Long-term growth and yield responses of olive trees to different irrigation regimes

The aim of this work was to evaluate long-term effects of different irrigation regimes on mature olive trees growing under field conditions. A 9-year experiment was carried out. Three irrigation treatments were applied: no irrigation, water application considering soil water content (short irrigation), or irrigation without considering soil water reserves and applying a 20% of extra water as a leaching fraction (long irrigation). Leaf water content, leaf area, vegetative growth, yield and fruit characteristics (fruit size, pulp:stone ratio and oil content) were determined yearly. Results showed that growth parameters did not show significant differences as a consequence of applied water. Yield was increased in irrigated trees compared to non-irrigated ones, but little differences between short and long irrigation were observed, only when accumulated yield from 1998 to 2006 was considered. Irrigation did not cause significant differences in fruit size or pulp:stone ratio either. Irrigation regimes similar to those applied in this experiment, under environmental conditions with relatively high mean annual precipitation, does not increase growth, yield or fruit characteristics when compared to rain-fed treatment, and consequently, the installation of a irrigation system could be not financially profitable.