Impact of Various Agrivoltaic Systems on Different Apple and Plum Varieties

Abstract

Agrivoltaic (AV) systems impact fruit orchards in multiple ways. These influences vary according to the design of the specific AV system as well as agronomic system and environmental factors determined by the location of the respective agricultural plot. This study suggests a holistic approach to optimize the output of AV systems that includes management practices, optimized AV characteristics as well as adapted plant types and varieties. To contribute to this approach, experiments were conducted at two sites in Karlsruhe (static as well as tracked modules over apple fruits) and Nußbach-Oberkirch (two different tracking algorithms over apple and plum fruits) in South Germany in 2024 and early 2025. Sugar content of plum fruits was reduced under full-sun tracking for all cultivars, but not for agronomic tracking for the cultivars Moni and Franzi. Apple trees showed impacts on flower formation at the Vollmer farm and delayed ripening of up to two weeks at the LTZ site. Additionally, fruit characteristics showed low suitability for long-term storage. The prediction of optimal harvest dates by assessing the Streif Index was difficult. These problems could be caused by low starch assimilation during the vegetation period, which impacts assumed starch degradation and thus the Streif Index. Therefore, it might be helpful to adjust the calculation of the Streif Index for AV systems.