Mechanical harvesters or mechanical aid equipment could be used on this fruiting wall of Bing cherries on Gisela 12 rootstock.

Mechanical harvesters or mechanical aid equipment could be used on this fruiting wall of Bing cherries on Gisela 12 rootstock.

Dr. Matt Whiting is using a new approach as he works to develop cherry orchard systems that can incorporate mechanization.

He has enlisted eight to ten growers in Washington State to cooperate in his orchard systems research, which is part of a comprehensive three-year project budgeted at around $140,000 a year. Funding comes from the Washington Tree Fruit Research Commission, Oregon Sweet Cherry Commission, and Washington State University’s IMPACT Center. Two other components—efficient orchard systems and crop load management—were separate ongoing research projects but now are wrapped into one. Some of the cooperating growers are converting new acreage to modern orchard designs, while a few have already planted limited acreage of cherries on vertical or angled fruiting walls.

"It’s going to be a good industry partnership," he said. "We’ve abandoned the old research model of having all trials at WSU plots and are now partnering with industry."

With experimental orchards located throughout the state, Whiting said that the research would be more powerful because it will include different varieties, soils, rootstocks, and climates. "We’ll be able to assess all of those things at the same time," he said, noting that research can move faster than when trials are only in one or two locations.

Although configuration, establishment, and maintenance of each orchard will differ, the orchards share a common vision of tree architecture that includes fruiting walls, which allow excellent adaptable to mechanical-assist operations.

Whiting will schedule field days in the grower blocks after harvest and during the dormant season to give orchardists an opportunity to learn the practical issues of tree training—what worked and what didn’t—from the grower cooperators.

In addition to conducting the grower trials, Whiting will continue collecting data from two established test orchards at the WSU-Roza experimental farm.

He will further evaluate the sweet cherry mechanical harvester for efficiency and its effects on fruit quality throughout storage. The harvester, developed by the U.S. Department of Agriculture and funded by the Research Commission, will pick entire rows of fruit at the Roza cherry block with comparisons made of hand harvesting in the same block.

Crop load

Whiting will also develop strategies for consistent and balanced cropping in the new orchard systems to optimize precocity, fruit set/pollination, yield, and quality. Experiments are designed to better understand genetic and environmental factors that limit consistent fruit set or promote higher fruit set. These studies will look at pollen germination, pollen tube growth, ovule viability, and stigma receptivity, he said, with a goal of developing more precise recommendations of pollenizers.

The research is complementary to fruit set work done by Dr. Anita Azarenko at Oregon State University involving the genetics that relate to pollen compatibility, he added.

"We know that the new orchard system will be difficult to manage with pruning loppers," Whiting said.

The new system is based on a fruiting wall that has a uniform number of upright fruiting wood, repeated from tree to tree. "With the new system, we’re not making heading cuts as we did in the past. The pruning approach to crop load management is well documented for Gisela rootstocks, but pruning is not part of the vision for orchard systems of the future."

He believes that the biggest challenge in the more efficient orchard systems will be crop load management.

Whiting is continuing previous cherry thinning trials, but he’s now looking at crop load management for the full 15 months of fruit development, and not just in the current cropping season. (See the March 15, 2007 issue of Good Fruit Grower for his most recent thinning report.)

He is studying the role that different rates, timing, and isomers of gibberellic acid have on fruit bud initiation, as well as postbloom thinning. "How late can you go in and thin and still get a benefit?" he asked. "Is a month before harvest a waste of time or not?"

Whiting may find that different thinning strategies and different timing are needed to improve crop load yields and consistencies.