Wednesday, July 4, 2012

Training Systems of Apple Trees in Intensive Orchards

The number of apple trees per acre in new orchards has gradually been increasing. Orchard intensification is motivated by the desire to produce fruit early in the life of the orchard to rapidly recover establishment costs. Intensification is possible by using dwarfing rootstocks that control tree size, induce early cropping, and produce large quantities of fruit relative to the amount of wood produced.

Apple trees grown on dwarfing rootstocks have shallow or brittle roots systems and trees grew poorly and often leaned or fell over. Therefore these plants require support systems. However, Intensive orchard systems are more profitable than traditional low-density orchards on semi-dwarfing rootstocks. However, because the establishment costs for intensive orchards are high, trees must be trained and pruned properly to induce and maintain high yields.

Motivation for orchard intensification.

The primary reasons for orchard intensification include:
1.) early fruit production, and
2.) reduced pruning and harvest costs of mature orchards.

Yield is positively related to the amount of sunlight intercepted per acre. Profit, which is influenced by yield as well as fruit size and quality, is probably at an optimum when an orchard intercepts about 70% of the available light. Traditional orchards, using vigorous rootstocks, were typically planted at a spacing of about 22 feet x 16 feet with 132 trees per acre. For the first five or six years after planting, fruiting was discouraged to promote vegetative growth so trees would fill their space as rapidly as possible. The first crop was usually harvested four or five years after planting, but high yields were not obtained until trees finally occupied their allotted space. Maximum yields did not occur until about 12 to 14 years after planting.

Intensive orchards are typically planted at narrow spacing depending upon the training system adopted but one thing is very clear that a small crop is often harvested the year after planting, because trees have so little space to fill, peak production is usually achieved during the 6th or 7th year after planting. Once trees fill their allotted space, maximum yields are similar for all types of orchard systems. Because the primary advantage of intensive orchards is early fruit production, these orchards should be planted only on excellent sites with a low probability of crop loss due to frost or hail.

Intensive orchard training systems.

The three basic types of training systems used for intensive orchards are
1. "Trellis,"
2."Slender Spindle," and
3."Vertical axis or French Axis."

There are many modifications of each system, and orchardists will need to adapt a system to suit their own particular situation. The basic systems will be discussed in coming posts