1. Regenerative Agriculture
  2. Soil

How To Measure Soil Health With The Haney Test

  Estimated read time:

An essential tool in the regenerative playbook is the Haney soil health test, which measures soil biological health by looking at nutrient availability and microbial activity. It reflects the complex ecosystem of the soil instead of relying only on the narrow measurement of “N, P and K.”

Developed by Rick Haney, a USDA-ARS researcher at the Grassland, Soil and Water Research Laboratory in Temple, Texas, this integrated approach uses chemical and biological soil test data to mimic nature’s approach to soil nutrient availability as best as can be done in a lab. The test, which the USDA has adopted as its official Soil Health Nutrient Tool, helps farmers and ranchers answer three important questions:

  1. What’s the current condition of my soil?
  2. Is my soil in balance?
  3. What can I do to improve my soil?

While it does help answer these questions, it’s important to note it will not completely answer them. By giving producers a better understanding of microbial activity and the nutrients naturally available in their soil, the Haney test can help them make smarter, more regenerative pasture-management decisions; guide their fertility program; improve their crops; and reduce input costs. In a large-scale study, Haney ran 3,200 samples, helping growers reduce nitrogen input costs by $15 per acre.

handling the soil

How It Works

The Haney soil health test integrates chemical and biological measurements to assess multiple soil test values, including:

  • Plant-available nutrients
  • Soil respiration
  • Water-soluble fractions of organic carbon (C) and organic nitrogen (N) and the ratio between them

It also provides nutrient recommendations for N, phosphorus (P2O5) and potassium (K2O) for a variety of crops, along with cover crop recommendations.

Note that the Haney test isn’t a complete evaluation of soil health, as it doesn’t account for things like water infiltration rates, water holding capacity or bulk density. It’s also just a snapshot in time of your soil health, since organic matter pools are in constant flux depending on microbial activity, management practices and the season.

Interpreting Test Results

The Haney test provides a unique health score for your soil, with measurements on available nutrients and microbial activity, along with cover crop recommendations — all critical data for making management decisions that will improve soil fertility and yield.

Your soil health score can range from 0 to 50 — the higher the better, though most soils will not score above 30. While land management has considerable influence on your score, your score potential can also be limited by regional constraints (e.g., soil type, geography and environmental factors). Certain soils will have greater soil-health score potential over others, even when similar management practices are introduced.

Below is a quick overview of key measurements that will be included in your test report. For a more detailed overview of how to interpret results, see the Haney Test Interpretation Guide from Ward Labs.

testing soil

Soil Respiration Test

What it is Measures how much CO2-C soil produces in 24 hours following a significant drying and rewetting event
What it tells you More CO2 = more microbial activity = higher potential for nutrient cycling, soil aggregate and organic matter formation
What the #s mean For agricultural soils, <10 ppm is very low, and >200 ppm is very high
  • While soil type and climate can limit soil respiration potential, soil-health and farm management decisions can make a difference
  • Healthier soil can sustain higher respiration value during times of drought or extreme heat

Water Extractable Organic Carbon (WEOC)

What it is Measures organic carbon (food) readily available to microbes
What it tells you The quality of organic matter in your soil system (not a direct measurement of soil organic matter)
What the #s mean Most soils range from 50 to 800 ppm, with the majority falling between 100 to 300 ppm
  • Native and perennial systems typically have higher WEOC values than row crop systems
  • Inputs (e.g., manure, compost, cover crops) can increase carbon loading and cycling for higher WEOC levels
  • WEOC values fluctuate by season, with freezing and thawing events helping with the mechanical breakdown of residues

Water Extractable Organic Nitrogen (WEON)

What it is Measures organic N available to microbes
What it tells you Organic N acts like amino acids and proteins, boosting the carbon that microbes eat
What the #s mean Soils can contain 5 to 100 ppm WEON, with most soils falling between 10 to 30 ppm
  • 30 ppm WEON = ~60 lbs of N to the acre at 6-inch sample depth
  • Higher WEON promotes plant growth, but it’s important not to disrupt the C:N balance

Organic C to Organic N Ratio (C:N Ratio)*

What it is Measures the ratio of organic C from the water extract to the amount of organic N in the water extract
What it tells you Measures the balance between WEOC and WEON for optimal soil function
What the #s mean
  • A high C:N ratio >20 = no net N and P mineralization/N and P are unavailable to the plant
  • A low C:N ratio <8 = burning up carbon and hurting soil health
  • C:N ratio between 8:1 and 15:1 = more N and P are released in the soil and available to growing plants

Organic C (energy) and organic N (nutrition) are both required for optimal soil function:

  • High WEOC/Low WEON = lots of energy, but low-quality nutrition
  • Low WEOC/High WEON = lots of nutrition, but little energy to carry out important functions

* The Haney C:N ratio of the water extract is not the same as the total C:N ratio of your soil or the manure or cover crop you are using, or the C:N ratio of the organic matter in your soil.

Organic N to Inorganic N Ratio

What it is Measures ratio of organic N [part of soil organic matter (SOM) and harder to access by soil microbes] to inorganic N (plant-available N)
What it tells you How much N is readily available in the soil
What the #s mean
  • Ratio <1 means most N in soil is nitrate and ammonium, resulting in N immobilization
  • Crop rotations or cover crops can raise ratios above 2 and 3
  • Healthier soil builds an organic N pool greater than residual inorganic N (ratios >5)
  • Organic N balanced with organic C fuels biological system → feeds the plants → more efficient use of N
  • To mine organic N from SOM requires destroying SOM
cows grazing pasture

For additional details on pulling samples, visit Ward Labs at www.wardlab.com. Specific questions regarding biological/soil health testing may be directed to biotesting@wardlab.com.

Kristina Tober is a writer based in Steamboat Springs, Colorado. Hearkening back to her family's roots as cherry farmers in Northern Michigan, Kristina is passionate about the positive impact farmers and ranchers have on people and the planet, and the potential for regenerative practices to help sustain their operations for generations to come.