Delineating citrus management zones using spatial interpolation and UAV-based multispectral approaches.

• A novel methodological protocol for mapping citrus management zones was developed; • Stem water potential values and multispectral data were used as inputs; • Spatial interpolation and stepwise regression models were implemented; • Absolute classification method offers affordable interpretation of the maps. The ability to delineate site-specific management zones is a key feature for precision agriculture applications. In this study, a novel methodological protocol for mapping the water status, i.e. the stem water potential (SWP), of citrus orchards was developed. Specifically, observed stem water potential (SWP obs) values and unmanned aerial vehicle multispectral information (i.e., vegetation indices, VIs, and spectral bands, SBs) were integrated to implement a twofold approach based on: (i) the spatial interpolation (SWP int) of the SWP obs , and (ii) the stepwise regression models (SWP proxy) between the SWP obs and the VIs (scenario 1) or between the SWP obs and the SBs (scenario 2). Then, the derived crop water status maps (SWP int and SWP proxy) were customized by applying an absolute (scientific-driven), a relative (quantile-driven), and an automated clustering (K-means) classification method. The accuracy of the proposed approach, evaluated by comparing SWP int and SWP proxy with SWP obs using linear regression models, showed reliable results, with average mean absolute error and root mean square error values ranging from 0.13 to 0.19 MPa and from 0.19 to 0.24 MPa, respectively. These results provide practical insights for identifying the spatial-temporal variability of the SWP of the citrus orchard under study. Additionally, the study highlights the importance of using a scientific-driven classification to support the adoption of precision irrigation criteria and decision-making process by non-expert users, as indicated by the assessment of the Silhouette index. [ABSTRACT FROM AUTHOR]