Assessment of Continuous Apple Growth Under Dynamic Agrivoltaic Systems Using Fruit Dendrometry

Abstract

 Heat stress could negatively impact apple fruit growth. In this study shading with a dynamic agrivoltaic system (DAV) during summer was tested to evaluate if a less stressful environment can maintain fruit growth by improving water flows to the fruit. The study was conducted in an experimental ‘Golden’ apple orchard in France in 2023 with a control zone and a zone protected with DAV. Air temperature and incident radiation at the tree level was continuously measured for each zone. Fruit growth and vascular fluxes were continuously measured by using fruit dendrometers during summer (between May and September). Twelve fruits per zone were monitored according to three different conditions: ‘intact’ fruits (i.e. normal vascular connections), ‘girdled’ fruit (i.e. disconnected from the phloem, and ‘detached’ fruit (i.e. disconnected from both phloem and xylem). Daily courses of leaf, stem and fruit water potential were measured one day during summer. A reduction of 50% of incident daily radiation and air temperature was observed in the DAV zone. Absolute growth rate in DAV fruits was higher than the control when temperatures were higher than 30°C. The less stressful environment improved tree organ water status, supporting a better fruit hydration despite a potential reduction of xylem intake. This mechanism seems enough to maintain fruit size in trees shaded with DAV.