC
- Day 44 of flowering: 1450 PPM and 3.0 EC (this is the max EC level)
- Day 45 of flowering: 1500 PPM and 3.0 EC
- Day 46 of flowering: 1550 PPM and 3.0 EC
- Day 47 of flowering: 1600 PPM and 3.0 EC
- Day 48 of flowering: 1650 PPM and 3.0 EC
- Day 49 of flowering: 1700 PPM and 3.0 EC
- Day 50 of flowering: 1750 PPM and 3.0 EC
- Day 51 of flowering: 1800 PPM and 3.0 EC – This is the max CO2 level you can have in your grow room. Continue the rest of the flowering period without raising anything, and make sure to do that root wash 10 days before harvesting.
How to Use CO2 in Cannabis Grows; here's a step by step guide on how to correctly use CO2 to get the most out of your plants.
The amount of CO2 in the air has a profound effect on the rate of photosynthesis and plant growth. Photosynthesis speeds up as the amount of CO2 in the air increases, as long as there is enough light to power it (to an upper limit). Photosynthesis slows to a crawl and virtually stops at a CO2 concentration of around 200 ppm. Lacking CO2, plants continue respiration and growth for a short time, until their sugars are used up; then they slow down their metabolism to conserve energy. Only when more CO2 is available can the plant processes continue.
At 100 ppm CO2 respiration and photosynthesis are equal so there is no net loss or gain.
Photosynthesis consists of a complex series of reactions in which light energy is used to convert carbon dioxide and water to sugar, releasing oxygen as a byproduct.
Cannabis uses CO2 in the presence of light. Photosynthesis occurs when the plant receives light. The marijuana plant draws in CO2 from the air by tiny openings on the undersides of leaves called stomata. They function much like pores in the skin, but have guard cells that can open and close. They regulate the absorption of water, gas, oxygen, (O2), and CO2 into the plant, as well as the evacuation of water and O2 from the plant.
Light level, temperature and CO2 level must all increase for the plant to utilize resources most efficiently.
CO2 regulators attach to CO2 tanks and allow the grower to pre-set and adjust the amount of CO2 being released into the room. This CO2 regulator is adjustable from 0.5-15 cubic feet (0.014-0.42 cubic meters) per hour and is available from C.A.P. Controllers. The pressure regulator, flow rate valve and solenoid switch which opens and closes the valve are all regulated by the ppm meter.
When the plants receive between 4500- 5500 fc (48,240 lux) of light, they can utilize between 1200-1300 ppm of CO2. While very few gardens are supplied with more than 7500 fc (80,400 lux) of light, at that intensity the plants can use up to 1500 ppm of CO2, the enrichment rate recommended by some manufacturers.
A closed closet or other small gardening space can be recharged with CO2 simply by opening the door or curtain to let in fresh air. This increases the CO2 content of the closet passively, as air naturally equalizes the concentrations of oxygen (O2) and CO2 inside and outside the growing space, exchanging the higher O2 levels with CO2. Adding a small fan expedites the air exchange.
In this garden, air is enriched as it passes through the tubes.
Learn why the amount of CO2 in the air has a profound effect on the rate of photosynthesis and marijuana plant growth.