43. Gartenbauwissenschaftliche Tagung - (DGG) und des

82
Gemüsebau/Obstbau „Umweltparameter und Produktqualität“
The Effect of Diffuse Light on Sweet Pepper, Tomato and Cucumber
Production
S. Hemming 1 , T. Dueck 1 and N. Marissen 2
1
Plant Research International, Wageningen University and Research Center, Bornsesteeg 65,
NL-6708 PD Wageningen, silke.hemming@wur.nl and tom.dueck@wur.nl
2 Applied Plant Research, Wageningen University and Research Center, Linnaeuslaan 2-A,
NL- 1431 JV Aalsmeer, nollie.marissen@wur.nl
In Dutch glass greenhouses light is not distributed equally. Fruit vegetables with a high leaf
area index intercept a high quantity of light with the upper leaves, the lower leaves receive
much less light and hardly contribute to photosynthesis and therefore to growth and production.
If it is possible to shift light from the upper crop layer to the lower crop layer the
photosynthetic efficiency of the whole plant will be increased. This can be realised by making
all incoming light into the greenhouse diffuse. Greenhouse covering materials, which are able
to transform direct light into diffuse light can be used for that purpose.
A quantitative analysis of effects of the use of diffuse light on the growth and production of
sweet pepper, tomato and cucumber in Dutch horticulture is given. The light-transforming
properties of several (new) greenhouse covering materials are analysed and with the help of
light models translated into potential amounts of diffuse light in the greenhouse. With the help
of plant growth models the effect of diffuse light on light penetration in the canopy, light use
efficiency of the crop, photosynthesis of the crop and crop production are analysed.
Diffuse light is able to penetrate deeper into the canopy of crops with a high leaf area index.
Especially during the winter months more PAR is penetrating into the lower crop layers. However,
the crop is too small to intercept all the light. At the same time the amount of direct
light, which can potentially be transformed into diffuse light, is low. Therefore it can be concluded
that diffuse light seems to have no advantages during winter months. During spring,
summer and autumn months especially the middle crop layers receive and intercept more
PAR, when light is made diffuse. This results in an increase in crop photosynthesis and fruit
production. During these months the fruit production under a highly diffusing covering material
is increased by 5-10% compared to a clear reference material. The production increase is
depending on the crop, the light-transforming properties of the covering and the total light
intensity.
BHGL – Tagungsband 24/2006