Cost-benefit analysis of inoculating blueberry bushes with ericoid mycorrhizae

Final Report for FNE12-770

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
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Project Information


We sought to answer the question, is the cost of buying and using inoculation products justified? We also intended to investigate whether it is practical for a farmer with basic scientific background and equipment to measure mycorrhizae colonization at the farm.

Here are the primary conclusions for the project:

1. There was no significant difference in Ericoid mycorrhizae colonization levels between treated bushes (inoculated with commercial product) and controls. In fact, many controls exhibited very high colonization levels, implying that Ericoid was present before planting either in the nursery media or the native field soil.

2. Our four-year-old blueberry bushes were still too small to produce sufficient fruit yield to analyze for row-by-row comparisons of inoculated bushes vs controls or for drawing correlations between Ericoid colonization levels and yield. 

3. After many hours of trial and error, we were able to refine an efficient, low-cost, non-toxic “farm lab” method for clearing and staining blueberry roots for Ericoid mycorrhizae observation and quantification under the microscope.   We have summarized what we have learned throughout this process in the form of a manual titled “Mycorrhizae Observation Made Simple.”  It is attached here.

Our hypothesis was that inoculated bushes would receive a higher dose of inoculant and Ericoid would colonize roots to a greater degree than in the controls.  Our results indicate otherwise, that inoculation had no effect on boosting colonization levels.  Furthermore, some uninoculated bushes scored very high in Ericoid colonization, indicating they already contained high amounts of Ericoid, likely from nursery potting media, prior to the project.  Ericoid could also be present in our native field soil, but with no Ericaceous plants growing there or in the vicinity for hundreds of years (or perhaps ever), it is highly unlikely that the source of Ericoid was the native field soil.


We sincerely thank Mark Starrett from UVM Plant and Soil Science Department, who served as our the project adviser. Dr. Starrett has studied Ericoid mycorrhizae, and found that many peat-based nursery media products contain Ericoid (Gorman and Starrett 2003).  This study built on Starrett's research, which implied we might find Ericoid colonization in controls that were not inoculated with commercial product, i.e. Ericoid might be present in the nursery potting mix for all 1000 bushes (treated and controls) that we bought in and outplanted.

While researchers have found Ericaceous plants colonized with Ericoid mycorrhizae (EM) can grow bigger and use nutrients more efficiently compared to the same plants without mycorrizae colonization (Scagel 2005, Yang et al 2002, Zinati et al 2011), very little research has been done to quantify the economic impact of EM in commercial blueberry fields. Commercial EM inoculant products have recently become available. We sought to answer the question, is the cost of buying and using inoculation products justified? We also intended to investigate whether it is practical for a farmer with basic scientific background and equipment to measure mycorrhizae colonization at the farm.

Our research was structured into two basic steps:

Step 1.
To verify whether roots became colonized after inoculation compared to roots that we did not inoculate.  In conclusion, we measured 120 root samples and found extremely high colonization levels in some and hardly any colonization in others.  Our data showed no significant difference in colonization levels between treated bushes and controls.  At this point it is still unclear what the source of inoculum was for plants that exhibited colonization.  It could have been the commercial product, it could have been the potting media from our plant source nursery or it could have been the native field soil (although this is highly unlikely because no Ericaceae plants have been known to ever grow in the vicinity).    It is likely Ericoid was present in the potting media from a nursery in Michigan where we sourced our plants.  This concept is in line with our adviser, Mark Starrett's, prior research that found Ericoid present in many commercially available peat-based potting mixes.

The important question in our minds moving forward is why there was such extreme variation in colonization.  Regardless of inoculum source, what rootzone conditions foster Ericoid symbiosis and what can a manager do to create these conditions? 

Step 2.
To determine if bushes with colonized roots yielded more fruit than bushes with less colonization.  In conclusion, unfortunately our four-year-old bushes were still too small to produce a large enough crop for sampling for any comparisons or correlations.  We did, however, measure canopy volume for every bush from which we sampled roots for Ericoid quantification.  Canopy volume is a proxy for bush vigor and future yield.  We did not observe statistically significant correllations between Ericoid colonization levels and canopy volume, although we suspect further research is needed to draw  more accurate conclusions in this regard.

We think that canopy volume variation in our field was caused by soil factors other than Ericoid status.  Our clue stems from our finding that Ericoid colonization levels were all over the map in our field.  A lot of variation in soil conditions could explain why we measured such variation in Ericoid levels.  The variation in soil conditions could also explain the variation in bush canopy volumes we measured up and down bushes in the same row.

Throughout the study we tinkered with methods for setting up a “farm lab” and observing Ericoid mycorrhizae. Our goal was to develop mycorrhizae observation methods that are practical for other growers who might want to assess mycorrhizae colonization as a diagnostic tool on their own farms. 

Most farmers engaged in sustainable agriculture derive livelihoods from this microbiological, plant root interaction of mycorrhizae symbiosis, yet we typically only experience it in theory. Farmers are not able to confirm the existence of mycorrhizae in fields or on crop roots without sending samples to sophisticated labs or paying for testing services at high costs.  We summarized a simple, low-cost, non-toxic method of mycorrhizae observation that worked well for us.  Please see "Mycorrhizae Observation Made Simple," attached to this report.  We welcome your feedback and suggestions for how to further improve these "farm lab" methods for blueberry and for other crops.

Many thanks also to Josh Roberts while he was at UVM and Alison Brody and Jon Gonzales of the UVM Biology Department for their assistance with developing clearing and staining methods and their overall enthusiasm and encouragement with this project.

Project Objectives:

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.


Click linked name(s) to expand/collapse or show everyone's info
  • Josh Roberts
  • Mark Starrett


Materials and methods:

Over the course of the three-year project we inoculated 500 bushes (planted alongside 500 un-treated controls), analyzed leaf tissue nutrient concentrations for every row in the field, developed mycorrhizae observation methods, collected root samples, collected bush canopy volume data, processed root samples, quantified mycorrhizae colonization, analyzed data,  hosted one workshop on the farm, delivered two speaking engagements on the topic of Ericoid mycorrhizae, corresponded via email and phone with about ten farmers and produced "Mycorrhizae Observation Made Simple," a how-to manual describing our lessons learned on low-cost, non-toxic "farm lab" methods.  The manual is specific to measuring Ericoid colonization, but the methods should be adaptable for anyone working towards measuring mycorrhizae colonization levels on their own farm.

We did not create the intended "Economic Cost Benefit Analysis for Ericoid Mycorrhizae Inoculation" booklet because the content for such booklet was lacking at the end of our study.  We measured no statisitically significant benefit of inoculating.  Costs of inoculation were detailed in our earlier annual reports.  It is important to emphasize that while inoculation didn't seem to benefit our farm, there still is strong evidence in the literature - from greenhouse, lab and on-farm studies -- of the many benefits derived from mycorrhizae symbiosis.  Many factors, many of which we still don't understand, effect successful colonization. 

We hosted a workshop on the farm in August 2014 attended by twelve aspiring and current blueberry growers and representatives from UVM Extension and Northeast Organic Farming Association. We didn’t have results to share at the time, but we did cover the topic of on-farm mycorrhizae assessment methods. Growers were introduced to the process involved in clearing and staining roots and learned how to identify Ericoid mycorrhizae under the microscope. We integrated these topics into a broader discussion of best practices for blueberry stand establishment and management.

We developed a low-cost, non-toxic method for clearing, staining and observing Ericoid mycorrhizae on blueberry roots in a “farm lab.” Researchers typically observe mycorrhizae in university labs equipped with autoclaves (devices that supply high pressure and temperature) and a full line of glassware and other specialized, calibrated equipment. However, we believed that while the methods might seem complicated, they can in fact be performed with basic chemicals, glassware and equipment, basic lab skills and locally available materials.

Our farm lab was nothing more than a cleared off workshop table in our welding shop where we stored reagents and glassware, and conducted all experiments on the roots. Our method was adapted from Vierheilig et al. “Ink and Vinegar, a Simple Staining Technique for Arbuscular Mycorrhizae Fungi” (Vierheilig et al. 1998). After various experiments and trial and error, we were able to refine a method using a crock pot as a hot water bath. While it is not perfect, the method worked adequately for clearing, staining and observing over 100 samples in a standardized manner. We have published the farm lab method in a “how-to” manual with photos titled "Mycorrhizae Observation Made Simple" to accompany this final report.

We collected root samples in early October 2014 from all 40 rows of bushes in the study. This was not as easy of a process as we had imagined. Initially we had imagined using a soil probe (3/4” diameter and ~2 feet long) to do four borings around each bush being sampled. Our four-year-old bushes did not have sufficiently developed root systems for this; the borings resulted in too few roots in each sample. The only way we could extract adequate roots was to dig down with a hand fork (three-pronged claw) in several places under the canopy of each sampled bush. We dug down 8” deep until blueberry roots were visible, then clipped a sampling of various roots to make up a composite sample for each sampled bush. We sampled three bushes per row. The three samples per row were taken from low, medium and high vigor bushes based on a brief visual scan of all 25 bushes in each row. Aside from this, we randomly selected bushes to be sampled.

We tagged every bush that we sampled for roots so we could also collect bush canopy volume data. We took two canopy width measurements, on the axis parallel to the row and perpendicular to the row. We averaged these two data points to get an average canopy diameter. We also measured canopy height from the ground to the tip of highest healthy cane. We calculated canopy volume as the volume of a cylinder.

We were not able to compare yields of berries between inoculated and non-inoculated bushes. The bushes, at ~four years of age, were simply still too small. Some varieties did yield a small amount of fruit, but there was not enough for us to confidently weigh yields considering the random pressure we had from wild turkey.

In November we processed 120 root samples in preparation for quantification of root cell colonization. Samples were held in loosely closed plastic bags in field soil in the refrigerator for about 3-4 weeks prior to washing and moving to the farm lab for the chemical procedure and slides preparation.

Most of the 120 samples made it through the clearing and staining and slide preparation steps. Unfortunately we had one or two sample identifications wash off during heating in the hot water bath. A few other slides got cracked due to glycerin sticking to the underside of the slide and in effect gluing them to the slide notebook. These mistakes reflect our skill level as amateur lab scientists and are to be expected in these kinds of procedures.  We hope "Mycorrhizae Observation Made Simple" will help others avoid our mistakes and common pitfalls.

Viewing almost 120 samples under the microscope was tedious but fascinating to observe mycorrhizal structures, hyphae and arbuscules. Aside from collecting data for our comparisons, we also gained a better understanding of how the mycorrhizae tends to associate with blueberry roots.  To quantify samples, slides were randomly toggled on 200X magnification, then scrolled to the nearest feeder root for viewing on 400X magnification to count % of root cells containing arbuscules.  This was done three times for every sample to arrive at a mean % root cell colonization for every sample.

Research results and discussion:

There was no significant difference in Ericoid mycorrhizae colonization levels between treated bushes (inoculated with commercial product) and controls in any of the four blocks of the study. In fact, many controls (not inoculated with commercial inoculant) exhibited very high colonization levels. Our data was attached to our 2014 report.

Based on these results and our doubt that Ericoid was present in native field soil prior to planting blueberry bushes, we believe Ericoid mycorrhizae were present in the potting media from the 1000 bushes we bought in from a nursery in Michigan. This would be consistent with results from Starrett and Gorman, who found Ericoid in the majority of peat-based potting media tested in their study (Gorman and Starrett, 2003). We hypothesized that inoculating with additional commercially available inoculant at the time of outplanting would significantly increase Ericoid colonization levels, but our results indicate otherwise.

It was not a stated objective of our study to confirm a relationship between mycorrhizae colonization levels (regardless of inoculation method) and bush vigor in the field. However, it was very easy to tag bushes and take a quick canopy volume measurement while sampling roots, hence we decided to see what we could find with data analysis.  Also, bush vigor can be regarded as a general proxy for future fruit yield (although small bushes can certainly yield more in some cases than larger bushes). We observed very weak correlation between Ericoid colonization levels and bush canopy volume in some varieties (Nelson and Bonus), but weak inverse correlation for other varieties (Bluejay). Additional data is needed to corroborate these results.

We know that biomass, flowering and yield are influenced by the chemical and physical characteristics of soils.  When examining how soil biology, such as mycorrhizae, effects bush characteristics, it will be difficult to affirm any direct cause and effect unless soil chemical and physical characteristics are constant across all treatments or samples.  Moreover, various studies confirm that the ability of arbuscular mycorrhizae to function depends on baseline soil conditions, such as pH, nutrient availability and composition of soil organic matter.  Any analysis of the effectiveness of mycorrhizal inoculation practices across treatments is incomplete without first confirming that soil conditions are conducive to colonization. Any analysis of the relationship between mycorrhizae colonization and bush characteristics (biomass, yield, flowering characteristics) is incomplete without standardizing for soil variables.    

While we did take baseline soil tests for all four blocks in the study and confirmed no difference in soil pH, we did not have the capacity to do a detailed account for all variables -- or even baseline soil measurements for every bush sampled for roots-- in our study.

We assumed going into our study that we had no difference in baseline soil pH, nutrient availability and organic matter composition across all treatments within the same block in the field. After completing this study we think it is not safe to assume, for purposes of assessing mycorrhizal activity, that baseline soil conditions are constant across all roots in the same plant root ball, across all plants in a row, or across all rows in a block.  We hypothesize that minor differences in soil conditions across a rootzone or up and down a single plant row or across rows in a block can have a major effect on mycorrhizae colonization levels, especially in the early years of establishing an orchard. 

Our bushes over the three-season course of this project exhibited noticeable variation in growth all over the field. These were subtle variations, but lead us to believe there was significant variation throughout the field in soil conditions.  Up and down the same row, regardless of inoculation treatment, some bushes grew very vigorously while some grew very slowly. We kept to a strict standard throughout the study of conducting management identically across all bushes in a row and row by row in a block, so there must be another explanation for the variation in bush characteristics.

What explains the variability in growth of our bushes? It's possible that the genetics of bushes vary within the same variety. It is possible that during the 2 years bushes were propagated and managed in the nursery prior to arriving at our farm, there were differences in how each bush was managed, giving some bushes a head start and holding some bushes back. Aside from this we can only look to our field’s soils. We suspect there is significant variability of soil indicators within a row or across treatment rows. We would not even be surprised if there is significant variability in soil variables in the root zone of a single bush. If this is true, theoretically one root sample from one side of a bush’s root zone could display an entirely different level of Ericoid mycorrhizae root cell colonization than another root sample from another side of the root zone.

Theoretically, two bushes of the same variety, planted the same way, inoculated or not inoculated in the same manner and managed in the same way could display different levels of Ericoid colonization if soil conditions vary enough across or within root zones to alter Ericoid colonization and function. We suspect the variability in field soil factors explains the extremely wide range of Ericoid colonization levels we observed in bushes in all blocks and treatments, regardless of whether or not bushes were inoculated.

Finally, we can report a few results from our trials with comparing and developing appropriate Ericoid observation methods. We tested a variety of methods for clearing and staining Ericoid.  Here are some basic lessons learned:

• Clearing in 10% KOH works much better than 15% KOH, which can be too powerful and destroys the roots.
• We tested many different time periods for clearing in KOH to achieve adequate clearing while not destroying roots from oversoaking. We tested 12 hours, 24 hours, 2 days, 3 days, 4 days and one week. We also tested various temperature regimes. We tested at room temperature, “low” setting and “high” setting on a crock pot hot water bath. We found that 24 hours of clearing in a hot water bath on “high” setting in the crock pot was optimum.
• We tested the same variables of time and temperature with staining roots. We found that a 12 hour stain on “high” setting in the crock pot hot water bath was optimum.
• Ink and vinegar is a safe, non-toxic stain that can be used, but it must be mixed fresh before each staining.


Gorman NR, Starrett MC. 2003. Screening Commercial Peat and Peat-based Products for
the Presence of Ericoid Mycorrhizae. J. Environ. Hort. 21(1):30–33.

Scagel CF. 2005. Inoculation with Ericoid Mycorrhizal Fungi Alters Fertilizer Use of Highbush Blueberry Cultivars. HortScience 40(3):786-794.

Vierheilig H, Coughlan AP, Wyss U, and Piche Y. 1998. Ink and vinegar, a simple staining technique for arbuscular-mycorrhizal fungi. Applied and Environmental Microbiology 64: 5004–5007.

Yang WQ, Goulart BL, Demchak K, Li YD . 2002. Interactive effects of mycorrhizal inoculation and organic soil amendments on nitrogen acquisition and growth of highbush blueberry. J. Amer. Soc. Hort. Sci. 127:742-748.

Zinati G, Dighton J, Both A. 2011. Fertilizer, Irrigation, and Natural Ericaceous Root and Soil Inoculum (NERS): Effects on Container-grown Ericaceous Nursery Crop Biomass, Tissue Nutrient Concentration, and Leachate Nutrient Quality. Hortsci. 46(5):799-807.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:

We hope farmers will refernce "Mycorrhizae Observation Made Simple" for ideas on how to observe mycorrhizae on their plant roots.  The purpose of the how-to manual is to provide farmers with a practical method for observing and quantifying mycorrhizae on roots of their crops.

Why is the publication important?

(From the manual's introduction)
There is an enormous base of research and evidence to prove that mycorrhizae fungi in soil form symbiotic associations with crop plant roots, resulting in improved nutrient uptake, nutrient use efficiency and a host of other benefits to the plant. Yet those of us who derive our livelihoods from this microbiological, plant root interaction typically only experience it in theory. Farmers are not able to confirm the existence of mycorrhizae in fields or on crop roots without sending samples to sophisticated labs or paying for testing services at high costs.

The booklet walks you through a low-cost method to observe mycorrhizae on plant roots first hand. It is for farmers with basic scientific background and access to a microscope. The procedures can be done on the farm in what we call a “farm lab,” a simple, small table space with a 120 VAC outlet in a shed, shop, barn or other building. After using the method, you might be able to confirm whether or not crop roots have mycorrhizae symbiosis, to what degree or what % of cells have been colonized by the beneficial fungi. This is valuable information for soil fertility planning, decisions about fertilizer applications (theoretically the more mycorrhizae symbiosis the less fertilizer needed), or whether to purchase one of the myriad of mycorrhizae products on the market and confirm its effectiveness.

The method was adapted for blueberry roots, however it can be used for other plants. It might take some refining and tinkering, but that is what “farm lab” mycorrhizae observation is all about. By starting with our method and trying some of the tricks we used, farmers will be well on their way to finding the method that works best for them.

Project Outcomes

Assessment of Project Approach and Areas of Further Study:

We answered the questions we set out to study.  For us, at the stage of outplanting 1 gal pots into the field it probably does not make sense to inoculate with a commercial Ericoid inoculant. However, we will always want to confirm the presence of existing Ericoid in potting mix or wherever our plants come from because there is abundant evidence from other research pointing to the benefits of having mycorrhizae symbiosis.  We plan to use the method we developed from this project for determining whether or not mycorrhizae colonization is present.  The cost of conducting these "farm lab" tests is much lower than the cost of commercially sourced inoculant, hence we will not be sourcing commercial inoculant at current prices unless we determine the costs of mycorrhizae testing are higher than the costs of inoculant.

We also plan to continue to investigate the soil conditions conducive to Ericoid-blueberry plant symbiosis.  This is a key new concept generated from this research and we have various new hypothesis we would like to investigate to explain the results we witnessed from this project.

There is evidence in the literature that certain types of organic matter are better as "fungus food" than others.  We would like to investigate practical ways of supplying the soil with this.  Specifically with Ericoid, research suggests that the polyphenol fraction of organic matter is what Ericoid have evolved to break down.  One of the main benefits of Ericoid mycorrhizae is its unique ability to break down recalcitrant organic matter (like polyphenols) and release tightly bound up Nitrogen in the process.  The hypothesis is without organic matter high in polyphenols, Ericoid has nothing to work on.  If the fungus doesn't do its job and provide the host plant with nutrients, the host plant doesn't provide the fungus any carbon, etc, etc.  There are other soil conditions that, based on previous research, are likely at play as well in terms of fostering mycorrhizae symbiosis.  We would be eager to test these variables along side colonization levels to investigate linkages.

Potential Contributions

In summary, our project revealed more questions than answers and we feel this topic is worthy of further inquiry.  An important research question is to what degree do soil factors, such as pH, nutrient availability and organic matter composition (both % and type of organic matter) vary from one rhizosphere to another within close areas of proximity in an average farm field or commercial blueberry stand? Another important research question is to what degree will variability of each of these soil factors effect Ericoid colonization and function for the benefit of the blueberry bush and producer?  Another way to phrase this is: What was it about the soil conditions in the rhizosphere that explain why we found such high colonization levels in some roots and such low colonization levels in others, regardless of inoculation practices?  Then the obvious question is what can a producer do to manage rhizospheres in a particular way to foster symbiotic associations between Ericoid mycorrhizae and blueberry bushes? We suspect it is not enough for a blueberry producer to simply inoculate roots with Ericoid mycorrhizae or confirm that inoculant is present in nursery or field soil. Soil around every root and under every bush needs to be right for the mycorrhizae to function optimally.

We talk often with farmers who are interested in developing and maintaining healthy mycorrhizae symbiosis in their fields.  Yet we operate on theory, without being able to confirm mycorrhizae presence and benefit.  The farm-scale mycorrhizae observation methods we refined as part of this project could provide a starting point for confirming whether or not mycorrhizae exist on plant roots.  This is valuable information for soil fertility planning, decisions about fertilizer applications (theoretically the more mycorrhizae symbiosis the less fertilizer needed), or whether to purchase one of the myriad of mycorrhizae products on the market.  Moreover the method can be used to confirm these products' effectiveness.  For these reasons we see farmers adopting the practice of setting up appropriate scale "farm labs" to measure mycorrhizae.  It is not for everyone, but for farmers with a basic scientific background, access to a microscope and about $100 to start, it can be doable.

We also hope this research inspires farmers to help us answer the questions that were stimulated (directly above) from this project- namely what can managers do in their fields specifically to boost mycorrhizae symbiosis in a measurable and significant way.  We encourage farmers to set up side by side experiments to determine whether specific practices effect mycorrhizae colonization.  Coupled with the confidence to be able to measure colonization, they will be able to confirm the effectiveness of these management practices.  

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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.