Half-topping 'A4' macadamia trees has a markedly different effect on yield than full-topping

摘要

Mechanically hedging the tops of macadamia trees to control tree size is referred to as topping. Topping the entire upper canopy causes a substantial reduction in yield and is not a recommended industry practice. Here we compare topping just half the upper canopy with full-topping, and with control trees that were not pruned, to test whether half-topping is a more acceptable means of size control, with less of a yield penalty. We used macadamia cultivar 'A4' as the subject for the study. The trees were topped horizontally at anthesis. Full-topping reduced yields by 78% in the first year and 63% in the second year compared with the control trees. By the end of the second year the height of the fully-topped trees was approximately the same as that of the control trees. In contrast, topping just the western half of the upper canopy resulted in little yield penalty. Yields were reduced non-significantly by 14% in the first year, and negligibly in the second year, compared with the control trees; and by the end of the second year, the regrowth on the topped halves of the trees was only two-thirds the height of that on the full-topped trees. The results are encouraging because topping is simple and cheap, and would be an attractive tree size control option for growers at the yield penalty described here for the half-topped treatment.