CO2 Levels in Low Tunnels Peppers and melons (2001-2002) - 4 pages
Plants use the energy in sunlight to convert carbon dioxide (CO2) and water into sugars that form the basic building blocks for plant growth. Plant growth rates are strongly influenced by the availability of CO2. Under normal field conditions, CO2 levels are typically between 350 and 400 ppm. Once CO2 levels drop to 200 ppm, photosynthesis and growth slow, while higher than normal CO2 levels can accelerate plant growth. Deficient CO2 levels commonly occur within the confines of greenhouses as the rate at which the greenhouse crops absorb CO2 exceeds the rate it is replenished by introducing fresh outside air into the greenhouse. When greenhouse growers add CO2 to overcome this problem, they can substantially boost their yields if they add CO2 well in excess (ca 1000 ppm) of the normal atmospheric levels.
In Saskatchewan, many growers are using low tunnels constructed of polyethylene or woven fibre to create the warm, sheltered microclimate preferred by crops like tomatoes, peppers and melons. Like a greenhouse, the low tunnels work by restricting the movement of air in the vicinity of the crop - but the covers may also restrict replenishment of the CO2 utilized by the crop. This study examined the CO2 levels inside a standard low tunnel and explored the potential for adding CO2 into the tunnels as a means to enhance productivity.