Performing Department
Horticulture
Non Technical Summary
Consumer demand is increasing for fresh-market blackberries, but the ability for U.S. blackberry producers to meet this demand and stay profitable is threatened. Main issues include declining yield caused by soilborne pathogens and climate variability, and rising production costs which continue to erode profit margins. Breeding for disease resistance is an option, but this is time-consuming, does not solve all issues, and should not be relied on solely. The future sustainability of blackberry production and improved food security requires (i) development of new knowledge and innovative approaches to increase yields and (ii) outreach efforts targeting a broad fruit grower audience spanning across food systems. We propose an integrated research and extension project evaluating novel soilless long-cane production techniques for the increased success and profitability of blackberry production. Objectives 1 and 2 develop new information on how cultivar selection and targeted cultural practices influence long-cane yield and fruit quality. Objective 3 evaluates breakeven and risk analyses for both long-cane and field-based blackberry systems and quantifies the magnitude of key profitability drivers. Objective 4 focuses on rapid and long-term application of research results targeting small and large operations. Soilless systems that reduce losses from disease and increase yields will also increase the profitability and success of blackberry producers, benefitting local and regional economies. Considering the national scope and increasing trend for soilless culture, we anticipate the output from this project will be critical in progressing the blackberry industry forward and building food system resilience.
Animal Health Component
100%
Research Effort Categories
Basic
0%
Applied
100%
Developmental
0%
Goals / Objectives
The long-term goal of this Foundational Knowledge of Agricultural Production Systems project is to increase fresh food resiliency with soilless "long-cane" production of blackberry. The context of this goal is that consumer demand is increasing for fresh market blackberries, but the ability for U.S. blackberry producers to meet this demand is threatened by declining yields and consistency from (i) soil-borne diseases, particularly Fusarium, and (ii) increased climate variability and extreme weather events. Soilless "long-cane" production techniques are designed to mitigate these and other production issues; these systems are used in other countries and by early adopters in North America and show promise to help strengthen and sustain the growth of the U.S. cane berry industry.Our objectives for reaching our goals include the following:Evaluate cultivar effects on yield and fruit quality in long-cane blackberry.Evaluate long-cane cultural strategies for effects on yield and fruit quality.Evaluate the economic feasibility and risk of long-cane blackberry.Develop novel extension outreach materials targeting long-cane and field producers.
Project Methods
Soilless long-cane production systems. Long-cane experiments will be conducted in plastic-covered high tunnels located at the University of Arkansas Agricultural Field Station, Fayetteville, AR, as well as the University of Arkansas Fruit Breeding Station, Clarksville, AR (see Facilities and Other Resources, Budget Justification). Fayetteville and Clarksville are approximately 100 miles apart and have USDA Hardiness Zone designations of 6b and 7a, respectively. A new larger high tunnel will be installed at Fayetteville (year 1) to match the size of the Clarksville location tunnel for Objectives 1 and 2. Tunnels will be equipped with long-cane trellises, pressure-compensated drip irrigation, multi-injector, and fertilizer stock tank systems.During experiments plants will be fertilized at each irrigation using a custom long-cane fertilizer recipe supplied by Nourse Farms (Whately, MA) and modified by PD Dickson. Irrigation controllers will pulse irrigate approximately 8 to 20 times per day depending on climate conditions and to ensure a 20%-30% leaching fraction, following standard guidelines for soilless culture. Solution volume, electrical conductivity (EC), pH, and nutrients will be monitored daily in the applied and leached fertilizer solution for each research plot to monitor root zone fertility, moisture levels and leaching, and to make fertilizer decisions (standard practice for soilless culture). Row spacing will be 2 m for each experiment, in-row spacing will depend on treatment (see below).Sourcing of blackberry long-cane materials and supplies. For each experiment, dormant long-cane blackberry plants will be purchased from a professional and licensed long-cane propagator in the U.S. (Nourse Farms, Whately, MA) and shipped frozen to the appropriate research location (Fayetteville or Clarksville, AR). Plant material will meet European quality specifications of a 2-m tipped height, at least 25 nodes per cane, and 5 canes per plant. Plants will be stored in PD Dickson's cold storage facility at -1.5°C until needed for experimentation.Cultivar selection for long-cane research. Blackberry cultivars with high-yielding potential as long-canes (determined by Co-PIs Worthington and Fernandez) will be selected from the University of Arkansas Fruit Breeding Program. 'Von' and 'Loch Ness' will be trialed as standard reference (control) cultivars in Objective 1 since these are already used in long-cane production.Up to 12 long-cane blackberry cultivars will be evaluated over three pull-out dates for effects on yield and fruit quality over time. For pull-out date treatments, dormant plants will be removed from cold storage and transferred into production during (approximately) February, March, and April. Experiments will be held at Fayetteville and Clarksville locations under the direction/supervision of PD Dickson and Co-PI McWhirt and repeated over years 1 and 2 for sufficient replication and estimations of yield variance. For each experimental run, dormant plants will be repotted in 7-L containers in 100% coconut coir substrate (FibreDust, LLC), placed in tunnels at 2-m between-row spacing and 0.7 m in-row center spacing with drip fertigation. During production, the developing lateral branches which produce flowers and fruit will be trained horizontally and supported by the long-cane trellis. Weather stations placed at canopy level will record climate conditions (air temperature, photo flux density, humidity) every 15 minutes. Fruit harvesting will occur twice per week and harvest data for each experimental unit will consist of measuring ripe berry number and total harvested fruit weight per plant. Harvested fruit will also be separated into marketable and unmarketable (misshapen or deformed fruit) categories. Sub-samples of marketable fruit will be taken at each harvest event and stored at -20°C for later determination of fruit soluble solids (°Brix) and titratable acidity (citric acid equivalents). Calculated response variables per experimental unit will include individual weight of marketable berries, percent marketable fruit, marketable yield per linear meter and per square meter, and the soluble solids:titratable acidity ratio of marketable fruit (important fruit quality and taste parameter) per experimental unit. Cultivar and pull-out date effects on each response variable will be evaluated over time (harvest events) and between locations/years.Co-PI Knuth will collect data to use later with eye-tracking software for each experiment and cultivar (see Objective 3). This will involve Co-PI Knuth traveling to Arkansas experiment sites, taking high-resolution videos/pictures of harvestable crops, tracking the time it takes workers to harvest in research plots where videos/pictures were taken, and going back through the research plots to carefully measure harvest efficiency. Data will also be collected on the same blackberry cultivars grown in the field using a standard T-trellis at the Clarksville location (location of AR Fruit Research Station), where these cultivars are already maintained and harvested as part of the Arkansas Fruit Breeding Program. Prior to harvesting, Co-PI Knuth will provide basic training to workers to match commercial harvesting practices. These data will be collected at >10 harvesting events for each cultivar treatment per experimental run and location for sufficient replication and statistical power. It is not feasible for Co-PI Knuth to travel to AR for each data collection event and therefore she will provide training to PD Dickson and Co-PI McWhirt staff to take pictures/videos, train workers, and collect these data in her absence.In addition to cultivar selection, we have identified several plant management strategies from commercial long-cane raspberry growers likely to have major effects on blackberry long-cane yield and harvesting efficiency: planting density, thinning of lateral branches and fruit, and the practice of "double-cropping" for long-cane. Increasing the planting density is expected to increase total yield/acre but decrease harvesting efficiency, fruit yield per plant, and individual fruit weight (also affects costs). The removal of developing lateral branches, which essentially removes developing fruit (a.k.a. fruit thinning), is reported by growers to increase individual fruit weight (a desirable market trait) and percent marketable fruit, with little or no effects on total yield. The practice of "double-cropping" long-canes is intended to achieve two harvests per season and is based on the concept that only a fraction of a blackberry's flowering/fruiting potential occurs naturally due to mechanisms within the plant's morphology and physiology [24], and a higher potential can be realized through horticultural manipulation. The double-cropping strategy involves removing the inflorescences and fruit receptacles from the lateral branches after all berries have been harvested from the first main flush of flowering/fruiting, leaving lateral branches with only vegetative leaf tissue. This followed by an increase in nitrogen fertilization of approximately 30% to stimulate additional growth from each remaining leaf node, creating a second flush of flowers that would otherwise have remained dormant.