Pomegranate trees (Punica granatum L.) is a deciduous fruit tree included in the so-called group of minor
fruit tree species, not widely grown but of some importance in the south east of Spain. Pomegranate trees
are considered as a culture tolerant to soil water deficit. However, very little is known about pomegranate
orchard water management. The objective of this research was to asses the feasibility of using trunk
diameter variation (TDV) indexes, obtained by means of LVDT sensors, as a plant water stress indicators
for pomegranate trees. The experiment was carried out with mature trees grown in the field under three
irrigation regimes: control well watered trees; trees continuously deficit irrigated at 50% of the control
regime (SDI); and trees that had a summer water stress cycle being irrigated at 25% of the control rates
only in July and August (RDI). The seasonal variations of maximum diurnal trunk shrinkage (MDS) and
trunk growth rates (TGR) were compared with midday stem water potential (stem) measurements.
During the course of the entire season, control trees maintained lower MDS values than the SDI ones.
In the RDI treatment, as water restrictions began, there was a slow increase in MDS, in correspondence
with a decrease in stem. When water was returned at full dosage, the RDI quickly recovered to MDS
and stem values similar to the control. However, lower MDS for a given stem values were observed
as the season advanced. The magnitude of differences between well watered and deficit irrigated trees
was much larger in the case of MDS than for stem. However, the tree-to-tree variability of the MDS
readings was more than four times higher than for stem; average coefficient of variation of 7.5 and 36%
for stem and MDS, respectively. On the other hand, TGR did not clearly reflect differences in tree water
status. Overall, results reported indicated that MDS is a good indicator of pomegranate tree water status
and it can be further used for managing irrigation. However, the seasonal changes in the MDS-stem
relationship should be taken into account when attempting to use threshold MDS values for scheduling
irrigation.