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The moving target of soil health

Dustin Sawyer for Progressive Forage Published on 27 February 2018
Soil health

It’s no surprise that soil health is still a buzzword. Though the idea of soil health is an old one, there has never been a quantifiable measure of what one would call a “healthy soil.” Many top researchers have been working on developing this measure for decades.

A few years ago, the USDA Natural Resources Conservation Service (NRCS) threw fuel on the fire by adopting one of the pre-eminent soil health measures as a Soil Quality Enhancement Activity under its Conservation Stewardship Program. The adoption of the Soil Health Nutrient Tool, known colloquially as the Haney test, ushered in a renewed interest in soil health, its measurement and our understanding of the soil ecosystem.

Though the Haney test remains the sole soil health assessment recognized by the NRCS, it also remains a relatively subjective measure with limited interpretation.

The concept of soil health is pretty straightforward. The soil is a living, breathing organism composed of organic and mineral fractions existing in harmony together, like a cocktail. Traditional soil testing focuses on the mineral portion of that cocktail to provide insight on the availability of nutrients for crops. There is a difference with soil health measures, which also look at the organic components of the soil.

This organic portion is made up of its own cocktail of living and dead microflora, bacteria, fungi and the compounds they excrete. This is important, because the interaction between the organic and mineral portions of the soil is the driving force behind such important soil characteristics as water-holding capacity, cation exchange capacity and aggregate stability.

The fundamental goal of a soil health measure is to better understand the organic component of the soil and how that component relates to the physical and chemical properties of the soil.

Dr. Richard Haney, soil scientist of the USDA Agricultural Research Service (USDA-ARS) has made it part of his life’s work to understand soil organic components. Haney developed a suite of tests known as the Haney test after studying the relationship among the organic, physical and chemical properties of the soil.

The Haney test is a comprehensive analysis of the soil that combines traditional fertility measures, such as phosphorus and potassium, with less conventional measures, like water-extractable organic nitrogen. The test then aims to quantify those measures and relationships into one easy-to- understand score that can range from 0 to over 50. Generally speaking, the higher the score, the healthier the soil.

I say “generally speaking” because of one major limitation to the Haney test: The soil health score cannot be compared across different fields. For instance, a score of 20 in one field does not mean the field is healthier than a neighboring field with a score of 15. Instead, the measure is intended to help a steward of the land measure progress as he or she tries to improve the soil health within a single field.

The idea is to obtain a soil health score and then see if the score can be increased over time through the use of improved management practices. An increased score, say moving from a 7 to a 12, indicates the soil will be better able to sustain healthy plants, offer greater yields and hold nutrients better than before.

The inability to use the Haney test uniformly across multiple fields creates a major limitation to the use of this measure if we want to try and assess the overall health of a large tract of land, like an entire state. That limitation has given rise to many organizations with the shared goal of improving upon the assessment so that soil health can be assessed on a large scale.

Chief among these groups are the Soil Health Partnership and the Soil Health Institute. Each of these two groups has its own set of analyses that aim to help us better understand the complex relationships that exist in the soil.

In August 2017, the Soil Health initiative offered an endorsement of 19 measurements they dubbed as their “tier 1” list of recommended soil measurements, which are tests intended to offer a more complete picture of soil health than the Haney test.

It’s important to note that while the list of tier 1 measures has been identified, the methodologies behind these measures have yet to be defined. In other words, it’s been decided what needs to be done, but not how to do it.

The Soil Health Partnership has its own group of soil analyses they use. Rather than trying to develop a replacement to the Haney test, the Soil Health Partnership has chosen to include the Haney test in its original form as the core of their assessment.

They then supplement the Haney test with traditional fertility analysis, phospholipid fatty-acid analysis and further soil health measures pioneered at Cornell University.

The Soil Health Institute and the Soil Health Partnership have the shared goal of developing a widely adopted soil health assessment that can then be used to determine the overall health of the soils of the U.S. as a whole.

These two groups have molded and refined the concept of soil health from a nebulous idea into a tangible concept with a definitive purpose for land stewards and farmers alike. More than likely, future farmers will consider soil health to be a staple in their language instead of just a buzzword.  end mark

PHOTO: Soil health assessment that can then be used to determine the overall health of the soils and compare soils across the entire U.S. Photo by Mike Dixon.

Dustin Sawyer
  • Dustin Sawyer

  • Laboratory Director
  • Rock River Laboratory
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