GOhydro - D1.2 Evaluation of Optimized Growth Environments in Controlled Experiments v2.0
Creators: name: Cowden, Reed
name: Bhim Bahadur Ghaley
name: Rusu, Teodor
Publisher: name: Zenodo
Year: 2023

description: Microgreens are plants at the young phenological stage between sprouts and baby greens, with a growing period of around 6-16 days from germination to harvest. They are gaining increasing attention because of their short production cycle, dense growing conditions, and their beneficial attributes such as high nutrient density, secondary metabolite content, and gastronomic applications, all of which contribute to their categorization and use as ‘functional foods.’ However, the degree and impact of environmental parameterization on Microgreens production is not firmly established, with some crucial gaps such as light recipes being of critical importance. This is of contemporary importance given the current energy crisis; identifying pathways to reduce energy use and evaluate outcomes for production efforts can have beneficial impacts. With this in mind, the objective of this deliverable was to investigate experimentally the effects of nutrient solution fertilization, seeding density, and light spectrum combinations and intensities on fresh weight and dry weight accumulation in four Microgreen species and varieties: Sinapis alba (Mustard var. White Candy), Brassica oleracea var. sabellica L. (Kale var. Black Mandingo), Brassica oleracea (Radish var. Daikon Panzer), and Brassica oleracea convar. acephala var. gongylodes L. (Kohlrabi var. Red Cardinal). Our objective was to evaluate 10 different growth environments in highly controlled experiments conducted in a Climate Chamber in the University of Copenhagen’s Taastrup Campus, Taastrup, Denmark. The results of these experiments have shown that there are significant differences between light recipes for both FW and DW biomass accumulation. Furthermore, there were differences between seeding density, light type, and fertilization as well for FW and DW biomass accumulation. We have shown the degree of these differences for each of our four Brassicaceae Microgreen species. Overall, the best light recipe was the High Far-Red, which produced the best outcomes. This was a very strong relationship for FW, but for DW, there was more variety for light recipe influences. The effect of fertilization was also very clear, as it improved fresh biomass accumulation by around 1.5-2.0 times depending on the light recipe used. We have also presented results on the production of biomass per unit dollar input. We showed that the 24VHELEDs were much more economically productive than the highly expensive OSRAM research lights. Furthermore, their ease of use, waterproof qualities, low weight, and durability, led us to the conclusion that they are the better choice for growers in almost all cases; therefore, we recommend environmental recipes 9 and 10 for use by Microgreen growers. Furthermore, although there was a general improvement to FW biomass of about 1.13 times via using the more expensive OSRAM lights (recipes 1-8), they are around 50 times less productive per unit dollar input than the 24VHELEDs. In sum, therefore, we recommend growers use 24VHELEDs of a similar recipe to ours used here, which had a high green and red component; however, our research also demonstrated the efficacy of using light recipes with a high component of Far-Red light. Therefore, an ideal combination would be finding 24VHELEDs that also have Far-Red bands included in their light recipe, to approximate our HFR recipe, which had best overall productivity. Furthermore, photons with larger wavelengths have lower energy requirements per photon; therefore, using light recipes with higher amounts of Red or Far-Red light can lower energy costs of light recipes. Overall, we showed that Microgreens were sensitive to their environmental inputs, and we have contextualized the outputs for both overall production and for relative production metrics to offer valuable insight into Microgreen production options.