Abstract
<title>Abstract</title> <p> <bold>Context:</bold> Precision irrigation has the potential to improve water-use efficiency in almond production by accounting for within-orchard spatial variability, yet few multi-year, commercial-scale evaluations of variable-rate micro-irrigation (VRI) have quantified its effects on soil water dynamics, plant water status, and yield. <bold>Aims:</bold> This study quantified spatiotemporal variability in irrigation application, root-zone soil water content, plant water status, and yield under commercial VRI management to evaluate their relationships and inform site-specific irrigation. <bold>Methods:</bold> Fourteen monitoring locations were established in a commercial almond orchard and monitored over three growing seasons (2019–2021). Irrigation, soil water content, and midday stem water potential (SWP) were monitored using flow meters, neutron probes, and a pressure chamber, respectively. Yield was estimated from field sampling and commercial harvest records. Correlation analysis, principal component analysis, and hierarchical clustering were used to characterize spatiotemporal variability. <bold>Results:</bold> Pronounced spatial variability was observed in irrigation (609–990 mm), soil water content (0.05–0.60 m³ m⁻³), plant water status, and yield. SWP declined seasonally from approximately −0.1 MPa in spring to as low as −3.2 MPa in late summer. Yield was negatively correlated with SWP (r = −0.67) and precipitation plus irrigation (r = −0.57), while correlations with soil water content were weak (r = −0.11 to −0.28). Monitoring locations were grouped into high- and low-input irrigation clusters; despite substantially lower irrigation in the low-input cluster, no statistically significant differences in yield or SWP were detected (p > 0.05). <bold>Conclusion:</bold> Greater irrigation and soil water availability did not necessarily improve almond yield, indicating opportunities to optimize irrigation without compromising productivity. <bold>Implications:</bold> This study provides one of the few multi-year, commercial-scale evaluations of VRI in almonds and demonstrates that integrating soil, plant, and irrigation monitoring can support data-driven, site-specific irrigation management to improve water-use efficiency and advance precision agriculture under water-limited conditions. </p>