Millennium planting density trial of 'Bramley's Seedling' apple on M.9 and M.27 rootstocks from 2000 to 2016

As Irish apple growers transition to high density orchards, it becomes more important to establish the relationship between planting density and orchard profitability. These new orchards have a much higher capital charge at establishment but greater potential to support high early yields. In 2000, a range of different densities was planted on two rootstocks: M.9 at 672, 961 and 1492 trees ha^‑1 and M.27 at 1279, 1492 and 1957 trees ha^‑1. As trees matured, yield increased annually for the first eight years. Higher planting densities had repaid their establishment costs by the 7^th harvest whilst the lower densities took until the 9^th harvest. By the end of the 13^th harvest, M.9 planted at 1492 trees ha^‑1 density had the highest cumulative yield . The M.27 plantings did not perform as well as the M.9 but the highest M.27 density continues to close the gap on the M.9. In the last two years of the experiment, M2.7 plots provided the highest yields.