Journal of Agricultural Meteorology
Online ISSN : 1881-0136
Print ISSN : 0021-8588
ISSN-L : 0021-8588
Full Paper
Improvement in lettuce growth by light diffusion under solar panels
Akira TANISuguru SHIINAKazuki NAKASHIMAMakio HAYASHI
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2014 Volume 70 Issue 3 Pages 139-149

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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 production 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 normal greenhouse conditions. On the other hand, the ratio of leaf width to length increased under diffused light conditions 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 the 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.

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© 2014 The Society of Agricultural Meteorology of Japan
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