Maximum daily trunk shrinkage reference values for irrigation scheduling in olive trees

Measurements of maximum daily trunk shrinkage (MDS) were performed on adult olive (Olea europaea L. cv. Manzanillo) trees in an experimental farm in Seville (Spain). The objective was to study the feasibility of obtaining maximum daily trunk shrinkage baselines or reference values for use in irrigation scheduling. The trees were irrigated daily above their water requirements in order to obtain non-limiting soil water conditions. The results indicated it is possible to obtain baselines for MDS, despite a certain scattering of the data points representing the relations between MDS and the climatic variables (reference evapotranspiration, solar radiation, vapour pressure deficit and temperature). MDS behaviour was best correlated with midday vapour pressure deficit and midday air temperature (r2 = 0.83 and 0.79, respectively).