Competitive pear system
Chuck Peters hopes to harvest 60 bins of pears per acre by emulating Two-dimensional apple growing systems.
Chuck Peters' experimental pear planting includes both upright and angled trellises
Chuck Peters hopes an experimental planting at his pear orchard in Yakima, Washington, will help define the most competitive systems for growing pears in the future.
Peters removed a four-acre block of 50-year-old d'Anjou pears that was no longer competitive and replanted last spring with high-density Bartlett pears—some upright and some on an angled trellis. The trees are on Old Home by Farmingdale 69, a rootstock that has proven successful in high-density pear systems in California.
Peters said the tree fruit industry has invested heavily in developing competitive orchard systems for apples, but little had been done to develop pear-growing systems that might be adaptable to mechanization in the future.
During a recent tour of the planting organized by Washington State University Cooperative Extension, Peters explained how he developed his experimental block, which has a total of 5,500 trees. Rows are spaced ten feet apart, and trees are spaced two, four, and six feet apart. Trees on the angled trellis are planted in double rows with trees leaning 11 degrees from vertical, forming a 22-degree angle between the V. The relatively upright angle is designed to minimize sucker growth and put the energy into growing the tree. Sleeping-eye Bosc trees on OHxF.69 have been planted as pollinizers.
Peters hopes that one of the finding's from the experiment will be where the point of diminishing returns is in terms of the number of trees per acre.
The trees will be two-dimensional and emulate the systems that Auvil Fruit Company of Vantage, Washington, and Allan Brothers of Naches, Washington, have been using for apples, Peters said.
The Bartlett trees had about ten strong feathers when they were delivered by the nursery. As they were not adaptable to his system, the branches were removed before planting. The trees were also headed at five feet.
The lowest of the seven trellis wires is relatively high, at about 36 inches, to avoid pickers having to bend down to pick fruit off the lowest branches. Peters figures it's easier for workers to go a foot higher up the ladder to pick fruit than to get down on their hands and knees.
During the growing season, the new lateral shoots were fastened down to the wire below at a sharp angle, rather than being tied up to a wire, to avoid suckering on the bend.
Peters was asked how he plans to control tree growth without a dwarfing rootstock. Since the growth regulator Apogee is not used on pears, he's hoping that early fruiting will be sufficient to slow down tree growth. When the leader grows to about three or four inches above a wire, the growing tip is broken out to force lateral branching. One employee spent about four hours a day in the block, five or six days a week, doing tree training during the growing season.
Peters is letting spurs grow on the leader between the wires because he calculates that it will take 110 fruiting sites per tree to produce a crop of 60 bins per acre of size 90 pears, and he thinks it would be difficult to accomplish that with just the wood on the wires. A 60-bin crop would be double the average yield of pear orchards in Washington.
Peters is using a weed mat for weed control, but a problem he encountered soon after the trees were planted was that the irrigation water ran off the weed mat rather than through it, so the trees didn't receive adequate water at first. He had to use soap and water a couple of times to break the surface tension of the mat.
The irrigation emitters are spaced 22 inches apart, which Peters now thinks is too far apart for a high-density planting. If he were starting over, he'd use a 14-inch spacing, he said. He irrigates for four hours on alternate days, with an extra cycle per week during particularly hot weather. The trees are fertigated with 15 pounds of nitrogen per acre per week.
Peters said he was hoping to pick some fruit in the second year, but because he had to remove the branches at planting and the irrigation problem set the trees back somewhat, cropping will be delayed. He hopes the trees will grow up to the top wire (13 feet high) during the second season, but doesn't expect them to crop until the third year.
Pear growers pay an assessment of $1 per ton for research, and most of the pear research projects focus on pest control or postharvest physiology, Peters said. The pear industry also contributes towards research on automation and mechanization for tree fruits, yet lacks the plant materials to ever benefit from those expenditures, he added. He'd like to see the assessment rate increased to fund more research that would help make the pear industry more competitive.
"Maybe we just don't have the plant materials for this industry to survive down the road," he said. "If we don't change to improve our efficiencies, we can't survive. When you look around, all we've got is old pear orchards and primarily because there haven't been any plant materials that are better."
Peters noted that WSU has put together a top-notch research team in genetics, genomics, and tree fruit breeding, and he hopes they will be able to work on dwarfing rootstocks for pears that would be comparable to Malling 9 in size and precocity.
"We're going to have to step up to the plate and take a look at that if we're going to move this industry forward," he said.