The Effect of Diffuse Light on Crops
ABSTRACT Light is not evenly distributed in Dutch glass greenhouses, but this can be improved with diffuse light. Modern greenhouse coverings are able to transform most of the light entering the greenhouse into diffuse light. Wageningen UR Greenhouse Horticulture has studied the effect of diffuse light on crops for several years. Modelling and experimental studies showed that crops such as fruit vegetables with a high plant canopy as well as ornamentals with a small plant canopy can utilize diffuse light better than direct light. Diffuse light penetrates the middle layers of a high-grown crop and results in a better horizontal light distribution in the greenhouse. Diffuse light is absorbed to a better degree by the middle leaf layers of cucumber, resulting in a higher photosynthesis. The actual photosynthesis of four pot plant species was found to be increased and crop temperatures were lower during high irradiation. The yield of cucumbers was increased, and the growth rate of several potted plants was increased. These investigations have resulted in a quantitative foundation for the potentials of diffuse light in Dutch horticultural greenhouses and the selection and verification of technological methods to convert direct sunlight into diffuse light.
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ABSTRACT: responses of red and yellow sweet peppers grown under photo-selective nets, Food Chemistry (2014), doi: http://dx.doi.org/10.1016/j.foodchem. 2014.10.034 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Food Chemistry 10/2014; 173. DOI:10.1016/j.foodchem.2014.10.034 · 3.26 Impact Factor
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ABSTRACT: Power generation by roof-mounted photovoltaic (PV) modules may provide additional income to farmers if the crop production is comparable to that under normal greenhouse conditions. However, fluctuating irradiance caused by the partial shade of PV modules has been reported to reduce crop production. In the present study, we have shown for the first time the possibility of improving lettuce growth by using light diffusion films under roof-mounted PV modules. The effects of different light conditions (direct but fluctuating, and diffused but uniform irradiations) under PV modules on the morphology, yield, and photosynthesis of hydroponically grown lettuce were investigated. Lettuce growth was inhibited, resulting in lower dry weight and relative growth rate (RGR) with longer leaves, under the fluctuating light by roof-mounted PV modules compared to that under normal greenhouse conditions. On the other hand, under diffused light conditions, the ratio of leaf width to length increased and the values were comparable to those in the control in spring, summer, and fall cultivations. Although the net photosynthetic rate of fully expanded leaves of lettuce grown under diffused light was lowest, their dry weight and RGR were comparable to the control in summer and fall cultivations. Diffused light might penetrate into the lower layers of the leaf canopy, thereby increasing CO2 fixation of the whole canopy. Our results suggest that the application of light diffusion films is a viable option for improving crop productivity under roof-mounted PV modules.Journal of Agricultural Meteorology 01/2014; 70(3):139-149. DOI:10.2480/agrmet.D-14-00005