SMARTER probe system for precision irrigation in pear tree orchards toward a higher water use efficiency in agricultural soil

Limited rainfall makes irrigation critical for plant growth and optimal yield. In this context, soil moisture management plays a key role in optimizing irrigation practices, improving plant performance, and enhancing fruit quality. However, conventional monitoring systems, based on single or multiple sensors installed along the soil profile, often fail to deliver accurate and representative information on water availability within the root zone. The aim of this research was to evaluate the effectiveness of a real time system made of in situ probes, able to predict the moisture in the soil unit explored by root, for the development of an irrigation recommendation. In a two-year (2024-2025) research experiment carried out in northern Italy, on mature pear fruit trees cv. ‘Abbé Fétel’, grafted on seedlings and planted at a distance of 4 x 2,4 m apart, to evaluate the effectiveness of a smart irrigation system (SMARTER) compared to a traditional one (CONTROL). The main goal of the study was to use a probe system to detect the total amount of water in the first 100 cm of soil depth and wisely select the amount of water to irrigate the crop. Water management in the CONTROL treatment followed the advisory service guidelines, based on daily evapotranspiration, soil texture, and crop phenological stage. In contrast, the SMARTER system applied irrigation according to soil water content measured by potentiometric probes located according to the grid of nine sensors (placed ad different distance and depth from the emitters). 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 replacing the optimal water level for the phenological stage. The first year (2024), two treatments were applied: SMARTER vs CONTROL, with an irrigation system made of a single pipeline. While in the second year (2025), a new treatment was added, consisting of the same irrigation system, however water application rate was reduced to maintain only 40% of the volume of soil at a matric potential > -0.1 MPa (SMARTER 2). During the growing season, stem water potential was evaluated as a measure of the plant water status and at harvest the total yield was compared to the control. In comparison to CONTROL, the SMARTER system decreased the volume of water used for irrigation of 36% and 19%, in 2024 and 2025, respectively; while in 2025 the SMARTER 2 showed a 52% of water saved compared to the CONTROL. Total yield and fruit quality were not affected by the treatments during the two-year trial. However, in 2025 growing season, fruit size was increased by SMARTER and SMARTER 2 compared to CONTROL. In conclusion, the real time, in situ smart system used in this experiment, showed an important potential to decrease the volume of water commonly used in the traditional irrigation system, without affecting the total production and fruit quality.

Keywords: soil moisture, water potential, soil matric potential, Pyrus communis, drip irrigation, evapotranspiration rate