In a greenhouse at the College of New Caledonia’s (CNC) Quesnel campus, researchers have dug into a number of solutions potentially extending the growing season in northern climates. The length of the season in north central B.C. is often shaped by the cool weather and shorter days befalling the region as autumn approaches.
The focus of the project was to test the concept of mini-domes within a greenhouse with a combination supplemental light as a potential alternative to extend the growing seasons of romaine lettuce, butter crunch lettuce, and scallions. CNC Biology instructor Jennifer Catherall said these crops tend to have a lucrative sow earlier in the year but can be difficult to grow late season in greenhouses due to lower light intensities at that time of the year.
“With climate change, we’ll potentially face hotter summers and milder winters,” she said, in a news release. “This study offers opportunities to continue growing cool season crops later in the year. This adds food security for the region as small growers produce further into the off season.”
For this project, CNC’s Applied Research and Innovation received funding from the Canadian Agricultural Partnership under the Farm Adaptation Innovator Program delivered by the Climate & Agriculture Initiative BC and partnered with the Scientific Advisory Committee of the Cariboo Agricultural Research Alliance and Mackin Creek Farm.
Two crops were sowed. One, in late August and another in the middle of September. The crops were observed under four growing conditions including LED lights in a dome, LED lights with no dome, a dome with no LED lights, and finally no dome and no LED lights.
“The addition of LED lights inside the mini-dome provide the plants with supplemental light and also extra heat,” said CNC researcher Araham Gazana. “These two are essential to keep the plants alive and growing during harsh winter conditions.”
Harvested in mid-November and mid-December, the study measured total weight, average height and diameter of onion bulbs and lettuce heads per treatment. Researchers also collected air temperature both inside and outside the greenhouse and domes, soil temperature and volumetric soil water at 10-centimetre depth and overall energy consumption.
“The vast amount of data we collected allowed us to better understand things like air and soil temperature fluctuations inside the mini-domes throughout the winter, and their real contribution in terms of temperature gain,” Gazana said.
The study found that the addition of only an insulating dome without supplemental light did not appear to provide substantial benefit to plant growth. This, Catherall said, could be the result of CNC’s polymer greenhouse, noting that growers with a traditional greenhouse might see better results from a dome. The use of low-cost supplemental LED lighting at the correct light intensity, however, resulted in an increase in production.
“Plants grown with lights grew bigger and faster,” Catherall said. “This method could allow for producers to harvest lettuce and scallions just prior to winter farmer’s markets and diversify the produce that’s usually available at this time of year. Future studies could test hardy Asian greens and Mesclun salad greens grown in a similar environment.”
Mackin Creak co-owner and manager Rob Borsato said market gardeners, horticulturalists, and others involved in the growing and selling of local produce are always exploring ways to extend the growing season.
“The research at CNC demonstrates exciting possibilities with the production of fall-planted, fall-harvested marketable lettuce and onions,” he said. “It’s especially exciting to realize that with relatively low inputs, marketable crops can be grown in a greenhouse that, for many of us, likely would otherwise be unused at this time of the year.”