"Since results on the morphological and physiological effects of LED and HPS on cannabis were limited, first trials performed in our 20m2 phytotrons involved a comparison of LED and HPS lighting." PlantResearch is an R&D facility located in Made, the Netherlands with a dedicated R&D team performing R&D and product development for the horticulture industry. Since 2021, the company has been granted a permit to perform cultivation trials and analyses on medicinal cannabis. The results of their recent cannabis trials showed that LED increased THC at a lower energy consumption.
Light spectra of the installed HPS (left) and LED (right) lighting
For the trial, Fluence VYPR R4 LED lights and Philips Master Green Power HPS lights were used. Cannabis cultivars Amnesia Sweep and Early Queen Haze at a PPFD of 700 µmol/m2.s were compared during the short day period. The cultivation on rockwool was supplied with CANNA Hydro nutrition at constant EC levels of 2.0, 2.8 or 3.6 mS/cm (including tap water of 0.4 mS/cm). During the short-day period a 1.6 °C higher air temperature was maintained during daytime under LED to compensate for the lower radiant heat transfer of LED compared to HPS. However, the total energy consumption was 20% lower under LED in comparison to HPS, due to the lower energy use of the LED lighting.
The EC in the slabs/drain gradually increased during the SD period in all EC treatments, particularly in the high EC treatments up to 8 mS/cm. However, although the high EC treatments reduced plant height, plant and bud weight and THC content were not affected. Mineral tissue analysis of fan leaves and buds showed clear differences in the distribution of elements (e.g. relatively high Ca and relatively low N and P in leaves compared to buds). No consistent significant effects of EC level or light source on nutrient concentrations were found, and no clear leaf nutrient deficiencies were apparent until the last 1-2 weeks before harvest.
Plant length was clearly reduced in both cultivars under LED. According to the researchers, it was striking that both cultivars also showed a similar 3% (absolute) increase in THC concentration by the LED treatment. In contrast, a clear differential response was found for the cultivars in bud yield: Amnesia Sweep produced 30% higher and Early Queen Haze 13% less bud mass under HPS than LED.
Considering the 20% lower energy consumption under LED it was shown that LED outperformed HPS in THC production per unit energy by on average 30%: 0.21 g THC/kWh under LED vs. 0.16 g THC/kWH under HPS.
Successive research at PlantResearch is focused on optimizing yield and THC concentrations under higher LED levels.
For more information:
PlantResearch
www.plantresearch.nl