Cost-benefit analysis of inoculating blueberry bushes with ericoid mycorrhizae

Cost-benefit analysis of inoculating blueberry bushes with ericoid mycorrhizae

Summary

One thousand one hundred 2-yr-old blueberry bushes were planted to compare a control group with a mycorrhizae innoculated group, according to proposed plan. Five hundred bushes were inoculated with a commercial Ericoid Mycorrhizae product, 500 bushes were not inoculated as control, and 100 bushes were planted on end rows as field buffers. Through hands-on practice, the costs of the inoculation process were thoroughly investigated. Benefits will be assessed in the third year of the project in 2014. Two key findings for 2012 were: 1.) The additional time spent on inoculating the root ball adds 10% of the total time of all other steps of the planting process. 2.) Planting 50 bushes without inoculating costed roughly $300 (variable costs, and not including cost of planting stock); while inoculating adds roughly $100 to that cost. We also established the ‘farm lab’ in 2012, clearing a table in our weld/wood shop to make way for beakers, microscope, and reagents for mycorrhizae observation. More time will be needed than initially planned for verification that ‘farm lab’ methods are legitimate and produce accurate results in terms of Ericoid mycorrhizae observation and quantification. Our project advisor, Mark Starrett at University of Vermont Plant and Soil Science Department, has hired a graduate student, Josh Roberts, who will be mirroring this project as part of his own graduate research. This is a welcome development, as we will now have more capacity to troubleshoot lab methods. Our goal for 2013 is to confirm accurate ‘farm lab’ methodology, to continue in 2014 as planned with full quantification of mycorrhizae on roots of field planted bushes.

• Blueberry root ball closeup, not inoculated
• Filling tub with Ericoid inoculant
• Inoculating root ball
• Roots to the right are inoculated with the product

Objectives/Performance Targets

We had two primary objectives for Year 1:
1. Document the actual costs of inoculating blueberry roots with Ericoid mycorrhizae at the time of field planting.
2. Establish accurate mycorrhizae observation methods to quantify % root cell colonization of potted roots from the nursery BEFORE bushes are planted in the field.

We met objective #1, but did not meet objective #2, although we are on track to meet objective #2 in 2013.

Objective # 1: Documenting Costs of Inoculation

Through hands-on practice in planting 1100 bushes in rows of 50 bushes, the costs of the inoculation process were thoroughly investigated. The key finding was inoculation doubles the time it takes to plant the root ball. However, when all steps of the planting process are taken into account, the relative additional time spent on inoculating the root ball is roughly only 10% of the total time of all steps of the planting process.

5.5 work-hours were spent planting a 50-bush row with inoculated plants, and 5 man/woman-hours were spent planting a 50-bush row without inoculating plants. Total cost to inoculate a 50-bush row was $397.80; while total cost to plant a 50-bush row without inoculation was $306.00. See attached excel spreadsheet for our actual time and materials budget for planting a 50-bush row, including notes on how these figures were derived.

Objective # 2: Quantifying Percent Inoculation on Roots From the Nursery

In order to confirm that inoculation has a different effect on root colonization of mycorrhizae than mycorrhizae that might be present in growing media, our plan was to examine roots from each of the ten varieties before planting. Our plan was to quantify % of root cells colonized with Ericoid.

We realized soon after establishing the farm lab that root preparation methods, while not too complicated to be done outside of a conventional laboratory, were completely new to us. There are many variations in how roots can be cleared of pigment and stained in order to view the mycorrhizae. We realized that we needed to test the methods themselves, before we could start gathering actual data on % root cell colonization of bushes from the nursery. We underestimated the amount of time necessary for comparing different methods before we could begin official analysis. However we did make progress that puts us on track in 2013 to confirm a methodology that is both accurate and appropriate for the ‘farm lab’ setting.

With the help of Josh Roberts and Mark Starrett, we confirmed that ink and vinegar can be used as a substitute in staining for Chlorazol Black E (CBE), which is known to be a carcinogen. This is a major finding, dramatically increasing the level of safety for anyone working through the mycorrhizae staining process. To our knowledge, no one has confirmed the ability to stain Ericoid mycorrhizae with ink and vinegar before, hence the finding is a contribution to horticultural lab science.

The ink and vinegar method produces clearly visible Ericoid, but the process is not fail safe, as we learned. The samples must be stored in water, which degrades the samples over time. Staining with CBE, on the other hand, allows for sample storage in lactoglycerol, which enables a dramatically longer shelf life for samples.

We did succeed in observing Ericoid on select plants that had been inoculated in preliminary trials prior to this project. We had several Blue Gold plants in one gallon pots whose root balls had been inoculated in June 2011. Starrett and Roberts processed the samples using conventional clearing and staining (KOH solution and autoclave for clearing root pigment, and CBE in lactoglycerol for staining). Percent root colonization was not quantified, but “roots were teeming with Ericoid mycorrhizae.” This result implies product effectiveness. Benefits to plant growth or yield are yet to be determined.

• Marginal Costs of Inoculating Blueberry Bushes at Time of Planting

Accomplishments/Milestones

Milestone #1: Planted 1100 blueberry bushes in randomized paired block design, with 500 bushes inoculated with Ericoid mycorrhizae, 500 controls and 100 bushes as field buffers.

See attached field plan for varieties and block layout.

Milestone #2: Set up ‘farm lab’ equipped with microscope, glassware, and reagents for clearing and staining blueberry roots for mycorrhizae observation

We achieved this milestone, and became familiar with the basic process involved in mycorrhizae observation

Milestone #3: Establish a baseline measure for % root cell colonization of bushes from the nursery before planting.

This milestone was not achieved, due to the fact that many variations on root clearing and staining and cell counting methods exist, and we could not start to quantify our samples without being certain that we were using the best method. We look forward to 2013 for further testing of the methods in order to discern the pros and cons of each, and applicability to the farm lab setting. We will share our research of the methods at the end of the project in the form of the outreach publication, “Appropriate Farm-Scale Mycorrhizae Observation Techniques.”

Other farm business-related milestones:

1. We dug a pond in 2012 that will serve as the reservoir for irrigating the experiment field. Assuming average rains, the volume should be sufficient to irrigate each root ball area with 4″ per week, which we have found to be optimal for blueberries on our sandy soil.

2. We have salvaged about two hundred 10′ cedar posts from a nearby field. According to plan, we will use these posts to install deer fence in 2014.

3. We also built a foundation for a greenhouse to be built into one of our lower field’s south facing hillsides. The greenhouse will be a winter production facility for raspberries and fish. This is not related to the experiment, but could be if blueberry bushes were brought out of dormancy early (February) for the study of Ericoid mycorrhizae.

• Field Map

Impacts and Contributions/Outcomes

Primary outcome of 2012, project year 1, was we proved that Ericoid mycorrhizae can be observed on blueberry roots by a farmer with basic scientific background and access to a microscope and basic lab equipment and reagents, all worth under $1,000. The theoretical benefits to having mycorrhizae presence in root systems are well known, but up to now we have not been able to verify this presence, or make production decisions, such as reduced need for fertilizers, based on the presence of mycorrhizae. Now blind faith is no longer needed in mycorrhizae products on the market, and the presence of mycorrhizae can be verified in order to understand if there will be potential benefit to using one soil substrate over another, or one inoculant product over another. We felt very empowered when observing root cells and Ericoid fungus under the microscope for the first time.

It is one thing to observe the presence of fungus on roots, but another to confirm that the fungus is having a significant effect on fruit yields or plant vigor. 2013 will be all about refining methods, so systematic quantification of benefits can be done in 2014.

Another project outcome for 2012 was arriving at an accurate assessment of the actual costs of inoculating a commercial blueberry planting with Ericoid mycorrhizae. There are many costs associated with establishing a blueberry field, and high up front cost is a significant barrier. Last thing growers need is another cost added. Having an accurate assessment on the costs will help us weigh the benefits, in order to determine if the practice is worth adopting long term

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