10-Minute Talks From Research Community

Quade Digweed
Agriculture & Agri-Food Canada

Phase Change Materials & Light Abatement  

Phase change materials can store large amounts of heat by melting and freezing at a temperature close to the greenhouse setpoint. Two mini greenhouses at the Harrow Research and Development Center were outfitted with phase change materials to study their effects on greenhouse energy balance under light abatement conditions.  The phase change material was able to store heat during the day to reduce heating demands at night, and to reduce the overheating effect from greenhouse lights under light abatement curtains.

Shining Light on Eggplant Production

While the use of supplemental lighting has become popular for cucumber and tomato production, lit cultivation of eggplant is uncommon, likely due to the lack of research and knowledge surrounding the crop. It was hypothesized that adding supplemental light to winter-grown eggplant would increase yield, while longer photoperiods would shift energy use to off-peak times, therefore decreasing the cost of electricity. Dynamic (change in light intensity and spectrum) long photoperiod lighting [up to 24h, continuous light (CL)] has proven effective at reducing electrical cost and minimizing injury in other Solanaceae species when monochromatic blue light is provided at night. To test if CL or other longer photoperiods were effective at increasing yield and decreasing electrical costs in eggplant production, we researched the effects of supplemental light photoperiods on eggplant growth and yield.

Entraining The Circadian Rhythm With Dynamic LED Recipes to Increase Crop Biomass and Yield

Previous supplemental lighting research has shown electricity cost savings without compromising greenhouse crop yield by using alternating LED spectra under continuous light. The success is hypothesized to be caused by entraining the plants’ circadian rhythm. The experiments presented in this webinar were performed in completely controlled environments (no sunlight), that held other entraining variables constant, to isolate the entraining effects of LEDs. The underlying philosophy is to create a dynamic universal LED recipe that induces rhythms by pulsing different qualities of light at different times of the day. The circadian entraining recipe induced 23.2% higher total plant biomass for tomatoes and increased cucumber yield by 36.6%. Also, young mini-cucumber plants had greener fruit. Our research adds insights to enhance the grower’s toolbox and will be continued in on-site vertical farm and greenhouse experiments.

Yun Kong
University of Guelph

Screening Vegetable Genotypes and Identifying Plant Traits Sensitive to Narrow-waveband LED Light For Controlled Environment Production

To identify traits and plants sensitive to narrow-waveband LED lighting, phenotypic plasticity responses were assessed in 18 vegetable genotypes from seed germination to cotyledon unfolding under a combination of red (85%) and blue (15%) LED lights, compared to darkness. The LED lighting provided a photosynthetic photon flux density of approximately 316 μmol m⁻² s⁻¹, with a 17-hour photoperiod. Our findings revealed that shoot color, shoot length, and root branching exhibited greater plasticity indices than other plant traits in response to LED lighting, indicating their higher sensitivity across the tested genotypes. Moreover, small- vs. large-seed species, and red- vs. green-leaf/root cultivars within the same species demonstrated elevated phenotypic plasticity indices in most cases, suggesting their heightened responsiveness to LED lighting. Potentially, the selected genotypes and identified traits will provide useful information for plant breeding and production in a controlled environment using LED lighting as the sole light source.

Rupp Carriveau
University of Windsor

Agri-Grid: Sustainable Greenhouse Energy Resilience

In a changing climate, crop protection and the massive reduction in land use afforded by commercial greenhouses represent an adaptable and secure food production pathway for Canada.  This highlights the importance of greenhouse energy decarbonization.  Economic and operational resilience requires that transitions must balance innovation against unnecessary risk. Agri-Grid builds a modeling environment with data from five different greenhouse operations, two commercial wind farms, grid-connected electrolytic hydrogen production, natural gas blending operations, and a small modular reactor (SMR) to develop business cases for the decarbonization of greenhouse agriculture.  The impacts of blended fuels on cogeneration and CO2 crop provision will also be included.  Agri-Grid will preview the operational characteristics of SMRs and the considerations for their integration into agricultural microgrids. A final focus includes the costs of hydrogen production, transportation, storage, and use; and how these factors impact where hydrogen is produced relative to where it is consumed.

Ashleigh Ahrens
University of Guelph

Extending the Flowering Photoperiod by 1-Hour Boosts the Yield of Indoor-Grown Cannabis By More Than 30%

Indoor-grown cannabis is normally flowered under 12-h photoperiods. We have found that some indoor-grown cannabis cultivars can produce robust flowering responses under photoperiods up to 14-h, with minimal delays in flowering initiation. Since longer photoperiods inherently increase the daily light integral (DLI), higher yields are also possible. We grew two indoor-grown cannabis cultivars (‘Gorilla Glue’ and ‘Incredible Milk’) to commercial maturity under 12-h and 13-h photoperiods, where the 13-h photoperiod represents an 8% increase in DLI. We found there were minimal or no delays in flowering initiation and 35% to 50% higher inflorescence yield under 13-h vs. 12-h photoperiod treatments. This talk will discuss our results and elucidate opportunities for cannabis cultivators to manipulate photoperiod to improve yield and quality within their production systems.