Growth and yield in irrigated and non-irrigated olive trees cultivar Coratina over four years after planting

This study aimed to verify the cumulative effects of water deficits over four years on canopy and root growth and on yield in olive trees cv. Coratina. The trials were carried out at Gaudiano di Lavello (N 41° 03', E 15° 42') on trees planted in 1992 at distances of 6 x 6 m. During the first year of growth all plants were irrigated when soil water potential at 35 cm depth reached -0.08 MPa. From the second year on no water was applied to part of the grove, while the rest was irrigated according to the criterion used in the first year. At the end of the first year the soil volume explored by roots was 0.5 m3 p-1; in the second and third years the irrigated plants explored 2.9 and 8.6 m3 p-1 respectively, compared to 2.3 and 5.1 m3 p-1 in the dry treatment. Leaf area after the first year of growth was 0.6 m2 p-1. In the three subsequent years the irrigated trees showed leaf areas of 1.9, 6.1 and 6.9 m2 p-1, respectively, against 1.2, 3.8 and 4.9 m2 p-1 for the dry plants. The root-canopy ratio was 0.19 (g g-1 of dry weight) in the first year, and in the second and third years 0.18 and 0.16 (g g-1) for irrigated plants against 0.28 and 0.25 (g g-1) for dry ones. Yield from irrigated trees was 131, 548 and 1460 kg ha-1, in the second, third and fourth years respectively, while non-irrigated plants produced 39, 100 and 1020 kg ha-1. The results show that water deficit reduced soil volume explored by roots, leaf area and yield. The most marked effect was on canopy growth, making for a modified roots-canopy ratio compared to irrigated plants.