During both the 2016 and 2017 reporting periods, 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 modifications were made to the harvester to improve effectiveness. Graduate student Sheriden Hansen began working on the project in June 2015. Her efforts focused on: (1) 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. She also carried out experiments to evaluate the effects of training system on spray droplet distribution within the canopy as well as total light interception. During Fall 2017, Ms. Hansen analyzed the data for her renewal pruning and summer hedging studies, and wrote and successfully defended her M.S. thesis.
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.
Tart cherry production is based on a low-density system that does not come into production until 5 to 7 years after planting and only reaches full production in years 10 to 12. We hypothesize that a high density management system will allow for fruit production earlier in the life of the orchard, that the fruit will be higher quality, and that the orchard will be more conducive to pest and disease management.
The 2010 orchard is an incomplete factorial of 4 rootstocks, 4 in-row tree spacings (4, 6, 8 and 10 foot) and three tree training systems. Each rootstock-training system-spacing combination is replicated in four plots that are each approximately 30-feet long. With the experimental unit consisting of uniform plot length (varying number of trees per plot), better facilitates machine harvest and offers a more direct comparison of systems. The rootstocks included are three dwarfing rootstocks imported from Germany (Gisela®3, Gisela®5 and Gisela®6) and the current industry standard ‘Mahaleb’, which itself is slightly dwarfing compared to the industry standard sweet cherry rootstock ‘Mazzard’. The design is an incomplete factorial because not every rootstock or training system is included in every spacing. For example, the large ‘Mahaleb’ rootstocks and the multi-leader systems are not included in the closest spacings, and the very dwarfing Gisela®3 is not included at the widest spacings. The training systems are based on “columnarized” pruning, where renewal cuts are made back at the main leader on approximately a 3 to 4 year cycle. The targeted result is permanent leaders with weaker fruiting lateral shoots that are frequently replaced. The key difference among the three training systems is the number of leaders per tree. The “tall spindle” system having a single central leader, the “parallel vee” having two leaders that are both in line with the row, and the candelabra having three to four leaders, also oriented within the row. Multi-leader divide the vigor across multiple growing points to reduce tree growth and more easily maintain an orchard size suitable for the canopy-shake berry harvesters.
Clearly the attention to detail in this pruning process is much less intense than for a higher value crop such as peaches or apples. For a processed crop like tart cherries, pruning focuses on 4 to 6 renewal cuts per tree per season.
The 2012 planting has two rootstocks (G.5 and Mahaleb) but includes closer spacings and less intensive pruning strategies. Tree spacings range from 3 to 6 feet in row. Trees were either left unpruned or pruned back heavily at planting. Subsequent pruning will be mechanical. There are a total of 11 treatments, also replicated four times in 30’ plots. The first harvest of this planting was in 2014.
The 2013 planting features the same rootstocks and similar training approaches as the 2012 planting, but is scaled up to 250’ plots, and is on a commercial tart cherry farm. The site tends to produce less vigorous trees than at Kaysville, so it will also provide a test of soil conditions. Custom-propagated trees were ordered in 2014 for delivery in 2016 and will feature several new rootstocks from the Michigan State University breeding program. Two Utah orchards will be established, one on a commercial farm in Utah County and the other at the Kaysville Research Farm. Additional orchards will also be established at locations in Wisconsin, New York and Michigan as part of an NC-140 rootstock trial.
Economic feasibility of the HD tart cherry management system is examined in the research of the enterprise budget. Investigation of economic feasibility is not a simple computation as tart cherry yield, price, and sales are stochastic and the two production systems have different pre-productive periods and total orchard lives, where the HD system may result in earlier yields in the life of the orchard. The enterprise budgets for both conventional and low density systems will be created for the estimated life of the orchard, including the initial planting costs, pre-productive period, and various expected yields over the productive life. Time value of money techniques such as net present value will be used to examine the effects of the timing of the expected yields and costs over the life of the orchard for the two systems.
Generally farmers who are risk-averse would be concerned with the risk of adopting a new management system. Simulation, which incorporates stochastic components, is used to assess production, price, and sales risk between the HD tart cherry management system and traditional management system. Simulation based on data from objectives 1-4 and enterprise budgets allows for a variety of situations to be considered by combining price, yield, and sales risk and produces a probability distribution of economic return, showing the likelihood of differing levels of profit. Risk analysis provides farmers valuable information about adopting the HD tart cherry management system.
Objective 1. Rootstock, row spacing, and tree training was evaluated in two experimental orchards at the Kaysville research farm. Treatments were harvested on July of 2015, 2016 and 2017 with a prototype over-the-row harvester. Problems were experienced each year with the harvester, and modifications were made in each year. Much of these modifications involved working with 3rd party fabricators, as the company that built the prototype harvester had gone out of business.
After completion of the harvest at Kaysville in 2016 and 2017, the harvester was transported to a grower cooperator orchard in Santaquin, Utah. A one-acre test planting established in 2013 was mechanically harvested in both years and local growers were invited to observe the harvest and provide feedback. Approximately 30 growers observed in 2016, with approximately 15 growers attending in 2017.
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. 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.
Objective 2. In 2016 and 2017, water sensitive paper targets were placed within the canopy of tart cherry trees on multiple rootstocks and trained to multiple training systems. Targets were placed at multiple heights and locations within each canopy and then the trees were sprayed with water using a commercial speed sprayer delivering 50 gallons per acre to simulate distribution patterns of crop protectants. The targets were collected, scanned and droplet patterns analyzed to compare the effects of rootstock and training system on spray distribution in the canopy.
Findings: Spray distribution was generally quite uniform across the canopy across the different pruning and training systems. There did appear to be more uniform spray distribution in the hedged single leader training system than in the unhedged comparison. The degree of uniformity indicates that pruning to maintain light distribution, and matching the appropriate sprayer to the size fo the tree are the best approaches for getting uniform spray coverage and minimizing non-target pesticide exposure.
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 repeat hedged in 2016 and 2017, with plots harvested for yield using the prototype mechanical harvester in all three 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: Results indicate that branches cut to 10 cm or longer tend to provide adequate renewal growth, but that this critical length varies with rootstock, branch diameter and the severity of other pruning cuts on the tree.
Light distribution patterns in these treatments were also compared in 2016 and 2017 within the various treatments using a trailer mounted ceptometer (described below). Although light distribution results are still being analyzed, it appears that canopy uniformity is impacted more by rootstock and maintenance pruning than by initial training system or hedging practices.
Objective 4. Sampling was carried out in 2015 and 2016 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 these spot samples, 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 in Fall 2016, the machine was modified, and additional measurements were taken in 2017. Data for light distribution in the two high-density tart cherry orchards at Kaysville, along with a conventional orchard have been collected. 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. USU Ag Economist Ryan Larsen is now working to survey growers and adapt the MSU budgets to Utah conditions.
Objective 6. To date, three 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, one is a larger scale planting for mechanical harvest established in 2013, and the third is a rootstock trial planted in 2017. Plans were to establish several additional commercial test plantings but problems with nursery propagation made it impossible to establish these additional plantings.
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.
Part of the research is conducted at the Kaysville Research Farm, owned and operated by the Utah Agricultural Experiment Station Farm. The other part of the research is conducted on commercial farms belonging to producer-cooperators. This project is utilizing multiple educational approaches:
First, research reports are presented at two annual grower meetings, the Utah State Horticulture Society annual convention, and the Northern Utah Fruit Growers Meeting.
Second, growers are invited to field days and farm tours where the methods are being demonstrated. In even-numbered years, these tours are at the Kaysville Research Farm, and in odd years the tours are in Utah County and feature one of the two commercial orchard sites.
Third, the two commercial orchard sites are managed by the farmer, and provide hands-on practical experience that they can then share with other producers.
Educational & Outreach Activities
Presentation at the annual conference of the Utah State Horticulture Association (USHA): 22 Jan 2016; 19 Jan 2017; 19 Jan 2018
Presentation at the winter Northern Utah Fruit Meeting: 3 Feb 2017
Featured stop on the USHA summer farm tour: June 2015; 29 June 2017;
Featured stop on the Kaysville Fruit and Vegetable field day: 28 June 2016
Featured stop on the USHA winter orchard tour: 18 Jan 2017
Presentation at the Northwest Michigan Orchard and Vineyard show: Jan 2015
- The importance of early canopy establishment to optimize yields.