ISHS Acta Horticulturae 614: VI International Symposium on Protected Cultivation in Mild Winter Climate: Product and Process Innovation
INFLUENCE OF VAPOUR PRESSURE DEFICIT ON TOMATO CROP TRANSPIRATION |
| Authors: | E. Medrano, M.C. Sánchez-Guerrero, P. Lorenzo |
| Keywords: | Irrigation control, Fogging system, Soilless culture, Lysimeter. |
| Abstract:
The effect of air VPD on the transpiration rate of a tomato crop (vs. Forteza) was studied in multispan greenhouses. Measurements were carried out during ontogeny in two greenhouses (i) without air VPD control (maximum VPD 2.5 – 4 kPa) and (ii) with a fog-system operating when air VPD was higher than 2 kPa. Transpiration rate was determined every ten minutes by weighing plants with an electronic balance. The leaf transpiration vs inside radiation relationship at high VPD was two-fold greater than at low VPD. However, leaf transpiration response to air evaporative demand was equal in both greenhouses. A multiple regression analysis, based on the simplified Penman-Monteith formula, was established between the measured transpiration rate and the radiative and advective components. Either at high or low VPD, the model gave a good prediction of the hourly water consumption, using the same multiple regression coefficients. This simplified model, that considers the influence of air VPD on the transpiration rate, can be used in different levels of greenhouse humidity control. | |
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