Cost-benefit analysis of inoculating blueberry bushes with ericoid mycorrhizae

Project Overview

Project Type: Farmer
Funds awarded in 2012: $8,890.00
Projected End Date: 12/31/2015
Region: Northeast
State: Vermont
Project Leader:
Ben Waterman
Watermans Berry Farm

Annual Reports

Information Products


  • Fruits: berries (blueberries), berries (cranberries)


  • Crop Production: biological inoculants, application rate management, tissue analysis
  • Education and Training: farmer to farmer, on-farm/ranch research
  • Farm Business Management: budgets/cost and returns, feasibility study, agricultural finance
  • Production Systems: agroecosystems, holistic management, organic agriculture
  • Soil Management: soil analysis, nutrient mineralization, soil microbiology

    Proposal summary:

    Inoculation of Ericaceous plants with Ericoid mycorrhizae can potentially increase fertilizer savings, boost plant biomass and nutrient use efficiency, and reduce nutrient leaching into groundwater. However, on-farm research confirming these effects of inoculating blueberry bushes with Ericoid is rare. Unlike other mycorrhizal inoculants for other plant families, commercial Ericoid inoculant products for Ericaceous crops like blueberry or cranberry have only recently come on the market.

    Our field trial will investigate, in randomized paired block design, whether or not inoculation of 500, 3-year-old blueberry bushes with Ericoid mycorrhizae at the time of transplanting into the field leads to increased nutrient uptake and fruit yields several years later. These effects will be compared with 500 non-inoculated bushes as controls. This trial, combined with outreach in the form of two workshops and two small e-publication handbooks, “Appropriate Farm-Scale Mycorrhizae Observation Techniques” and “Economic Cost/Benefit Analysis forEricoid Mycorrhizae Inoculation,” will provide meaningful information with which farmers can make decisions on whether it makes sense for them to inoculate stands of Ericaceous plants, such as blueberry or cranberry. It will build a base of knowledge upon which farmers can develop mycorrhizae observation skills, verify effective colonization, and realistically assess the potential outcomes of inoculation—all critical steps to harnessing the benefits of Ericoid or other mycorrhizal fungi symbiosis within the context of a commercial operation.

    Project objectives from proposal:

    Our field experiment will compare two treatments for amending blueberries at the time of planting in a randomized paired block design: One treatment will be commercial Ericoid mycorrhizae (EM) inoculant plus peat and compost. The control will be just peat and compost. The treatment and control will be compared with respect to percent colonization EM on blueberry roots, blueberry plant nutrient uptake, and fruit yields.

    Field preparation:
    The experiment site has historically been a hayfield. Soils are mapped as Adams loamy fine sand. We’ve conditioned soil on one acre for the past two years, involving soil acidification with elemental sulfur, green manure cover crops of pea/oat/vetch and clover, amending with horse manure, and preparing 22, 4’ wide by 225’ long rows, spaced 12’ apart. All residues were plowed under this fall and rows will be conditioned again one more time before planting with a Perfecta II field cultivator. Immediately prior to planting, 2’ wide by 1’ deep holes will be dug to receive bushes, spaced 4.5’ on-center within the rows. The one acre field has some variance with slopes 5-10% down to the west and southwest. This will be the primary reason to conduct the experiment in blocks.

    Planting and baseline data collection:
    1100 blueberry bushes grown in 1 gallon pots are scheduled to be shipped from the nursery for planting in June 2012. Our experiment will be divided into four blocks to decrease variation that might be due to subtle differences in microclimates and soil types across the one acre field. Blocks will be laid out in 110’ x 125’ quadrants with Block I occupying the lowest elevation to the Southwest, Block II the next highest elevation to the West, Block III the next highest elevation to the South, and Block IV the highest elevation to the Northeast.

    Immediately before planting, two types of baseline data will be taken.
    1.) Composite soil samples will be taken from each block to be analyzed at the UVM Extension soil testing lab.
    Soil tests will provide supplemental information on the context in which the experiment will take place.

    2.) Composite root core samples will be taken for each variety of blueberry shipped (10 cores from separate plants will be combined to make up one sample), and analyzed for root length colonization (methods outlined in next section, below). This will provide an important comparison of container nursery stock EM colonization with
    EM that might be introduced in the field by either commercial inoculant or natural inoculant in peat.

    Each block will be planted with five replications, consisting of a pair of a row of 25 treated bushes and a row of 25 controls. This equates to 250 bushes total per block. Across the four blocks, a total of 1000 bushes will be treated or controls; 500 bushes will have received the EM + peat + compost treatment, and 500 bushes will have received the peat + compost as controls. The two end rows on either side of the field will be planted with another 50 bushes each as a buffer; aside from that, these rows will not be part of the experiment.

    When planting the treatment, two grain shovels full of peat and one grain shovel full of compost will be mixed with soil in a 2’ diameter x 1’ deep planting hole. One-qaurter cup of the inoculant product will be applied to the moist root ball before planting. For the control, two grain shovels full of peat and one grain shovel full of compost will be mixed with soil in a 2’ diameter x 1’ deep planting crater. Two cups of organic fertilizer (Pro Holly, 4-6-4) will be mixed into the planting hole for both treatment and control.
    For each replication pair, treatment or control will be assigned at random by a coin toss. Heads will determine that the first row of 25 bushes planted in a pair will be treatment, tails will determine the first row of 25 will be control. All 50 bushes within each pair will be of the same blueberry variety. Planting will proceed this way in
    rows of 25 bushes (pairs of 50) until all five pairs and 250 bushes are planted within each block. All four blocks will be planted, mulched, and irrigation installed by July 1, 2012. Deer fencing will be installed in 2013, and bird control in 2014 before fruiting.
    We will operate and maintain the field as uniformly as possible after planting and in future years. The one acre is a manageable size to be able to conduct most management tasks, such as mowing, weeding, foliar spraying or fertilizing on the entire field all in one or two subsequent days.

    An experiment log will be kept throughout the entire project that details all activities completed. Photos will also be taken at every critical stage, with the understanding that they will be shared with other growers interested in the project. Immediately after planting is complete, we will finalize a map of the full one acre field, detailing borders for each block, which rows received treatment and control, and varieties making up each pair of rows. This map will be critical for properly organizing samples during the data collection stage.

    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.