This study examines the suitability of trunk dendrometers for assessing fruit growth under deficit irrigation (DI) for two consecutive years in a mature citrus orchard. Two DI programmes were applied during the maximum evapotranspirative demand period: sustained-deficit irrigation, applied at 50% ET C on average, and low-frequency deficit irrigation, applied according to plant-water status, establishing different irrigation-restriction cycles. Additionally, a control treatment at 100% ET C was monitored for the entire irrigation season. Trunk daily growth (TDG) and fruit daily growth (FDG) were estimated together with stem-water potential at midday (Psi stem) and the maximum daily shrinkage of the trunk (MDS). Significant relationships were determined for Psi stem vs. TDG ( R2=0.60), and vs. FDG ( R2=0.78). In addition, significant relationships were established between TDG vs. FDG ( R2=0.60), and between the daily increment of MDS (DeltaMDS) and FDG ( R2=0.50), revealing the strong connection between trunk and fruit variations caused by water stress. According to these findings, the DI effects on fruit growth can be monitored by means of TDF or temporal evolution of Psi stem, promising automation possibilities for appropriately regulating irrigation under DI programmes, and predicting its effects on fruit size by continuous field measurement.
