Soil health reflects the physical, chemical, and biological condition of soil. Unlike traditional soil fertility tests that focus on crop nutrient needs, soil health testing evaluates the soil’s ability to function as a vital living ecosystem. Improving on-farm soil health results in soil becoming more resilient to drought and heavy rain events, improves the nutrient-cycling efficiency of soil, reduces soil erosion (Soil Health Institute, 2021), and supports long-term soil productivity and farm profitability in Ohio (Soil Health Institute and Cargill, 2021). The goal of soil health testing is to help producers and land managers understand the current status of on-farm soil health, and to provide direction for future improvements in on-farm soil health.
Core Soil Health Indicators
The concept of soil health is, in essence, the intersection of the chemical, physical, and biological properties of soil (Figure 1). A number of indicators contribute to soil health and influence the ability of soil to support plant growth and environmental functions:
- Chemical soil health indicators (ohioline.osu.edu/factsheet/anr-0204) refer to nutrient content (e.g., nitrogen (N), phosphorus [P], potassium [K], sulfur [S], and micronutrients), pH, and the chemical interactions that take place within soil.
- Physical soil health indicators (ohioline.osu.edu/factsheet/anr-0203) refer to the interactions between soil texture, structure, bulk density, porosity, aggregate stability, hydraulic properties and organic matter content.
- Biological soil health indicators (ohioline.osu.edu/factsheet/anr-0205) refer to a suite or subset of tests, including organic matter content, microbial activity (measured via soil respiration or as carbon present in microbial biomass), the amount of active carbon present which identifies the amount of “food” present for microrganisms (the permanganate-oxidizable carbon [POX-C] test), the amount of N stored or cycled over time (autoclaved citrate-extractable [ACE] protein or potentially mineralizable N tests), various enzyme activity tests (e.g., beta-glucosidase enzyme activity to determine microbial degradation rates of cellulosic material), and, potentially, microbial DNA testing.
Common Soil Health Testing Packages
- Haney Test. Microbial respiration and water-extractable carbon (C) and nitrogen (N) comprise the soil health score. The Haney Test separately determines soil nutrient concentrations, yet these values are not incorporated into the final Haney Test soil health score. The Haney Test soil health score only provides an indication of the biological health status of soil and is relatively inexpensive (~ $50) compared to the other testing packages.
- Phospholipid Fatty Acid Analysis (PLFA). Provides a profile of the microbial community (e.g., fungi versus bacteria) to quantify the structure of the microbial community. This test only provides an indication of the biological soil health status, and is relatively more expensive (~ $100+) than the Haney Test.
- Comprehensive Assessment of Soil Health (CASH). – This Cornell soil health testing lab tool measures soil health. This test appears to work well in the Midwest, Mid-Atlantic, Northeastern, and extreme Northwestern (i.e., west of the Cascade mountain range) regions of the United States. This test quantifies the physical, chemical, and biological health of soil, including its available water capacity, soil texture, aggregate stability, organic matter, active carbon, nitrogen cycling enzymes, respiration, pH, plant-available nutrients (phosphorus [P], potassium [K], calcium [Ca], magnesium [Mg], sodium [Na], iron [Fe], manganese [Mn], and zinc [Zn]), and salt content. The CASH test is relatively more expensive (~ $100+) than the Haney Test.
- Soil Management Assessment Framework (SMAF). A U.S. Department of Agriculture, Natural Resources Conservation Service (USDA, NRCS) tool for measuring soil health in relation to a specific region. This test appears to work well across the United States but also appears to utilize more conservative testing functions than CASH. This test quantifies the physical, chemical, and biological health of soil, including clay percentage, aggregation, bulk density, soil carbon, microbial carbon, nitrogen mineralization, carbon cycling enzymes, pH, salt content, and plant-available P and K. The SMAF test is relatively more expensive (~ $100+) than the Haney Test. A comparison of the CASH versus SMAF soil health tests (doi.org/10.1016/j.geoderma.2025.117492) reviews how these tests quantify soil health across diverse land uses.
On-Farm, Low-Cost Tests
The Ohio Soil Health Card (ohioline.osu.edu/factsheet/sag-1) is a low-cost alternative to laboratory testing. This approach uses four visual assessments:
- Soil tilth as in structure, crusting, and compaction.
- Soil life as in earthworms present, smell, and residue decomposition.
- Soil air and water relationships such as drainage, water holding capacity, and water movement.
- Plant vigor such as uniformity in growth and color, seedling emergence, and root system structure.
The Ohio Soil Health Card can be used in combination with routine soil tests (e.g., nutrient levels, pH, organic matter content) to further assess soil health.
When and How to Sample
Soil health tests can be sensitive to the timing of sampling, and thus it is recommended that samples are taken during the same time of year during each sampling campaign. It is also recommended to avoid sampling when fields are extremely wet or dry. Composite samples (about 10–12) are typically obtained from the top 6–12 inches of soil depending on tillage. It is recommended that initial soil samples be obtained similarly to how samples are obtained for soil fertility analysis by dividing fields into separate sections based on factors like soil type, topography, tillage history, crop rotation, organic amendment application, etc., and then collecting soil samples in a zig-zag pattern. These soil samples are then analyzed for a baseline soil health evaluation. Each soil sample should fill about 2/3 of a gallon Ziplock bag (try not to disturb the soil aggregates). Remember to mark the sampling locations in a smartphone app. Samples should be collected every 3–5 years and can be useful for assessing and tracking the impact of management changes on soil health over time.
Using Soil Health Test Results
Don't just ask: What is missing? Rather, ask: What is and what is not functioning?
By asking what is and what is not functioning rather than trying to determine what is missing in the results of a soil health test allows specific management strategies to be considered that are more likely to improve or add to what may be missing. It is also important to combine lab data interpretations with in-field and on-farm observations which allows for more practical and comprehensive soil health plans to be implemented.
Soil Health Testing at SWEL at Ohio State University
The Soil, Water, and Environmental Testing Lab (SWEL) can perform the Comprehensive Assessment of Soil Health (CASH) (swel.osu.edu/testing), a soil health testing framework developed by the Cornell Soil Health Laboratory. Included in this evaluation is testing for the physical (i.e., density, aggregate stability), chemical (i.e., available nutrients, pH), and biological properties (i.e., microorganism activity, carbon content) of soil. The measured values in CASH are reported in combination with soil health scores that are derived using soil texture as a baseline because soil texture is an unchangeable soil property. Scoring for each soil health test is based on the concept of one of three curves:
- More is better (e.g., aggregate stability).
- Less is better (e.g., salt content).
- Optimal range (e.g., soil pH) (see Figure 2).
Conclusions
Soil health testing provides critical insights into the capacity of soil to function as a dynamic, living system that supports crop productivity, environmental quality, and farm resilience. By incorporating soil health testing into on-farm management, producers can gain a more complete understanding of their soil beyond traditional nutrient testing. This allows for more informed decisions to be made that may further enhance biological activity in soil, improve soil structure, and maintain long-term soil fertility. Regular soil monitoring paired with site observations and adaptive management can help track the success of conservation practices and ensure continued farm productivity.
Additional Resources
- Baseline Assessment of Soil Health in Ohio
(soilhealth.osu.edu/sites/soilhealth/files/imce/WhitePapers/Baseline%20Ohio%20Soil%20Health.pdf) - Biological Soil Health
(ohioline.osu.edu/factsheet/anr-0205) - CASH Framework
(soilhealth.cals.cornell.edu/manual) - Chemical Soil Health
(ohioline.osu.edu/factsheet/anr-0204) - Haney Test
(agcrops.osu.edu/newsletter/corn-newsletter/2019-07/haney-test-soil-health) - Ohio Soil Health Card
(ohioline.osu.edu/factsheet/sag-1) - Physical Soil Health
(ohioline.osu.edu/factsheet/anr-0203) - Soil Health
(ohioline.osu.edu/factsheet/anr-0202) - Soils and Soil Health
(ohioline.osu.edu/factsheet/anr-0136) - SWEL Website
(swel.osu.edu/testing)
References
Soil Health Institute. (2021). How does soil health increase resilience to drought and extreme rainfall?
soilhealthinstitute.org/news-events/how-does-soil-health-increase-resilience-to-drought-and-extreme-rainfall-2
Soil Health Institute and Cargill. (2021). Economics of soil health systems on 100 farms.
soilhealthinstitute.org/app/uploads/2022/01/100-Farm-Fact-Sheet_9-23-2021.pdf