ISHS Acta Horticulturae 119: III International Symposium on Water supply and Irrigation in the open and under Protected Cultivation
TRANSPIRATION AND EVAPOTRANSPIRATION OF THE GLASSHOUSE CROPS |
| Authors: | R. de Graaf, J. van den Ende |
| Abstract:
In 1975, a special glasshouse was built at the Naaldwijk research station for the purpose of research into the transpiration and evapotranspiration of glasshouse crops. Three lysimeters have been installed in this glasshouse which make it possible to compile water balance data over minimum periods of one week by measuring the quantities of water applied and the quantities of water recovered from the drainage system. The information may be used to calculate the evapotranspiration. More detailed measurements of the transpiration over short periods are carried out with the aid of individual plants or groups of a few plants growing in containers placed on scales. The data obtained with the lysimeters and scales are compared and related to the global radiation and the energy introduced into the glasshouse via the heating system. The daily transpiration and weekly evapotranspiration totals of the crops tested in the spring, summer and autumn months showed a close correlation with the daily and weekly totals of the global radiation. For several crops the plant size at which maximum crop canopy and radiation interception were reached, could be determined. Where the crop provided maximum cover, there was hardly any difference in the evapotranspiration of tomatoes, cucumbers, and sweet peppers. In heated crop there was a significant effect of the heating on transpiration and evapotranspiration. Transpiration and evapotranspiration were also considerable during the nights, particularly in the cucumber crop which was heavily heated. A linear relationship could be established for this crop between the transpiration and the energy introduced into the glasshouse via the heating during the nights in winter and spring. | |
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