Integrating soil-based sensor technologies for irrigation decision support in date palm trees

Date palms, an economically important crop, are extensively grown in the Arava Valley, Israel. Despite their adaptation to arid climates, they are intensively irrigated, commonly with two high-flow emitters per tree, based on recommended amounts derived from crop evapotranspiration estimates, to ensure high productivity and manage soil salinity. Until now, date palm farmers in Israel have made only limited use of soil sensors for irrigation management. This study aimed to integrate soil-based sensors for irrigation decision support into date palm cultivation. We hypothesized that increasing the irrigated area around the tree and giving the trees less water than recommended would increase water use efficiency and maintain optimal yields. To achieve this, sixteen fully mature date palm trees were irrigated under two irrigation systems: a larger irrigated area around the tree with fifty drippers (D) and a smaller area with two emitters per tree (E), both having the same total flow rate; and two irrigation levels: 50% and 100%. Soil-based sensors (TDR, tensiometers, and suction cups) were used to continuously monitor soil water status and electrical conductivity (ECpw) at depths of 40 and 80 cm. Fruit yield and quality (i.e., fruit mass, blistering, and moisture level) were also analyzed. Across all treatments, soil water content was higher at 80 cm, with E100 and D100 showing the highest values (20–50%), while D50 and E50 showed the lowest values, particularly at 40 cm depth (10–20%). Soil tension values displayed the following order, E50>D50>D100≈E100, at both depths. ECpw on D100 and E100 averaged 3 dS/m throughout most of the growing season at both depths, while D50 and E50 showed elevated levels, especially at the lower depth, of up to 26 dS/m (D50). There was no significant difference in yield or yield quality between treatments. It is concluded that the irrigation system had less impact than the irrigation level on ECpw and soil water status. Therefore, sensors show an enormous potential to provide farmers and researchers with data that can be integrated into irrigation scheduling algorithms.