B. von Elsner and J. Xie
Institute of Horticultural and Agricultural Engineering, University of Hannover
Herrenhaeuser Strasse 2, D 30419 Hannover, Germany

Keywords: Greenhouse shading, interference pigments

During summer with high solar radiation greenhouses need shading. So shading paint or woven shading fabric is used in order to reduce insolation, high leaf temperatures or plant burning. As fabrics can be adopted to changing global radiation by movable installations, shading paint reduces permanently, also in cloudy conditions. A way to increase consumption of photosynthetic active radiation (PAR) is less lowering of radiation in the range of PAR while increase of reduction of NIR. This can be achieved by interference pigments acting by selective reflection, scattering and transmission. Merck Company, Darmstadt, Germany, is producing such pigments. During a summer experiment 2 different types of pigments in 2 concentrations were compared with conventional white wash on experimental plastic film greenhouses. The results clearly show that resulting inside temperature is dependant on overall reduction of global radiation. The inside spectral radiation regime follows the expected distribution in PAR and NIR. No influence of angle of sun’s altitude could be found. The preliminary results encourage to develop a marketable product of white wash with interference pigments which is going to be tested on commercial greenhouses.

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