Yield-density relations for apple trees on a dwarfing and a semi-dwarfing rootstock.

Abstract

In a planting system trial started in 1962 Golden Delicious trees in low-density plots at 1 100 trees/ha on M.9 and 660 trees/ha on M.2 came into bearing slowly and yields levelled off at about 40 tons/ha. In high-density plots at 3 300 and 2 260 trees/ha on M.9 and M.2, respectively, yields quickly increased to about 75 tons/ha in 1967 and 1968, but thereafter declined; this was associated with more intensive pruning and fruit thinning to restore tree vigour and fruit quality. Yield per unit of growth was initially higher but finally much lower in high-density plots, indicating that fruiting suffered more than growth from competition between trees. Yield per unit of growth was much higher on M.9 than on M.2, especially at high density. Fruit size was slightly better on M.9, and at high density the problems in maintaining fruit size were not as serious as on M.2. Growth control in the high-density M.2 plot became difficult and tree thinning may be advisable. Under the conditions of the trial the optimum density for Golden Delicious on M.9 is probably above 3 000 trees/ha and on M.2 below 2 000 trees/ha. (Abstract retrieved from CAB Abstracts by CABI’s permission)