Evaluating Biological Soil Functioning

A vibrant healthy soil arises not from soil itself but from the interactions of plants, microbes and animals in the soil environment.

THE CONCEPT: Soil Biological Health is an emerging concept of soil fertility which seeks to include biological traits along with conventional nutrient analyses. This form of evaluation integrates as many factors as practical which are thought to be responsible for sustainable soil fertility.

INTEGRATION: Actually, “soil health” is a misnomer: since soil alone cannot be healthy.  Rather, healthy functioning of soil arises to the extent that plants, microbes and soil-inhabiting animals actively participate in building and sustaining their environment.  The phenomena of organisms acting to modify and improve their habitat is recognized in modern biology as niche construction.

THE CHALLENGE: Farmers are often characterized as needing to shift management practices favoring soil building.  But agricultural scientists are equally implicated.  Scientific practices of soil analysis have traditionally not recognized biological factors as playing an important role in productivity and have stressed yield and nutrient input. Current farming practices and the pursuit of science bear equal responsibility for the deepening dilemma of soil degradation and carbon loss.

Cornerstone soil tests that integrate biological traits include Solvita®-CO2 for microbial activities and Solvita®-SLAN for humus quality.

Woods End’s brand Solvita® has advanced across several markets and is inspiring soil conservationists, farmers, grain processors and composters in new ways to gauge the quality of their environment.

SOIL TESTING: The challenge in testing soil fertility is to provide practical results that match reality. This is not easily reduced to precise mechanisms. As an analogy, a century of scientific medical-biology advances in human health has failed to produce a single lab test which reveals “healthiness”. There is no reason to expect soil health testing will be any more successful, and given the recent history of soil scientists debunking “soil quality”, the challenge to succeed is enormous.  Moreover, at the human health level, consciousness enables self-evaluation, which completes the analysis: health expresses itself at the level of the individual. Translating this into the perspective of the inanimate soil and farm environment, many obstacles must be overcome to make a truly useful analysis. All inquiry on soil quality and long term fertility must be individuated to the local environment.

WOODS END ROLE: Woods End Laboratory was founded in the early 1970’s to provide alternative soil testing services to farmers choosing biologically-oriented farming methods. These early farmers were constrained to translating post WWII era inorganic N-P-K tables into biological management, resulting in highly inaccurate recipes. The concept of biological nutrient release and its calibration to conventional soil tests was largely unknown. Woods End Laboratory sought to overcome these  barriers with research on the ways that “green manure” crops interact to improve soil nutrient release. Also, Woods End pioneered nutrient release models for gauging mineralization of nitrogen contained in manures and composts, and developed some of the earliest calibrations of soil-tests with non-chemical fertilizers. More recently Woods End developed Solvita, a form of bioassay which enables biological functions in soil to be observed with reasonable accuracy. This test has been calibrating the pioneering European work on soil biological indicator scales. The goal is to enable laboratories to incorporate cost-effective biologically-oriented tests into existing structures while providing practical interpretations.

DYNAMIC SOIL AGGREGATES: A key innovation at Woods End is “VAST”, a test which helps establish the prerequisite that for soil health, testing must be more comprehensive. While VAST was originally developed early in the 1980’s within Woods End, it has been made available recently to soil labs under the Solvita brand. The test provides a powerful visual and quantitative means to assess the stability of soil micro-structures, the intersection of degradative and soil-building biological forces.

CORNERSTONES OF SOIL HEALTH TESTING – Solvita Soil Health Suite: Putting all the new tests together – active respiration, aggregate stability, organic nitrogen pools – results in a comprehensive soil bio-chemistry test, the Solvita Soil Health Suite, that may serve as an indicator of healthy functioning.  Combining this test with rainfall, soil-temperature and physiographic models helps tailor it to the local environment, the only way that soil health tests can ultimately be usefully interpreted. Woods End labs is one of the few labs presently working on this integration – and if history is any guide, it is a work in progress.

Aggregates – the foundation of “erosion resistance” and basis of a new test offered to soil labs by Wood End Labs

MOVING FORWARD With new excitement for soil quality evident across wide sectors of farming, a caution is needed. Historically soil test methods have evolved slowly. Soil improvement and soil decline themselves are very slow over decades or centuries, and are not readily noticed.  There are new concerns about sensitivity of soil tests to adequately show relevant gains. For example, it has been determined statistically that it is not possible to measure soil carbon changes in less than 2 years without a sample size of hundreds probes per individual field. For routine sampling, a resolution more precise that 5 tons/carbon/acre is barely possible. By drawing on some of the best long-term soil management studies conducted around the world over the past 5 decades, it may be possible to adjust to the required “imprecision” in short-time of soil quality measurements.

As a summary, the Solvita Soil Health Suite:

  • Accounts for soil microbial activity, with a view that this is very nutrient-relevant;
  • Evaluates N + P mineralization potential, the core of the nutrient supply mechanism for plants
  • Represents nutrients such as organic-amino-N likely to be “plant relevant”

For instructions on sampling soil, download the ‘Soil Sample Info Form‘ or contact: lab@woodsend.com