Using Actively Aerated Compost Tea in Organic Vegetable and Fruit Production

Final report for FNC20-1206

Project Type: Farmer/Rancher
Funds awarded in 2020: $17,262.00
Projected End Date: 12/31/2022
Grant Recipient: Old Plank Farm
Region: North Central
State: Wisconsin
Project Coordinator:
Stephanie J. Bartel
Old Plank Farm LLC
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Project Information

Description of operation:

Old Plank Farm is a small-scale diversified vegetable farm dedicated, since 2009, to growing high quality produce for members of a Community Supported Agriculture (CSA) program. Our produce is grown using sustainable practices, and our harvests are used to create mixed boxes of vegetables each week for each CSA customer during our 20-week season. Our current scale of operation includes approximately 15 acres of vegetables, serving a 400-member CSA. Sustainable practices already in place at Old Plank Farm include fertilizing with compost and cover-cropping.

Pigeon River Orchard is a small family owned and operated apple orchard within the city limits of Sheboygan, WI. The orchard is on approximately two acres of land. Apple varieties grown include: Honeycrisp, Cortland, MacIntosh, Zestar, Sweet 16, Liberty, Initial, Red Free, Wolf River, Sansa, Snow Sweet, Winecrisp, Evercrisp, Cox Pippin, Rubinette, Paula Red, Pittman’s Pineapple, Red Delicious. Pigeon River Orchard employs integrated pest management practices on an as needed basis. A small half-acre section of land on the north side of the orchard has been in experimental organic growing methods for about 5 years. Our compost tea research was done within this section of orchard.


Potentially harmful organic fertilizer and pesticide products are on the rise. Water-soluble fertilizers, such as OMRI-approved Chilean Nitrate, can end up leached into water systems just as easily as synthetic fertilizers. Organic pesticides often harm beneficial pollinators, according to Xerces Society studies. Dependence on these products undermine a farm’s ecological sustainability.

One alternative may be Actively Aerated Compost Tea (AACT). AACT is a biological soil inoculant produced by extracting microbes from compost containing a healthy soil foodweb. It can double yields, deter pests and eliminate diseases...or it can destroy entire crops; the line between these outcomes depends on the skills of the AACT producer. The problem is making effective AACT requires more skills than most farmers possess. 

I propose to make AACT with the help of soil biology consultants. My objective is to show that properly-made AACT can be a cost-competitive, ecologically-sound alternative to organic fertilizers and pesticides. This project will compare net profits of vegetables and fruits grown using AACT and those grown using organic fertilizers and pesticides. My second objective is to complete training in soil biology, biological compost production, and AACT production, and to share my skills with farmers in the Midwest region.

Project Objectives:
  1. Make effective AACT with the help of lab testing and working with certified consultants and compost products that follow Dr. Ingham's healthy soil food web parameters.
  2. Compare net profits of crops grown using AACT and crops grown using organic fertilizers and pesticides. 
  3. Complete Soil Food Web Courses; use skills to make AACT without off-farm testing, consulting or compost resources.
  4. Share results and methods with local farmers. My long-term objective is to complete a Soil Food Web consultant training program. Further investigation could look at other positive effects of AACT (ie reduced irrigation needs, food quality).


Click linked name(s) to expand/collapse or show everyone's info
  • Kristin Plucar - Producer


Materials and methods:

At Old Plank Farm, we will plant test plots of the following vegetables: cabbage, tomatoes, peppers, melons, and potatoes. Half of each crop will be treated with AACT and the other half with Sustane, a bagged organic fertilizer product. I chose these vegetables for their variety of growth habits, and because each has responded well to using Sustane in the last two seasons. This trial is a small sample of the variety we grow; the planting sizes are planned based on our current scale of operation.  

  1. Cabbage (variety “Storage No. 4”) 2400’ bed-feet, 2 rows/bed spaced 24” within each row; approx 2400 transplants (4 beds in our field).
  2. Tomatoes (varieties Marianna paste, Sungold cherry, and Big Beef hybrid slicer) 2400’ bed-feet, 1 row/bed spaced 36” apart within row; approx 800 transplants (4 beds). 
  3. Peppers (variety Revolution) 2400’ bed-feet, 2 rows/bed spaced 24” within each row; approx 2400 transplants (4 beds)
  4. Melons (variety Halona) 2400’ bed-feet, 1 row/bed spaced 2 plants every 4’; approx. 1200 plants (4 beds)
  5. Potatoes (variety Satina Golds) 4800’ bed feet, 1 row/bed spaced 1 seed potato every 1’; 480 lbs seed potato (8 beds)

24 beds (of our 120 total vegetable beds), or approximately 2.5 acres will be used as our test plot. 

At Pigeon River Orchard, our apple test plot will be approximately ½ acre of trees that have been in organic production for one season. Half the plot will be treated with Neem oil when pest management is needed. The other half will be treated with AACT.

Initial application rates of AACT will be planned at 40 gallons per acre. We may adjust the volume depending on the recommendations from Harrington Organics soil consultants based on our soil test results, and on the outcome of each spray.

Research results and discussion:

Old Plank Farm 2022 Research Summary by Stephanie Bartel

SARE 2022 research log - Sheet1-4

The above spreadsheet (pdf) has the project data summary including yields and cost data. Below is a brief discussion of these results:

We tracked our fertilization methods/costs and our harvest records for five (out of thirty five) of the major crops grown at Old Plank Farm: Cabbage, Tomatoes, Peppers, Melons, and Potatoes. Unfortunately, our potato crop was destroyed by potato beetles in early growth stages. Neither compost tea nor Sustane fertilizer helped the crop to grow out of the pest invasion. Based on my studies from Dr. Elaine, compost tea has the potential to ward off pest damage such as this, but a more rigorous spraying routine would have been needed, and a more fungal dominated tea would have been needed to be brewed. Despite using the recommended recipe of Dr. Elaine for a fungal tea, we still tended to see bacterial dominance when analyzing our tea under the microscope. Even so, some fungal presence was noted, and we used most of the brews that we made this season.

Our results show that the yields were lower for all crops treated with compost tea than for those treated with Sustane. However, the cost of compost tea is also lower, so that the final results indicate a higher profit margin for the compost tea test plots. In short, our results show that compost tea can be more financially viable than crops treated with bagged fertilizer. 

These results are the efforts of our experiments in the 2022 growing season. This was my first research project, and I feel that I overlooked some variables that should also be considered before drawing firm conclusions from my work. For instance, if lower yields accompany compost tea, the cost of land/space is increased. This alters the whole financial picture, perhaps only slightly, but enough that a farmer may need to consider it before committing to switching from bagged fertilizer to compost tea. Finally, I only calculated the cost of the tea brews that we used. The learning process (aka associated failures!) took time and money too. And while I hope that studying some of my work (or asking me questions) can speed up the trial and error process for other farmers, it cannot take the place of each individual's responsibility for learning the process for themselves. Compost tea will not be as easy to use as opening a bag of fertilizer, until some start-up work has been achieved.




COMPOST TEA Research Year 1 Progress Summary by Kristin Plucar

MAY – AUGUST 2020 


North Orchard/Row 3 

80 ft row. 

12 Zestar planted approximately 2 feet apart (south side) 

17 MacIntosh planted approximately 2 feet apart (north side) 

North Orchard/Row 4 

12 Zestar planted approximately 2 feet apart (south side) 

17 Evercrisp planted approximately 2 feet apart (north side) 

Rows are planted 12 feet apart and run north to south.  


  1. May 11, 2020 
    • Soil inoculation with compost extraction 
    • 3 gallons of extraction per row 
    • 1 ½ cups of extraction applied to the base of each tree 
    • Notes: soil was somewhat cold and dry when compost extraction was applied, and it  froze that evening, which could have compromised the effectiveness. 
  2. May 15, 2020 
    • Foliar application with brewed compost tea 
    • 3 gallons of tea per row 
    • Spray application (sprayed trunk and leaves of tree as evenly as possible) 
  1. June 19, 2020 
    • Foliar application with brewed compost tea 
    • 3 gallons of tea per row 
    • Spray application (sprayed trunk and leaves of tree as evenly as possible)
    • Notes: Sprayer clogged a number of times during this foliar application, and tea may  have weakened due to the time taken to unclog the sprayer. 

    4. July 1, 2020 

    • Foliar application with brewed compost tea 
    • 5 gallons of tea per row 
    • Spray application (sprayed trunk and leaves of tree as evenly as possible) 

YIELDS, August: 

Zestar: No noteworthy yields  

Evercrisp: 6 bushels total (consistent with Evercrisp not treated with compost tea) MacIntosh: 1.5 bushels total (consistent with MacIntosh not treated with compost tea) 


It is difficult to make a general assessment of the compost tea’s effectiveness in one season. Overall, the  Zestar apples in both test rows did not produce much fruit, due to lack of blossom pollination in 2020  and overproduction in 2019, leading to underproduction in 2020. Compost tea would have had no impact on either of these two factors.  

The Evercrisp and MacIntosh apples in both test rows did produce well, and the trees looked healthy.  There was some evidence of apple scab (a fungus) that could have been influenced by the compost tea,  but there is no marked difference in the amount of scab between the test rows and the rest of the trees  in the orchard.  

There was not much observational difference between the compost tea test rows of trees and the rest  of the north orchard. As with other perennial crops, it would be interesting to see the effects of regular  use of compost tea over the course of more than one growing season. 

Participation Summary
2 Farmers participating in research

Educational & Outreach Activities

3 Consultations
1 Curricula, factsheets or educational tools
1 On-farm demonstrations
2 Tours
1 Workshop field days

Participation Summary:

17 Farmers participated
2 Ag professionals participated
Education/outreach description:

2020  update: We have not yet begun education and outreach related to our project. We canceled the field day at Pigeon River Orchard because the owner was uncomfortable having a tour during the pandemic. An Old Plank Farm field day (and related outreach material) will be held in 2021, and a AACT brewers guide compiled from Stephanie's soil microbiology course will be made available at the end of our project. 

2022  update: We hosted an on-farm field day at Old Plank Farm towards the end of our season working with AACT. This event included microscope and compost extraction demonstrations, project overview and discussion, lots of question and answer time, and a field tour. While we did not receive any press coverage for our fairly small event, I was able to circulate an invitation to the event in the months leading up to it through our farm's weekly newsletter. Over 1000 subscribers received this information via our newsletter. Subscribers include farm customers, members, employees, other neighboring farmers, and the general public. 

Field day participants looking through the microscope to spot soil biology up close! Stephanie demonstrating a compost extraction using the five-gallon bucket method scaled most appropriately for home gardeners Stephanie Bartel, project leader, leading discussion at Old Plank Farm's field day, Sept 3, 2022.

A summary of this project report and related fact sheets was sent to those participants who requested it by leaving their email at our field day. A briefer summary of our work (and continuing work in the coming seasons) will be sent in our weekly newsletter as it relates to current events on the farm.

We found that many participants of our field day were home gardeners. Although our work was done on a larger scale than a home gardener, I found that the general discussion and questions were still relevant to our work. 

We also hosted one additional field tour, at the request of another small group of farmers in our area who were interested in learning about compost tea and seeing our farm. I found this informal (unpublicized) tour/discussion was very productive because of the small group size. The three farmers were inspired by the methods I described and the crops growing in our fields, and they asked if I would be a consultant for their start-up operation. While I'm not able to do this yet (I'd like to see more reliable results before I start advising others at on-site meetings!), I appreciated their enthusiasm for my work. Two of my employees at the farm (not involved in this project but aware of what we were doing), reiterated that my knowledge and expertise would serve others well if I'd do consulting work related to compost tea. It is definitely a consideration for the future.

Learning Outcomes

12 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Lessons Learned:


Pre Brew Checklist

Post Brew Spraying Checklist-2


Based on the educational training I received from Dr. Elaine through this grant, I have a more complete understanding of soil microbiology. I feel that as a result of the grant work and related coursework, I can better comprehend the use of compost tea, and I can troubleshoot the many problems involved in working with the microscopic world (Brewer's checklists that I created are attached above), but I am not an expert on using the theories I have learned...yet. This was one of the major disadvantages of my project; to conduct a more conclusive experiment, I would have first needed to master the art of making and applying compost tea. Instead, I tried to conduct an experiment while still learning the nuts and bolts of the methods I was trialing. I found that I spent a tremendous amount of time just learning the material and the basics of working with compost tea; much more than I budgeted for or anticipated. 


Soil Food Web School - FC Certificate

2021: No work was done on the Old Plank Farm field trials due to labor shortages during critical times of the project. However, all of the coursework from Dr. Elaine's 4 Foundation Courses has been completed. I, Stephanie, participated in 65 lectures pertaining to the background of soil microbiology, making compost that breeds the specific microbiology needed for growing healthy fruits and vegetables, making compost teas, and using a microscope to analyze the work being done with compost and teas. I passed all four courses with grades of 93% or better. I had read a lot about this subject in past years, but completing the courses with Dr. Elaine gave me a deeper understanding of how to successfully use compost teas. Therefore, we will be completing our trials on our farm during the 2022 season.



The start of our project aligning with the beginning of the coronavirus pandemic made for a rocky beginning. Although I had a couple years’ experience working with compost tea on a small scale, I initially felt under qualified to take on a scientific endeavour involving breeding bacteria in a newly-germ-focused world. Could there be risks about the microbe world that I didn’t understand? After some additional research and discussion, we decided that breeding soil microbiology would not include any risk in breeding the virus as well, although you can be sure we washed our hands and wore gloves while working with our tea, which is good practice in any circumstances!

So, other than canceling field days, we decided to proceed with our work. We ordered our supplies and took initial soil samples. Results showed that breeding beneficial fungi would be our primary goal in making high-quality tea. We had a late (cold) start to spring planting, but generally got our crops in the ground on schedule. Our new 100-gallon brewer was late to arrive due to shipping/lock-down delays at the manufacturer, but we were able to work with my smaller (5-gallon) brewer to get started making tea for the apple orchard test plot. The brewer manufacturer, Earthfort, sent us recommended recipes for use in their brewer, and that is what we started making in late spring. The first few batches were a flop. The compost bag, meant to contain the material through the duration of the brew, broke open on the first run, clogging the brewer and spoiling the batch. After that we switched to using two paint-strainer bags, rigged up to float at the top of the brewer, and had less clogging problems. 

Other than a poor-quality bag, we are pleased with the potential of the brewer. It aerates the water sufficiently, and is easy to clean. Scaling up AACT production proved to be the biggest challenge and the reason we have decided to repeat our trial plots in 2021. This in itself was our most valuable lesson from our first year of working on our grant. I spent many months and many failed batches of tea when I was first working with our 5-gallon brewer (in past years); I had assumed this experience would speed up the process when I scaled to 100-gallons for our grant project, but it didn’t very much. Brewing AACT requires precision and discipline, and learning to work with it on a scale that will ultimately be effective on your scale of production is important. (In other words, just because you manage to make good tea on a small scale, don’t assume you will be successful right away when you try to make enough for your larger fields! Different equipment can yield a very different product). 

Problems related to larger scale production included:

1. Temperature and timing of the brews are more challenging because we couldn’t bring the brewer inside to stabilize the brew more easily and it was in the sun too much initially, when we were also having high-80-degree days in early June;

2. precisely measured recipe ingredients (which are not directly proportional to water volume);

3. electrical issues stalling the brew (bigger aeration pump draws more electricity, so don’t put it on the same circuit as the one with the folks camping at your farm and cooking in their RVs!); and 4. clogged spraying equipment from compost escaping the brew bag. 

Therefore we decided to give up on the vegetable trial because we felt that the results would neither prove nor disprove what we set out to learn, which is whether or not a crop managed using well-made AACT could be more profitable than when managed using organic, water-soluble fertilizer.

Over the winter I enrolled in Dr. Elaine Ingham’s soil microbiology courses and am more excited to renew our work in the field in 2021. We also expect to be able to host a field day to share compost-making techniques as well as our field trials. After this season, I plan to compile the results of our 2021 grant experiments as well as fact-sheets and AACT-making checklists for reference guides--based on the microbiology course material--that farmers can use to start making their own tea.

Project Outcomes

1 Farmers changed or adopted a practice
1 New working collaboration
Success stories:

Although I cannot lay claim to immediately changing another farmer's methods as a result of my work, I do believe that the introduction to my work that other farmers and gardeners received may benefit their growing practices in the coming seasons. We held our field day in September, and it is my hope that some of the participants will experiment with compost tea in their gardens next season. Although I could not present a complete understanding of making and using compost tea in just one day, my intent was to introduce people to the subject so that they can learn more about it on their own. Most importantly, dispelling myths around compost tea was a large part of our discussion, because it is a subject that is so easily misunderstood and misused (making sure people don't soak manure in water and put that on their vegetables was one of my goals!). I think that the sustainability of compost tea over bagged fertilizer is more valuable than the financial difference, although that is not something I could prove within the scope of this project.

As for my own changing practices, I plan to continue to use compost tea again next season, now that I've had several years to experiment with it. This project gave me enough of an introduction to soil biology that I can see it is worth studying/applying further. All of Dr. Elaine Ingham's lectures and coursework that I completed made a lot of sense in terms of long-term sustainability for soils, farms, and farmers. My short-term work was just the beginning of what I'm able to do, simply because her methods are very technical and detail-oriented, and take a lot of practice. One of my employees helping on the project stated, wisely, that "making compost tea is like making sourdough bread: it can go wrong in so many ways that aren't obvious to a beginner, but once you get good at it, it's a reliable and relatively easy thing to do, which yields uniform results every time!" This is more than just a fun analogy, it's true: both bread-baking and compost-tea-making involve working with the microbes found in nature. Its success is an art as much as it is a science.


According to case studies done by Dr. Elaine, she has proven very significant increased yields and profits from using compost tea instead of other fertilization methods. I did not achieve as good of results as her in my first attempts during this project, but I did find that our results pointed us in the right direction; we did not lose money by using compost tea. Therefore, I plan to continue studying her work and using her methods on our farm. This research opportunity provided by SARE has been an influential part of my farm's quest for using more sustainable farming practices. I'm grateful for the support throughout this project.

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.