2018 ASHS Annual Conference

Sweet cherry orchards have changed with the availability of precocious, highly productive, and vigor-controlling rootstocks such as the Gisela (Gi) series from Germany. These rootstocks have led to new ideas about the applicability of high density production systems to cherry orchards, resulting in new canopy training systems such as Tall Spindle Axe (TSA), Super Slender Axe (SSA), Upright Fruiting Offshoots (UFO) and Kym Green Bush (KGB). Leaf area is particularly important for cherry trees on highly-productive dwarfing or semi-dwarfing rootstocks at high densities. High quality fruit reguires an optimum leaf area to fruit ratio. This study characterized the differences in leaf area at canopy maturity for several new sweet cherry training systems as part of a visiting international doctoral research fellowship project funded by TUBITAK/BIDEB. The study was conducted with seven-year-old ‘RadiancePearl/Gi5’ and ‘RadiancePearl/Gi6’ scion/rootstock combinations trained as SSA, UFO, and TSA at Michigan State University’s campus Horticulture Teaching and Research Center. Planting distances were: TSA 1.2 x 2.5 m (tree x row spacing), UFO 1.1 x 2.5 m, and SSA 0.7 x 2.5 m. The site has a sandy soil, is drip-irrigated, and the orchard is covered from spring through summer with high tunnels. Fertility has been managed organically, weed control is managed organically with weed barrier fabric, and pest control has been semi-organic (minimal pesticide applications). Leaf area was calculated using a formula for measured leaf length and width values (Demirsoy, 2009) and leaf area per orchard area used 17.5 m² as the total orchard area occupied by each plot of training system trees. The highest values for total leaf area per orchard area for both ‘RadiancePearl/Gi5’ and ‘RadiancePearl/Gi6’ were obtained with the SSA canopy architecture, followed by the UFO, and finally the TSA. The SSA values were 58 to 113% higher than TSA values and 19 to 88% higher than UFO values. The high LA values for the SSA training system are due to a higher proportion of one-year-old new shoots, which have large individual leaves that result from the annual renewal of every fruiting branch, compared to the other systems that have a higher proportion of smaller spur leaves on older sections of fruiting wood. Leaf area per fruit measurements resulted in no significant differences due to high variability and low replication (due to spring frost damage to part of the orchard). However, with both scion/rootstock combinations, the UFO trees had the largest fruit.