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Irrigation Figure 1 Cherry diameter No difference in fruit size was found. 35 - 30 - 25 - 20 - 15 - 10 - 5 - 0 - Treatment 1, fully irrigated 65 percent ETº Treatment 2, 55 percent ETº Treatment 3, 45 percent ETº Treatment 4, regulated deficit irrigation Cherry trunk growth is most pronounced following harvest, and this was when the greatest stress levels occurred. For exam- ple, Treatments 2, 3, and the regulated deficit reached values of -2 MPa and -1.6 MPa, during 2009 and 2010 postharvest periods, respectively. High temperatures and low humidity after harvest were associated with the heightened stress observed in 2009. Irrigation starts switch to T1 level RDI Harvest 0 20 40 60 80 100 DAYS AFTER FULL BLOOM NOTES: Above data represents fruit diameter measurements taken weekly in 2011. SOURCE: Todd Einhorn, Oregon State University • Treatment 1: Fully irrigated at 65 • Treatment 2: 55 percent ETº from 2009–2011 • Treatment 4: Regulated deficit irriga- tion of 45 percent ETº from spring through pit hardening, 65 percent ETº end of pit hardening through harvest, and 45 percent ETº postharvest from 2009–2011. Omeg Orchards previously identified 65 percent ETº as an effective irrigation level to attain good cherry yield and fruit quality on water-deficient sites, thus, 65 percent ETº was considered fully irrigated. Stress indicators We used several plant-based measure- ments (stem water potential, fruit, shoot and trunk growth) to identify the critical, sensitive time periods of cherry fruit and tree growth. Stem water potential of Treat- ment 2 (55 percent ETº), Treatment 3 (45 percent ETº), and Treatment 4, the regu- lated deficit irrigation, remained above -1.4 MPa (MegaPascals) in all years throughout the preharvest interval. For comparison, fully irrigated Treatment 1 trees in 2011 had values of -1 MPa; how- ever, in 2009 and 2010 when the treat- ment was irrigated at 65 percent ETº, stem water potential did not differ from other treatments. Weekly measurements of fruit growth, a sensitive indicator of stress, were not affected by irrigation treatment in any year of the study (Figure 1). Shoot growth was also unaffected. Roots located at two- and three-foot depths compen- sated for these deficits by extracting sup- plementary water, which served to limit the development of tree water stress dur- ing the preharvest interval (Figure 2). Trunk growth showed the greatest sen- sitivity to irrigation level with growth increases over the three-year period for the fully irrigated treatment and Treat- ment 2 of 27 and 23 percent, respectively, and 21 percent increases for Treatment 3 and the regulated deficit treatment. www.goodfruit.com GOOD FRUIT GROWER APRIL 1, 2012 33 percent ETº in 2009 and 2010, and 96 percent ETº in 2011 • Treatment 3: 45 percent ETº from 2009–2011 Production Lapins fruit quality was considered excellent in all years. Excessive fruit set in 2009 translated to yields of about 14.5 tons per acre. Significant differences were not observed among treatments. Fruit size peaked on 9.5 row. In 2010, Treat- ments 2, 3, and regulated deficit yields were reduced by approximately 15 per- cent, compared to the fully irrigated Treatment 1. Similarly, in 2011, Treatment 3 and the regulated deficit treatment yields were reduced by 10 percent, though these were not significant (Table 1). Because fruit growth and size were unaf- fected by irrigation treatment in any year of the study, as shown in Figure 1, lower yields were attributed to trees having fewer fruit. The interaction of heavy fruit loads in 2009 (limiting carbohydrate FRUIT GROWTH (mm)