Effects of Irrigation on Growth and Yield Components of Hazelnut (Corylus avellana L.) in Central Italy

Long term evaluation of hazelnut response to irrigation is important in areas with limited water availability. Drought conditions are becoming common in the regions of Central Italy, such as Latium, which is the second area of hazelnut production in Italy. The trial examined the response of adult plants of cultivars 'Tonda Gentile Romana', 'Tonda di Giffoni' and 'Nocchione' to different levels of irrigation over the years 2005 to 2007 in an experimental orchard established in 1992 at the Experimental farm of the University of Tuscia. Three volumes of irrigation corresponding to the restitution of 50, 75, 100% ETc calculated from class A evaporation were applied by means of drip irrigation and compared with an un-irrigated control. Vegetative growth (trunk cross-sectional area and crown volume) and yield components were positively affected by irrigation. The highest plant yield was obtained at the 75% ETc for all cultivars and years. Nut and kernel weight and size were slightly greater in the irrigated treatments than in the control. The percentage of empty and defected nuts was higher under conditions of limited water availability. The oil content in the kernels of 'TGR' and 'Nocchione' was slightly higher in 75% and 100% ETc than in the other treatments. In conclusion, water supply of 75% ETc could be valid irrigation levels for hazelnut cvs. 'Tonda Gentile Romana', 'Tonda di Giffoni' and 'Nocchione', in areas characterised by insufficient rainfall during the year.