2017 ASHS Annual Conference

While the adoption of high-density apple orchards during the last decades has resulted in a significant improvement in yield and fruit quality, there is great disparity of opinion on the optimum density or the optimum tree shape. A 2 hectare replicated field trial was planted in 1997 at the New York State Agricultural Experiment Station in Geneva, New York, with 4 apple varieties (‘Empire’, ‘Fuji’, ‘Gala’, and ‘McIntosh’), where we compared 8 tree planting densities (598, 840, 1026, 1283, 1655, 2243, 3262, and 5382 trees/ha), and two tree shapes (conic and V). At the lowest 2 densities, trees were planted on M.7 rootstock (598 trees/ha) and M.26 rootstock (840 trees/ha). At all of the higher tree densities, trees were planted on M.9. There was a strong negative correlation on tree planting density and trunk cross sectional area for all the varieties and training systems, with the exception of ‘McIntosh’ on a V tree shape where no clear differences for 598-1655 trees/ha were observed. With ‘Fuji’ and ‘Gala’, and for both tree shapes, the highest yields were strongly positively correlated with tree planting density. With ‘Empire’ and conic tree shapes, highest yields were observed when planting 3262-5382 trees/ha. On the other hand, highest yields were more correlated to 1283 and 1655 trees/ha than to 3262-53282 trees/ha when using V tree shapes. With ‘McIntosh’, highest yields were also observed with highest densities when using conic tree shapes, whereas there was no a clear correlation when using V tree shapes and this variety. Planting density had a strong positive effect on light interception over the years. There were no significant differences between tree shapes during the first 4 years, after that, more light was intercepted for the V tree shapes. Cumulated yield was a linear function of light energy intercepted by the canopy. Color distribution tended to be more affected by planting density than by tree shape on ‘Empire’. Planting density significantly affected firmness, soluble solids, fruit size and color distribution on ‘Fuji’ and ‘McIntosh’. On the other hand, neither fruit size nor soluble solids were affected by planting density with ‘Gala’.