S16 - Session O3 - Foliar Calcium applications and crop load regulation in sweet cherry (Prunus avium L.) trees trained in KGB

Authors: Maritza Matteo *, Juan Pablo Zoffoli, Marlene Ayala

Pedestrian training systems as the KGB have been implemented by Chilean sweet cherry growers to facilitate labors and reduce production costs. Few information about the effectiveness of foliar Calcium (Ca) and fruit thinning on sweet cherry fruit quality and cracking prevention in KGB trees is available. 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, at San Francisco de Mostazal, O'Higgins Region, Chile (34º 0' S, 71º 41' W). The first year, a two factor experiment using foliar Ca applications (CaCl 2; 0.8%) three times during fruit development 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 (0% Control, 0.2%; 0.4%; 0.8%; and 1.6 % CaCl 2 ). Fruit quality, rheological properties, cracking incidence (CI) and yield were evaluated. The first year, CaCl 2 applied at Stage I improved firmness (p < 0.01) and the modulus of elasticity (p < 0.0001), while interactions between the application time and crop load were observed for soluble solid content (p = 0.002) and CI (p = 0.044). The second year, the highest value for fruit´s firmness (p < 0.0001) was observed with CaCl 2 concentrations ranging from 0.4 to 1.6%, and the highest modulus of elasticity (p = 0.0003) for 1.6% CaCl 2 , while no differences were observed for SSC (p = 0,9) and CI (p = 0.135). According to our results, we recommend foliar CaCl 2 in early stages of fruit development and crop load reductions, to increase fruit quality in the highly productive combination 'Lapins'/'Colt' trained as KGB.