Bi-axis: an alternative to slender spindle for apple orchards

The use of the dwarfing M.9 rootstock is widespread in apple orchards due to the high tree efficiency it induces. Today it is possible to purchase a given type of tree congruent with the desired orchard design. Alongside the traditional chipbudded trees produced in a two-year cycle, there are types like two-year knip plants, trees obtained with the June bud (1-year-old) and bench-budded plants in a oneyear cycle. These different types of plants are suitable for the spindle training system. The innovative ‘bi-axis’ system requires a pre-formed, split-branch tree produced in the nursery that obviates the need for heading in the orchard and the one-year delay in shoot-system formation. The spindle system is widely employed in apple orchards to boost planting densities up to 4,000 trees per hectare. The bi-axis system utilizes the novel idea of training plants with 2 axes so as to divide the vigour over more branches. Two sets of trials are underway with ‘Fuji’ in different environments, i.e. an upland orchard in Trento Province and a lowland one in the Po valley, to compare the vegetative and cropping traits of bi-axes against the traditional spindle in high density plantings. The comparison of the two systems has so far shown some differences in tree growth patterns and yield. Vigour is distributed over two axes in the Y- tree shape which helps control tree-growth. Shoot length is almost halved in the bi-axis system compared to the spindle. No significant differences in yield and crop quality were found in the first 2-3 years, but the bi-axis trees seem to produce better fruit red overcolour than spindle after fourfive years