The tall spindle is the optimum orchard system for eastern U.S. growers, says a Cornell University horticulturist.
Growers around the world are working to increase apple orchard system efficiencies to improve profitability. While there are several ways to improve orchard efficiency, increasing yields may be the most practical tool. Research shows that the tall spindle system can produce high yields of quality fruit for eastern U.S. orchardists.
Several factors are driving the need to improve orchard efficiency, said Dr. Terence Robinson, Cornell University horticulturist. Around the world, orchard costs (labor, fuel, inputs), fruit quality requirements, and establishment costs are all increasing, he said during the Great Lakes Expo in Grand Rapids, Michigan. But even more important, competing regions are producing high quality fruit with high yields. "It has become critical that growers in the eastern United States become aggressive in improving orchard efficiency," he said.
Robinson suggested strategies for growers to use to drive down the cost per box of fruit:
- Increase early yields and mature yields to reduce per box costs by planting at high densities with good light interception
- Improve the price received for fruit by growing new premium varieties
- Improve fruit quality by growing thin, narrow canopies to improve light distribution
- Lower orchard costs by reducing establishment costs and/or labor costs
Robinson believes that growers looking to improve their orchard efficiency will do better if they improve yields, change to high price varieties, and improve fruit quality, rather than try to cut costs. "Lowering costs is not a way to try to stay in business," he said. Controlling costs is an important way to stay in business, but it is not the way to salvation because it's not possible to maximize profitability doing that, he said.
For years, researchers have recommended that orchardists replant 3 to 5 percent of their acreage each year, which allows them to capitalize on new varieties and orchard systems. A new orchard is a long-term commitment, and growers must be forward thinking when they replant, Robinson said. "It becomes critical that you make the right decisions the day you plant the orchard, because you're going to be married to that orchard for 20 years."
By replanting old, large-canopy tree systems and updating blocks with new, high-premium varieties and modern training systems, growers in five years will be in the best position to take advantage of future advances in terms of mechanization, he said.
After reviewing years of data about orchard systems for growers, Robinson, along with New York Extension educators Steve Hoying and Allison DeMaree, developed basic principles to guide eastern U.S. orchardists in their replanting efforts.
Tree density—Density is one of the most important factors in improving orchard efficiency. Studies have shown that for New York and the northeast apple regions, the economic optimum density is between 900 to 1,300 trees per acre. This means an in-row spacing of three to four feet between trees with rows 11 to 12 feet apart. The vigor of the variety planted must be considered when spacing the trees. Planting vigorous varieties too tightly will require more pruning than if the in-row spacing is increased from four to five feet. Increasing the tree density doesn't necessarily increase yields beyond a certain point, Robinson said. He has found the optimum density to be 1,000 trees per acre.
Early yields—Producing fruit as early as possible is critical to orchard efficiency. "Producing fruit in the third year is no longer good enough," Robinson said, adding that the way to reduce costs is to plant 5/8-inch caliper trees with ten or more feathers with wide crotch angles that are about six feet tall and require little pruning at planting. A New York Gala trial produced 37 fruits per tree in the second leaf, equivalent to 300 bushels per acre. Second-leaf production can potentially reach 85 fruits per tree—1,100 bushels per acre—depending on rootstock and variety, he added.
Rootstocks—Precocious, dwarfing rootstocks are key to making high-density plantings work. Several are available, with some of the newer Cornell-Geneva rootstocks showing resistance to fireblight, crown rot, replanting disease, and wooly apple aphid. Robinson has high hopes that CG.41 will be suited to the tall spindle system.
Light interception and distribution—Because trees need to intercept 75 percent of the light to produce high yields and high quality fruit, Robinson recommends the tall spindle system for eastern growers. Pedestrian systems do not intercept enough light.
A narrow canopy improves the ability to produce high quality fruit. Robinson described the optimal tree shape for the eastern United States as the tall spindle—having a tall leader ten feet tall with about 15 branches spaced up and down. Each branch is columnar to optimize light exposure and avoid shading, he said. Large limbs in the upper canopy should be removed to make sure the upper part of the tree is composed of only small-diameter branches.
Labor efficiency—The tall spindle system lends itself to partial mechanization of pruning. Platforms can be used for dormant pruning. The tall spindle is also adaptable to side wall hedgers or shearers that can be used for summer pruning. More importantly, tall spindle trees can be pruned by a "simplified pruning recipe" that can be easily explained to and followed by workers, thus reducing pruning costs. In the future, if robotic machines become available, they also will work on the tall spindle.
The tall spindle has fruiting branches that remain for three to six years, but no permanent scaffolds, Robinson explained. Tree height is maintained by cutting the leader to a fruitful side branch, keeping the height to 90 percent of the alley width. By removing large-diameter branches, there is little export of carbohydrates to the trunks and roots, and the tree height can be maintained. "Large limbs create large trees," he said, noting that high-density systems require removal of large branches.
"I'm totally convinced that the best way to go for eastern growers is the tall spindle system that has high densities, can take advantage of simplification of pruning system and adaptability to partial mechanization and improved labor efficiency," he said. "Yields under this system, if done right, are higher than the yields we're used to. It's more challenging in a vigorous location in the South, but it can be done."