Overview of Soil Health Tool Box
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 relates to an emerging concept of soil fertility in an active rather than in a passive state. Since the late 19th century soil has been seen largely as a mere physical base on which plants grow in proportion to the nutrients removed. This idea, itself once revolutionary and innovative, is being supplanted by a newer view propounded by farmers that see biology as a necessary component in the fertility cycle. The present challenge to growers and soil labs as well as agricultural officials, is negotiating this change. The rapid growth of the agricultural nutrient industry following WWII led to a very successful business model of soil testing directly linked to supply of fertilizers. This in turn has resulted in a crop production infrastructure synchronized with nutrient supply-demand models. Modifying and possibly overturning this approach to allow biological models to be employed successfully, if it is to be a smooth transition, will require new understandings, new instrumentation and new blood. The fact that soil and plants interact in the search for and supply of nutrients and that soils actively sustain and defend plants while plants feed soil is just too important to be ignored, and could be the last frontier in the challenge to truly feed the world sustainably.
Two tests by Solvita – CO2-respiration and Labile Amino-N, help reveal soil biological potentials.
NEW SCIENCE: Soils participate to provide a wholesome environment for plant growth, even as plants actively participate in building and sustaining soils. Properly grasping this can lead to more successful long-term crop production strategies. The best way to describe the emerging scientific view is to recognize what modern ecologists call niche construction, the phenomena of organisms acting upon their environment to modify and improve it.
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 inappropriate 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 form in soil. Similarly, to keep adding twice as much nitrogen into soils than plants actually use for production, is a practice that needs to change. Modifying the soil testing approach can help.
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 sectors of soil labs and soil consultants who on a day to day basis support farmers and are answerable to their success.
Lab Analyzer for Soil Water Soluble Carbon and Soluble Organic Nitrogen is a component of soil health measurement.
EXPANDING CARBON TEST: The additional linkages helping create the Soil Health Tool package were refinements drawn on published research on water soluble carbon in soil and its role as indicator of plant and microbial exudates and food. This pool links directly to CO2 respiration of the soluble carbon test and a 24hr CO2-burst protocol. This work was underway by 2000 if not earlier. The new soluble carbon test relates to the biologically active soil carbon pool. The CO2 burst innovation helped make 24hr testing realistic and reproducible in a lab environment. Basal respiration – the original Solvita test – remains a foundation stone for investigating soil properties as they exist naturally.
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) methods to characterize availability. In most cases, the choice of the best extract depends on the actual soil and especially what it’s pH is. 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 questionable.
A European soil chemist where Brinton trained noted that the normal reagent concentration that soil and plants effectively experience “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 reponse calibrations are then run on these reagents, locking in the soil-test fertilizer crop response model as a static mechanical system.
CORNERSTONES OF SOIL HEALTH TESTING: Putting all the new tests together – active respiration, water soluble carbon, agrregate stability procedures and gentler extractants – results in a SOIL HEALTH TOOL. Woods End labs is presently one of 2 -3 commercial labs now offering this approach, building on Woods End’s efforts over 30 years to integrate biological tests into chemical procedures. As a work in progress, it needs a period of time where it may be compared to past approaches.
SHORT-TERM HOPES? 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 is slow and takes place over decades. So too, declines are also slow and therefore not noticed to the extent that they should have been. 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 of 100 samples per field examined. 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 3 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 likely to be “plant relevant” from lighter-weight extractants
- Evaluates quality of the pool of soil organic carbon.
– for instructions on sampling soil, contact: firstname.lastname@example.org
– list of upcoming events about the Soil Health Tool and Soil Health