Influence of aluminized thermal screens on greenhouse microclimate and night transpiration
The aim of this work was to characterize the influence of a thermal screen on: the greenhouse microclimate, energy savings and crop transpiration. Measurements were carried out during winter in a glasshouse cultivated with a rose crop and equipped with an aluminized thermal screen. Air temperature and humidity were recorded at 0.3 m, 0.8 m and 1.8 m high inside the greenhouse. Net radiation over and under the thermal screen; and under the rose crop, leaf temperature and crop transpiration were simultaneously monitored. The results indicated that the thermal screen induced a more homogeneous microclimate, and increased air temperature and canopy temperature by about 2.5°C and 3°C respectively. Canopy net radiation was increased while transpiration was similar in both cases, showing cyclic fluctuations that appeared to be due to internal physiological control processes rather than to response to microclimatic variables. The air vapour pressure deficit VPD in the lower part of the canopy was similar in both cases, as well as the canopy to air VPD and the dew-point temperature. These results suggest that the use of a thermal screen brings several advantages, such as a more homogeneous greenhouse microclimate, a reduction in heat consumption and a significant increase in canopy temperature in the lower part of the crop, but does not improve the humidity conditions.