Efficiency of tree-based water status indicators at the onset of water deficit in citrus

Abstract

This experiment evaluates the potential of using parameters based on tree trunk fluctuations for detecting water deficit in citrus trees under two different water saving-irrigation strategies: sustained deficit irrigation and partial root-zone drying. Three irrigation treatments were applied: 1) Control: trees were irrigated with 100% of their evapotranspirative needs (ETc); 2) 60 sustained deficit irrigation (SDI): 60% ETc; and 3) partial root-zone drying (PRD): 100% ETc needs, applied to only one-half of root zone. Maximum daily shrinkage (MDS), trunk growth rate (TGR), and MDS ratio (ratio between MDS of stressed trees and control trees) were determined. Day-to-day MDS values varied largely and could not be used to determine tree water deficit. TGR did not show significant differences among treatments at this level of stress. Nevertheless, the MDS ratio was a reliable indicator to measure tree water status, and it was more sensitive for detecting water deficit at the onset of a water deficit in trees under SDI than in trees under PRD.