First a little Plant Science 101 - For a successful, productive garden, hydroponic, indoor and greenhouse growers must control six "essential elements" - air, light, nutrients, water, humidity and temperature. Remove or alter the ratio of only one of these elements, growth will slow, and plants could eventually die. In this article, we will review the air element, specifically carbon dioxide (CO2), it's role in the most vital plant process - photosynthesis - and how to effectively implement CO2 systems.
The average level of CO2 in the atmosphere is about 300 parts per million (ppm). If the level decreases below 200 ppm in an enclosed growing area, plant growth slows to a halt. Through years of testing and research, the optimum enrichment level of CO2 for plant growth has been agreed to be about 1500 ppm. With carbon dioxide, under good conditions, plant growth rates and flowering will increase 20-100%. CO2 systems can be used from seedling right through harvest.
Carbon dioxide is an odorless, invisible and non-flammable gas. It is also safe for humans in the maximum concentrations recommended for plant growth.
Photosynthesis begins when stomata, pore-like openings on the undersides of leaves, are activated by light and begin breathing in carbon dioxide (CO2) from the air. This CO2 is broken down into carbon (C) and oxygen (O). Some of the O is used for other plants processes, but most is expelled back into the air. The C is combined with water to form sugar molecules, which are then converted into carbohydrates. These carbohydrates (starches) combine with nutrients, such as nitrogen, to produce new plant tissues. CO2 is vital to plant growth and development, and yet is often the most overlooked element in indoor gardening.
Successful indoor growers implement methods to increase CO2 concentrations in their enclosure. The typical outdoor air we breathe contains 0.03 - 0.045% (300 - 450 ppm) CO2. Research demonstrates that optimum growth and production for most plants occur between 1200 - 1500 ppm CO2. These optimum CO2 levels can boost plant metabolism, growth and yield by 25 - 60%.
Plants under effective CO2 enrichment and management display thicker, lush green leaves, an abundance of fragrant fruit and flowers, and stronger, more vigorous roots. CO2 enriched plants grow rapidly and must also be supplied with the other five "essential elements" to ensure proper development and a plentiful harvest.
Commercially available CO2 generators offer the most economical, practical and consistent method of enriching indoor gardens. Using atmospheric control systems in conjunction with CO2 generators, ensure the most effective production and use of CO2.
Atmospheric control systems with automatic override or defeat, and CO2 monitoring logic, enrich and maintain optimum levels in the environment during the photo (light) periods, when most plants can absorb CO2; and they defeat CO2 production during dark periods. Automating your CO2 enrichment system pays for itself quickly with shorter crop cycles, improved quality and higher yields.
When enriching an indoor garden with CO2, proper light is essential for effective assimilation. For plants to use CO2 efficiently, light spectrum and intensity should be appropriate for the plant species in your garden. Remember - CO2 enriched plants under intensified lighting demand higher levels of nutrients, water, space and room temperatures of 80-85 F. (27 - 29 C.).
As CO2 is a critical component of growth, plants in environments with inadequate CO2 levels - below 200 ppm - will cease to grow or produce. And, growers should be cautious when experimenting with CO2 levels above 2000 ppm. CO2 is heavier than oxygen and will displace the O2 required by both plants and human to function and live. (FYI: OSHA max allowable for human exposure is 5000 PPM). So, air circulation and ventilation is critical to profitable CO2 enrichment.
Plants use all of the CO2 around their leaves within a few minutes leaving the air around them CO2 deficient. Without air circulation and ventilation, the plants' stomata are stifled and plant growth is stunted.
Proper air circulation with oscillating fans and in-line blowers, will eliminate potential stagnation problems and ensure efficient CO2 enrichment.
If you have never enriched your garden with CO2, start with 700 - 900 ppm (double the normal atmospheric levels). If yields improve, increase CO2 enrichment to 1200 - 1500 ppm. If there is no response to the CO2 enrichment, double-check your other five "essential elements" to ensure they are not limiting factors.