Investigating the Use of Compost Tea for Rapid Restoration of Soil Ecology on Four Indiana Farms

Final Report for FNC03-476

Project Type: Farmer/Rancher
Funds awarded in 2003: $17,959.00
Projected End Date: 12/31/2005
Matching Non-Federal Funds: $17,582.00
Region: North Central
State: Indiana
Project Coordinator:
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Project Information


Throughout the North-Central Region degradation of the soil from years of tilling and the use of pesticides and salt-based fertilizers has contributed to soil erosion, degraded water quality, and decreased nutrient cycling due to an impaired soil ecology. These problems continue unabated today. Restoring soil health can take many years and often many variables and costs are faced before attaining success. The use of compost tea as a method of restoring soil health and for foliar health is a promising strategy, but is new and mostly unknown among Midwestern farmers.

Four different Indiana farms, all part of the Wabash River Drainage Basin, investigated the use and effectiveness of aerobic compost tea for soil health restoration. Each farm is different in terms of the type of crops being grown. Farm one concentrated on commercial scale corn and soybean production, farm two on forage crop production, farm three on prairie and pasture restoration in a sensitive ecological area, and farm four on vegetable and orchard production. The study treatments were 1) use of aerobic compost tea vs. 2) water only – control. All four farms have a land history of conventional pesticide and fertilizer use, but are transitioning to organic techniques of management. Baseline comparison sites were also established for conventional no-till beans, native tall-grass prairie restoration, organic cropland, and long-term organically managed pasture near the four farms in this study.

Our main objective was to quickly improve and maintain soil health using sustainable, cost effective methods. Good quality compost is widely known to improve soil quality and health, as is cover cropping with deep rooted plants. However, the use of compost on a farm scale is a large investment of funds and locating a large enough supply to cover a field is an additional barrier to this approach. In recent years comments from some potato, grape, and strawberry producers in Western States, along with a growing number of gardeners, golf managers, horticulturalists and others extol the virtues of aerobic compost tea for improving soil and plant health.

There is scientific evidence for a robust soil food web producing self-sustaining nutrient cycles and high biomass in native prairie and old growth forests. There is also strong evidence that this soil food web profile of organisms can be successfully extracted from compost into water and allowed to reproduce in an aerobic environment, thus greatly reducing the amount of compost necessary for soil application of the same number of organisms. Therefore, we chose to focus our efforts on investigating the efficacy and impact of using aerated compost tea on our own fields. Furthermore, we could not identify any scientific reports on agricultural fields after using compost tea, and no evidence of compost tea being applied on a farm scale in the Midwest. We decided our idea would be a good candidate for a SARE producer project.
Aerobic compost tea, made at the level of compost tea standards, contains many of the soil micro-biota necessary for a functioning soil system. If the use of compost tea can be shown to be effective at quickly restoring soil health, and the transition to adapting to and using compost tea is cost effective, then this may lead to a wider adoption among farmers. Restoration of soil health may then result in decreased reliance on pesticides and fertilizers, thus leading to a more sustainable farming system.

Compost tea standards and expert recommendations were closely followed for brewing of tea and for application rates to fields. We hired an expert compost tea consultant to help train up in the making and application of compost tea. Baseline tests determined the soil in all plots to be lacking in beneficial fungi. Recipes for producing fungal dominated compost tea were made and thoroughly tested for quality and biological parameters to ensure we were applying high numbers of beneficial fungi and other soil organisms. Our test results show that we applied good to excellent levels of beneficial bacteria and fungi to the soil (see Appendix Table 1). Extracting larger soil organisms such as protozoa and beneficial nematodes has proven very difficult and inconsistent. With careful observation and changes in the recipe for the compost tea we were able to achieve fungal dominated teas with excellent numbers of organisms.

Using typical tank sprayers free of residues, the aerobic compost tea was immediately applied following the 24 hour brewing process at a 20 gallon per acre rate as a soil drench in fall and spring. The spraying protocol was to use low pressure and flood spray tips with screens removed to ensure survival of the living organisms in the tea solution. This rate of application was recommended by soil food web experts for quick restoration of the soil ecology. Following the baseline soil samples, tea was applied the first fall and then the following spring, and then repeated again for a total of four applications per treated plot during the study duration.

Simple strip-plot design with two plots and one treatment per plot (Aerobic Compost Tea vs. Control Water) with three replicates for each treatment were established on each participating farm. Soil samples were taken within a 40’ x 90’ square within each replicate and ten core sub-samples were mixed for each replicate. Baselines soil samples were taken in September 2003 and analyzed for soil food web indicators (Active and Total Bacteria and Fungi, Protozoa, Nematodes, and Mycorrhizal Root Colonization) at the Soil Food Web New York lab along with standard soil chemistry parameters. Soil health indicators of soil moisture, soil temperature, earthworm counts, water infiltration rates, soil compaction, and plant cover were measured using USDA and Purdue Extension methods. This protocol was repeated again exactly two years later in September of 2005, after the four applications of compost tea had been completed.

This was a multiple producer SARE project with four producers and one Extension specialist involved. The producers include Jim Tarnowski and Judy Berkshire, Dana Goodman, Jim Thompson, Michelle Conyer and Mark Trela. Brent Ladd is an Extension specialist with Purdue University and helped coordinate the project along with soil sampling and data analysis.

There were no significant effects on soil health indicators or soil food web organisms from the application of aerobic compost tea (see tables 2-5 in the Appendix). However, there were significant changes for several parameters of soil health and organisms when comparing all plots between the baseline samples of 2003 and the ending results from 2005 (see tables 6-10, Appendix). This result is even more surprising given that soil moisture levels were considerably lower and soil temperatures higher during the 2005 sampling. Baseline data from 2003 showed that all field plots were lacking in beneficial levels of fungi. Both beneficial and fungal properties of the soil greatly improved during the two year study. In addition, aggregate stability, infiltration rates, and cation exchange capacity of the soil all significantly increased when comparing baseline results from 2003 with final results in 2005. We believe this positive result is due to the increased attention we each gave to soil health by reducing or eliminating tillage and salt-based fertilizers and pesticides, while increasing cover cropping and the time that the soil had living plants growing.

The soil food web analysis helped to validate our good soil practices and this was a benefit. Also, the observation of the earthworm counts, water infiltration rate, compaction testing, and other soil health tests were valuable for raising our awareness. The study reinforced that living plants in the soil at all times is very important. For some of us, we came full circle back to our original intuitions about soil and Mother Nature. Using our own native understandings of our soil and the ecology of the farms we inhabit we feel better equipped with knowledge and awareness to continue using good soil building practices and our own observations.

One of us was already purchasing microbes to apply to the soil and was glad to learn how to brew compost tea in place of the purchased microbes. Learning how to accurately calibrate a sprayer and apply the tea at recommended rates was also something most of us learned.

We learned a lot from one another in this study. The interchange of problems and solution, and different approaches informed each one of us in how we approach our own land. Many of us have discontinued tilling the fields and gardens form the knowledge we gained out of this study.

Outside of the study plots a few of us were applying much higher rates of compost tea to other plants and did see noticeable benefits. In one case, fire-blight problems in an orchard were brought under control with the use of foliar spraying. In another case, tomato starts were watered with compost tea and other were not. The compost tea fed tomatoes were much healthier and larger. It may be that we need to apply a much higher per acre rate of the compost tea to see soil benefits. Some of us feel there may be usefulness of the compost tea for foliar feeding and disease protection, but doubtful about its usefulness as a soil application.

Disadvantages of the compost tea brewing are that it is expensive, takes considerable time and knowledge to brew decent teas, cleaning the brewer is a pain, and often the brew overflows or the equipment malfunctions. Tea brewing required a lot of baby sitting for the 24 hours it is brewing. Brewing the tea is more of an art than a science. The learning curve is very steep.

Furthermore, in order to apply the tea, we had to make trial and error adjustments to spraying equipment, and had many problems with clogging of screens and filters. Great care has to be taken to get the tea with living organisms applied. The tea needs to be applied during cooler periods of morning or evening in summer, and just previous to rainfall. Another disadvantage in terms of soil health is that a tractor and sprayer must be driven over the field for each application and this adds to compaction of the soil.

Although the soil food web analyses are insightful, they are also very expensive – over $200 per test. This is prohibitively costly for anyone on a farm scale.

In speaking with soil microbiology researcher, Rhodale farms, and others around the county investigating compost tea using scientific methods, none of them have found any clear benefits from soil or foliar uses. Some results have even showed negative impacts on plants. This is perplexing given the exponential growth in compost tea use around the country, the number of companies selling compost tea makers and equipment, and the increasing number of expert speakers on the benefits of compost tea at national organic tea among soil ecologists researching the soil food web. There is clear evidence that the biodiversity of organisms in the soil is critical for full soil function and health, but so far no one has corroborated that the use of compost tea is effective in aiding the soil. Some of us find it troubling that the leading researcher and proponent of compost tea in the world has not published any peer reviewed and scientifically verified data supporting the claims that compost tea is effective. Some of us feel this begs the question: Is compost tea a magic elixir or simply snake oil? A lot of money is being made in the compost tea industry today.

In conclusion we would advise other producers to trust in their own native soil observations and their intuitions about soil health. Rely on the tried and true methods of building soil health including: greatly reduce or eliminate tillage, especially deep tillage, eliminate pesticide use and salt-based fertilizer use. Employ the use of diverse cover cropping systems such that you always have a living crop in the soil. Use diverse crop rotations, and have animals as part of the system. Get to know other producers in you area or region who are trying to improve soil health and exchange knowledge with them. We also advise producers to thoroughly investigate compost tea before investing money and time in this process. We advise this because we can find no credible scientific verification for the benefits of compost tea, and our own study found no impact on the soil health from the use of the compost tea. A further step with investigating compost tea will be to observe results form using various application rates of much greater quantities than we did in our study.

Unfortunately our results show there were no effects on soil health due to the compost tea treatments. Therefore we feel there may be a negative economic impact because brewing and applying compost tea was expensive and very time consuming. We did find that our other soil health practices of reducing or eliminating tillage and artificial fertilizers and pesticides, while increasing cover cropping have been the most likely reason for improved soil. In some cases there were significant changes in soil health in just the short time period of two years. There are of course many other studies and practical observations from farmers and ranchers showing these conservation practices to be of benefit. This study did raise our awareness of the complexity and great value of healthy soil, so this directly impacts the environment on our farms. We feel there were beneficial social impacts from the two years of getting to know each other, our unique approaches and knowledge of soil practices that we exchanged with each other.

A more extensive and longer study of compost tea may be necessary in order to understand if it is beneficial for soil restoration. Soil food web analysis is very expensive and our study attempted to maximize the number of samples analyzed. However, a more thorough analysis of compost tea for soil restoration will require extensive funding and time. Due to the large body of anecdotal evidence that compost tea is beneficial, it would be worthwhile to investigate this potential tool further. Given that no peer reviewed studies have been published on the effectiveness of compost tea for soil, our study is a unique contribution. A more extensive controlled study is needed to make any strong conclusions about the usefulness of compost tea for sustainable agriculture.

We held a field day for farmers, gardeners, and conservation specialists on soil health. Presentations were made about the significance of soil food web, and in the field demonstrations and hand-on activities took place for all participants on learning how to measure and observe soil health indicators. Participants could also view and ask questions about compost tea, brewing the tea, and application. There were thirty people in attendance at the field day.

We designed a project poster for display in Extension offices, libraries, and for the field day. We also designed a web site to describe the project and our results. The web site is located at Final results not yet reported on the web site.

Media outreach included stories in local newspapers, and this generated some additional interest.

Some of us feel that administrative duties on this grant have made us reconsider ever being involved in a SARE project again. We feel the SARE program is important for small producers, but we have the following recommendations for improving your program:

1. Spread the tax burden among all participants for the multiple producer projects. Placing all the burden on one individual is unfair. Better yet, make these funds receivable as tax free.
2. The timing on the funding and release of funds is troublesome. We really needed most of the funding up front to really do the things needed in this project, instead of getting only half of the funds. Also, the program would do well to release funds in January so that producers can further plan and prepare to start in the spring rather than waiting until September or October for the funds.
3. Make the budget process much more flexible. It is very difficult to project so precisely the costs and needs of the project up front. Allow more flexibility for producers to choose and make decisions about how the funds are allocated. Reduce the required amount of match.
4. Allow 100% reimbursement on specialized equipment integral to the project. For instance our tea makers were expensive and we are only using them for this study, but the grant only paid 40% of this.
5. No one from SARE ever made a site visit. We prepared and were ready, and even held a field day and were told that we would receive a visit. This would be important for SARE program to visit first hand.
6. We had difficulty in getting cooperation from other USDA and Land Grant offices locally. For instance they refused to display our project poster and information. If the Central SARE office could make personal phone calls to the USDA county service centers and Extension agents in the counties where the SARE projects are taking place this could encourage them to be more open and cooperative.


Participation Summary
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.