Development of irrigation program using leaf water potantial in flame seedless and Italia table grape varieties in the Mediterranean region

This research was conducted over two consecutive years (2008?2009) in the experimental vineyard of the Department of Horticulture at Cukurova University in Adana located in the Eastern Mediterranean Region of Turkey on 12 years old Italia and Flame Seedless varieties in order to determine the optimal timing of irrigation for high quality yield using mid-day leaf water potential values. In the study, for different treatments based on various threshold levels of leaf water potential, were considered: (I1: ?l = -1.0 MPa; I2: ?l = -1.3 MPa; I3: ?l = -1.6 MPa) and non-irrigated control treatment (I4). In general, lowest yields were obtained from the non-irrigated control treatment in the experimental years. The effect of irrigation treatments on yield, vine growth and juice quality differred among the varieties and years. The differences can be attributed to varying weather and soil water conditions occurred in the experimental years. Irrigation positively affected the yield in the varieties considered. Highest yields of Flame Seedless variet can be obtained when irrigated at leaf water potential value between -1.0 ? 1.3 MPa (-10 or -13 bar); on the other hand, highest yield in Italia variety can be obtained when irrigated at at leaf water potential value of -1.3 MPa (-13 bar). Highest water use efficiency (WUE) was obtained in non-irigated control treatment and WUE decreased with increasing irrigation amounts. The results revealed that grape varieties considered in the study should be deficit irrigated for higher yield and WUE.Key Words: Leaf water potential, irrigation programming, drip irrigation, water useefficiency, grapevine.