Precision soil moisture monitoring: use of a multi-sensor profiling for optimizing yield and fruit quality of yellow fleshed kiwifruit in northern Italy

The control of soil moisture is fundamental for optimizing water supply, plant performances and fruit quality. Traditional monitoring systems rely on a single sensor, or several sensors positioned along the soil profile not giving reliable information on soil water availability in the soil volume occupied by roots. In a 3-years field experiment we tested the effectiveness of PLUTO, an original approach able to define soil moisture profiles thanks to a bi- and tri-dimensional grid of sensors. The study was carried out, from 2021 to 2023, in northern Italy, on kiwifruit Zezy002 (A. chinensis var. chinensis) grafted, in 2012, onto micro-propagated Hayward (A. chinensis var. deliciosa) planted at a distance of 4.5 m x 2 m apart. During the experiment a traditional irrigation system (CONTROL) was compared to smart irrigation (PLUTO). Water management in the control treatment was carried out according to the advisory service, only based on daily evapotranspiration. On the other side, according to PLUTO water was applied taking into consideration the soil water content measured by potentiometric probes located according to the grid of sensors. Irrigation started when soil matric potential dropped below -0.1 MPa in more than 50% of the volume of soil explored by the root system and was aimed at returning the same amount of water lost the day before and estimated by evapotranspiration. During the experiment, compared to the CONTROL, PLUTO reduced the volume of water without impairing plant water status and yield. Fruit juice soluble solid concentration and fruit dry matter at harvest was increased by the smart irrigation system with a similar response also after 2 and 4 months of cold storage. PLUTO water management also induced a lower fruit firmness and yellow pulp color (defined by H angle) at harvest. In conclusion, the definition of irrigation volumes and timing according to smart irrigation system were able to reduce water consumption and increase fruit quality. Taking into consideration that the cost of sensors is progressively decreasing, PLUTO provides a cost-effective, operative, and precise solution to monitor soil water availability.