Scheduling deficit irrigation of citrus trees with maximum daily trunk shrinkage

The feasibility of scheduling deficit irrigation using maximum daily trunk shrinkage (MDS) was evaluated during two consecutive seasons in a citrus orchard planted with mature ‘Clementina de Nules’ trees, in Valencia, Spain. Results showed that MDS in well irrigated trees varied largely according to the environmental conditions (higher correlation was obtained with global radiation), and therefore, the absolute values of MDS cannot be employed as the only variable to schedule irrigation. To avoid the effects of the climatic conditions we scheduled deficit irrigation using the MDS ratio, which is the MDS of any treatment related to the MDS of a control, well irrigated, treatment located in the same plot. We explored the feasibility of scheduling irrigation based on the MDS ratio in a deficit irrigated treatment, where water was applied as necessary, from July until mid October, in order to maintain the MDS values at 125% of that of the control treatment. Despite the large variability observed in the MDS measurements in both years no significant reduction in yield and fruit weight was observed in the deficit irrigated treatment compared with the control, allowing seasonal water saving between 18 and 12%.