Soilless production of wild rocket as affected by greenhouse coverage with photovoltaic modules

Solar photovoltaic greenhouses have become more popular, especially in the countries of southern Europe, due to specific government remuneration policies. However, many agronomic questions need to be addressed. This research was carried out in three types of commercial greenhouses covered with different materials (polycarbonate modules [PCM], traditional [TPM] and innovative semi-transparent [IPM] photovoltaic modules) with the aim to verify the compatibility of solar energy production with the production of high-quality wild rocket (Diplotaxis tenuifolia L.). IPM may satisfy the entire electricity demand of a commercial greenhouse. Yield for rocket grown in TPM was lower than for IPM and PCM. Antioxidant properties and dry weight decreased as a consequence of decreasing cumulative photosynthetic photon flux density. Nitrate content in TPM was higher (about 10,000 mg · kg-1 FW) than the maximum limits allowed by EC Regulation No. 1258/2011, whereas it was lower in IPM and PCM (1,805 and 668 mg · kg-1 FW, respectively).The results suggest that it is possible to combine solar energy production with high-quality wild rocket production, using innovative semi-transparent PV modules.