Soil tests for soil health
September 30, 2024
Soil tests are critical in building soil health and understanding the inherent properties of your land. These tests can inform farm management decisions, and ultimately optimize production on both yield and grain quality. Soil tests are often best conducted in the fall, so now is a great time to approach the topic! It is important to remain consistent in pulling soil samples at the same time each growing season to not skew subsequent years’ results from differing environmental conditions. Typically, experts recommend taking soil samples and conducting tests every three to five years, or more frequently (up to annually) depending on your operations’ nutrient management plan.
There are varying types of soil tests available:
- Physical: Assess soil structure, texture, density, porosity, aggregation, etc.
- Chemical: Assess chemical soil properties such as pH, organic matter, and nutrient levels such as nitrogen, phosphorus, potassium, sulfur, etc.
- Total nutrient digestion (TDN): Provides a comprehensive evaluation of soil’s nutrient potential, unlike most tests which provide only what is available. TDN tests allow for a complete analysis of nutrient potential which can be unlocked through microbial activity.
- Phospholipid fatty acid (PLFA): Uses PLFA’s found in cell membranes of living organisms to assess the soil microbial community. This is important when it comes to soil health because varying microbes and their communities aid in processes such as nutrient cycling and organic matter decomposition.
- Haney test: Provides a comprehensive soil health assessment by combining chemical and biological soil properties. This test allows for soil health evaluation for both plant and microbial life, providing information on many categories including soil respiration, nutrient availability, organic matter, etc.
The bottom line is do your research, reach out, talk to your farm consultant or agronomist, and determine which test type will work best to continue to propel you and your operation forward. Learn more here!
To take a soil sample on a given field for lab testing, there are several methods that you can use depending on your farm’s geography. Some methods may work better than others because of land formations or equipment limitations. For a field that shows more variability, selecting a sampling method that takes landscape differences into consideration is recommended. This allows for benchmarks in different areas to create more meaningful, farm-wide test results.
- Random Composite: This sampling method is useful for small fields with naturally flat topography. Soil cores are taken from 15-20 sampling points at random intervals and locations in the field. This method largely ignores marginal locations and therefore is generally poor at capturing landscape soil variability.
- Directed Random: This method is like the Random Composite Sampling Pattern, except that the field is broken up into sections based on production. Areas of the field that are producing less yield, such as saline areas, and high-producing areas with high organic matter, are separated into management zones that are sampled individually. Additionally, the area that represents the most average yielding section of the field also becomes a management zone. Multiple random samples are then taken in all three zones.
- Benchmark: This method uses a singular, small zone in the most historically average-producing area of the field. Multiple soil samples are taken in a grid pattern within the marked zone which gives an average for the field, and in subsequent years, pulling samples from the same spot will indicate soil fertility changes year over year.
- Landscape-Directed Benchmark: This method utilizes a small sampling area like the Benchmark method but bases the different subzones of the field on topography. Instead of taking samples from areas of high-, low-, and average-production amounts, the management zones are broken into high knolls, level/average areas of the field, and low-lying areas. These areas can then be managed separately based on the soil test results.
- Grid: In this method, the field is divided into a grid and samples are pulled from each square in the grid pattern. The grid method is the most common soil sampling method for creating variable rate fertility maps, as it gives the most accurate picture of the nutrient requirements of any given area within the field. It is also the most labor- and cost-intensive sampling method described in this list.
Learn more about soil sampling guidelines here.
Soil health labs
Listed here are some examples of potential laboratories which you can interact with to complete testing on your farm. It is important to choose a lab that is within your means and meets your testing needs based on your soil health goals. Once you understand their capabilities, it will be important to understand how to submit your samples to different labs. Labs may have specific guidelines on how they want samples to be taken, labeled, and submitted for testing. Look at some of the following labs, research others, and begin thinking about how testing facilities like these can help you better understand and manage your farm.
United States and Canada:
- Regen Ag Lab (Haney Test)
- Ward Laboratories
- AgSource
- AGAT Laboratories
- Western Laboratories
- Earthfort LLC
- 635 SW Western Blvd, Corvallis, OR 97333
- CARA Soil Health Lab (Canada)
- 141 5 Street E, Oyen AB, T0J 2J0
- A&L Laboratories Inc (Canada)
- 2136 Jetstream Road, London, Ontario N5V 3P5
- North American Soil Testing Laboratories Directory
How to read a soil test?
Check out these two articles on how to read a soil test if you have questions on what a test will tell you, what it means, and how to begin to decipher results.
https://www.fbn.com/community/blog/how-to-read-a-soil-analysis-report
https://www.cropscience.bayer.us/articles/bayer/reading-interpreting-soil-test
Nutrient Management Planning Guide. Nutrient management planning guide – Open Government. (2015, August 17). https://open.alberta.ca/publications/7086752
