ADOPTION AND IMPLEMENTATION OF INTENSIVE PLANTING SYSTEMS FOR APPLE - THE NEW ZEALAND EXPERIENCE

Intensive planting systems on semi-dwarf and dwarf rootstocks (1250-3000 trees/ha) are the preferred production systems for new apple orchards in New Zealand (NZ) today. Despite this, the shift from conventional central leader planting systems (650-900 trees/ha) to intensive planting systems for apple has occurred relatively slowly during the past twenty years. The earliest commercial plantings of intensive systems began in the 1980s and coincided with important improvements in central leader tree management based on adapting and improving Vertical Axe management for the NZ intermediate vigour planting systems on MM.106 and M.793 rootstocks. The improved tree management encouraged increases in planting densities up to 1250 trees/ha on MM.106, but with problems of excessive vigour in the later years. The same tree management style was applied in intensive planting systems on M.26 and M.9 rootstocks and remains essentially the same today. The advent of virus-free Mark rootstock stimulated a initial brief flurry of interest in intensive systems before a more sustained interest in systems on virus free M.9 from the late 1990s. Typically, NZ intensive planting systems are tall (3.5+ m) slim discontinuous hedgerows of trees with many well-spaced weak side branches off the un-headed central leader – generally similar to the South-Tyrol tall spindle tree. During the 1990s, increasing international supply of bi-colour cultivars, declining prices, customer demands for higher quality fruit and new cultivar opportunities stimulated strong interest and increasing adoption of dwarf tree intensive production systems. Fruit growers recognised that crops of greater consistency and overall higher fruit quality are produced on dwarf trees. These attributes for quality needed to be combined with more efficient production methods - ensuring the rapid onset of cropping from the second year from planting and a very high proportion of the crop consistently achieving export quality standard. This interest in intensive systems has accelerated with the recent plantings of Jazz™, where growers are keen to achieve rapid production with a high paying cultivar. Presently we estimate that 15% of the NZ apple industry is planted in intensive systems, with M.9, in all its forms, the most preferred rootstock. Present impediments to more widespread adoption include a continuing constraint in supply of dwarf and semi-dwarf rootstocks, inconsistent nursery tree quality and a scarcity of development capital for many growers after successive years of low market returns. An issue for the long term sustainability of intensive apple planting systems in NZ is to develop new dwarf and semi-dwarf rootstocks with the qualities of M.9 combined with resistance to woolly apple aphid (Eriosoma lanigerum), fire blight (Erwinia amylovora) and well-adapted for replanting intensive systems into old orchard land.