OLIVE FRUIT AND ROOT GROWTH ON DIFFERENT IRRIGATION REGIMES IN CENTRAL ITALY

The influence of two different Regulated Deficit Irrigation (RDI) on root and fruit growth was studied in two Italian olive cultivars (‘Frantoio’ and ‘Leccino’). Trees were exposed to irrigation with 35 and 70% of the total evapotranspiration (ETc) whereas rainfed plants were used as control. Total yield per plant did not show any significant difference among the treatments, but single fruit and pulp-to-pit ratio showed increased fresh and dry weights on irrigated trees mainly due to mesocarp. Such increases were significant for irrigated treatments compared to control but no differences were found within the two RDI treatments. Water availability reduced summer drop of pioneer and especially of fibrous root growth compared to control. Higher amount of water induced a higher fibrous root growth, but no differences were observed for pioneer roots. The results showed that 35% ETc supply was sufficient to overcome a limited period of water shortage improving fruit and root system development. On the other hand additional water supply up to 70% ETc did not show visible advantages on the short time period and therefore does not seem to be recommendable in central Italy.