Successful composting depends on understanding the microbial life within your compost pile. This is where soil testing kits become invaluable tools for gardeners and farmers alike. Modern testing technology allows you to analyze your compost’s biological activity with scientific precision, ensuring you create nutrient-rich amendments for your soil.
Understanding Compost Biology
The foundation of excellent compost lies in its microbial ecosystem. Billions of bacteria, fungi, and other microorganisms work together to break down organic matter into valuable nutrients. These microscopic workers determine whether your compost becomes a powerhouse of plant nutrition or simply decayed organic matter with limited benefits. Bacterial populations typically dominate the early stages of composting, breaking down simple compounds like sugars and proteins. As the process continues, fungal networks develop to tackle more complex materials such as cellulose and lignin. The balance between these microbial communities directly affects the quality and effectiveness of your finished compost.
The Science of Compost Testing
Traditional methods of evaluating compost quality relied heavily on visual inspection, smell tests, and temperature monitoring. While these indicators provide useful information, they cannot reveal the true biological potential of your compost. Modern soil testing kits offer scientific analysis that goes beyond surface observations. Microbial biomass testing measures the total amount of living microorganisms in your compost sample. This measurement indicates the biological activity level and helps predict how effectively the compost will benefit your soil. The fungal-to-bacterial ratio represents another critical measurement that influences how compost affects different types of plants. Vegetables and annual crops typically prefer bacterial-dominated compost, while trees, shrubs, and perennial plants benefit from fungal-dominated amendments. Understanding these ratios helps you tailor your compost for specific garden applications.
microBIOMETER® Technology Advantages
The microBIOMETER® advanced testing platform system brings quality analysis to home composters and small-scale farmers. These tools eliminate guesswork by providing quantitative data about microbial populations in compost samples. The testing process involves extracting microorganisms from compost samples and analyzing the color intensity of the solution using specialized reagents, measurement cards, and the microBIOMETER® app. Results appear within minutes, allowing you to make immediate adjustments to your composting process if needed. This standardized approach ensures reliable results that you can track over time to monitor improvements in your composting methods.
Conclusion
Regular testing throughout the composting process helps identify optimal harvest timing. Compost that appears finished may still contain high levels of bacterial activity, indicating continued decomposition. Investing in soil testing kits transforms composting from an art into a science-based practice. Understanding the microbial life in your compost empowers you to create consistently high-quality amendments that maximize plant health and soil fertility. Modern testing technology makes this level of analysis accessible to gardeners at every skill level, building confidence in composting success.
Prolific Earth Sciences is excited to announce the release of microBIOMETER® PRO. This extensive update has been three years in the making and features improved precision, increased consistency between phones, advanced nutrient metrics and sample geolocating. Please update your microBIOMETER® Reader app to 3.8.6 to access the PRO version.
What’s NEW!
• Test card. We redesigned the test card to reduce variance in results between phone models and better adjust for different lighting.
• Results. The results are now expressed as microbial biomass instead of microbial carbon.
• Moisture: We have changed the moisture assumption in our algorithm from 40% to 20% which is more in line with average soils. We also added a feature to allow users to adjust the moisture assumption to reflect soils with moisture contents closer to 10% or 30%. Moisture assumption for compost testing remains at 40%
• Geolocation: This new feature allows users to save the location where their sample was collected and perform the test at a later time while keeping the recorded sample location.
• Advanced Nutrient Metrics: As an understanding of how microbes contribute to nutrient availability increases, we have added calculated metrics to help users understand how their soil microbes are contributing to nitrogen and carbon stores in the soil. These are results extrapolated from microBIOMETER® results and the calculation and assumptions are detailed in the app informational pop-ups and our website FAQs.
• Soil and Compost: The PRO version will test both soil and compost, however, will no longer support direct testing of compost tea or extract.
With the exception of the test cards, all the supplies as well as the instructions will remain the same whether using the Classic or PRO version. The updated app will prompt you to choose a version so you can still use the classic test cards. We will also be selling Classic cards in refills for the foreseeable future. However, all new Starter Kit purchases will now be the PRO version only and contain the new test cards. For customers with ongoing trials, you may want to continue with the Classic test cards to track changes based on historical benchmarked tests.
In the updated app, we have made significant changes to units, underlying assumptions, and calculations. Therefore, we encourage users to continue with one version within a study or experiment since comparing the absolute values of the two is difficult. We have always encouraged using microBIOMETER® as a benchmark test and to focus on the changes over time. We will continue to supply the microBIOMETER® Classic test cards so that ongoing studies and trials can continue. However, we strongly recommend using the PRO version for all new testing and studies.
We would like to thank all of our customers that have given us feedback over the years. Your comments, both good and bad, have helped us improve the microBIOMETER®. Please keep sharing! And as always, we appreciate your continued support.
Bucknell University is a private liberal arts college in Lewisburg, Pennsylvania with excellent research facilities and innovative teaching. Students get the opportunity to work closely with professors in their chosen field.
Students in the Biology 203, Integrative Concepts in Biology, laboratory have a unit all about soil. The students visit the Bucknell Farm to learn about the properties of healthy soil. They then pick a location on campus to study. Students study the health of the soil in different conditions, such as soil with native flowers growing compared to soil under a tree. They measure microbial biomass, soil respiration rate, and various other soil properties to determine the overall health of the soil.
“The microBIOMETER® test allows students to quickly and easily measure microbial biomass and the relative amounts of bacteria and fungi in the soil. It is easy to use for non-experts with very quick results! We have measured huge differences in the microbial biomass at locations across Bucknell’s campus and have been surprised to have very high levels of biomass in the grassy areas, too!” – Rebekah Stevenson, Director of Core Course Laboratories – Biology Department
American BioChar Company is a Michigan-based company run by longtime green industry couple, Mark & Laurie Mann. For more than two decades, they have been researching and developing programs and products to improve soils, root conditions, and plant growth in urban, rural, and agricultural landscapes.
Over the last 3 years, they have conducted trials on blueberry farms in SW Michigan, using the microBIOMETER® and other soil-metric tests. The trials compared soils of blueberry bushes treated with their VITAL Blend soil amendment to those with untreated soil. Data was collected in the spring, summer and fall each year to demonstrate the natural ebb & flow of microbe communities in soils. Not only does the data show the steady increase of soil microbial biomass, but overall the trial sites have improved soil structure and more nutrient dense crops.
“The biggest impact we have in using the microBIOMETER® is demonstrating the successful transformation within the soil, following applications of our different biochar blended soil amendments. It provides confidence in our product and helps move the client conversation toward the biological benefits of our product. When a client is able to see and track the fungal to bacterial ratio for their soil overtime, it is very empowering.”
American BioChar is also undergoing several other trials throughout the mid-west with corn, cannabis, soybeans, and tree rhizospheres, using both their VITAL Blend and their new GRATEFUL Blend living soil. As both blends provide active and fixed carbon to soil, these trials were aimed to enhance and increase soil biology and restore nutrient density. Pre- and post- application photos can show how these products improved overall crop production.
Recently, Laurie Mann and microBIOMETER® president Laura Decker participated in Heart & Soil Magazine‘s Soil Summit discussing “How to Increase the Speed of Microbe Growth”. Click here to watch!
Gurpreet Kaur, a PhD student with the Nutrient Management Spear Program (NMSP) at Cornell University, has been working with microBIOMETER® soil testing kits to evaluate the impact of dairy manure application and field history on soil health and yield in corn fields in New York.
This project is part of a larger “New York Value of Manure Study” funded by New York Farm Viability Institute (NYFVI) and Northern New York Agricultural Development Program (NNYADP).
With support from the Toward Sustainability Foundation and microBIOMETER®, soil health assessments were done for three trials in 2023. The team selected three fields, differing in manure history from no manure history to yearly applications, and took soil samples at three different timesteps during the growing season. Among other measurements, Kaur is valuating microbial biomass and fungal to bacterial ratios using the microBIOMETER® test kit. Preliminary results obtained to date show the impact of field manure history on microbial biomass. As part of the project, several Cornell University undergraduate students are learning how to conduct the microBIOMETER® test as well.
There are many soil tests on the market so it can be difficult for farmers to ascertain whether or not they’re choosing the right one. The truth is, there are pros and cons to every soil test. Therefore it boils down to finding which ones align best with your farming goals and which are easily and readily available to you without needing to stretch your resources too much.
Since microBIOMETER® is a relatively new soil test on the market, a lot of questions are raised on how this test is different from other commonly used soil indicators such as the Haney Soil Test and PLFA test. While all three are soil biological health tests, their methodologies are very different and the tests measure different parameters.
The microBIOMETER® is an on-site soil test that measures the microbial biomass and fungal to bacterial ratio of living and dormant bacteria and fungi. The test process works by measuring the color intensity of the microbial solution created and comparing the color to the test card comparator. This patented, colorimetric analysis process is generated through our microBIOMETER® Reader App and produces results within 25 minutes of starting the testing process. Test prices range from $13.50/sample to $6.75/sample. The low cost, rapid result detection, and on-site testing of living soil are what makes this test stand out against others. The microBIOMETER® has a slightly limited scope, however, as it’s only able to measure the overall biomass of fungi and bacteria. It does not differentiate between microbial species nor does it measure any other parameters.
The Haney Soil Test is a lab test that focuses on assessing a variety of soil parameters such as pH, microbial biomass, water extractable organic carbon and nitrogen, soil respiration, and inorganic plant available nutrients such as NPK. This test uses multiple methods in order to obtain results, including the Solvita CO2 Burst test to indicate soil microbial respiration and biomass, and the use of unique soil extracts to determine organic and inorganic nutrient availability. While this test offers a large array of soil parameters, there is controversy in the science community about using the Solvita CO2 Burst test methodology as a way of accurately predicting microbial biomass. This is because the soil is dried then rewetted to trigger a release of CO2 to measure microbial activity. Drying soil decreases microbial biomass, and while rewetting it will increase biomass again, it doesn’t necessarily repopulate back to the original microbial composition. The Haney Soil test is offered at several labs throughout the country and recommendations are included with results. Generally, this lab test costs about $50/sample and takes about 3-4 weeks to receive results.
The PLFA Soil Test is a lab-based technique that analyzes phospholipid fatty acids (PLFA), which are found in the cell membranes of living organisms, to determine an estimation of living microbial biomass, fungal to bacterial ratio, and to identify the general presence or absence of microbial functional groups in bacteria, fungi, and protozoa. For this test, labs first dry the soil overnight then use multiple solvents to extract fatty acids from the sample. Then, mass spectrometry is used to identify the sample’s microbial composition based on specific PLFA biomarkers. This testing process takes a few days to complete and generally costs about $60/sample depending on the lab. It is one of the most utilized testing methods since it gained popularity in the late 80’s. Since then, it was discovered that some of the PLFA biomarkers used for identification aren’t limited to one microbial group, therefore making it difficult to determine the accuracy of some results.
The value of each of these tests is to determine a baseline assessment of your soil health. The information obtained from any of these tests will help you gain a better and more rounded understanding of what’s happening in your soil.
Kenley Mitchell, a 5th grader at Sargent Elementary School, utilized microBIOMETER® in her science fair project titled “Getting Dirty: Does Soil Affect a Dog’s Microbiome?” Kenley won first prize in her category and received the overall best project award for the San Luis Valley Regional in Alamosa, CO!
Project Abstract:
For my project, I tested a dog’s microbiome and compared it to the health of the dog’s soil. I also looked at the time the dog spends in the soil. I ran two samples. The first sample was a stool sample. The second sample was a soil sample. Both were taken at the same time. I tested dogs that are in the city vs. country dogs. I found out that farm dogs have a healthier microbiome, but city dogs have healthier soil. The farm dogs’ average microbial biomass in the soil is 221.0 ug C/g. The city dogs’ average microbial biomass in the soil is 273.4 ug C/g. Farm dogs average for F% is 20%. City dogs average for F% is 32%. Farm dogs average for B% is 80%. City dogs average for B% is 68%. The farm dogs were outside in the soil for longer periods of time. The farm dogs might be healthier due to spending more time in the soil.
Francis Lawton an 8th grader at St. Timothy School in Los Angeles, CA utilized microBIOMETER® in his science fair project titled “The Effect of Greywater on Plant Growth, Soil Microbial Biomass Carbon, and Soil Fungi to Bacteria Ratio. Francis took first prize at the fair and moved on to the Los Angeles County Science & Engineering Fair where he placed 3rd in his category of Ecology. He also received a special award from USAID (U.S. Agency for International Development). Francis then took part in the California State Science & Engineering Fair in the category of Earth & Environment (Air/Water) and placed 2nd!
Have a science fair project coming up and would like to incorporate microBIOMETER®? Please contact us!
Project Abstract:
This project was designed to find out if greywater and treated greywater can safely hydrate plants, and promote plant growth, just as well as tap water. I live in drought-prone California and it’s important to find different ways of conserving water. My experiment tested the watering of grass pots with three different types of water (independent variable): Tap water, Greywater, and Greywater treated with Activated Charcoal. Over the course of 8 weeks, I measured plant growth, soil Microbial Biomass Carbon (MBC) levels and soil Fungi to Bacteria (F:B) ratio (dependent variables). Many controlled variables ensured a valid experiment. I hypothesized that each of the water types would result in the same growth rate, soil MBC and soil F:B ratio. My hypothesis, however, was incorrect. Greywater resulted in stunted growth and spiked the F:B soil ratio so high that the pot sprouted 13 fungi heads. Tap water and Treated Greywater, however, were equally good in terms of healthy plant growth and both pots had the two best average F:B ratios closest to 1:1 (which is the best ratio for grasses). Neither of these pots produced fungi. Soil carbon levels (MBC) fluctuated for all three plants, however each plant maintained an “Excellent” level. This indicated that each water type was fine for watering grass if you don’t mind stunted grass growth and some fungi in your lawn. My experiment also proved that Activated Charcoal effectively “adsorbs” chemicals in greywater that alter a soil’s F:B ratio.
The microBIOMETER® was developed with the need in mind to deliver a device that could be manufactured very reasonably so that it could service the whole world. For over 50 years scientists have known that microbes are the best indicator of soil health. One of the common methods used for determining soil microbial biomass is the Chloroform Fumigation Extraction (CFE) test. However, being a costly lab-based test makes it an unattainable option for many. Another method that’s often used to assess soil microbial communities is microscopy. While microscopy is one of the best ways to assess soil microbes, microscopes can be expensive, are often too large and heavy to bring into the field, and are not necessarily easy to use or easily accessible for growers around the world. In 2014, Dr. Fitzpatrick began developing the microBIOMETER® to address these shortcomings.
The microBIOMETER® was designed to detect bacteria and fungi by their pigmentation on a specially designed membrane. An extraction powder was developed that contains different salts, which, combined with precise whisking, separates the microbes from the soil particles. The addition of this extraction powder also helps to precipitate the soil so that the microbes stay suspended as the soil precipitates to the bottom of the test tube.
Once the microbes are separated from the soil, they can be detected by spectrophotometry. However, like a microscope, a spectrophotometer is both expensive and too large to use in the field. The solution, in keeping with the goal of manufacturing a very cost-effective device, was to make it a lateral flow membrane. Almost all medical devices do a vertical flow, but a vertical flow has many technical problems. In a vertical flow, different types of membranes are put together and then a clamshell type device is used to press it down, but this pressure then has to be regulated. And Dr. Fitzpatrick, having worked with many clamshell devices, knew this method caused a great deal of seepage around the outside. A lateral flow, on the other hand, is more rapid than a vertical flow which allows the sample to be put on more rapidly than you can when you’re using a vertical flow device. The flatness of the device is important as well. Most other devices that are vertical have a rim around the area where the membrane is which is called a sample well. If you look down the well you cannot see the bottom because the well walls are casting a shadow. But microBIOMETER® is flat, therefore, a shadow does not pose a problem.
To perform the test, three drops are applied to the membrane in the test card. The microBIOMETER® membrane was carefully chosen so that it would not bind any of the common pigments you might find floating in soil. It only collects microbes on the surface of this membrane. The membrane also whisks away the liquid and traps the microbes on the surface. The color that it gives to the membrane can be compared to a grayscale, which tells you that the intensity of the color, not the color itself. The intensity of the color correlates with the quantity of microbes you have. Just like with the colorimeter or spectrophotometer, the intensity of the color is linearly related to the concentration of microbes. Dr. Fitzpatrick came up with this grayscale idea while thinking about a quilting secret. Quilters want to make sure they not only have different colors but have different intensities of color as well. Therefore, we’re not just measuring color but also measuring the intensity of the color.
The next step in the development was to figure out how to read the test cards. In the early version of the microBIOMETER®, a red filter with a grayscale was used, turning it monochromatic. A piece of red cellophane was put over the grayscale in the sample window and the results were determined by how dark the center was. This earlier version of microBIOMETER® is still being used by customers who are non-tech users.
At this point, the test could be read visually but it lacked precision, and data storage and tracking capability. For this, it was decided a phone app was needed. One of the barriers to lab testing in developing countries is cost, but another is infrastructure. However, cell phones are ubiquitous. If an app to read the test cards and store the data was created, soil stewards all over the world would have the ability to track soil health over time and assess their management practices while making changes in real time.
The challenge to the cell phone is that cell phones have a camera and manufacturers utilize different software. Therefore, the image viewed isn’t raw and overcoming the differences between various phones becomes necessary. The microBIOMETER® does that with the monochromatic grayscale backing. This in essence “tricks” all phones to be in the same range in their software and white balance. The issue of different color temperatures was also encountered. When you’re out in the sun on a cloudy day or you’re in the shade on a sunny day that light is extremely blue. When you’re sitting in your living room and you have a 60-watt light bulb, that light is yellow/red. And if you’re at the office with a fluorescent light that light turns out to be white -where red, green, and blue are all equal. Therefore, accounting for differences not only in cell phones but in ambient lighting conditions became important as well.
This stage of test development consisted of vigorous testing and a good amount of trial and error. The process involved running around with a test card from light source to light source with five or six different phones making sure the readings were consistent. By utilizing the camera’s flash in conjunction with a monochromatic backing, the images between phones became uniform. Once the patented algorithm that compensated for differences in light color and intensity and phone software was finalized, in 2018, the microBIOMETER® was released to market.
A few years later, in 2020, Dr. Fitzpatrick and Dr. Trexler tossed around the idea of adding another soil test to the microBIOMETER® platform; the fungal to bacterial ratio. During one of these discussions, Dr. Trexler inquired if there was a way to use size to differentiate bacteria and fungi. As a microbiologist, Dr. Fitzpatrick knew that bacteria are much smaller than fungi and therefore could be differentiated based on size. Dr. Trexler then wrote software that could detect and pick out the bacteria and fungi. It was discovered that when looking at a fungal to bacterial ratio on the microscope, a slight change in the color was evident; fungi are a very, very slightly different color than bacteria. There was a correlation between the color of the sample and the fungal to bacterial ratio that was detected microscopically, which turned out to be a groundbreaking discovery. After trying various methods for determining the fungal to bacterial ratio by color, it turned out cell phone cameras had the ability to pick up the difference. This discovery led to the fungal to bacterial ratio data being added to the microBIOMETER® app.
The following year, another exciting feature was added to the platform; Project Management (PM). A big advantage of reading results with a cell phone is that the data can be stored on the cloud. When the app was first written, there were a few different data fields for each sample. There was crop quality, crop type, soil class, and a couple other generic fields. It was soon realized that people using the test were likely more knowledgeable about what data and metrics assisted with farming. So, the app was updated to allow users to create their own fields based on their needs. This development was the release of Project Management (PM). Now, users can have as many fields of data as they want and it’s completely adjustable. Another benefit of PM is it lets users create a project and anyone on the team can upload their test results to the project. Before PM, everyone’s samples were on their own phone and in their cloud account. Now all the samples, regardless of who performed the test, are in one place and can be easily downloaded for analysis. Users can create as many projects as they want to keep trials separate from each other, but with all the data aggregated. There is one microBIOMETER® customer who currently has 20 different projects that match up with each of the properties they manage.
microBIOMETER® allows users to quickly determine if they are achieving the improvements they are looking for; track soil microbial activity over time and see how it varies with practice in order to assess what is working and what is not. With an innovative, yet inexpensive soil test like microBIOMETER®, $7 to $14 compared to much more expensive tests, growers can sample more per acre, allowing them to acquire a better understanding of their crops. With the ease of multiple sampling combined with data storage, users can view year over year and season over season results to see if their microbiology is increasing and if their soil health is increasing as a result.
It is important that the microbiology increases because there’s an incredibly high correlation between soil biology and soil health. We know that as microbial activity increases, so does the water holding capacity of the soil. It also makes crops more resistant to excess water – which can lead to erosion. Soil microbes build soil structure, which mitigates drought as well as flooding risk because it improves the texture of the soil. Microbes make a glue-like substance which enables them to stick to the soil. This stickiness remains after the microbes die and causes the soil to become clumpy. These clumps allow the soil to hold more oxygen, as it provides more aeration. Growers can improve the amount of carbon in their soil since the stored carbon in your soil is the bodies of dead microbes. When a microBIOMETER® soil test is performed, you’re looking at a snapshot of the microbes. They’re constantly turning over and they are food for other predators in the ecosystem. But that turnover demonstrates that you have a large number of microbes and that the entire ecosystem is being fed.
When you feed the soil ecosystem – from microbes to earthworms to mammals – that’s when you achieve the healthiest soil. Many creative and innovative practices are being developed that understand that healthy soil is part of a healthy system. The start is a healthy microbial ecosystem and microBIOMETER® gives you a glimpse into that very, very quickly. There’s nothing else like it.
This article is based on the video The History and Science behind microBIOMETER®
Both microbial biomass and respiration are parameters used to assess soil health. Soil respiration is the measure of the carbon dioxide produced by the microbes in a given weight of soil while microbial biomass is the measure of the mass of microbes- both active and dormant.
Microbial biomass (MB) is an excellent predictor of soil health because the size of the microbial population correlates with the available nutrients in the soil. Interestingly, MB is low in soil treated with high levels of mineral fertilizers. Research has shown that the stimulus for the plant to grow a microbial population is its need for nitrogen and phosphorus. If these nutrients are artificially supplied, the plant is not being stimulated to feed the microbes that usually provide these nutrients to the plant. This can alter plant-microbe interactions and cause an increased need for pesticides in order to protect the plant, as microbes play a fundamental role in the function of the plant’s immune system.
Microbial respiration measures the amount of carbon dioxide (CO2) produced by the microbes in a given weight of soil. The soil is dried and then rewetted and put in an airtight jar that allows measurement of the amount of CO2 produced over 24 hours. The CO2 is produced by the activity of the microbes in the rewetted soil. Between 20% and 70% of the microbes die during drying, but their dead bodies often provide nutrition for the survivors to use and regrow the population to its original level. Respiration reflects the regrowing work that is being done. The respiration level is often mistakenly believed to predict microbial biomass, though it doesn’t.
People often assume a high respiration rate is good because it means there is a lot of microbial activity occurring. However, it doesn’t necessarily mean the soil is healthy. Microbes in a low pH or toxic soil have to work harder, and therefore their respiration rate is higher, just as your respiration rate in the gym is higher than when you are watching TV. High respiration rates can indicate an unstable microbial population, which, for example, can be seen after excessive tillage occurs. Tillage aerates the soil, so right after there is often a boost of microbial respiration. That increased activity however does not always last, as the other damage done by tillage – disruption of microbial life and destruction of existing plants- can lead to a decreased soil microbial population over time.
The use of soil primers stimulates an increase in soil organic matter (SOM) decomposition, which temporarily increases microbial respiration. Excessive decomposition of SOM can cause a loss of stored soil carbon and other mineral nutrients, allowing for the increased production of CO2. Basically, when you stimulate the soil using a fertilizer or biostimulant, it’s an all-you-can-eat buffet for the microbes. It wakes them up and they start growing and reproducing. But whether they can continue to grow depends on the continual supply of existing nutrients and plant life in the soil. It’s very important that there be sufficient food for the microbes after stimulation. For most soils, this requires that the fertilizer have the correct C:N ratio for the soil and crop. A fertilizer with too high a C:N ratio will cause the microbes to harvest some of the stored carbon, nitrogen and other nutrients in the soil, boosting respiration. This means the stored carbon is being depleted and released into the atmosphere as CO2, the microbes won’t be able to nourish the plant and build soil structure as needed. Adoption of less invasive management practices, such as select-till and reduced chemical fertilizers can reduce CO2 emissions from agricultural soils by retaining soil organic matter.
Priming can be a good way to understand the difference between and uses of respiration data and microbial biomass data. Testing for both initial respiration and long term microbial biomass population can tell you if the priming worked and if the increase in microbial activity led to increased soil microbial biomass and therefore increased soil health and fertility.
