The agronomic response of sweet cherry (Prunus avium L.) 'Prime Giant' to a 4 year-long experiment involving deficit irrigation strategies in a Mediterranean climate was studied in a commercial orchard located in the southeast of Spain (Jumilla, Spain). Four drip irrigation treatments were imposed: (i) control treatment (CTL), irrigated without restrictions at 110% of seasonal crop evapotranspiration (ETc); (ii) sustained deficit irrigation (SDI) treatment irrigated at 85% ETc during pre-harvest and post-harvest periods and at 100% ETc during floral differentiation; (iii) regulated deficit irrigation (RDI) treatment irrigated at 100% ETc during pre-harvest and floral differentiation and at 55% ETc during post-harvest, and (iv) farmer treatment (FRM), irrigated according to the farmer's normal practice. The crop's response to the different irrigation treatments was analyzed in relation to tree water status. Soil water deficit reduced tree midday stem water potential (Psi(stem)), stomatal conductance (gs) and net photosynthesis (Pn). Branch maximum daily shrinkage (MDS) responded rapidly to irrigation changes during pre-harvest and post-harvest. The lowest Psi(stem), values were reached by SDI during pre-harvest and by RDI and FRM during post-harvest. RDI did not lead to Psi(stem),, water potentials falling to below the threshold of -1.6 MPa in any season, although, FRM caused, Psi(stem) to fall below 1.8 MPa in 2017.
RDI reduced vegetative growth and did not cause significant lower yields or fruit quality. However, with SDI there was a trend towards smaller fruits and a slightly higher soluble solid content. Post-harvest deficit irrigation increased water productivity without penalizing fruit yield or the quality parameters studied, and allowed water savings of 39% compared to CTL at a time when other fruit tree species require more water. Moreover, RDI and SDI led to significantly less cracking incidence and a lower cracking index, which could extend fruit shelf life.This work was supported by the Spanish Economy and Competitiveness Ministry (MINECO) and the European Agricultural Funds for Rural Development. Reference: AGL2013-49047-C2-1-R, AGL2016-77282-C3-3-R and the "Fundacion Seneca, Agencia de Ciencia y Tecnologia" of the Region of Murcia under the Excelence Group Program 19895/GERM/15. Victor Blanco acknowledges the research initiation grant received from the Technical University of Cartagena (UPCT). The authors are grateful to Pedro and Agustin Carrion-Guardiola, "Finca Toll." farm owners, for letting them use their facilities to carry out the tests
