Assessment of sustainable deficit irrigation in a Moroccan apple orchard as a climate change adaptation strategy Nabil El Jaouhari a , Aziz Abouabdillah b , Rachid Bouabid b , Mohamed Bourioug b , Lotfi Aleya c, ⁎, Mohamed Chaoui a a Faculté des Sciences, Université Moulay Ismail, B.P. 11201, Zitoune, Meknès, Morocco b Départment d'Agronomie et d'Amélioration des Plantes, Ecole Nationale d'Agriculture de Meknès, km. 10, Route Haj Kaddour, B.P. S/40, 50001 Meknès, Morocco c Laboratoire Chrono-Environnement, UMR CNRS 6249, University of Franche-Comté, F-25030 Besançon, France HIGHLIGHTS • Mediterranean region is considered a “hot spot” for climate change. • In many regions of Morocco, farmers overestimate plant water requirements. • Smart irrigation for apple trees requires determination of a correct Kc. • SDI of apple trees with 75% ETc shows an increase in crop yield. • Fruit firmness increased with 50% of re- duction of the applied water GRAPHICAL ABSTRACT abstract article info Article history: Received 13 May 2018 Received in revised form 9 June 2018 Accepted 9 June 2018 Available online xxxx Editor: D. Barcelo This study was conducted over three consecutive years, 2015, 2016 and 2017, in the Imouzzer Kander region lo- cated in northwestern Morocco. The main objective is to evaluate apple tree responses to two sustainable deficit irrigation strategies with 75% (T2) and 50% (T3) of calculated crop evapotranspiration (ETc), compared to a con- trol irrigated with 100% ETc (T1). During the three experiment years, estimated reference evapotranspiration (ET 0 ) was 630, 684 and 728 mm, respectively, in 2015, 2016 and 2017. Under the two restricted regimes, shoot length and fruit size evolution were not significantly affected. During the fruit set of 2017, no significant effects of sustainable deficit irrigation on the relative water content were observed, whereas they increased sig- nificantly during the fruit-swelling stage for the T3 treatment. Likewise, net CO 2 assimilation (A n ) was not af- fected by the irrigation dose, whereas it increased significantly and inversely proportional to the amount of applied water during fruit swelling. Thus, under our experimental conditions, the trees subjected to extreme def- icit irrigation (T3) were not stressed at either stage. Moreover, deficit irrigation at 75% ETc increased apple yield significantly. In contrast, deficit irrigation at 50% ETc throughout the cycle was not enough to maintain an accept- able fruit size for the three studied campaigns. However, the best qualitative performance, notably for fruit firm- ness and sugar content, was attributed to this irrigation regime (T3). © 2018 Elsevier B.V. All rights reserved. Keywords: Malus domestica (var. Gala) Sustainable deficit irrigation ‘SDI’ Crop evapotranspiration Reference evapotranspiration Ecophysiological responses Fruit quality Science of the Total Environment 642 (2018) 574–581 ⁎ Corresponding author. E-mail address: lotfi.aleya@univ-fcomte.fr (L. Aleya). https://doi.org/10.1016/j.scitotenv.2018.06.108 0048-9697/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv