Productivity and radiation use efficiency of lettuces grown in the partial shade of photovoltaic panels

• Published in: European journal of agronomy 2013-01, Vol.44, p.54-66
• Main Authors: Marrou, H., Wery, J., Dufour, L., Dupraz, C.
• Format: Article
• Language: English
• Subjects: Agricultural sciences; Agrivoltaic system; Agronomy. Soil science and plant productions; Biological and medical sciences; Earth Sciences; Environment and Society; Environmental Sciences; Fundamental and applied biological sciences. Psychology; Leaf area; Lettuce; Life Sciences; Radiation Conversion Efficiency; Radiation Interception Efficiency; Sciences of the Universe; Shade
• ISSN: 1161-0301; 1873-7331
• DOI: 10.1016/j.eja.2012.08.003

► Relative yields were higher than the relative light availability in the shade. ► Measured radiation interception efficiency (RIE) was increased in the shade. ► Increased RIE in the shade resulted from increased foliar areas and leaf sizes. ► Morphological traits may help selecting best varieties for agrivoltaic systems. Combining photovoltaic panels (PVPs) and crops on the same land unit were recently proposed as an alternative to the conversion of cropland into photovoltaic plants. This could alleviate the increasing competition for land between food and energy production. In such agrivoltaic systems, an upper layer of PVPs partially shades crops at ground level. The aim of this work was to (i) assess the effect on crop yield of two PVPs densities, resulting in two shade levels equal to 50% and 70% of the incoming radiation and (ii) identify morphological and physiological determinants of the plant response to shade. Experiments were conducted on four varieties of lettuces (two crisphead lettuces and two cutting lettuces), during two seasons. In all cases, the relative lettuce yield at harvest was equal or higher than the available relative radiation. Lettuce yield was maintained through an improved Radiation Interception Efficiency (RIE) in the shade, while Radiation Conversion Efficiency (RCE) did not change significantly. Enhanced RIE was explained by (i) an increase in the total leaf area per plant, despite a decrease in the number of leaves and (ii) a different distribution of leaf area among the pool of leaves, the maximal size of leaves increasing in the shade. Our result provides a framework for the selection of adapted varieties according to their morphological traits and physiological responses to PVP shade, in order to optimize agrivoltaic systems.