Vol.:(0123456789) 1 3 Irrigation Science https://doi.org/10.1007/s00271-019-00622-w ORIGINAL PAPER Irrigation of ‘Hass’ avocado: efects of constant vs. temporary water stress Avner Silber 1,2  · A. Naor 2,3  · H. Cohen 2  · Y. Bar‑Noy 2  · N. Yechieli 2  · M. Levi 2  · M. Noy 4  · M. Peres 2  · D. Duari 2  · K. Narkis 1  · S. Assouline 1 Received: 9 July 2018 / Accepted: 30 January 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract The main objectives of the present study were to assess the water demand for heavy fruit load of ‘Hass’ avocado throughout the growth periods and to investigate the efects of defcit irrigation during sensitive phenological phases on yield. The experimental set-up allowed the comparison between trees responses to three irrigation strategies during the entire growth period (no water stress; excessive irrigation; constant water stress) as well as the comparison between regulated defcit irrigation (RDI) managements applied during the early or the late growth period. The yield of no water stress treatments during three experimental years was very high (25–31 t ha −1 ) while the yields of water-stressed trees were signifcantly lower (16–21 t ha −1 ). More importantly, the yield of no water stress trees was not susceptible to alternate bearing while the yield of water-stressed trees was considerably reduced during of-crop years. Irrigation rates and the actual evapotranspiration coefcient K L = ET/ET 0 for the no water stress treatment may serve as a reasonable guide for irrigation management. Fruit load should be taken into account while planning irrigation and fertilization management and plant-based methods should be used for controlling the irrigation management (scheduling and quantities). Analyses of trunk diameter variation data that lead to evaluation of trunk growth rate and maximum daily shrinkage refect phenological stages and periodicity of shoot, fruit and root growth, and also may provide an integrative, “holistic viewpoint” of overall tree status. Introduction Avocado (Persea Americana Mill.) is indigenous to the humid subtropical and tropical regions of central and north- ern South America (Lahav et al. 2013), but nowadays, is grown all over the world due to its very high fruit nutritional value (Schafer et al. 2013). The development of irrigation technologies was the key factor that facilitated avocado plantation spreading to Mediterranean, semi-arid and arid areas where irrigation is crucial (Carr 2013; Lahav et al. 2013). The vegetative growth of avocado trees is generally vigorous, bearing a potential photosynthetic capability for producing more than 30 t ha −1 of fruit containing 17% oil (Wolstenholme 1986). Unfortunately, the worldwide average avocado yield is generally low (Campisi-Pinto et al. 2017) as a result of high rates of fower and fruit abscission (Gar- ner and Lovatt 2008) and alternate bearing (annual cycle of high and low yield, Lovatt 2011). Recently, Holzapfell et al. (2017) reported that water stress signifcantly amplifed the efect of alternate bearing. The total number of fower, bud and fruitlet abscised is huge (approximately 1.3 million per a single tree) and only 1% of the fruitlet reach maturity (Lahav and Zamet 1999). Weekly abscission rate of 140 thousand fowers and 5 thou- sand fruits per single avocado tree which annually accumu- lated to almost 500 thousand fowers and 15 thousand fruits has been reported (Slabbert 1981). Optimal water status during fowering is required for proper fruit-set as there is an increased demand for water to meet the high water tran- spiration from fowers (Whiley et al. 1988). Flower or fruit Communicated by R. López-Urrea. * Avner Silber avnersilber@gmail.com 1 Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Centre, P.O. Box 15159, 7505101 Rishon LeZion, Israel 2 Northern R&D, Israel, P.O. Box 90000, 12100 Rosh Pina, Israel 3 The Shamir Research Center, P.O. Box 97, 12900 Kazrin, Israel 4 Shaham, Extension Service, Ministry of Agriculture, P.O. Box 28, 50250 Bet Dagan, Israel