Night interruption enables electricity savings without compromising raspberry (Rubus idaeus L.) cv. Polana and Prelude development in vertical farms.

Main conclusion: A two-hour night interruption does not significantly impact development in hydroponic Rubus idaeus L. cultivars Polana and Prelude, supporting its use in night interruption for cost savings. As agriculture moves indoors, artificial lighting regimes can modify circadian rhythms, which in turn may impact plant development. Night interruptions have been shown to speed up development in some crops. While positive night interruption impacts are observed in some raspberry Rubus idaeus L. cultivars, this has not been tested on cultivars Polana and Prelude. We tested whether night interruptions impact the growth of raspberries. The hydroponic performance of a common floricane- and primocane-fruiting cultivars, 'Polana' and 'Prelude' respectively, were compared under a 16-h day and 2-h night interruption versus a continuous 18:6 h light-dark photoperiod. Plant growth was measured using the number of buds and flowers produced. Phenological development was also measured using time to budding, flowering, and fruiting stage. Night interruption did not significantly impact either the number of buds (F_1,57 = 0.99, p = 0.32) and flowers (F_1,57 = 2.47, p = 0.12) or speed of development to the budding (F_1,57 = 0.94, p = 0.34), flowering (F_1,57 = 1.43, p = , 0.24) or fruiting stage (F_1,57 = 1.29, p = 0.26). This indicates that night interruptions are a viable option for reducing electricity costs in hydroponic raspberry systems for cv. Polana and Prelude. However, differences between cultivar were observed for bud phenology timing, where Polana budded earlier under the night interruption, whereas Prelude did under the control (F_1,57 = 5.55, p = 0.02). There were also significant differences within cultivar in the number of buds (F_1,57 = 0.99, p = 0.02) and flowers (F_1,57 = 2.47, p < 0.001). Developing agronomic recipes for controlled environment agriculture is key for industry progress, as high energy expenditure is a notable challenge within vertical farming. Our findings yield positive results in the advancement of controlled environment agriculture as energy expenses can be decreased for certain raspberry cultivars. Future research should entail replicate experiments on other Rubus idaeus L. cultivars to further understand effects of night interruption on vertically farmed raspberries.