Woods End Laboratories

Healthy Soil

Healthy Science

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Overview of Soil Health Testing

Soil Health Tool

A vibrant healthy soil consists of a matrix of biology that directly links with the supply of nutrients, soil structural integrity and plant disease defense

Introducing Soil Health:

THE CONCEPT: Soil Health is an emerging concept of soil fertility that sees soil in the active rather than the passive status of crop support.  A legacy of the 19th century, soil is commonly viewed as a physical base on which plants grow – in proportion to nutrients supplied. This idea, once revolutionary, is no longer so, and is being supplanted by a dynamic view that recognizes soil biology as an essential component in productivity.

The new challenge to growers and soil labs is negotiating this changeover to soil test methods sensitive to and indicative of biological forces under-pinning soil vitality. Hence the focus at Woods End on “natural soil testing”- the development of laboratory methods that are less chemically intrusive and more biologically viable.

Modifying  this common laboratory physical-chemical analysis model to allow biological approaches is challenging. It requires, for one, supplanting intensive soil-grinding which destroys micro-aggregate structure and disrupts carbon structures – ignored until recently. It may require new instrumentation.

NEW SCIENCE:  Soils participate to provide a wholesome environment for plant growth, even as plants and soil-inhabiting animals actively participate in building and sustaining soils.  Properly grasping this can lead to more successful long-term crop production strategies and also a change in soil handling methods. One way to describe the emerging scientific view about building soil is to recognize what modern ecologists call niche construction, the phenomena of organisms acting upon their environment to modify and improve it. Without performing tests that reveal these organisms, scientists may be operating partly in the dark to provide long term measurement strategies.

Soil Health Tool

The KEY TEST and cornerstone of soil biology testing by Solvita – CO2-respiration which evaluates microbial activities and Labile Amino-N which reveals accumulated organic nitrogen, a hidden store of reserve nitrogen.

SOIL TEST CHALLENGE: To progress and remain truly scientific, soil testing must take account of the underlying biological properties of the entire functioning plant-soil system. Farmers face increasingly harsh economic realities and can no longer ignore factors that are clearly implicated in sustainability. For this reason, there is a large potential economic upside to improved soil management. It is  not appropriate to continue adding phosphorus to soils that have received more than a ton/acre of P in the last decade, most of which is still present but “hidden” in reserve forms in unstable equilibrium. Similarly, to keep adding twice as much nitrogen into soils than plants actually use for production, is a practice that needs to change. This implicates soil test models.

WOODS END ROLE:   Woods End Laboratory was founded in the 1970’s based on the challenge of performing nutrient calculations for farmers choosing biologically oriented farming methods. Early biological (organic & sustainable) farmers were forced to translate N-P-K tables into manure or compost nutrients even though the mechanisms of biological nutrient release and its calibration to conventional soil tests were largely unknown if not improperly applied. Woods End Laboratory performed early research on the ways “green manure” crops interact with soil to improve nutrient release and pioneered nutrient release models for mineralization of nitrogen contained in manures and composts. More recently Woods End developed Solvita, a rapid assay method for soil biological CO2 respiration. The goal behind Solvita was to start enabling  modern laboratories to incorporate cost-effective biological testing into existing structures. In Woods End’s view, academicians can perform research, propose complicated test methods, and criticize innovation, but the real answer lies in the market-oriented ag services

Solvita VAST – volumetric aggregate stability test – a breakthrough procedure allowing rapid screening of water stable soil aggregates.

sectors of soil labs and soil consultants who on  a day to day basis support farmers and are answerable to their success.

DIVING DOWN INTO SOIL AGGREGATES: A key linkages helping create a broad-based Soil Health Tool package was addition of a reliable but very rapid water stable aggregate test, called VAST and marketed 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.

EXPLORING SOIL EXTRACTS: Since its inception Woods End soil lab has explored a variety of means to represent nutrients available to plants.  We continue to explore this arena and have examined European (CAL) and newer American (H3A) and carbonic-acid methods to characterize nutrient availability.  In most cases, the choice of the “best” soil extract depends on the actual soil makeup and soil region. Harsh or highly buffered soil extractants tend to over-represent soil nutrients and therefore must be constantly calibrated to soil conditions and crop growth. The  modern practice to fertilize to high reserve nutrient levels is increasingly problematic as environmental pressure on water quality increases.

A European soil chemist where Brinton trained once noted that the normal reagent concentration that soil and plants effectively exexperience “should be about 0.01 molar”. Instead, labs commonly use high molar concentrations and highly buffered reagents – in some cases 50 times more powerful than anything present in soil.  Crop response calibrations are then run against these reagents, locking in the soil-test fertilizer-crop model as a static mechanical system that becomes a self-reinforcing tool. While extremely successful to attain high yields

Aggregates – the foundation of “erosion resistance”

CORNERSTONES OF SOIL HEALTH TESTING:  Putting all the new tests together – active respiration, aggregate stability, organic nitrogen pools – results in a SOIL HEALTH TOOL.  Woods End labs is presently one of 5-6  commercial labs now offering this approach in an integrative fashion, building on Woods End’s efforts over 30 years to bring biological tests into soil-chemical conversation. As a work in progress, it needs a period of time where it may be compared to past approaches.

SHORT and LONG TERM HOPE With new excitement for soil health evident across wide sectors of farming, a caution is needed for those who seek to prove (or disprove) quickly the theme of soil improvement via new soil tests. Soil improvement itself is slow and takes place over decades, as soil test methods have slowly evolved. So too, soil declines are often very slow and not readily noticed to the extent that they should have be.  A new example concerns sensitivity of soil tests to show relevant gains in a short time frame. It has been determined in the EU that it is not possible to prove gains/losses in soil carbon in less than 2 years without a statistical sample size of hundreds of samples per 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 and organic-plot studies conducted especially in Europe over the past 5 decades, we can learn to appreciate the required “imprecision” in short-time of soil quality measurements.

As a summary, the Soil Health Toolbox:

  • 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


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