Progress 09/01/24 to 08/31/25
Outputs
Target Audience:Blueberry growers and county agents in the southeast. Changes/Problems:We changed the proposedexperimental design (split-plot)to a factorial arrangement of treatments in a Randomized Complete Block Design (RCBD). This design was selected over a split-plot design for several practical and experimental reasons: (1) it allowed for greater flexibility in field layout, (2) it was more appropriate given the limited number of plants available in each row, and (3) a change to a RCBD did not interferewith or jeopardize the research objectives. Additionally, the RCBD helped control for field variability and improved the precision of treatment comparisons across the trial sites. An exception was the Alma Research Farm, where pruning trials had already beenestablished a month beforethe start of the project. In theAlma Research Farm, a split-plot design was established, with pruning treatments as main plots and timings as subplots. On September 27th, 2024, Hurricane Heleneand a snowstorm in January caused severe damage to the 'Titan' field located in Appling County. Although the site had been incorporated into the project as one of the 3-year-old commercial fields, the plants did not recover adequately. In the 'Titan' field, we collected soil samples, established fall pruning treatments, and took phenological measurements. Physiological measurements were not conducted. However, as temperatures rose in spring 2025, the plants exhibited significant problems, including nutrient deficiencies, reduced vegetative growth, and portions of the canopy that appeared burnt. Given the severity of the damage, the 'Titan' site was dropped from the study. To maintain the integrity of the experimental design and ensure high-quality data collection, we replaced the site with the Alma Research Farm (Bacon County). This location has similar pruning trials already underway, and although the blueberry variety differs from 'Titan',pruning treatments match those used in the other project sites. This adjustment preserves the project's capacity to meet its original objectives while ensuring that measurements are conducted on healthy, productive plants under comparable experimental conditions. Therefore, theAlma Research Farm was added as a replacement for the 'Titan' commercial site, which was lost after severe weather conditions.From this point forward, the 'Titan' site is no longer part of the study, and the Alma Research Farm is considered the permanent replacement. The proposal's approach for the 3-year-old fields was changed; it should be clarified that all phenological parameters, along with fruit production and fruit quality measurements, were originally planned to begin in the third year of the project. However, we decided to initiate these measurements earlier in fields already in production, to ensure the collection of data that would be directly useful for the project outcomes and to maintain a more consistent and robust approach. We also had a delay in plant delivery from the nursery, which postponed our planting date,followed by adverse weather conditions. What opportunities for training and professional development has the project provided?A graduate student was hired as part of the project. The graduate student has beentrained in blueberry production management practices and has become familiar with blueberry production systems in Georgia. The student interacted with growers and county agents. The graduate studentset up experimental plots in growers' fields and research farms. The graduate student became familiar with the LI-6800 portable photosynthesis system, LI-600, root scanner, and the ceptometer. In addition, the student participated in industry meetings and gained experience in the process of publishing scientific articles. How have the results been disseminated to communities of interest?The harvest season concluded during the first week of July. We are currentlyanalyzing fruit samples for total soluble solids, titratable acidity, and anthocyanin content. Once these analyses are complete, preliminary results will be shared with growers, county agents, industry stakeholders, and researchers at the Alma meeting on January 7th, 2026, and the Southeast Fruit and Vegetable Conference on January 8th-10th. What do you plan to do during the next reporting period to accomplish the goals?In the upcoming reporting period, we will applythe pruning treatments to the 1-year-old fields at the Alapaha Research Farm andcollect datafrom this field onlight canopy measurements,Leaf Area Index (LAI), light interception (PAR), and fluorescence. Assessment ofroot growthusing aroot scanner. We are finalizing the protocol foranalyzing root images using data froma parallel small-scale pruning trial. These initial findings will help identify trends and optimize methods to performroot monitoring in the Alapaha fields. Objective 1.Determine the impact of selective pruning techniques and pruning timings on the physiological and phenological traits of blueberry plants.For all 3-year-old fields ('Farthing' - Alma Research Farm and 'Optimus' - Bacon County commercial farm). We will measure cane diameter to assess changes in plant structure after pruning. Collect and quantify dry weight samples for carbohydrate analysis to assess the effect of pruningtreatments on carbohydrate allocation. Continue light-related measurementsto monitor canopy development and light-use efficiency. Implement photosynthetic performance under different treatments (LICOR-6800). We will also continue phenological assessments. Objective 2 - Evaluate the impact of selective pruning and different pruning timings onfruit quality, harvest efficiency, and disease control.For all 3-year-old fields ('Farthing' - Alma Research Farm and 'Optimus' - Bacon County commercial farm), we will continue collectingyield and fruit quality data. We will cooperate with theplant pathology specialist to finalize protocols and set a timetable for monitoring disease incidence after pruning treatments, ensuring disease assessments are integrated into the overall evaluation of treatments.Objective 3 - Quantify the economic return of incorporating selective pruning techniques into blueberry production systems. We will continue collecting data on pruning time, harvest efficiency, and labor requirements.We plan to meet withthe economistto determine which economic analyses are appropriate for quantifying the economic return of the different pruning treatments. Prepare to scale the experimental plots to commercial farms at the end of Year 2, once the most effective pruning treatment has been identified according tothe proposal.Objective 4. Develop and disseminate multiple educational materials for blueberry producers and county agents.Share project findings with growers, industry stakeholders, and researchers through the Alma Blueberry Meeting (January 7, 2026) and the Southeast Fruit and Vegetable Conference in Savannah, GA (January 8-10, 2026). Following the suggestion of a proposal reviewer, plan and organize field days/demonstration events at commercial grower sites throughout the life of the project to provide public, hands-on demonstrations of the pruning treatments and their impacts.Publish at least two social media posts during the season on the lab website and official social media channels (Instagram, X, LinkedIn) to share updates, key findings, and visual documentation of the trials.Present preliminary results at the International Society of Horticultural Science Congress in Japan, 2026, to share progress with the global scientific community.
Impacts
What was accomplished under these goals?
Selective pruning is not a common cultural management practice in blueberry production systems in Georgia and Florida. Most growers practice a non-selective version of mechanized summer pruning (hedging) immediately after harvest, with the primary purpose of reducing plant height. The severity of hedging can compromise the canopy structure and carbohydrate reserves because it allows a higher number of vegetative shoots to grow during the summer. Thus, our project examines the effects of selective pruning techniques and the timing of pruning on fruit production and quality in blueberry fields in Georgia and Florida. To accomplish our overall objective, pruning trials were established across two commercial farms and two research farms. The cultivars used in the research and commercial farms were 'Farthing,' 'Brightwell,' 'Titan,' and 'Optimus.' Blueberry fields with three or more years of establishment were subjected to the following treatments: T1: removal of unproductive canes and laterals, T2:Removal of the two main canes, T3: No pruning (control), T4:Hedging (non-selective mechanical pruning - commercial), T5: Hedging combined with the removal of unproductive canes and laterals, and each pruning treatment was applied atthree different timings (fall, summer, and combined summer+fall). Each treatment combination was replicated four times, with five plants per replicate. Data was collected on the three most representative plants within each treatment plot. In younger fields (less than a year), efforts focused on shapingand managing the young plants in preparation for treatment application a year after planting (Alapaha Research Farms). In each of the experimental sites, treatments were arranged in a randomized complete block design (RCBD).Before pruning treatments were implemented, soil samples were collected from all 3-year-old fields to establish baseline nutrient status. Additional soil samples were collected after harvest to detect seasonal changes in nutrient availability or soil properties that might be related to the treatments. Leaf tissue samples were collected every two months from April to October to monitor nutrient dynamics and identify potential treatment effects on nutrient uptake-- crucial information for interpreting differences in yield andfruit quality.Objective 1. Determine the impact of selective pruning techniques and pruning timings on the physiological and phenological traits of blueberry plants.This objective focused on evaluating how different pruning techniques and timings influence both the physiological performance and phenological development of blueberry plants. Data collection began in Fall 2024 in the 3-year-old 'Optimus' field at a commercial farm in Alma, Bacon County.Physiological assessments:Leaf Area Index (LAI) was measuredduring peak vegetative growth. SPAD readings were also takento detect potential differences in chlorophyll content among treatments. Fluorescence measurements (LI-600) were performed to assess light interception and photosynthetic efficiency, while photosynthetically active radiation (PAR) readings were taken to link canopy structure with productivity potential. The physiological assessments will be taken twice during the growing season (April and August/September).Phenological data:Phenological traits were evaluatedin all 3-year-old fields ('Farthing', 'Optimus', and 'Titan'). Assessments included flower bud developmentin early spring, dates of full bloom, and fruit set to evaluate how pruning influenced plant phenology. Later in the season, the 'fruit coloring'stage was assessed to estimate the ripening stage of the berry cluster under different pruning treatments.Management of young plantings:At the Alapaha Research Farm, 1-year-old 'Farthing' and 'Brightwell' plants were established on March 3, 2025. All flower buds and blooms were manually removed during the first season to encourage vegetative growth and canopy development, to ensurethat plants invested resources into structural organs rather thanfruit production. No physiological or phenological data were collected from these young plants this season; measurements will be taken in subsequent years once pruning treatments are established. Objective 2: Evaluate the impact of selective pruning and different pruning timings on fruit quality, harvest efficiency, and disease control.This objective focused on the 3-year-old 'Farthing' field at the Alma Research Farm and the 3-year-old 'Optimus' field at a commercial farm in Bacon County. Pruning weights:At the end of each pruning event (started in summer 2025), all fresh biomass removed from each treatment plot was collected and weighed. This provided a quantitative measure of pruning intensity, enabling us to relate pruning severity to subsequent plant responses, including yield, fruit quality, and regrowth potential.Harvest and fruit quality measurements: All fields were mechanically harvested using a commercial over-the-row blueberry harvester. Total yield and fruit quality were measured to evaluate the impact of pruning treatments on machine harvest efficiency. A final manual harvest was conducted tocollectall fruit left on the plant after mechanical harvesting. The amount of unharvested fruit provided a direct measure of mechanical harvester performance across pruning treatments. In addition, fruit was visually inspected and sorted to determine the percentage of green, unripe, or damaged berries, another important indicator of machine harvest efficiency and overall fruit maturity and uniformity. Total yield was measured from the three most representative plants per plot using a calibrated scale. Berry weight wasdetermined by weighing a ½ pint of berries and counting the number of berries per pint. While the original proposal specified 100 g, the ½ pint method was adopted to align with USDA industry inspection standards (e.g., berry size classification: small, medium, large). Fruit quality measurements include berry firmness, size, total soluble solids, titratable acidity, and anthocyanin content.Harvest timing: the first harvest date, as well asall subsequent harvest dates, and total harvest time (recorded during the final manual harvest) were recorded. These records allow us to determine whether pruning treatments influenced ripening patterns, fruit availability, and labor requirements. Objective 3. Quantify the economic return of incorporating selective pruning techniques into blueberry production systems. To address this objective, we began collecting detailed operational and cost-related data for each treatment. At every pruning event, the time required to prune each plot was recorded to estimate labor costs across treatments. We also documented tools and equipment purchases needed to implement the trials: four cordless electric hand pruners, two cordless electric pruning saws, and one battery-powered hedge trimmer, to account for equipment investment in cost analyses. During harvest, we recorded the start date, all subsequent harvest dates, and the total harvest time per plot to evaluate labor requirements and harvest efficiency. Mechanical harvest efficiency was assessed by measuring the proportion of fruit left on the plants after machine harvesting (as explained in Obj.2). In parallel, yield was recorded for each plot to calculate productivity and relate output to labor and equipment inputs. Objective 4. Develop and disseminate multiple educational materials for blueberry producers and county agents.Activities have not yet been initiated. As outlined in the proposal timetable, this objective is scheduled for later phases of the project, following the collection and analysis of sufficient field data to support the development of accurate, research-based recommendations.
Publications
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