Olive fruit growth and productivity under different irrigation regimes and crop loads

A field study was conducted on young olive trees (Olea europaea L. ‘Leccino’) in Tuscany (Italy) to assess the combined effect of crop load and different irrigation regimes on fruit growth parameters and productivity. To establish heavy or low crop loads trees were hand-thinned between 5 and 6 weeks after full bloom (AFB). Drip irrigation was used to impose three irrigation regimes whereby pre-dawn leaf water potential (PLWP) was maintained: a) greater than -1.1 MPa (FI, fully-irrigated); b) between -1 and -3.3 MPa (DI, deficit irrigated); c) between -2.1 and -4.5 MPa (SI, stress irrigated). The effect of crop load on fruit tissue growth depended on the irrigation regime. Fruit mesocarp fresh weight was affected by both irrigation level and crop load, whereas endocarp fresh weight was affected only by the irrigation regime. Within each irrigation treatment, the mesocarp fresh weight was higher at low than at high crop load. However, as for dry weight, the mesocarp of SI or DI trees was smaller than that of FI trees only in high cropping trees, but not for low cropping trees. High crop loads significantly decreased fruit oil content (% dw) of FI trees. Comparing trees with high crop loads, DI showed higher fruit oil content than FI. Fresh fruit yield of SI and DI trees was 36 and 76% that of FI trees, respectively. FI and DI trees had similar fruit number; fruit number for the SI trees was 66% that of FI treatment. Oil yield per tree was similar for the FI and DI treatments, but less for the SI trees, which produced only 51% of the oil of FI trees (68% if expressed on a trunk cross sectional basis).