Insights into the potential of semi-closed greenhouses and future perspectives for tomato crops

In the particular context of the combination of climate change and continuing increases in global food demand, semi-closed greenhouses (sCGH) have been developed to improve climate management (both cooling and heating), reduce pest pressure (insect-proof), increase light transmission (fewer vents on the roof) and control relative humidity (dehumidification through active ventilation system) while reducing energy consumption. Thus, (sCGH) adoption is spreading widely in the south of France, where both climatic and insect pressures are high. The potential of sCGH is also intriguing in more moderate climates, such as the north-west of France, because of dehumidification requirements. Ctifl (Carquefou, France) led a 3-year experiment (2014-2016) on an Ultra-Clima® sCGH from KUBO in comparison with a conventional greenhouse (GH), using tomato crops. We explored an integrated approach to evaluate the benefits of the sCGH, including innovative work on plant physiology (transpiration activity, photosynthesis, and plant architecture), energy consumption and economic approaches (yield, input costs, return on investment). Photosynthesis was barely affected, unlike plant transpiration activity (plants were less stressed in sCGH) and plant architecture (leaf area index and specific leaf area decreased in sCGH), which highlighted significantly different plant physiological behaviour in the sCGH. Considering these data, climate management has to be adapted to grow tomato crops in sCGH. In association with a decrease of gas consumption by over 16%, yield increased by 8.7%, leading to an extended profit of €4.50 m(-2) in sCGH compared with GH. The return on investment is estimated to 6.7 years. Despite the high potential of sCGH, this integrated approach allows us to point out and discuss some specific improvements needed to satisfy growers in moderate climatic regions.