Comparing Compost Tea and Compost Extract Impact on Microbiology

Progress report for ONC22-100

Project Type: Partnership
Funds awarded in 2022: $26,159.00
Projected End Date: 03/31/2024
Grant Recipient: Minnesota Soil Health Coalition
Region: North Central
State: Minnesota
Project Coordinator:
Mark Gutierrez
Minnesota Soil Health Coalition
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Project Information


This project will measure and compare the soil health changes from the use of compost extract and compost tea in a soil health system.  One of the advantages to a soil health system is that as the soil biology improves and organic matter is rebuilt this can lead to a reduction of synthetic pesticides and fertilizers needed which can increase a farmer’s profit per acre.  There are a lot of products on the market that will help stimulate and feed the microbiology in soil.  Many of these products promise improvements to the crop.  If a farmer reduces synthetics as a result of their soil health system, but then trades one dependency for another by purchasing commercial biology stimulators, profit per acre is impacted which can reduce the incentive for a soil health system. 

This research will demonstrate that a compost extract or a compost tea is effective in stimulating the biology in the soil and it is a product farmers can create and manage on their farm at a low cost.  This project will target Minnesota crop farmers and demonstrate a low cost solution to improving soil biology.

Project Objectives:
  • Measure and compare soil health changes from 24 hour compost tea in different crop systems (regeneratively farmed hemp, corn, alfalfa, and conventional corn)
  • Measure and compare soil health changes from compost extract
  • Educate about the construction, costs and benefits of homemade compost tea and compost extract
  • Empower farmers to produce their own soil biology stimulants
  • Educate farmers with practical tools to positively transform the environment and local food production using soil science and regenerative agriculture
  • Share results with other farmers through our member newsletter, website, YouTube and a field day


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Materials and methods:

For parent materials in the compost.  We used a variety of plant resources from right on the farm.  High-carbon/brown material component consists mainly of aged wood chips.  They are ramial chips from pasture land made from cleared brush and ran through a chipper mounted on the 3-point hitch of a tractor.  A lot of it is buckthorn, prickly ash, and small tree limbs.    The piles are aged so they have started to break down and have an active fungal component already present.  If  leaves are available they will be mixed in for diversity.  

Green material might consist of grass-hay bales, fresh-cut meadow, or a mix of grass-hay bedding and chicken manure.  

High nitrogen materials usually consist of a bale of really nice, green, leafy alfalfa hay and chicken manure.  There is also some horse manure, which with alfalfa as the primary way to heat up the pile.

Following Dr. Elaine Ingham's Soil Food Web method for management of the compost.  Ratios are approximately 50-60% brown/high carbon material, 30% green/grassy, and 10-20% high nitrogen.  Total quantity of materials for each batch is approximately 40 to 50 five-gallon buckets-worth.  Parent materials are well incorporated and hydrated to about 50% moisture, then piled into a chicken-wire container.  We have a compost thermometer and  closely monitor temperature.  We made about six or seven complete batches last year, and by the end the piles consistently reached 150-160 degrees within 24 hours, never letting the piles exceed 175 degrees.  Piles are turned twice, by hand with manure forks and shovels.  Time between turns depends on where the internal temperature tops out, but can range from 24 hours to 72 hours typically.  The goal is to get everything into the hot center of the pile one time, so when we turn the pile it's a very intentional process, not just stirring everything up.  Middle goes to the bottom, top goes to the middle, and bottom goes to the top.  After the second turn, temperature continues to be monitored, with the goal of over 130 degrees and holds there for a couple of days.  After that, the pile is left to cool down and mellow out for about 30 days.  

For the corn, we brewed up a batch of extract using about 10lbs of compost to 200 gallons of water, and applied that in-furrow with the corn at a rate of 5 gallons per acre.  In retrospect, we believe that was too light of an application - both with the amount of compost used in the brew, and with the liquid application rate.  Overall, the corn with the extract actually got taller than the part of the field that received no extract, especially on a clay hill with low organic matter.  Mike dug up half a dozen of each plant and sprayed off their roots, to assess the morphology.  There was no observable difference in root mass between the plants that received the extract versus those that didn't.  

Our main corn crop is a 94-day Brevant Roundup Ready hybrid and a couple of acres of a 94 day non-GMO workhorse variety from Albert Lea seed.  We did a compost application and control area for each type, so we can compare both the treated and untreated areas of the GMO and non-GMO varieties.  Everything received the same fertilizer program.  In total, we had a 16 acre field that we treated half with extract and half without and we also treated another entire 8.5 acre field just because we could.

For soybeans, we brewed a stronger batch of extract - 20lbs of compost to 250 gallons of water - and we applied that with the chisel plow that I modified with thin anhydrous knives to minimize the soil disturbance.  We treated half the field with about 7 gallons per acre, and the other half was left untreated.

Mike dug up three soybean plants from each area - treated and untreated - and looked at the root morphology.  He felt that the plants from the treated area of the field had better root branching and more nodulation.  

Participation Summary
3 Farmers participating in research

Educational & Outreach Activities

2 Consultations

Participation Summary:

3 Farmers participated
3 Ag professionals participated
Education/outreach description:

We plan to host a field day to share the results at the end of the project. We will also include a summary of what we learned and distribute it though our newsletter, website and social media.  We are also hoping to post something on YouTube. 

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.