Performing Department
School of Plant and Environmental Sciences
Non Technical Summary
Summary and JustificationProblem Statement. To enhance their competitiveness in both national and international markets, commercial tree fruit growers must apply orchard management strategies that are economically and environmentally sustainable, meet consumer demand for high-quality fruit, and enhance production efficiency. One of the critical factors that impact orchard profitability is tree planting density. Planting densities can range from 100-300 trees/acre in low-density orchards to more than 1000 trees/acre in high-density systems. From an economic perspective, growers need to select planting systems that produce high yield of high-quality fruit, economize on labor inputs and allow trees to bear fruit as quickly as possible. Doing so will minimize the grower's period of negative cash flow and ensure a positive return on investment as quickly as possible. To realize economic benefits, high-density orchards require specific production principles and practices including the use of dwarfing rootstocks. Some of the benefits associated with planting higher-density orchards include the ability to produce high-quality fruit, greater pesticide application efficiency, and capacity to train, prune, and harvest from the ground. Transitioning to uniform, high-density orchards would also put growers in the best possible position from which they can take advantage of new labor-reducing technologies as they are developed. Over the last 15 years, it has become increasingly apparent that the fruit industry in Virginia is transitioning toward a higher proportion of fresh fruit production. Low prices in the processing market (e.g., unfermented juice, sauce, sliced fruit) have encouraged growers to re-focus their efforts on orchard systems based on fresh market apples and to adopt high-density planting systems. However, adopting high-density production systems in Virginia could be hampered by three major challenges: a) The high costs associated with establishing high-density training systems (e.g., vertical axis, tall spindle, super spindle) that require wires and posts for tree support; b) the high soil fertility and warm, humid growing season that increases tree vigor and, in turn, affects the spacing between trees and rows; and c) the lack of knowledge of how rootstocks and rootstock-scion combinations would affect fruit quality and tree sensitivity to physiological disorders (e.g., bitter pit). The overall goal of this project is to determine tree training systems, planting densities and apple rootstocks that achieve the maximum yield and quality of major fresh market apple varieties in Virginia; and to provide practical knowledge to apple growers and stakeholders that would enhance their profitability and competitiveness.Approach. To achieve this goal, the PI is planning to use the established field-blocks of mature apple trees in the AHS Jr. AREC's research farm, develop new on-farm demonstration and research plots, and conduct economic analyses to evaluate the effects of two training systems, eight planting densities, 19 rootstocks and 27 rootstock-scion combinations on the yield and quality of four fresh market apple varieties. The research findings of this project will be communicated to growers and stakeholders in VA through extension-oriented journals, web-based blogs, regional and state fruit grower meetings, as well as fruit schools and field days.Relevance to Virginia and the U.S. The United States is the world's second-largest exporter of fresh and processed apple products and, as such, apple represents an important crop for the nation from an economic perspective. Of the 50 states that grow apples, 36 do so for commercial purposes. Virginia is ranked 7th in the nation for apple production (VDACS, 2017). The state produces around 200 million pounds of apples annually, from 10,557 acres of land (NASS census, 2012). The production of apples for the fresh market has more than doubled in the last ten years, whereas the production for processing has decreased by 25% (NASS survey, 2017). Such transition in the marketing strategies has been demonstrated in a questionnaire used by the PI in 2017 to identify and set research priorities that reflect the interests of Virginia tree fruit growers and stakeholders. The majority of the respondents (total number =107) to this questionnaire were tree fruit growers representing 40 counties in Virginia. Other respondents were private agricultural consultants, agribusiness field representatives, and Extension educators. Most of the apple growers, making up 63% of respondents indicated that they are selling their fruit for fresh market (i.e. farm market, pick-your-own, wholesale to retailers). More than 80% of respondents ranked research topics that focus on the evaluation of apple rootstocks, strategies to reduce physiological fruit disorder, or strategies to improve fruit quality as "very important" or "important"; whereas less than 5% of the respondents rated these topics as "unimportant" or "not very important".Anticipated outcomes and impacts. This research project is expected to enhance the competitiveness of the Virginia's fresh market industry through increasing the yield and quality of fresh apples, increasing labor efficiency, adopting better orchard management practices, raising awareness of factors critical to orchard profitability and producing new knowledge of conditions affecting trees responses to physiological disorders. Outputs of this project may include but are not necessarily limited to, demonstration plantings for grower review, conference presentations, fact sheets, extension publications, various electronic media, and research journal articles. Outcomes would be anticipated to include increased grower adoption of higher density, more efficient orchard management practices and materials.
Animal Health Component
0%
Research Effort Categories
Basic
10%
Applied
90%
Developmental
0%
Goals / Objectives
Examine the effect of rootstocks and training systems on reducing the costs associated with establishing higher density apple orchards in Virginia. The three specific objectives related to this objective are:Evaluate the production efficiency of four dwarfing apple rootstocks (G.11, G.16, G.935 and G.890) in supported (i.e., tall spindle) versus non-supported (i.e., central leader) training systems.Examine the effect of different rootstocks on the yield and quality of three fresh market apple cultivars ('Fuji', 'Gala' and 'CrimsonCrisp').Estimate the economic costs and benefits of the examined rootstocks under different training systems and for the three apple cultivars.Examine planting densities that would achieve the highest yield efficiency and fruit quality under Virginia's soil condition.This research objective would specifically aim to:Determine planting spacing that would achieve the highest and most-consistent annual yield of 'Fuji' apples.Investigate the effect of different planting densities on fruit quality traits.Examine the effect of apple dwarfing rootstocks on the quality attributes of fresh market apples. The three specific aims to be investigated are:Evaluate 14 dwarfing and semi-dwarfing rootstocks for their effects on the quality traits of 'Honeycrisp' apples grown in a high-density production system.Examine the effect of 14 dwarfing and semi-dwarfing rootstocks on the nutrient content of 'Honeycrisp' apples as it relates to the occurrence of bitter pits.Provide educational materials and decision-making tools to apple growers and stakeholders in Virginia for adoption of high-density production systems
Project Methods
Methods/ProceduresObjective 1: Three scion varieties ('CrimsonCrisp', 'Aztec Fuji', 'Buckeye Gala') on four Geneva rootstocks (G.11, G.16, G.935 and G.890) will be planted in the AHS Jr. AREC research farm in April 2018. For each scion-rootstock combination, two training systems will be compared (tall spindle & central leader). The same scion trees grafted on Bud.9 will be planted in all plots as controls. Trees under each training system will be arranged in the field as a split-split plot design. Briefly, each of the three replicates will be divided into two sides, and training systems will be randomly assigned to each side. Each side then will be split into three sections and the three cultivars will be randomly assigned to each section. Each cultivar will be split into five sections, and for each, a rootstock will be randomly assigned. The rootstocks will be planted with a spacing of 7.5 X 13 ft (446 trees/acre) for the central leader, and 4 X 13 ft (837 trees/acre) for the tall spindle plots. For the free-standing central leader system, the trees will be trained into a Christmas tree shape, by keeping the top branches narrower than the lower ones. To control tree vigor, the central leader will be periodically headed back into the 2-year-old wood. For the tall spindle systems, trees will be supported by conduit posts and four wires spaced at 2, 5, 8 and 11 feet from the ground. Assessment of tree growth parameters will start from the first year of planting, whereas yield and fruit quality traits will be evaluated starting from the third year. Tree growth (e.g. trunk cross-sectional area (TCSA), number of suckers, terminal growth, branch number, tree survival), tree productivity (e.g. fruit number, yield, cumulative yield), and fruit quality traits (e.g. fruit weight, diameter, firmness, crispness, color, starch pattern index, soluble solids, titratable acidity, pH, dry matter) will be evaluated for all varieties, rootstocks and training systems every year according to the methods described previously (Kumar et al., 2012, Iglesias et al., 2008, Musacchi and Serra, 2018, Peck et al., 2006, Tatsuki et al., 2007).The economic feasibility of each of the training systems and rootstock-scion combination will be determined based on the establishment costs in the first year of planting (e.g. cost of trees, wires, posts, and labor), the maintenance costs (e.g. cost of fertilizers, fungicide and pesticide sprays and labor for fruit picking and pruning), and the cumulative yield ($/acre) of each system within a five-year period. The economic analysis of different variables will be performed in the last year of this project through collaboration with Prof. Darrell Bosch, Department of Agricultural and Applied Economics at Virginia Tech.Objective 2: Trees of 'Fuji' on M.9 rootstock were planted in 2012 in the AHS Jr. AREC, at Winchester in order to evaluate the effect of different planting densities on tree and crop characteristics under Virginia's soil conditions (Supplementary File 1). Trees were planted at 2, 3, 4, 5 and 6 feet between trees and 12 feet between rows to provide densities ranging between 605 to 1815 trees/acre. Trees are supported by a trellis system composed of five wires and conduit posts and are trained and pruned according to the tall-spindle training system, as previously described (Dominguez and Robinson, 2015). Trees for the five planting densities and three replicates (n=4 trees) are arranged in the field as a randomized complete block design (RCBD). This research trial was active for three years after planting but subsequently discontinued due to the moving of the former PI (Dr. Gregory Peck) to a different institute in 2015. Trees of this field trial have been well maintained during the last three years, but data collected from this experiment up to now is not sufficient to address the objectives of the current proposal, especially in regards to the effect of tree spacing on fruit quality, cumulative yield and yield efficiency. Evaluation of tree (e.g. TCSA, shoot length, leader length), crop (e.g. yield (kg/tree, kg/acre), yield efficiency (kg/cm2 TCSA), and cumulative crop value ($/acre) and fruit characteristics will be conducted as indicated above to advance this project.Objective 3. 'Honeycrisp' scions grafted on 14 dwarfing and semi-dwarfing rootstocks (B.10, G.11, G.202, G.214, G.30, G.41, G.935, G.969, M.26 EMLA, M.9 T337, V.1, V.5, V.6, V.7) were planted in a commercial orchard (Saunders Brothers Orchard, Piney River) in Central Virginia in 2014 as a part of an NC-140 project that encompasses nine states. The purpose of this multi-state project is to evaluate the effect of different rootstocks on the tree and crop characteristics (e.g. TCSA, number of rootsuckers, yield (kg/tree)) of 'Honeycrisp' trees grown under a high-density planting system (907 tree/acre), and trained in a tall-spindle training system. The PI is serving as a collaborator and the Virginia voting member in this project. The effect of these rootstocks on fruit quality and sensitivity to bitter pit has never been investigated in Virginia; hence, it will be examined as a part of the proposed Hatch project as additional effort beyond the scope of the NC-140 outlined project objectives. Trees are arranged in the field according to the completely randomized design (CRD) with ten single-tree replications. The fruit quality data will be collected from all rootstock-scion combinations as indicated above.For the assessment of rootstock effects on the development of bitter pit, 20 fruits from each tree will be sampled at harvest and will be split into two groups (one for at-harvest evaluation and one for after storage). For at-harvest evaluations, fruit will be left at room temperature for one week to acceleratebitterpitinduction that would have emerged in storage. We will thenmake an evaluation on whether or notbitterpitis present (binary) and the percentage of coverage. It is alsoimportant to factor in crop load and fruit size in these evaluations since both are co-dependent factors contributing to bitter pit development. Therefore, crop load will be measured for all trees based on the number of fruit/ cm2 of TCSA. Internalbitterpit will also be measured by slicing the apple into 1cm cross-sectional disks and counting the number of internalbitterpitlesions on the top side of each disk working from the calyx end upwards. For post-storage evaluation, if thebitterpitis going to develop, it will usually emerge within the first two months of storage at regular atmosphere (RA), so our storage times will include three months of storage in RA. After storage, we will do the same evaluation that we did at harvest except without the seven days at room temperature. Recent soil testing results have indicated that Ca and other nutrients are available in sufficient quantities and soil pH lies within the acceptable range. Samples will be collected from leaves and fruits at harvest for nutrient analysis, using the Agricultural Analytical Services Laboratory of Penn State University College of Agricultural Sciences.Statistical analysis.Completely randomized, randomized complete block, and split plot designs will be analyzed as appropriate using the ANOVA, GLM, or MIXED procedures of SAS statistical software (release 9; SAS Institute, Cary, NC, USA). The Tukey-Kramer HSD test will be used to compare means if necessary. The required assumptions, including constant variability by treatment and normality of residuals, will be checked and a transformation will be applied to the data if necessary.