Effects of Water Availability on Hazelnut Yield and Seed Composition during Fruit Growth

Irrigation of hazelnut is widely applied because of its positive effects on productive behaviour in areas and years with limited rainfall and in soil with low water capacity. In recent years sub-irrigation has been applied in some Italian areas to mature hazelnut orchards and new plantations with the aim of optimising water use efficiency, reducing the cost of irrigation and enabling an easier soil management. The research analysed the effect of water supply by means of subirrigation on yield, nut traits and composition during fruit growth in a mature hazelnut orchard, cultivar Nocchione, in comparison to a not-irrigated control. The experimental field was located in the Monti Cimini district (Lazio, Central Italy), one of the most vocated areas for hazelnut cultivation in Italy. Meteorological parameters were weekly monitored. Irrigation improved yield and positively affected the seed/nut ratio. Some minor effects of water supply on nut composition and quality were observed. Nuts from sub-irrigated thesis revealed a moisture content at harvest slightly higher, a slightly lower concentration of phenols in seed and pellicle and higher percentage of linoleic and linolenic fatty acids in comparison to the not irrigated thesis, whereas protein, sugars, organic acids and oil content did not significantly change. Concerning the dynamic of kernel composition, water content decreased in seed and pellicle during fruit growth. Dry matter and soluble sugar accumulation was more regular in seeds from irrigated plants. Sugars concentration showed variations related to environmental constraints and fatty acid synthesis. Sugar profile changed during nut development. Starch content was significantly higher in irrigated thesis in almost all the dates of July. Oil accumulation reached the highest level in the first half of August.