Early Performance of Multi-leader Apple Training Systems in Korea

'Fuji'/M9 2-axis apple nursery trees were planted at 3.0 × 1.2 m for 2-leaders, at 2.8 × 1.6 m for 4-leaders and at 2.8 × 2.4 m for 6-leaders systems, and the growth, productivity and quality characteristics of these different leader systems were compared with those of a tall slender spindle planted at 3.0 × 1.0 m. Compared to the tall slender spindle, as the number of leaders per tree increased, the tree height decreased and the leader cross-sectional area decreased markedly. Shoot growth per tree for the tall slender spindle and the 2-leaders were high in the first and second year, but in the third and fourth year, shoots growth of the 4-leaders and the 6-leaders increased rapidly. Nevertheless, for the 6-leaders, growth was slower than that of the 4-leaders, with the canopy volume also significantly lower than that of the 4-leaders. In the fourth year, light interception was 35.7–36.3% in the tall slender spindle, the 2-leaders, and the 4-leaders, but only 24.4% in the 6-leaders. The cumulative yield per tree up to the fourth year increased with the number of leaders, except for the 6-leaders with slow canopy development. The cumulative yield per tree for the 2-leaders was 32.1 kg and that for the 4-leaders was 41.7 kg, 16% and 51% more than the outcome of 27.6 kg for the tall slender spindle, respectively. However, when converted into yield per ha, the tall slender spindle showed a value of 91.7 tons, the 2-leaders showed 89.2 tons, and the 4-leaders showed 93.1 tons, whereas that for the 6-leaders was only 40.8 tons. The quality of the fruit according to the number of leaders was not clear on average, but from the third year, the red coloration of the tall slender spindle tended to be somewhat lower than these outcomes from of the multi-leader systems, as the canopy of the tall slender spindle had developed significantly.