The delicate fruits of highbush blueberry are exposed to factors causing mechanical damage and yield losses during cultivation, harvesting, and postharvest handling. Foliar stimulation with silicon-based formulations may improve fruit firmness and postharvest quality, thereby increasing the market value of the produce. This study evaluated the effect of foliar silicon fertilisation on highbush blueberry fruit quality in terms of changes in mechanical properties, taking into account the applied spraying technique. The experiments were conducted using standard flat-fan and air-induction nozzles at different spraying speeds and varying spray liquid pressures. Treatment quality was assessed based on the degree of spray deposition, determined through analysis of silicon content in leaves and fruits. Instrumental compression and fruit detachment tests were performed to determine safe ranges of pressures and forces from the perspective of harvest quality. The results showed that the loads exerted by the picker’s hand during manual harvesting of the cultivar ‘Patriot’ remain within safe limits but are close to the critical threshold of fruit mechanical resistance (2 N). The greatest increases in destructive force and fruit firmness were obtained with the use of standard XR nozzles, reaching 3.19–3.34 N (up to 19%) and 2.03–2.21 N (up to 10%), respectively, compared with the control treatment. These findings provide practical guidance for optimising foliar silicon applications and spray parameters in highbush blueberry cultivation to improve fruit mechanical resistance and reduce the risk of harvest and postharvest damage.
Cieniawska et al. (Sat,) studied this question.