Improving Tart Cherry Sustainability

Improving Tart Cherry Sustainability

Summary

During the reporting period (2016), assessment of rootstocks and in-row tree spacing was carried out through measurement of yield for each rootstock, spacing and training treatment in three existing orchards. A prototype mechanical over-the-row harvester was used to harvest fruit in high density tart cherry systems, and some changes were made to the harvester to improve effectiveness. Graduate student Sheriden Hansen has now been working on the project since June 2015. During 2016, her efforts focused on: (1) a second year of evaluating renewal pruning techniques in high density orchards to facilitate over-the-row harvesting, (2) evaluating the effectiveness of mechanical summer pruning in high density orchards, and (3) quantifying the relationship between light micro-environment and fruit quality in both conventional and high density orchards. We also carried out experiments to evaluate the effects of training system on spray droplet distribution within the canopy as well as total light interception. Samples and data collected in 2016 are currently being analyzed.

Objectives/Performance Targets

 Project Objectives:

1) Determine the optimum combination of rootstock, row spacing and tree training.

2) Compare the distribution uniformity of crop protectant applications.

3) Determine the response of ‘Montmorency’ tart cherry to mechanical summer pruning.

4) Determine the relationship between light micro-environment and fruit quality in tart cherry.

5) Develop enterprise budgets for both conventional and high density systems.

6) Provide high-density cherry management experience to several early adopters.

Accomplishments/Milestones

Objective 1. Rootstock, row spacing, and tree training was evaluated in two experimental orchards at the Kaysville research farm.  Treatments were harvested on 18-19 July, 2016 with a prototype over-the-row harvester.  Additional problems were experienced with the harvester when the aluminum shaker head that was rebuilt in 2015 again fractured.  Replacement steel heads that were ordered in 2015 were installed and no further problems arose.  The more rigid steel heads seem to provide a more effective harvest than the original aluminum parts.  After completion of the harvest at Kaysville, the harvester was transported to a grower cooperator orchard in Santaquin, Utah.  A one-acre test planting established in 2013 was mechanically harvested for the first time on 26 July, 2016.  With harvest, yield measurements were taken for each treatment type and have been evaluated for productivity.  Growers from the Utah County area were invited to observe the Santaquin harvest, and approximately 30 growers came to observe the machine.      

Findings: Yields in most treatments continue to increase each year.  Yield for several of the single-leader treatments appear to have plateaued.  This may indicate full yield potential has been reached, or it may be the result of some aggressive pruning in the winter of 2015-2016 to remove large branches that were beginning to interfere with shaker function.  The 2017 harvest should indicate if the yields have plateaued, or if yield increases lagged due to more aggressive pruning.  For single leader training, the Gisela®5 and Gisela®3 rootstocks in the 4’ and 6’ spacings continue to have high productivity.  Productivity in the ‘Mahaleb’ rootstocks continues to lag, and these treatments also require more heavy pruning to maintain machine access.

Plans:  During the next funding year, all three existing plantings will be mechanically harvested and three additional plantings will be established with new rootstocks released by Michigan State University.  Work will continue to further refine each of these systems and to gather information on inputs and productivity.

Objective 2.  On 30 September, 2016, water sensitive paper targets were placed within the canopy of tart cherry trees trained to multiple training systems.  Targets were placed at 4’, 6’, and 8’ heights between trees and at the center of each tree.  The trees were then sprayed with water using a commercial air-blast sprayer delivering 50 gallons per acre to simulate distribution patterns of crop protectants. The targets were collected and scanned in Fall 2016. 

Findings:  Preliminary analysis indicate that spray droplet penetration appears closely correlated with visual observations of relative canopy density, which is obviously affected by tree spacing, training system and pruning. Close-spaced single leader trees had relatively dense canopies with reduced spray penetration compared to greater row spacing.  Hedging did increase spray penetration through the canopy compared to the unhedged controls. 

Plans:  These results will be compared to light distribution measurements also taken in 2016.  We may also repeat the experiment with a limited subset of training systems to confirm 2016 results.

Objective 3. Response of ‘Montmorency’ tart cherry to mechanical summer pruning was again assessed.  A Gillison Sickle Bar Hedger was provided by grower-cooperator David McMullin of Payson, Utah.  Replicated research plots included:  delayed dormant hedging, a mid-season hedging, alternate side hedging, and an unhedged control. These treatments were initiated in Spring 2015 and again hedged in 2016, with plots harvested for yield using the prototype mechanical harvester in both years.  A small planting in Santaquin was also subjected to hedging using a hand held trimmer and vertical guides.  These plots were hand harvested.  Data for these are currently being analyzed.

Also under objective 3, a study was carried out to evaluate the response of ‘Montmorency’ tart cherry to different renewal pruning cuts.  Branches that needed to be removed from the 2010 planting were marked, classified by diameter, and then cut to one of several pre-determined lengths.  These marked branches were then monitored through the season to determine number and length of new shoots.  This experiment was carried out in both 2015 and 2016.

Results: Preliminary analysis of the data indicate that rootstock and branch diameter do influence regrowth, but that branches 10 cm or longer tend to provide adequate renewal growth.

Objective 4.  Sampling was again carried out to determine the relationship between light micro-environment and fruit quality in commercial orchards.  Samples were collected in five commercial orchards in Utah County.  Fruit samples were collected at weekly intervals from 24 June to 15 July.   Fruit was assessed for whole fruit fresh weight, pit fresh weight, fruit sugar content, LCH surface color, as well as whole fruit dry weight and pit dry weight. Data for 2016 are currently being analyzed. 

Based on variability observed in the 2015 data, it was decided that examining this relationship on a larger scale might be warranted.  During the summer of 2016, a mapping ceptometer was custom built to map light distribution on an orchard scale.  A small scale boom sprayer was repurposed, with light meters placed along the boom, and a GPS receiver and data logger set to measure light interception as the device was towed through the orchard.  (Funding for this apparatus came from a companion grant received from the Utah Department of Agriculture and Food.)  Several test runs were carried out on 28 September 2016 to map light distribution in the two high-density tart cherry orchards at Kaysville, along with a conventional orchard.  These data are currently being analyzed. 

Objective 5.  During 2016, Michigan State University conducted focus groups and analysis to develop updated cost-of-production budgets for the Michigan tart cherry industry.  Since Michigan is the only other state with significant tart cherry acreage, crop budgets for this crop have not been developed for any other state.  MSU economists agreed to cooperate with us and recently shared both their results and survey methodology, which we will adapt and use to develop Utah-specific budgets in 2017.

Objective 6. To date, two test plantings have been established on commercial farms to give growers experience with this management system.  One is a small scale test plot established in 2010, and the other is a larger scale planting for mechanical harvest established in 2013.  Plans to establish additional commercial test plantings have been delayed due to problems with nursery propagation.  Trees have now been propagated for several larger scale plots that will be planted in 2017.  One of these orchards will be at the Kaysville research farm, with three additional orchards established on commercial farms in Utah and Juab counties.

Findings: Growers that have observed the plantings were impressed with the fruit density and the harvester efficiency.  The cooperating grower pointed out the challenge of managing fruit closer to the ground than in conventional orchards, with a high incidence of powdery mildew in the lower portions of the high density trees. However, he thinks that some adjustments to his equipment and management strategies will alleviate this issue in future years.

Impacts and Contributions/Outcomes

A research progress report was presented at the 2016 Utah State Horticulture Association meetings on January 22, 2016.  Approximately 60 commercial growers were in attendance, representing more than 80% of the commercial tart cherry acreage in Utah. 

The Kaysville research plantings were also featured on the fruit tour of the Kaysville Fruit and Vegetable Field Day held on June 28, 2016.  This tour had over 70 participants representing commercial growers, consultants and Extension professionals.

As mentioned above, the mechanical harvest of the Santaquin grower-cooperator planting turned into an informal field day, with approximately 30 growers from throughout the region coming to observe the harvest and make comments on orchard management.

The 2017 USHA Winter Farm Tour (18 January) will also feature the grower planting in Santaquin.  This tour typically has 50 to 75 growers in attendance.

Collaborators: