Abstract

Pedestrian training system as the Kym Green Bush (KGB) have been implemented by Chilean sweet cherry growers to facilitate labor and reduce production costs. Few information is available on effectiveness of foliar calcium (Ca) applications (timing and dose) and fruit thinning on sweet cherry fruit quality and cracking prevention in KGB trees. Accordingly, a 2-year study (2018/2019 and 2019/2020) using Ca sprays and thinning in the highly productive combination 'Lapins'/'Colt' was carried out. The experiments were implemented in a 6-year-old commercial orchard, using the KGB training system, at San Francisco de Mostazal, Chile (34 degrees 0'S, 71 degrees 41'W). The first year, a two-factor experiment using foliar Ca applications (CaCl2; 0.8%) during fruit development at 26 (Stage I), 39 (Stage II) and 62 (Stage III) days after full bloom (DAFB) and two crop load levels (i.e., natural crop load and 50% fruit thinning) was evaluated. The second year, five increasing foliar Ca concentrations were applied 23 DAFB (Stage I: 0% Control, 0.2, 0.4, 0.8, and 1.6% CaCl2). Fruit quality, cracking index (CI) and yield were evaluated each growing season. The first year, CaCl2 applied at Stage I significantly improved firmness and the modulus of elasticity, while significant interactions between the application time and crop load were observed for soluble solid content (SSC) and CI. Foliar Ca improves fruit quality in un-thinned trees. The second year, significant differences, and the highest values for fruit's firmness was observed with CaCl2 concentrations ranging from 0.4 to 1.6%, and the highest modulus of elasticity for 1.6% CaCl2, while no differences were observed for SSC and CI. According to our results, we recommend foliar CaCl2 in the early stages of fruit development and crop load reduction, to increase fruit quality in the highly productive combination 'Lapins'/'Colt' trained as KGB.