Response of table grape cultivar ‘Autumn Royal’ to regulated deficit irrigation applied in post-veraison period

A field experiment was performed from 2006 through 2008, to evaluate the effect of a postveraison regulated deficit irrigation (RDI) on the yield and quality of the seedless table grape ʹAutumn Royalʹ, especially on berry cracking. Three irrigation treatments were applied: a control (T1), irrigated at 100% of the net irrigation requirements (NIR), and two RDI treatments (T2 and T3) irrigated as T1 except from postveraison till harvest, when different percentages of NIR were applied, 80 and 60% NIR in T2 and T3, respectively. Irrigation timing was split from one daily application during 2006 and 2007 to two daily applications during 2008 Average yield in T1 was 46.3 and 46.1 t ha-1 in 2006 and 2007, respectively. RDI treatments presented similar yield values to T1, with a water saving in T3 of 94 and 144 mm in 2006 and 2007. However, in 2008 T3 treatment showed a yield reduction with respect to T2 of 13 t ha-1. The maximum yield was achieved in treatment T2 (52.6 t ha-1) and the minimum in treatment T3 (39.3 t ha-1) with a water difference of 54 mm. Berry cracking was greater than 10% in 2006 and 2007 without differences between treatments, while it was negligible in 2008. This result suggests that the change in irrigation timing performed in 2008 could have a beneficial effect in berry cracking since two irrigation applications were performed in that year, one at night and the other one at noon. However the results are not conclusive.