Nutrient and Weed Management Strategies for Organic Wild Blueberry Growers

Project Overview

Project Type: Research and Education
Funds awarded in 2019: $199,828.00
Projected End Date: 11/30/2022
Grant Recipient: University of Maine Extension
Region: Northeast
State: Maine
Project Leader:
Dr. Lily Calderwood
University of Maine

Information Products


  • Fruits: berries (blueberries)


  • Crop Production: application rate management, cover crops, cropping systems, fertilizers, irrigation, nutrient management, organic fertilizers
  • Education and Training: demonstration, extension, farmer to farmer, mentoring, networking, on-farm/ranch research, technical assistance, workshop
  • Farm Business Management: value added
  • Natural Resources/Environment: soil stabilization
  • Pest Management: cultural control, field monitoring/scouting, integrated pest management, mulches - general, mulches - killed, mulches - living, mulching - vegetative, physical control, weed ecology
  • Production Systems: organic agriculture, transitioning to organic
  • Soil Management: composting, green manures, nutrient mineralization, organic matter
  • Sustainable Communities: quality of life

    Proposal abstract:

    Problem and Justification:
    The price of conventional frozen wild blueberries reached a record low $0.27/lb in 2017, a price that does not justify crop maintenance. Meanwhile the crop grown organically sells for $5.00/lb. Small organic growers are stuck with low yields and large organic-transition farms will struggle with low prices until effective organic fertility and weed management strategies are developed and disseminated effectively. At a pH of 4.0, most soil applied fertility is not available for blueberry plants, yet these nutrients feed weed species. Foliar nutrient uptake is not well understood for this crop and increases the risk for disease. The weed management tools available for organic growers are limited to sulfur applications, weed whacking, and hand weeding. Furthermore, the shallow blueberry root system is susceptible to drought conditions that non-irrigated fields have experienced over the last three seasons. While applied research has been conducted on wild blueberry for many years, it is time to focus on soil and plant health for a new market.

    Solution and Approach:
    Of the respondents to the 2018 UMaine Organic Blueberry Grower Survey, 84% indicated that they would benefit from more nutrient management research and 92% indicated that they would like to have better weed  management tools available for organic production. The education outlined here is designed to go hand-in-hand  with research activities and to spur discussion of new ideas. More than 500 farmers from three states will be  reached and invited to participate in field days, conferences, webinars, and online resources. We have designed  applied research to fit directly with our education curriculum that will engage farmers. In order to achieve the  performance target, research will 1) evaluate OMRI approved fertilizers applied to the soil vs. blueberry leaves at  two different timings, where disease, insect pest, and weed pressure are measured, 2) trial tine weeding and  winter-kill cover crops as weed management tools, 3) conduct an irrigation demonstration, and 4) document the  cost of these practices. While the higher price for organic currently drives wild blueberry farmers to transition, the  benefits of this shift have the potential to reduce the amount of pesticide and high-input fertilizer applied to  thousands of acres in northern New England. 

    Performance targets from proposal:

    Fifty blueberry growers in Maine will adopt at least one new weed, nutrient, or irrigation management practice on  a total of 500 acres. Among these growers, 5 managing certified organic farms will increase their average yield  by 500 lbs/acre on a total of 100 acres. Additionally, 500 acres of conventional blueberry land will adopt practices  necessary to transition to certified organic production. 

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.