Organic greenhouse operators want to optimize use of light, energy and natural resources for four-season vegetable production. The goal is to reduce the eco- logical footprint, enhance food security, and improve farm sustainability and profitability. Frédéric Jobin-Lawler and Annie Lévesque, owners of Abri Végétal, support this approach by participating in research led by Martine Dorais, a professor at Université Laval, who is comparing vertical organic agriculture to the intelligent use of greenhouses as part of Organic Science (OSC) Cluster 3.
Abri végétal is a family farm in Comp- ton, Québec’s Eastern Townships, which produces organic greenhouse vegetables (tomatoes, cucumbers, etc.), herbs and microgreens. Their products are sold locally and exported to the US. The owners aim to reduce their carbon footprint, while adapt- ing to new market conditions (crop diversi- fication, increase in the length of growing season) and support scientific research.
Complementing the laboratory tests conducted at Université Laval, Abri Végétal is a real-life test site for three aspects of the OSC research: 1) production of microgreens in growth chambers; 2) intra-canopy cultivation; and 3) effect of biostimulants.
The producers sow various crops (Swiss chard, pak choi, mustard, shiso, amaranth, etc.), which are harvested after 21 days and combined to create a microgreen mix. Before the OSC project, the quality of their product was highly dependent on the quality of the potting soil. They want to optimize their production methods to ensure the quality of their product, while adding flavour and nutritional qualities not achievable in hydroponic systems. They are evaluating the impact of light, fertilizer and inoculant types on the microgreens.
During the first part of the project in growth chambers, light-emitting diode (LED) lights were tested with different light spectrum and different photo periods:
- long days and short nights (20 hours (h) sunlight, 4h darkness);
- short days and very short nights (5h sun and 1h darkness alternating over 24 hours);
- control: natural sunlight supplemented by high pressure sodium (HPS) lights.
These comparisons aimed to determine the efficiency and cost-effectiveness of the different systems. LEDs reduced energy consumption and heat emission. For microgreens, LED use in growth chambers is ideal because the temperature produced by HPS fixtures is unsustainable for the plants.
Frédéric looks forward to optimizing their methods of producing micro- greens in growth chambers. “I will have a lot of knowledge about the effects of photoperiods and the impact of the light spectrum. I will be able to apply this knowledge afterwards”.
In the second part of the research, Abri Végétal sought to optimize the 3000m2 of greenhouses by improving the yield per square meter. Instead of the usual gap between two crops, they overlapped crop spacing of different crops. Growing two crops is cost-effective because it increases the yield/m2.
They transplanted cucumber seedlings at the base of tomato plants that were nearing the end of their life. Timing of transplanting was chosen to give the young crop adequate light. The growers reduced the foliage of the old crop in favour of the young crop, and placed lights inside the tomato canopy to give the seedlings sufficient light. Frédéric has gained expertise by helping with the experimental setup. He now wants to add lights throughout the greenhouses.
Since diseases are favoured by continuous cultivation, different inoculum treatments (bio-suppressants) will be tested during the third part of the research activity. The bio-suppressants could limit the establishment of certain pathogens, such as Pythium. The treatments will be applied by inoculating potting soil with a new treatment or by using leachate from their soil (to tap into the microflora already present).
Through this research, Abri Végétal seeks, above all, to support the science; the producers know that sometimes the results do not meet expectations. “It’s as important to know what works as it is to know what doesn’t.”
At the end of a research cycle, researchers summarize and disseminate the results of the entire project to the various partners. Frédéric appreciates these presentations: “It allows us to have information quickly on what has happened elsewhere and it directs us towards new avenues of testing to be done at home.”
The greenhouse growers at Abri Végétal have a clear vision of the future of organic soil-based agriculture: “We have always believed in the principle of organic certification, that a plant should grow in the soil”. They want to offer consumers organic products that stand out for their terroir flavour, in addition to being products without synthetic pesticides.
By collaborating with OSC research, they hope to demonstrate that the soil is the best source of protection against many plant diseases. The preliminary results of the next part of the project on bio-suppressors look promising!
(OSC3) Originally published in Organic Science Canada magazine, Issue #4, Spring 2022
