Effective Co2 Use in the Garden
Good gardeners say great things about Co2. There is no question that increasing carbon dioxide levels in the garden has tremendous potential for creating faster, more productive crop plants. The trick is to use Co2 wisely – knowing how and when to add Co2 for maximum results.
The first step is to create such great growing conditions in your garden that your crops will benefit from extra Carbon Dioxide! Careful attention to light levels, temperature, air flow through the garden, exhaust fan capability, air intake, crop spacing, and nutrient supply will result in a first class garden. You will have healthy, vigorous plants ready and willing to take up and use extra Co2 efficiently. Overheated, crowded, and bug-infested plants are so busy just trying to survive that adding Co2 would be wasteful. Whip your garden into shape first – then plan when and where to add Co2 to get the greatest benefits.
Our plants go through several growth stages during their lives
- seedling/cutting stage,
- green growth,
- transition to flowering and crop production and
- production stages.
Each growth stage has its own “cultural” requirements. Seedlings need different light levels and fertilizer strengths than established crop plants, for example, and extra Co2 is more useful during some growth stages than others. Generally, adding Co2 help the most during periods of rapid growth, but a team of Canadian university researches and commercial growers have discovered some surprising and useful facts about carbon dioxide’s effects on specific stages of growth and how extra Co2 early in a plant’s life brings unexpected benefits months later!
Co2 Application: Rooted Cutting/Seedling Stage
The researchers and commercial growers discovered that adding Co2 to plants at the seeding/cutting stage for about two weeks produced two benefits; faster early growth and greater final crop yield, even without extra Co2 during green growth and crop production! This is useful information for hobby gardeners since a little extra carbon dioxide for rooting cuttings and seedlings can help plants so much.
If you use tall, clear covers over your baby plants, release a little Co2 under the cover to raise Co2 levels to about 1500 ppM. Remove covers to let in fresh air after a few hours, and be sure plants have only fresh air (no Co2) during dark periods. The two-week period leading up to transplanting is the most effective time for this Co2 technique. If you are already using Co2 for other purposes, try treating your “small fries” with this proven growth and crop stimulator.
Co2 Applications: Transplant Stage
Adding carbon dioxide during transplanting stage is not recommended, since plants are adjusting to new growing conditions and can make do with regular Co2 levels (average 300 ppM) in the air.
Co2 Applications: Vegetative (green growth) Stage
Once plants are ‘established’ in green growth stage (full light levels, full strength fertilizers, spreading roots and new top growth), it’s time to consider adding Co2 to your rapidly growing green plants. Your decision should be based on the length of time your crop will be in green growth as well as an impartial evaluation of the garden’s growing conditions. Plants with a long green-growth period (30 days and more) would benefit from Co2 enrichment, growing to a desired size more quickly. Growth hormones used along with extra Co2 and increased food strength, results in faster, healthier green growth plants.
Co2 Application: Long-Day Crops
Some crops, called ‘long day’ plants produce their crops during summer, while continuing to put out new leaves and stems. Tomatoes and roses are typical long-day crops, which benefit from supplemental Co2 right through the green growth/crop production stages. These plants do not go through a separate transition stage like short-day crops, so additional Co2 can be applied through the life of the plants during the light cycle.
Co2 Application: Short-Day Crops
“Short-Day” crops have a definite “transition” stage before flower or crop production begins thus upsetting Co2 applications. Short-day plants produce green growth during spring and summer, and flower and crop in autumn, responding to the longer nights by beginning crop production. Chrysanthemum and hardy hibiscus are examples of this category of plant.
Since Co2 is most useful when established plants are actively growing, shut off your tank until crops pass through the transition stage and save the extra Co2 for use when crops begin producing flowers. Holding off on extra carbon dioxide while plants go through the transition from growth to crop production should help keep plants bushy and compact while they decide what to do next and reduces ‘stretching’ problems so common in the early transition period. In fact, if your short-day crop has a history of stretching, cut off the extra Co2 two week before the end of the green growth stage.
Flower and Crop Production: Short Day Plants
Once crops are ‘established’ into crop production stage (full light levels, full strength food, plants actively producing) resume Co2 enrichment. If all goes well, you could consider increasing the nutrient strength for periods of maximum growth during this stage. Cut back on Co2 as growth slows and crop is finishing up.
Fine-tuning the Horizontal Co2 Delivery System
After 7-14 days, your crops tell you how many plants you are gaining from extra Co2. How much is it helping your crop plants?
You can reposition oscillating fans, add Co2 airlines to more oscillating fans or increase Co2 flow rate if growth rate is uneven or if some plants need more Co2. Usually growers become very enthusiastic about adding Co2 at this point since they can see how it is helping their gardens. If little or no effect on growth is seen, check growing conditions for limiting factors. High garden temperatures, poor air movement, bugs, disease or incorrect nutrient mix all interfere with Co2 uptake and growth.
The Co2 generators used for carbon dioxide enrichment are very efficient burners of propane or natural gas. By completely oxidizing the fuel, the generator gives off pure carbon dioxide and lots of heat as water vapor! Growers planning to install Co2 generators in their gardens should anticipate having to deal with excess heat and humidity from their new equipment. We approach this problem a number of ways.
One method involves placing the generator in a remote location and moving the Co2 through ducting to the air intake where it is delivered to the crop by oscillating fans. A fan attached to the duct draws the Co2-rich air from the generator, helping to dissipate heat and causing some of the water vapor to condense inside the duct. Catching condensation run-offs will help in removing condensation from the duct. Do this by sloping the duct slightly and placing a tray or bucket at the end.
Another method is to suspend the generator over-head, above the garden, and use timers or a Matador CO2 controller to monitor the Co2 levels for brief periods during the light hours. With all fans shut off, the Co2 generator goes on and carbon dioxide drifts downward onto the garden. When the generator shuts off by the set limits of the Matador CO2 controller, the fans are turned back on to cool the garden.