Influence of nursery tree design on early infrastructure development in sweet cherry and apricot cultivars

Abstract

Our research is developing new orchard planting systems to increase canopy light interception, light distribution and harvest index, thus aiming to more than double productivity of sweet cherry and apricot compared to current orchard systems. Planting a nursery tree that has greater dry mass should advance canopy development and encourage precocity. Bi-axis trees of three sweet cherry cultivars, ‘Lapins’, ‘Sweetheart’ and ‘Staccato’, and three apricot selections from the Plant & Food Research apricot breeding programme, were propagated by budding or grafting and compared with mono-axis trees propagated concurrently. In cherry trees, after one season of growth in the nursery, the combined length of the two primary shoots of bi-axis was longer than the single shoot of mono-axis trees by 62-73%, depending on cultivar. Shoot dry weight per tree for the combined bi-axis shoots was 5-31% greater than the mono-axis shoots. Root system dry mass was 20-48% greater in bi-axis trees compared with mono-axis trees. With apricot, total primary shoot length of the bi-axis trees was 42-83% greater than for the mono-axis trees. However, dry weight of the total bi-axis primary shoots, not including sylleptic shoots, was only greater than the mono-axis primary shoot for one apricot selection, and root dry weight was only greater for two of the selections. The bi-axis cherry and apricot nursery trees were planted into orchard plots in spring 2014 and 2015, respectively, in a replicated trial at a spacing of 3 m between trees and either 1.5 or 2 m between rows. Each primary axis was flattened at a 10 to 20° angle down the row to form two ‘cordons’, from which up to 12 upright shoots per tree were allowed to develop. After one season of growth in the orchard, the number of uprights that had developed per tree were 2.9 for ‘Lapins, and 4.2 for ‘Sweetheart’ and 4.1 for ‘Staccato’. The number of uprights developed for apricots was 7.4 for ‘Nzsummer3’, 7.3 for G12/92, and 7.7 for ‘Nzsummer2’.