Crown shape as a factor in optimizing light penetration in intensive sweet cherry orchards

Abstract

This article presents the results of research on light levels in intensive sweet cherry orchards of the cultivars Summit, Grey Star, and Lapins, trained according to the Steep Leader, Upright Fruiting Offshoots (UFO), and Kym Green Bush (KGB) crown shapes. It was established that the light level in the lower part of the sweet cherry tree canopy largely depended on crown shape, the effect of which accounted for 96–98% of the total variation. The highest light levels throughout the study period were recorded in trees trained according to the UFO system. Average illuminance ranged from 78.50 to 84.14 thousand lux, depending on the cultivar. Trees trained according to the KGB system exhibited lower light levels, averaging 7.29–17.43 thousand lux during the years of the study. Significantly lower light levels in the lower canopy zone were observed in trees trained according to the Steep Leader system, where illuminance ranged from 3.12 to 4.28 thousand lux. Analysis of the influence of the studied factors on changes in this parameter in the middle part of the canopy revealed a pattern similar to that observed in the lower canopy zone. According to the correlation analysis, the greatest negative effect on light levels was associated with growth parameters, including tree height (r = −0.93 in 2025 and −0.17 in 2026), canopy volume (r = −0.69 and −0.71), and canopy projection area (r = −0.70). At the same time, improved canopy illumination was found to have a direct positive effect on yield (r = +0.37) and a strong positive effect on fruit weight (r = +0.78). The results demonstrated that crown shape is the key factor determining the light regime of intensive sweet cherry orchards. The UFO crown shape provided the highest level of light penetration throughout the years of the study, while annual fluctuations were minimal. The Steep Leader crown shape showed the poorest light conditions; in the fourth year of growth, light levels were reduced by half compared with the third year. The KGB crown shape provided a moderate illuminance level of approximately 22 thousand lux, which was significantly higher than that recorded for the Steep Leader crown shape.