Optimizing kiwifruit quality through estimation of leaf stomatal conductance from sap flux density: the KIWIQUALI project

Most fruit crop irrigation is performed on an empirical basis, with very little awareness of the consequences on yield and on water use efficiency. A model is available for predicting leaf stomatal conductance from sap flux measurements in olive, which is a fruit crop that requires less water than kiwifruit vines. The main objective of the KIWIQUALI project is to estimate leaf stomatal conductance (gs) through models from sap flux density (Js) measurements in Actinidia chinensis, allowing assessment of the plant’s water status continuously and to improve irrigation management, while optimizing fruit quality. This goal will be reached through the following specific objectives: i) to adjust models for estimation of kiwifruit trees gs from continuous Js and atmospheric vapor pressure deficit (D) measurements; ii) to understand which irrigation level optimizes fruit quality and productivity; iii) to develop precision irrigation protocols based on gs estimation. To obtain measurements from plants with different levels of water status, kiwi vines in the Emilia Romagna region (Italy) were submitted to four irrigation treatments, being one well-watered (100% of crop evapotranspiration ETC) and three deficit irrigation treatments (ca. 68, 57 and 40% of ETC). The KIWIQUALI project will lead to innovative results as it will i) provide a model to continuously estimate gs on an isohydric, drought sensitive crop (kiwifruit), improving the knowledge on the hydraulic limitations and physiological responses of one of the most water requiring fruit crops; ii) improve understanding on how plant water status and physiological performance affects fruit yield and quality, and; iii) provide a tool to optimize irrigation scheduling of Actinidia chinensis. The first season of measurements will happen during the European summer (from June to ca. October), therefore, this contribution will present the KIWIQUALI project and its preliminary results.