Deficit irrigation effects on yield components of olive trees during the onset of fruit production

A 3-year deficit irrigation study was conducted on young olive (Olea europaea 'Frantoio') trees to determine the effect of reduced water supply from the onset of full fruit production on vegetative growth, fruit characteristics, and yield components. Irrigation was carried out from 5-6 until 5-19 weeks after full bloom (AFB) using subsurface drip lines. The volume of water applied to the fully-irrigated trees, calculated from effective evapotranspiration was 558, 1293, and 1857 m 3 ha -1 in 2006, 2007 and 2008, respectively. During the same irrigation period the deficit-irrigated trees received approximately 50% total water of the fully-irrigated trees. Deficit irrigation reduced the trunk cross sectional area (TCSA) to 69% of the fully-irrigated treatment over the three years. Yield components were differently affected by deficit irrigation. Over the 3-year period fruit yield and oil yield of deficit irrigated trees were 79 and 83% those of well irrigated ones, respectively but, when expressed on a TCSA basis, they were 89 and 100%. Fruit fresh weight and pulp/pit ratio were decreased slightly, although non-significantly, with the 50% deficit irrigation, whereas oil in the mesocarp basis was similar in both watering regimes. These results show that deficit irrigation starting from the onset of fruit production is sustainable, allowing substantial saving of water in olive orchards.