Effects of humidity on tomato (Lycopersicon Esculentum cv. Truss) water uptake, yield, and dehumidification cost

Air water-vapour pressure deficit is the prime factor controlling plant wat er uptake in greenhouses. In turn, plant water uptake affects several physi ological processes such as pollination, plant growth, and fruit yield. In t his study, plant water uptake and fruit yield were measured under four diff erent ambient water-vapour pressure deficits (VPD). Four identical greenhou ses were used to produce tomatoes under four different regimes of VPD. Gree nhouses #1 and #2 were kept under a low and high VPD, respectively, while g reenhouse #3 was kept under a low VPD during the day and a high VPD during the night. Greenhouse #4 was kept under a VPD dynamically controlled to mai ntain plant water uptake at 800 mL/plant per day. Plant water uptake and yi eld were highly correlated to ambient VPD as greenhouses #1 and #2 produced a low and high water uptake rate and yield, respectively. Greenhouse #3 pr oduced an intermediate water uptake and yield, while greenhouse #4 lead to a water uptake and yield as high as that of greenhouse #2. Dehumidification costs were also highly correlated to VPD, as low VPD produced low water up take requiring little dehumidification. Thus, managing plant water uptake c an lead to a more efficient crop production.