Investigating the Role of Near-harvest Deficit Irrigation on Sweet Cherry Fruit Quality

Water management plays an important role in fruit quality, particularly for fleshy drupes such as sweet cherry (Prunus avium L.). Approximately half of the nation’s sweet cherries are produced in Washington State where growers are divided on the role of near-harvest irrigation (i.e., water applied within a few weeks of harvest) on key fruit quality attributes like firmness, soluble solids, size as well as the fruits’ susceptibility to rain-induced splitting.  The objective of this research was to elucidate the role of near-harvest irrigation on sweet cherry fruit quality traits and cracking susceptibility. Two trials were conducted in a commercial ‘Lapins’/Mazzard orchard near Brewster, Washington. We established a trial with three irrigation treatments in a completely randomized design with three reps of three trees. The control treatment was irrigated regularly up to harvest (T1) and compared to trees that had irrigation cutoff 11 (T2) or 21 (T3) days before harvest. Soil water content, shoot and fruit growth, midday leaf gas exchange, and stem water potential were measured at two- to three-day intervals beginning at the onset of treatments. In addition, fruit susceptibility to splitting was assessed with a lab test on fruit harvested every three days. At harvest, yield per tree was evaluated and fruit quality traits were assessed. Both deficit treatments increased fruit soluble solids by 14% compare to control. At harvest, soil moisture in control treatments was 2.14 inches/foot greater than in deficit treatments.  Stem water potential at harvest was reduced by 0.3 and 0.4 MPa in treatments T2 and T3 respectively, compared to control (–0.75 MPa). Fruit susceptibility to splitting was reduced by 27% and 32% for T3 and T2 respectively, compared to control.  In the same orchard we established a larger scale trial, with ca. 4 acres plots, one receiving regular irrigation (control) and a deficit plot in which irrigation was withheld 15 days before harvest (T2).  Fruit quality and packout were assessed at commercial harvest by trained warehouse staff. At harvest, fruit from the deficit treatment were 7% lighter, 13% softer and had 11% higher titratable acidity compared to fruit from the control plot. Results from this first year of research suggest that manipulating near-harvest irrigation has variable effects on sweet cherry fruit quality.