Observations on the interaction among sap flow, stem diameter fluctuations, and water intake by ‘Lagorai’ raspberry

The rising interest in raspberry (Rubus idaeus L.) cultivation must nowadays meet new requirements to cope with environmental issues caused by traditional agricultural practices, as well as the abuse of water for irrigation. The objective of our work was to monitor the relations among sap flow, stem diameter fluctuations, and water intake with both overhead sprinklers and drip irrigation in ‘Lagorai’ raspberry plants grown under a tunnel in a soilless cultivation system. Irrigation was administered using a weight-based Spagnol G-Fenix irrigation controller, and the effect on the plants physiological features was detected using a PhytoSense device. Observations highlighted a direct correlation between solar radiation, temperature, and sap flow, with stem diameter fluctuations showing an opposite trend. The PhytoSense device was capable of detecting the effect of drip irrigation interventions on stem diameter without indicating any visible effect on sap flow. Sap flow, however, demonstrated a fluctuating trend as an immediate response to activation of the overhead sprinklers, emphasizing an unusual plant response. In conclusion, these observations might be used to optimize irrigation applications in raspberry and help growers to adopt a proper irrigation plan.