Effect of in-row spacing on individual tree growth, yield and orchard productivity on different rootstocks

In a rootstock trial the individual tree growth was significantly influenced by tree spacing between the range of 741-1111 tree/ ha on the following rootstocks: M.2, MA, M.7 and MM.111. The trees on these rootstocks responded to the wider spacing with increased growth up to a maximum point. No significant effect of spacing was found on the rootstocks M.26 and MM.106. However, although the wider space increased the individual growth, the calculated bearing surface of the orchard (TCSA cm(2)/ha, canopy volume m(3)/ha) responded differently. The bearing surface per unit area on M.26 and MM.106 showed a significantly decreasing trend due to the decreasing tree number. A slight tendency to decrease was also found on M.7, MM.111, MA and MM.104 because of the compensating effect of increased individual growth. On M.2 there was a maximum point found at 926 tree/ha density. Highest cumulative yield efficiency (CYE) of individual trees (kg/cm(2) TCSA) was found on MM.106 followed by M.2, M.26 and MA. Yield efficiency was not influenced by the spacing on M.26, MM.106, MA and MM.104, while the efficiency significantly decreased on M.7 at 741 tree/ha. On M.2 the 794 tree/ha spacing produced significantly higher CYE, while at 1111 tree/ha density the trees responded with significantly lower CYE. Strong correlation was found between the bearing surface, calculated as canopy volume m(3)/area unit and the yield/ha. The cumulative yield per hectare on semi dwarf M.26, MM.106 and M.7 showed an increasing trend within the tested range of spacings, while the vigorous group reached the maximum point. Thus the highest cumulative yield per area was produced by 'Idared' apple on MA at 926 tree/ha, followed by M.26 at 1587 trees/ha, MM.106 at 1389 trees/ha and M.2 at 794 trees /ha without significant differences within the group. The performance of yield efficiency calculated on a TCSA basis, which is widely used for comparison of rootstock productivity, means that a correct comparison can be made only at optimum spacing for each rootstock and site. This is especially important for the comparison of rootstocks from different vigour groups.