Soil Health Testing – Government Programs

Soil health has gotten a lot of attention the past few years. Research has shown that we can improve soil health by modifying certain practices in production agriculture. Practices such as reducing or eliminating tillage are not new and farmers continue to adopt these practices. Improving crop rotations is also a part of improving soil health. One relatively new practice has been to encourage farmers to include cover crops where they can in their farming system.
As farmers have adopted these practices, soil health has been improving and researchers have been trying to develop new soil testing methods which can measure the changes in soil health over the years. It is important to develop soil testing methods that can measure the changes in soil health over time. Some soil health measurements are already part of USDA NRCS programs and farmers receive payments for doing these soil health tests. We expect new or different tests will probably be included as part of government programs in the future. Developing new soil health testing methods that are meaningful for farmers and can be adopted by commercial testing labs is not an easy task and takes time.
The process begins with researchers developing tests they are confident can measure subtle changes in soil health quickly when a practice is changed. For example, if a grower switches to a no-till system, the new soil tests need to be able to pick up changes in biological activity, soil aggregation and soil chemistry within the first year or two of farmers changing these practices. Once the researchers have developed a group of tests they think will be able to measure these changes in the soil, the methods are then evaluated in commercial soil testing laboratories.
This step involves including these new soil testing methods into laboratory proficiency testing programs. Most soil testing laboratories are part of proficiency testing programs, such as the North American Proficiency Testing Program (NAPT) or the Agricultural Laboratory Proficiency program (ALP). These programs assist laboratories in monitoring their accuracy and precision when using accepted soil testing methods. In these programs, each laboratory receives a group of unknown soil samples several times each year. The laboratories test these unknown samples using accepted methods and submit their test results. The test results from hundreds of laboratories are compiled to determine the correct test results for each soil test method. Each laboratory is sent a report that shows how they did, with respect to getting the correct test values for each test method.
It is critical that any new soil testing method be evaluated by a large group of laboratories in these proficiency programs. We have to find out if new soil test methods are able to be reproduced in a commercial lab setting as they were in research labs.
One example of a new soil testing method being evaluated by these proficiency testing programs is the CO2 burst test or “Solvita test”. In the past two years this new method has been evaluated by a large group of commercial testing labs. What we learned in those two years is that it was not possible for a large group of laboratories to consistently get the same test values for the unknown soils when using this new test method. As it turns out, the test method did not work well on certain soil texture classes and the method needed to be changed to fix these issues. This method is still being modified in an attempt to get more consistent test results across a wide range of soil textures. Without evaluating this new method in a proficiency program with different soils by hundreds of laboratories, we would never have learned about the issues with this new method.
This is why new soil testing methods must be evaluated in this way to figure out if they will work on a wide range of soils and in a commercial lab setting. In the future, you may be hearing more about other soil testing methods for soil health that are being evaluated by researchers. Here are a couple tests that you may hear more about in the future.
Soil Protein: is a measure of the fraction of the soil organic matter which contains most of the organically bound N. Microbial activity can mineralize this N and make it available for plant uptake. This is measured by extraction with a citrate buffer under high temperature and pressure.
Active Carbon: is a measure of the small portion of the organic matter that can serve as an easily available food source for soil microbes. It is measured by quantifying potassium permanganate oxidation with a spectrophotometer.
Aggregate Stability: is a measure of how well soil aggregates resist disintegration when hit by rain drops. It is measured using a standardized simulated rainfall event on a sieve containing 0.25mm and 2.0mm soil aggregates. The fraction of soil that remains on the sieve determines the percent aggregate stability.
AGVISE Laboratories has participated in the NAPT and the ALP proficiency testing programs since they were established many years ago. We will keep our customers updated as new soil testing methods are evaluated by these programs.