VPD night settings

Is there a way to incorporate VPD for night; (lights off) so there will be two VPD settings for day and night

VPD at night doesn’t really matter much, so I would strongly suggest you focus on other aspects of the environment while your plants are resting - pest mitigation, etc.

Night time VPD doesn’t really matter anywhere near as much as daytime, so do what keeps your plants healthy & happy, and whatever is convenient for you.

Some research I did (specifically on nighttime transpiration):


According to the best of my research the difference between day & night transpiration is pretty big. See the figures and referenced studies below. Where did you arrive at your numbers?

Hemp:

From Tang, K., Fracasso, A., Struik, P. C., Yin, X., & Amaducci, S. (2018). Water- and Nitrogen-Use Efficiencies of Hemp (Cannabis sativa L.) Based on Whole-Canopy Measurements and Modeling. Frontiers in Plant Science, 9. doi:10.3389/fpls.2018.00951

Grapes:

From Medrano, H., Tomás, M., Martorell, S., Flexas, J., Hernández, E., Rosselló, J., … Bota, J. (2015). From leaf to whole-plant water use efficiency (WUE) in complex canopies: Limitations of leaf WUE as a selection target. The Crop Journal, 3(3), 220–228. doi:10.1016/j.cj.2015.04.002

From ESCALONA, J. M., TOMÀS, M., MARTORELL, S., MEDRANO, H., RIBAS-CARBO, M., & FLEXAS, J. (2012). Carbon balance in grapevines under different soil water supply: importance of whole plant respiration. Australian Journal of Grape and Wine Research, 18(3), 308–318. doi:10.1111/j.1755-0238.2012.00193.x