Soil Health encompasses physical, biological, and chemical properties of soil. Common assessment methods in each of these areas will help you make sense of what types of information soil tests can provide.
It is challenging to generate a list of ‘recommended’ measurements across all fields, as the list may vary depending on goals. To inform this process, there are some key questions a grower needs to answer:
What is the goal with these measurements? Are you trying to establish a baseline in your field? Do you seek to understand how a change in management will impact your soil?
What components are of greatest interest? Soil biology? Nutrient cycling? Compaction? Water infiltration and retention?
We recommend running soil health analyses on the same soil samples you submit for nutrient analysis (same depth, time of year, sampling densities and frequency).
How much time and money are you willing to invest? Are you willing to make measurements in the field yourself, or do you want to send samples out to a commercial soil testing laboratory? Does the lab you normally use offer any soil health analyses? Lab-based measurements are generally more reliable and reproducible than field-based measurements. Soil health testing can be expensive though.
Controlling testing expenses. Costs can be reduced by using the same soils you submit for standard nutrient analysis. There are a number of promising tractor-mounted sensors and other tools that can provide feedback on soil health. Few have been independently evaluated to date. Examples include Precision Planting's Smart Firmer (OM, H2O), Veris iScan (EC, OM, H2O), Delta Force (downward hydraulic force for compaction layers and soil hardness), AirScout imagery (soil temperature, crop stress). This information can potentially be far cheaper to produce than laboratory analyses. Consider using these tools to help make decisions.
What follows are the recommended tests for Ohio growers, based on costs, robustness of analysis and the information it provides. The Soil Fertility Lab has been working to develop methods into a quick and affordable soil health testing package. At this time, we do not offer services to the general public, but can run some samples for research purposes. We are working to develop capacity over the next several years with the possibility of limited commercial testing.
Soil Chemistry
- Routine nutrient analysis provides a great foundation for assessing soil chemistry
- Optimal pH and available nutrients are a critical component of a healthy soil
- Total organic matter is typically run with a standard soil test and serves as a critical component to soil health
- Key lab measurements (already included with standard soil test):
- Soil pH
- Extractable nutrients, especially P and K
- Total organic matter
- Key field measurements:
- None recommended
Soil Biology
- Soil biological function
- Key lab measurements:
- Soil Respiration – 24-hour CO2 measurement (ex. Solvita)
- Active Carbon – biologically available C pool
- Soil Protein – biologically available organic N pool
Soil Physics
- Soil physical structure can be difficult to measure in the lab, because most soils entering the lab are immediately dried and ground
- Key lab measurements:
- Aggregate stability via rainfall simulation
- Key field measurements:
- Soil Compaction
- Soil Infiltration
Organic Matter
If you soil test for routine nutrient analysis, you already test for a really important soil health measure – total organic matter. This is a number that you should pay attention to and constantly strive to increase. Numerous benefits are directly influenced by soil organic matter. However total organic matter is not an ideal indicator of nutrient availability, because the majority of this pool is in forms that turn over slowly over time and are hence not plant available. Active organic matter is only a small fraction (5-20%) of the soil’s total organic matter, but is very important to crop nutrition since nutrients in this fraction are rapidly cycled and taken up by crops.
We are working hard to develop meaningful and affordable soil health tests for farmers. Since soil organic matter influences so many soil properties, organic matter tests are of particular interest. We are working with three tests that measure the active pool of organic matter: 1) active carbon, 2) soil protein, and 3) respiration. These tests each provide unique information about the active organic matter of a soil. They are complementary and related, as these three components interact to determine how fast and how much a nutrient will cycle within the soil and become available to growing crops. The larger the pools are, the more fertile and resilient a soil will be.
Read more about this research at https://soilfertility.osu.edu/extension-and-outreach/soil-health-testing