BROOKS, Alta. — Greenhouse gas is increasing in Alberta, but this time it’s a good thing.
Researchers have figured out that pumping carbon dioxide into greenhouses helps vegetables grow bigger.
Jim Calpas, greenhouse crops specialist at the Crop Diversification Centre South near Brooks, Alta., said that combined with Alberta’s long hours of sunlight, carbon dioxide can boost tomato production 40 percent and peppers 30 percent.
At least two Alberta greenhouse operators have already started making structural changes to accommodate liquid carbon dioxide application. Calpas predicts more greenhouse construction as potential profits increase.
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Calpas said horticulturists have known about carbon dioxide’s yield-boosting properties for 90 years but research in the past 30 years has prompted producers to see carbon dioxide as an undiscovered gold mine.
He said greenhouse operators traditionally boosted yields by feeding nutrients directly to plants through the roots, either in the soil or hydroponically. But that extra plant growth also saps the normal amounts of carbon dioxide, usually in the daylight when it is most in demand.
Plants use carbon dioxide to make sugar, and fruits and vegetables, Calpas said.
“By supplying supplemental carbon dioxide, we can push the crop production one step further.”
It might not take that much more carbon dioxide.
There are about 350 parts per million of carbon dioxide in the outside air. Calpas’s research shows that boosting levels to 400 ppm can increase yields by 20 to 40 percent. Some feel the optimum carbon dioxide level may be 1,000 to 1,200 ppm.
Temperature control
Calpas said the Alberta climate presents a different set of factors.
Because daytime temperatures are quite high, greenhouses must be ventilated to keep temperatures low enough not to harm the plants.
That can mean a complete air exchange in the greenhouse every 45 seconds to one minute, which also means losing carbon dioxide.
“Our challenge the last three years has been to find out how to use the gas more efficiently so supplemental carbon dioxide is not lost out the greenhouse vents.”
Calpas has found that releasing the gas in measured quantities at the right time limits the escape of gas into the aisles and the atmosphere.
Metering also allows lower amounts of supplemental carbon dioxide to be used to attain the highest yield increase. He said the cost return is impressive. Tomato producers net $3 for every $1 spent on carbon dioxide. Yields increase to 66 kilograms per square metre of greenhouse from 47 kg. The gain isn’t quite as high for peppers. Producers get back $2 for every $1 spent.
Calpas said increased yields will also benefit the atmosphere.
