Long-term evaluation of super-dwarf rootstock: impact on tree growth, productivity and apple fruit quality

Impact of planting distances on apple tree growth, yield parameters and internal fruit quality was evaluated in a 14- to 17-year-old orchard planted on super-dwarf P.22 rootstock. Trial was performed at the Institute of Horticulture Lithuanian Research Centre for Agriculture and Forestry in 2014-2017. 'Auksis' apple trees were planted at the distances 3×1, 3×0.75, 3×0.50, and 3×0.25 m. The strongest growth, the highest number and total length of shoots, the highest amount of flower clusters and yield tree^‑1 was recorded at planting distances 3×1 and 3×0.75. The growth and yield tree^‑1 of very densely planted apples (3×0.25) was significantly lower, in spite of these trees being the most productive and giving the highest yield area^‑1. The average fruit weight, diameter and colour were the best at planting distances 3×1 and 3×0.75. Fruit quality parameters significantly decreased in the super dense orchard. Long-term evaluation of apple trees on super-dwarf P.22 rootstock revealed that planting distance 3×0.75 guarantee annual yields of high quality fruits even in a 14- to 17-year-old intensive orchard. In the case of orchard replacement after 10-12 years the optimal planting distance of apple trees on P.22 rootstock is 3×0.5 in order to get the highest yield in the young age.