Optimizing Nitrogen Availability In ‘Bing' Cherry Growth for High Yield and Fruit Quality

Cherry culture would benefit by efficient supply of demand-driven nutrients, nitrogen being the most critical. Our research addressed measures of tissue N flux and N application at specific physiological timings. Three California ‘Bing’ orchards (planted 1998) were selected by rootstock and location:   seedling P. mahaleb (Lodi), and clonal Gisela-6 (Gi6) and seedling Mazzard (contiguous orchards, Linden). Ten nitrogen treatments, varied by timing, form and amount (~45, ~90, ~150 lb/acre) of N, and rootstock/location effects were evaluated 2008-2010, with treatments adapted annually to project goals of optimized, demand-driven N for cropping, fruit quality and vigor. Patterns of N flux were similar across orchards; preceding ‘bud-swell’, storage N increased in buds with peak N levels at least 25% higher in fruiting spur leaves (FSL) during rapid fruit development than postharvest. Approximately half of tissue N present prior to bloom, fruiting and harvest was present postharvest (September), suggesting that about half the nitrogen available in the fruiting spurs was removed by the crop.  Highest fall N was found in vegetative and reproductive buds (VB, RB) treated with bloom-N + postbloom-N and 45 lb N/acre postharvest (PH), whereas all other treatments were either lower (VB) or only the 90 lb PH treatment was lower and other treatments were intermediate (RB).  Rootstock differences (tree architecture, precocity) strongly influenced cropping and vigor responses.  Location and use of CAN17 for dormancy-release strongly influenced frost damage risk, yet CAN17 (commonly used in California’s low-chill conditions) also reduced yields without frost.  In the Mahaleb orchard pre-leaf fall urea tended to enhance vigor and bloom-N + postbloom-N tended to reduce vigor; no effects on vigor were found in Mazzard or Gi6 orchards.  Cumulative yield and yield efficiency across orchards tended to be highest in those treatments with bloom-N (total N ~45, ~90 lb/acre) and lowest in CAN17 + 45PH + urea pre-leaf fall (~90 lb/acre N, Mahaleb; ~90 and ~150 lb/acre N, Mazzard).  Yield differences in the Gi6 orchard were not due to N treatments, rather tree-to-tree variability, with the exception of CAN17 treatments (reduced yields). Fruit maturity (by color) was unaffected by N treatment.  Fruit quality was generally not influenced by N treatment, although fruit size in the second harvest (Mahaleb and Mazzard orchards, 2010) was reduced by CAN17 + 45PH + urea pre-leaf fall (~90 and ~150 lb/acre N).