Crop-climate coupling in greenhouses. characterization and analysis
The present work analyses the degree of coupling between a greenhouse rose crop and the internal climate as a function of crop characteristics (leaf area index, LAI) and greenhouse climate functions (natural and forced ventilation, fogging) through the determination of the decoupling factor, Ω. The study was conducted during summer periods, in the Eastern coast of Greece. It was found that the maximum values of Ω generally occur near midday, being about 0.30 when forced ventilation was operating and about 0.40 when natural ventilation was used. Slightly higher values were found when the fog system was operating. Increasing LAI also increased the value of Ω. It was evidenced that the actual transpiration rate was closely correlated to the vapour pressure deficit. As main conclusions of this study, it should be pointed out that (i) none of the control equipment used during this study was able to reach values of Ω greater than 0.50 for LAI = 2, suggesting a relatively tight control of transpiration rate by the crop itself during most of the day and (ii) the aerodynamic term of the PM equation is by far the major component determining the intensity of vapour exchanges between the internal air and the canopy in the conditions of the experiments.