Comparison of Light Utilization Efficiency in terms of the Planting Distance, Orientation, and Tree Height for a High-Density Apple Orchard

The Shadow patterns of various apple planting systems, and tree height are tracked using Sketch Up (Trimble, Inc. 3D Design software). A Model of a tall spindle established by combining planting distances applicable to Korea. The row orientation was set to four directions: N-S, NW-SE, NE-SW, and E-W. Each planting system simulated hours without sunlight-interference by the adjacent row and the sunlight-interference percentage in the canopy according to the adjacent tree during the growing season. The hours without sunlight-interference by adjacent rows on June 21 were N-S rows at 3.98 to 7.20 hours, NW-SE rows at 5.30 to 9.27 hours, NE-SW rows at 5.27 to 9.02 hours, and E-W rows at 10.38 to 11.78 hours. Sunlight-interference percentages in the morning and afternoon were as follows: N-S rows at 14.8% and 14.8%, NW-SE rows at 32.2% and 21.1%, NE-SW rows at 31.5% and 41.8%, and E-W rows at 53.6% and 50.4%, respectively. For the N-S rows, the overall growing season was favorable. E-W rows were unfavorable among row orientations due high interference level by adjacent trees. As the tree height increased from 2.5 to 5.0 m regardless of the row orientation, the hours without interference by adjacent trees decreased. However, an empirical test for light transmittance and radiation in the planting systems not considered in this study is additionally required.