Updating Soil Testing Methods
Traditional soil testing was never designed with biology in mind. Conventional soil tests may not be telling the full story about your soil. Soil testing isn’t just about nutrient levels; it’s about understanding which organisms are being selected.
Traditionally growers use standard soil tests to guide fertilizer decisions. They collect soil samples, receive numerical results, and apply fertilizer based on the results. In biologically active soils, these conventional tests may not be telling the whole story.
Chuck Schembre, a soil scientist who has spent more than two decades studying soil fertility, says classic soil testing was never designed with biology in mind. Most conventional soil tests just show pH and your nutrients (N-P-K) and maybe some micronutrients. The methods, developed before and refined after World War II, were built to support fertilizer recommendations, not to capture the dynamic, living processes happening in the root zone. That gap matters more than ever as soil health practices expand.
The real question is how intentional are you about your soil sampling protocol. Depth, time of year, and consistency all influence results, and conventional sampling has historically been “pretty sloppy,” especially when probes are tossed into the ground without regard for the 6-inch benchmark needed to track carbon changes accurately. Traditionally, when soil was sampled, the top layer of residue was removed and then the soil was probed. Now with automatic soil samplers, that step is missed. Compared to old samples taken 10-15 years ago, this new method results in soil tests reporting an additional 1% SOM, although nothing really changed.
Megan Garley research focuses on sap analysis, or the movement of nutrients from root to leaf inside the plant. She noted soil is going to affect that process. Even a simple conventional soil test can show you more than what is typically analyzed. Most tests are not taken in the root zone. That’s where all of the nutrient uptake is taking place, and you’re missing a great deal if you are picking up samples where there are no roots.
Megan Kavanaugh Bio S.I. Technlogy says growers are farming the microbiome, and that is what is growing the crop. She points out that growers are managing living, breathing soil ratherthan a sterile growing medium. This idea reframes soil testing entirely; it is not just about nutrient levels, but about understanding which organisms are being selected for and why.
Kavanaugh’s second core message emphasizes cause and effect. Whatever you put into your soil, those are the microbes that you’re selecting. Heavy reliance on certain nitrogen fertilizer products can inadvertently favor certain bacterial populations while starving out beneficial fungi. The result is often a soil with “lack of functionality”, plenty of bacteria, but little fungal diversity; which has downstream effects on disease pressure, nutrient cycling and overall plant resilience.
Schembre, Garley and Kavanaugh emphasize that modern biological testing, including the Haney test, phospholipid fatty acid analysis (PFLA) and aggregate stability measurements, gives growers tools that conventional chemistry alone cannot provide. These tests give growers more information about the biological side of soil testing which most conventional soil tests ignore.
Schembre highlighted how the Haney test offers a more complete nitrogen picture. The Haney is going to show ammonium, nitrate and the organic form of nitrogen, which is information that conventional soil tests simply omit.
The three soil health experts agreed that growers do not need to overhaul their entire testing approach overnight. Instead, they recommend several changes. First, start with free, publicly available soil mapping to understand baseline soil type and characteristics. There are numerous resources online that allow farmers to soil map their fields. Second, incorporate a single comprehensive soil health test covering physical, biological and chemical pillars rather than relying solely on a conventional soil test that only covers nutrients and pH. The Haney Test and Cornell soil health test incorporate more information about biology than simple conventional soil tests. Third, standardize your sampling protocols, including consistent depth, time of year, and technique, to ensure year-over-year comparisons are meaningful.
Fourth, track biological indicators like soluble organic carbon and microbial activity over multiple seasons rather than expecting dramatic shifts after a single test. Biological tests are not constant; they change constantly but you can track and see long-term changes over time. Fifth, reduce blanket inputs, particularly fungicides and high-ammonium fertilizers. Observe how biological populations respond and change. Then use artificial intelligence to manage the data you collect. Don’t rely on it for recommendations, but use the collected data to see what is taking place in your field. These suggestions can help growers see the complete picture, especially the biological side of farming. Adapted from a SWCS NewsBrief article.