Biostimulation with phycocyanin-rich Spirulina extract in hydroponic vertical farming

Abstract

Vertical farming (VF) is a potential solution for producing high-quality, accessible, and climate-friendly nutrition for growing urban populations. However, to realize VF's potential as a sustainable food source, innovative technologies are required to ensure that VF can be industrialized on a massive scale and extended beyond leafy greens and fruits into the production of food staples or row crops. While technological advances have improved the energy efficiency of VF lighting systems, there has been insufficient research into biostimulation as an approach to reduce energy needs and improve crop quality and yield. We conducted a controlled trial to investigate the application of a phycocyanin-rich Spirulina extract (PRSE) as a biostimulant in hydroponically grown, vertically farmed lettuce (Salanova® Lactuca sativa and Salanova® Red Crisp). Phenotype analysis for Salanova® Red Crisp with PRSE application showed a reduced time from seed to harvest by 6 days, increased yield by 12.5%, and improved antioxidant flavonoid levels. Metagenomic analysis of the microbial community of the nutrient solution for Salanova® Lactuca sativa cultivation indicated a 62% reduction in the bacterial population for the PRSE treatment group (vs. 0.017% increase for the control group). An increase in the overall bacterial diversity and evenness was found in the PRSE treatment group as compared to a decrease in these parameters for the control group. This preliminary study reveals the utility of PRSE for plant growth promotion, improvement in crop yield, and potential prebiotic activity in hydroponic vertical farming. Moreover, it demonstrates that microalgae-derived biostimulants may play an important role in improving the economic and environmental sustainability of VF.