Traditional and Biological Soil Testing

Does it Matter?

Soil is more than just dirt, it's a living, breathing ecosystem that sustains plants, animals, and humans. Yet, when it comes to analyzing soil for agricultural or environmental purposes, many professionals still rely solely on traditional chemical soil tests. While these tests are valuable, they only tell part of the story.

To develop truly effective soil management programs, it’s crucial to understand both traditional soil tests and biological soil tests—and more importantly, how they complement each other.


Traditional soil testing is our baseline and focuses on the chemical and physical properties of soil.



Common tests include:

  • pH: Measures acidity or alkalinity, which affects nutrient availability.
  • CEC (Cation Exchange Capacity): Indicates the soil's ability to hold onto essential nutrients.
  • Macronutrients and Micronutrients: Levels of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and trace elements in the soil that can be available to your plants.
  • Organic Matter Percentage: Offers some insight into soil fertility.

These tests are excellent for identifying nutrient deficiencies, toxicity, and amendment needs. They guide decisions about fertilizer applications and help avoid over- or under-fertilization. However, they don’t tell you much about how well the soil is functioning as a biological system.


Soil biological testing looks at the living component of soil—microbes, fungi, protozoa, nematodes, and more.

Tests like:

  • PLFA (Phospholipid Fatty Acid Analysis): Indicates microbial biomass and community structure.
  • Microbial respiration tests: Measure biological activity and microbial health.
  • Haney Test or Soil Health Tests: Combine chemical and biological data to assess nutrient cycling potential and microbial activity.

These tests help us understand:

  • Is the soil biology actively cycling nutrients?
  • Is it suppressing disease naturally?
  • Are beneficial organisms present and balanced?

In essence, biological tests shine a light on how efficiently soil organisms are supporting plant growth, something traditional tests can’t show.


Why Would You Need Both?

If you’re only running traditional soil tests, you might add inputs that aren't needed—or overlook biological limitations holding back plant performance. Conversely, biological testing alone might suggest the soil is healthy, even if there's a critical nutrient deficiency. When used together, these tests can:

  • Fine-tune fertility programs: For example, traditional tests might show low phosphorus, but a strong microbial community from biological tests could mean plants can still access organic phosphorus pools.
  • Improve soil structure and water retention: Healthy biology promotes aggregation, which can’t be inferred from chemical tests alone.
  • Reduce input costs: By identifying when the soil biology can deliver nutrients naturally, you can reduce synthetic fertilizer use.
  • Guide regenerative practices: Understanding both chemistry and biology supports practices like cover cropping, compost application, and reduced tillage.


Practical Example

Imagine a field with compacted soil and low nitrogen levels. A traditional test might call for heavy nitrogen input. But a biological test shows poor microbial activity, especially nitrifiers. Instead of applying more synthetic N, you might first focus on improving microbial habitat, perhaps through organic amendments and aeration, so the soil can eventually fix and cycle nitrogen more efficiently.


Soil testing shouldn’t be a one-dimensional approach. Traditional tests provide the "what" of soil fertility, while biological tests offer the "how" and "why." By integrating both into your soil health program, you create a more holistic, resilient, and cost-effective strategy. Embracing both testing methods is the key to unlocking your soil’s full potential.