ORIGINAL PAPER Almond agronomic response to long-term deficit irrigation applied since orchard establishment Gregorio Egea • Pedro A. Nortes • Rafael Domingo • Alain Baille • Alejandro Pe ´rez-Pastor • Marı ´a M. Gonza ´lez-Real Received: 17 June 2011 / Accepted: 5 January 2012 / Published online: 13 January 2012 Ó Springer-Verlag 2012 Abstract This study assesses the long-term suitability of regulated (RDI) and sustained deficit irrigation (SDI) implemented over the first six growing seasons of an almond [Prunus dulcis (Mill.) D.A. Webb] orchard grown in a semiarid area in SE Spain. Four irrigation treatments were assessed: (i) full irrigation (FI), irrigated to satisfy maxi- mum crop evapotranspiration (100% ET c ); (ii) RDI, as FI but receiving 40% ET c during kernel-filling; (iii) mild-to- moderate SDI (SDI mm ), irrigated at 75–60% ET c over the entire growing season; and (iv) moderate-to-severe SDI (SDI ms ), irrigated at 60–30% ET c over the whole season. Application of water stress from orchard establishment did not amplify the negative effects of deficit irrigation on almond yield. Irrigation water productivity (IWP) increased proportionally to the mean relative water shortage. SDI ms increased IWP by 92.5%, reduced yield by 29% and applied 63% less irrigation water. RDI and SDI mm showed similar productive performances, but RDI was more efficient than SDI mm to increase fruiting density and production efficiency (PE). We conclude that SDI ms appears to be a promising DI option for arid regions with severe water scarcity, whereas for less water-scarce areas RDI and SDI mm behaved simi- larly, except for the ability of RDI to more severely restrict vegetative development while increasing PE. Introduction Almond (Prunus dulcis (Mill.) D.A. Webb) is a major tree nut species whose production and profitability are highly dependent on irrigation supply (Egea et al. 2010), espe- cially in regions such as the Mediterranean basin charac- terized by low rainfall and high evaporative demand during the almond growing season. Current limitation of water resources is threatening almond farm productivity, and this trend is expected to increase in the next decades (IPCC 2007). Therefore, farmers are obliged to deal with water scarcity by implementing sustainable agronomic practices aimed at maintaining crop yield with less water (Dodd 2009). Deficit irrigation (DI) practices have proven suc- cessful at increasing irrigation water productivity (IWP), that is, yield produced per unit of irrigation water applied, in many crop species (Fereres and Soriano 2007). DI consists of deliberately irrigating below maximum crop evapotranspiration (ET c ). Depending on the temporal pattern of stress imposed, DI strategies such as sustained deficit irrigation (SDI, Fereres and Soriano 2007) or Communicated by I. Dodd. G. Egea (&)  P. A. Nortes  A. Baille  M. M. Gonza ´lez-Real A ´ rea de Ingenierı ´a Agroforestal, Universidad Polite ´cnica de Cartagena, Paseo Alfonso XIII, 48, 30203 Cartagena, Spain e-mail: gregorio.egea@upct.es Present Address: G. Egea A ´ rea de Ingenierı ´a Agroforestal, Universidad de Sevilla, Ctra. de Utrera, km. 1, 41013 Seville, Spain Present Address: P. A. Nortes Departamento de Riego, Centro de Edafologı ´a y Biologı ´a Aplicada del Segura (CEBAS-CSIC), P.O. Box 164, 30100 Espinardo, Murcia, Spain R. Domingo  A. Pe ´rez-Pastor Departamento de Produccio ´n Vegetal, Universidad Polite ´cnica de Cartagena, Paseo Alfonso XIII, 48, 30203 Cartagena, Spain R. Domingo  A. Pe ´rez-Pastor Unidad Asociada al CSIC de Horticultura Sostenible de Zonas A ´ ridas (Universidad Polite ´cnica de Cartagena-CEBAS), Cartagena, Spain 123 Irrig Sci (2013) 31:445–454 DOI 10.1007/s00271-012-0322-8