Progress report for LS22-370
Project Information
There are over 28,000 acres of blueberry farms in the southeast. Something all these farms have in common is the extensive use of soil inputs. Growers use pine bark, large amounts of fertilizers, and large volumes of irrigation water to support agricultural production. These inputs increase blueberry establishment and production costs, reducing farm profitability and limiting who can grow blueberries in the southeast. Soil inputs also increase the likelihood of soil degradation, nutrient percolation, and water pollution. Reducing or eliminating the need for soil inputs is a critical step to increase the sustainability of blueberry farming systems in the southeast. Grafting blueberry on resilient rootstocks is an avenue to reduce the need for soil inputs, reduce establishment and production costs in blueberry farms, and broaden participation of underrepresented farmers in blueberry production. Previously, we have shown that commercial blueberry production targets can be attained with blueberry grafted on sparkleberry rootstocks. This project seeks to expand on earlier work by designing and testing a reduced input blueberry production system that uses less water, less soil amendments, and less fertilizers than blueberry farms in the southeast currently use. We will use participatory and multidisciplinary research methods to address sustainability across multiple dimensions. First, we will establish a grower advisory board and evaluate grafted blueberry plants in reduced input scenarios in a greenhouse trial. Then, we will conduct in-farm trials in Florida and Georgia where we will evaluate plant stress, agronomic productivity and soil health impacts. Additionally, we will quantify inputs and costs to conduct an investment analysis using data from the farm trials. This will allow us to assess the environmental and economic sustainability of reduced input blueberry farming. We will also seek to impact the social sustainability of blueberry farming through this project. We will utilize a multi-phased, data driven approach to promote adoption of the reduced input blueberry farming. We will work in collaboration with industry stakeholders, university faculty, and grassroots organizations to reach traditional and underrepresented growers. We will identify adoption gaps and information interests among growers. This will inform the design and delivery of educational materials and activities including multi-media products (videos, blog posts, articles, and social media), hands-on learning (field days for growers), and train-the-trainer workshops (regional in-service training for extension agents). We will evaluate the efficacy of educational and informational activities using surveys, follow-up interviews, and site visits to understand the extent of adoption. Ultimately, we expect the reduced input blueberry production system will 1) reduce reliance on practices that compromise soil health and water quality, 2) reduce establishment and production costs in blueberry farms, and 3) remove barriers for the participation of underrepresented groups in blueberry farming. These changes will move blueberry production systems towards environmental, economic, and social sustainability.
Our overall goal is to increase the sustainability of blueberry farming systems in the southeastern United States by leveraging the resilience of grafted blueberry plants. Specific goals include:
Objective 1: Develop input reduction thresholds for blueberry production
Objective 2: Design a reduced input production system that uses grafted blueberry plants
Objective 3: Evaluate reduced input blueberry production using agronomic productivity, environmental, and economic sustainability metrics
Objective 4: Increase adoption of the reduced input blueberry production system
Cooperators
Research
We constructed microcosms that imitate the blueberry production system in the southeastern U.S. (Figure 1). Microcosms consisted of a 70 cm by 40 cm container. The lower half of the container was filled with a well-drained Arendondo series soil collected from a blueberry farm. The top half of the container was filled fine pine bark. This stratification of the soil column represents the prevalent blueberry farming system in the region, where growers plant in raised beds made of pine bark that sit on top of native soil. We equipped is microcosm with drip irrigation according to commercial farming practices.
We planted grafted and own-rooted blueberry plants in these mesocosms. One year-old sparkleberry plants were side-grafted with scions of southern highbush blueberry cultivar ‘Sentinel’. One year-old ‘Sentinel’ plants were used as controls. ‘Sentinel’ is a new highbush blueberry variety that enjoys wide popularity among growers. Grower advisory board members Bert Sheffield and Kyle Straughn concurred with the cultivar selection.
We grew plants in the microcosms for 12 months. We used root observation tubes and a minirhizotron scanner to monitor root growth. We also used soil moisture, soil water potential, photosynthetically active radiation, temperature, and air relative humidity sensors to measure environmental conditions in the microcosms. We used RGB cameras and quantum sensors to measure plant size.
Edaphic and environmental conditions in the microcosms closely resembled blueberry farms and promoted vigorous plant growth. Own-rooted plants exhibited larger canopies than grafted plants (Figure 2A). This is consistent with the long establishment period of grafted plants in field conditions (Heller et al. 2023). Own-rooted plants also exhibited larger root systems (Figure 2B). However, there were notable differences in root distribution between grafted and own-rooted plants. Own-rooted plants exhibited higher root length than grafted plants in the first 22 cm of the soil profile (Figure 3A). There were no differences at depths between 22 cm and 44 cm (Figure 3B). Grafted plants exhibited higher root length than own-rooted plants at depths higher than 44 cm (Figure 3C). These results confirm field observations that suggested there could be contrasting root architecture between sparkleberry and blueberry (Lyrene 1997). Deeper roots in grafted plants might be an asset to promote reductions in irrigation and fertilizer use.
Educational & Outreach Activities
Participation Summary:
We made a presentation at the 2022 Annual Meeting of the American Society for Horticultural Science. This is the flagship scientific meeting of the horticulture industry. We also hosted a group growers, extension educators, and industry professionals as part of the 2023 Spring Field Day of the Florida Blueberry Growers Association.
We are currently preparing a manuscript detailing the findings of the microcosm study.
Project Outcomes
The graduate student working on this project was awarded the 2022 Grant A. Harris fellowship ($10,000 in instrumentation) to augment her work in the microcosm experiment.