455 Effects of Partial Rootzone Drying and Deficit Irrigation of ‘Granny Smith’ Apples on Fruit Quality during Storage D. urović 1,a , E. Mratinić 1 , D. Milatović 1 , S. urović 2 , B. orđević 1 , J. Milivojević 1 and D. Radivojević 1 1 Faculty of Agriculture, University of Belgrade, Nemanjina 6, 11080 Belgrade, Serbia 2 Institut PKB – Agroekonomik, Zrenjaninski put bb, 11213 Padinska Skela, Serbia Keywords: apple, regulated deficit irrigation, fruit maturity, storage, firmness Abstract The effects of partial rootzone drying (PRD), deficit irrigation (DI) and control irrigation (CI) on fruit quality during storage of ‘Granny Smith’ apples were studied during a two-year period. Trees were planted in 120-L plastic pots. Fruits achieved earlier maturing at DI treatment, compared with fruits from PRD and CI treatments. Regulated drought has a positive effect on fruit firmness and weight loss during storage. After six months of cold storage, the highest decrease of flesh firmness was found in fruits from CI treatment. Effect of irrigation on changes in contents of soluble solids and total acids during storage were not found. Positive effect of DI on fruit firmness, compared with PRD, was not determined. The weight loss on PRD and DI was similar. Positive effects of DI on fruit storage were not found compared with PRD. Contrary, PRD showed good effects on fruit size and yield, compared with DI treatment. INTRODUCTION Partial rootzone drying (PRD) and deficit irrigation (DI) are water-saving irrigation strategies. Deficit irrigation is a method that irrigates the entire rootzone with an amount of water less than potential evapotranspiration, and the minor stress that develops has minimal effects on the yield (English and Raja, 1996). Deficit irrigation (DI), if applied judiciously, saves water, decreases vegetative growth and therefore pruning costs, reduces leaching of biocides into ground water, and may improve fruit quality (Behboudian and Mills, 1997). Deficit irrigation applied either early or late in the growing season improved fruit quality in terms of increased firmness, soluble solids, and sugar concentration both at harvest and after storage (Mpelasoka et al., 2000). Fruit weight loss, one of the serious causes of fruit deterioration during storage, decreased in DI apple fruits (Kilili et al., 1996; Mpelasoka et al., 2000). A possible disadvantage of DI is a reduction in fruit size. Decrease of fruit size decreases the yield, respectively. One way to deal with this problem is to apply partial root drying (PRD). Partial root drying (PRD) is a further development of the deficit irrigation technique and with this technique half of the root zone is irrigated, while the other half is allowed to dry out. The treatment is then reversed, allowing the previously well-watered side of the root system to dry down while fully irrigating the previously dryside (Dry et al., 1998; Topcu et al., 2006). Topcu et al. (2006) concluded that PRD has more effect, compared with DI, on achieving yield of tomato, if the same amount of water is spent during both treatments. But, there were investigations on different species, such as grapevine (Dos Santos et al., 2003) and olive (Fernandez et al., 2006) which did not show any differences between these two treatments. The aim of this study was to investigate and compare the effects of partial root- zone drying (PRD), deficit irrigation (DI) and control irrigation (CI) on fruit quality during storage of ‘Granny Smith’ apples. a dejan.djurovic@agrif.bg.ac.rs Proc. II International Symposium on Horticulture in Europe Eds.: J.-C. Mauget and S. Godet Acta Hortic. 1099, ISHS 2015