Sep 18, 2015

Over-the-row harvester can work with high-density tart cherries

Michigan State University (MSU) researchers have been working on an evolving technology since 2008, which is leading to a new method of harvesting tart cherries planted in high-density systems.

Ron Perry, a professor of horticulture, recently hosted an MSU Extension demonstration using a twin-rower, rotating-tine harvester mechanism found to be efficient and effective in the removal of cherries.

“Growing tart cherries in high-density systems is something they have been doing in Poland and Serbia for some time with a great deal of success,” Perry told a growers’ meeting in Hart, Michigan, earlier this year. “(Studies have) concluded that economic return for tart cherries in traditional systems is very bleak.

“We have brought together a number of people with different disciplines and skills to address the questions involved in this approach. There are still many more questions, but at least we’ve started answering some of them.”

About 35 people attended a July demonstration at the Northwest Michigan Horticulture Research Center (NWMHRC).

“We spent most of the day harvesting the various treatments,” Perry said. “I am in the middle of summarizing the data, but it looks very similar to our work in southwest Michigan. We had only about a 60 percent crop at both sites on these fifth-leaf trees. We will have some quality data to provide growers from this year’s harvest. With only a 60-65 percent crop this year, we were able to harvest some 10,000 pounds per acre in the fifth growing season in both southwest and northwest Michigan. The commercial average for mature orchards in Michigan ranges between 8,000-10,000 pounds.”

The plot was established in 2011 with the support of Project GREEEN and the Michigan Cherry Producers. The planting has six varieties of tart cherries planted 5 x 13 feet.

“We are experimenting with treatments to maintain trees in a compact canopy to accommodate an over-the-row harvester used normally to harvest berry crops,” Perry said. “This work began in 2008 with the support of the Michigan Cherry Producers to determine the feasibility of this approach to growing and producing sour cherries. The traditional approach maintains trees at greater distances (15-20 feet apart) using trunk shakers and catch frame machinery.”

With the support of the Michigan Tree Fruit Commission, Michigan State Horticultural Society and the International Fruit Tree Association, Perry led the harvesting of the research plot using a Littau ORXL (2013 model) berry harvester. The researchers had tested the Littau Harvester at Oxley Farms near Lawton, Michigan, in July 2014.

“The machine removed fruit at a very high rate of efficiency with minimal canopy damage,” Perry said. “Since 2012, Oxley Farms has cooperated with us in a project to study horticultural approaches to restricting and maintaining a compact canopy, small enough to allow a berry harvester to successfully remove fruit.

“Oxley Farms allowed us to establish treatments in two rows amounting to over 300 trees. The company purchased a used Korvan 9000, twin-tower, rotating-tine harvester (Oxbo 9000) in 2012 with intent to harvest the planting. We successfully harvested fruit from the planting in 2013. The crop was severely reduced due to spring frosts in 2014.

“We were successful in developing a protocol for harvesting each group of trees with the machine within treatment parameters while retaining treatment integrity. We were successful in 2015 using the Littau Harvester and deployed these protocols with the harvesting at the NWHRC.”

Perry outlined the following challenges to using the harvesting approach.

Elevated sites are preferred. Similar to dwarf apples with shortened canopy heights, trees will need to be set on elevated site heights to avoid spring frost damage to a canopy and fruiting zone that ranges from 1-12 feet in height, compared to the standard tree, which ranges from 4-18 feet.

“Conversely and similar to dwarf/HD apples, the amount of flowers and fruit set is much greater than standard trees,” Perry said.

Keeping Montmorency canopies restricted to fit into current berry harvesting equipment like the Oxbo 9000 (4 x 8-foot tunnel) and Littau ORXL (55 inches x 8-foot tunnel).

“Our experience thus far indicates these harvesters can accommodate trees 11-12 feet in height by 10-11 feet wide,” he said.

Perry said Littau has developed a new prototype that is being manufactured to accommodate larger fruit crop plants, making tunnel dimensions 7 x 10.5 feet.

Transition costs were identified in going to the new system.

“The harvester price tag is similar or equivalent to traditional double-incline and wrap-around harvesters,” he said.

Advantages

What are the advantages of this approach?

Trees are smaller and shorter, Perry said. The drop distance to collection points is reduced from 10-18 feet in traditional trees to 1-10 feet, reducing fruit damage.

“All fruit harvested thus far in these rotary-tine harvesters are found in tanks to be clean, with little to no tearing and abrasions,” he said.

“You can harvest continuously at 1.5 mph down rows compared to shake and travel in a double-incline at 30-45 seconds per tree,” he said. “Users are able to devise a conveyor system to collect and deliver fruit directly into accompanying trailers/tanks; avoiding stop and start for resupply of tanks.

“Both harvests this year (southwest and northwest Michigan) were accomplished on trees where Ethephon had been applied late (southwest) or not applied (northwest),” he said. “Fruit retention force averaged 650-750 grams at both sites. Commercial recommendation is set at 150-300 grams. Fruit was removed at a rate equivalent to 99 percent or greater without damage, or very little damage (primarily small branches), to canopy.

The approach can allow harvesting in the third growing season – compared to trunk shaker systems, for which growers must wait until trunks are stout enough to take shaking, which is often the sixth growing season.

“We harvested nearly 22,000 pounds per acre (extrapolated), total, in the fourth and fifth growing seasons in our NWHRC plot in 2014 and 2015,” he said.

The system allows for avoidance of trunk shaker damage, which often shortens tree life.

“It can reduce harvest labor by one or two people, depending on the commercial setup,” he said. “It also can possibly widen product acceptance. Fruit may be able to go into dry flats and tanks and avoid cold-water collection that might affect juice and wine usefulness.”

Perry said acceptance of the concept has been gaining steam.

“Like anything, it will take time, just as it took transition from riding horses to using cars,” he said. “We already have three growers/early adopters with a total of 65 acres.

“It will depend some on industry interest, but since we already have early adopters it has been happening as we speak,” Perry said. “I would assume that by 2020 to 2025, you will see new acreage being established – but I don’t have a crystal ball.

“We started with high-density apples about 20 years ago, and now it is the dominant growing system,” Perry said. “There is the possibility that if the dwarfing rootstocks work as we anticipate, the process could be much quicker. The mechanism for harvesting twin-tower rotary-tine has proven, since we began this work, to be reliable, efficient with out fruit and tree damage.”

Perry stressed that it “will be the approaches to keeping canopies compact to accommodate the harvesters that will be the greatest challenge. So far, summer hedging and root pruning practices are impressive and doing the job. Ask again in year 15 if these are still viable practices.”

– Gary Pullano, assistant editor