Abstract

An experiment was conducted to evaluate the effect of irrigation cut-off (ICO) strategies on yield components, water productivity (WP), and gas exchange in drip-irrigated hazelnut (Corylus avellana L., cv. Tonda di Giffoni) trees during two consecutive growing seasons. The experimental design was completely randomized, with four ICO treatments and four replicates per treatment based on threshold values of the midday stem water potential (Psi(stem)). In the T1 treatment, Psi(stem) was maintained around -0.7 MPa, while T2, T3, and T4 treatments did not receive irrigation from the beginning of stage III (fruit growth curve) until trees reached approximately the following Psi(stem) thresholds: -1.0 MPa in T2, -1.3 MPa in T3 and -1.6 MPa in T4. Once reached the specific thresholds, irrigation was restored and maintained according to T1 in all treatments until harvest. Besides, measurements of Psi(stem), stomatal conductance (g(s)), net CO2 assimilation rate (A(n)), transpiration rate (E), yield components, alpha-tocopherol kernel content, and WP were evaluated in this study. Results indicated that values of Psi(stem), A(n), g(s), and E observed in T3 and T4 were between 24-29, 15-37, 15-40, and 11-32 % lower than those found in T1, respectively. T4 significantly decreased yield (kg tree(-1)), kernel (KW), and fruit (FW) weights, but KW/FW ratio and the alpha-tocopherol kernel content (mu g g(-1)) were not significantly different among treatments. Also, this study indicated that the T2, T3, and T4 treatments had 10, 17, and 25 days without irrigation, which produced water savings of 19, 24, and 29 % in comparison with T1, respectively. Finally, WP was significantly affected by ICO strategies, with the minimum and maximum values observed in T1 (0.51 kg m(-3)) and T4 (0.86 kgm(-3)), respectively.