ISHS Acta Horticulturae 534: International Conference and British-Israeli Workshop on Greenhouse Techniques towards the 3rd Millennium
WATER CONSUMPTION OF A CLOSED SOILLESS CULTURE OF GERBERA: USEFULNESS OF MODELS TO ESTIMATE EVAPOTRANSPIRATION |
| Authors: | O. Marfà, C. Biel, F. Blanch, J.I. Montero |
| Keywords: | Penman-Monteith equation, vapour pressure deficit, leaf area index, stomatal conductance, evapotranspiration, Gerbera jamesonii B |
| Abstract:
Closed systems in soilless cultures improve water and nutrient use efficiency. But, to attain good efficiency, watering must be automatically and correctly applied at short-time intervals. In closed soilless culture systems, the full crop as a unit can be considered as a big drainage lysimeter. So, the water balance obtained, i.e. the difference between the water volume applied by watering and the volume of leachate on a daily basis, can be an adequate measure of crop evapotranspiration. Gerbera plants were grown in grow-bags and the leachates were continuously recycled. Full crop evapotranspiration was measured daily during the growing period. Simultaneously, the evapotranspiration rate was measured at short-time intervals by continuously weighing plants placed on an electronic balance. Solar radiation (G), relative humidity and dry bulb air temperature were measured at short-time scales; leaf stomata resistance and leaf area index (LAI) were measured periodically. The evapotranspiration rate was also estimated (ETc,i) using the Penman-Monteith equation and compared with the measured values at short-time scales (ETm,i) and at the daily scale (ETm,d). The ratio ETm,d/G decreased from the centre of the growing period. This fact can be related to the progressive maturity of the leaves and the specific acaulic morphology of the gerbera plants resulting in a progressive decrease of the specific evapotranspiration rate measured at full crop scale. Results obtained using the Penman-Monteith equation to estimate the ET at short time scales gives an acceptable accuracy for the management of watering a closed soilless culture of gerbera in Mediterranean conditions. The accuracy obtained using this equation is higher than that obtained from the multivariant regression from G and VPD. | |
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