USDA Natural Resources Conservation Service
Soil health measurements have for many years focused exclusively on nutrient limitations and excesses. However, for long-term sustainability of soil resources, soil health measurements need also to provide information on the biological and physical state of soil. They also need to identify constraints and explicitly guide management of these characteristics.
These biological and physical processes drive agroecosystem sustainability, resilience to climate variability including drought or the ability of soil to absorb excessive rainfall, carbon sequestration and cycling, and the ability to sustain high and stable yields in agricultural production. Biological and physical soil characteristics stabilize plant nutrient availability and moderate nutrient loss.
The ability to adequately understand and measure the biological and physical state of a soil will result in better overall nutrient and soil health management practices.
A goal of the Soil Renaissance is to incorporate soil health measures into standardized soil testing that is readily available, affordable, and commercially viable.
Here are objectives to achieve the goal, and strategies to complete those objectives:
1. Evaluate and develop complementarity between several new soil health tests and standardized soil nutrient testing.
- Support the development of a standardized soil health testing.
- Aggregate a nationwide dataset that combines Cornell Soil Health Test and Haney Test indicators with known farmer and field management information. Further refine and/or combine both test packages.
- Identify additional soil health measures that meet criteria for good soil health indicators, beyond the Cornell and Haney tests.
- Create and refine a standard process for additional soil health indicators and a framework for developing recommendations for farmers and landowners based on soil health measures.
- Engage Land Grant universities in the development, evaluation and calibration of soil health tests and recommendations.
- Set up an independent body of stakeholders to maintain a process to provide input into continued improvements in soil health testing development, interpretation and recommendations.
2. Partner with agricultural service providers to incorporate new recommendations based on soil health testing into existing management practices.
- Develop educational materials on standardized indicators and associated management recommendations.
- Provide content on soil health testing and management to be integrated into the Soil Renaissance education and outreach efforts with growers.
- Create Farmer Case Studies on successes in soil health testing and data-driven soil health management to be used in efforts of Soil Renaissance Education and Economics teams.
- Train agriculture service providers and growers on soil health test interpretation and data-driven soil health management recommendations.
- Organize efforts to engage private-sector and Land Grant university laboratories in providing new, standardized soil health testing packages and soil health management recommendations.
- Integrate payments for soil health testing and management implementation into government programs, e.g. Conservation Stewardship Program (CSP) enhancements.
- Facilitate farmer-to-farmer learning and training opportunities on practical implementation skills for soil health management practices.
December 10, 2014: A Framework for Soil Health Measurement & Improvement of Soil Health
Current farming and ranching operations are businesses operating on very narrow margins, responding to diverse and changing weather patterns, striving to meet increasing global demands for feed, food, fuel, fiber, flowers, and other commodities, while protecting and preserving the soil and water resources upon which their livelihoods depend. Building on the early principles of soil-testing and technology advances during the latter half of the 20th century and initial decade of the 21st century, many of these businesses are making decisions, using standard soil testing, based on a reasonable understanding of soil chemical properties and constraints that relate to crop nutrient uptake limitations. Physical constraints are only sometimes managed explicitly, while unfortunately, due to their complexity and ever-changing dynamics, principles of soil biology and interactions between soil biological, physical, and chemical processes have often been overlooked. Soil health constraints on today’s agricultural land are thus predominantly biological and physical constraints to soil process functioning.
The Soil Renaissance is working to mobilize a re-awakening to the critical importance of those properties and processes that can help improve individual economic returns and help remediate unintended consequences or externalities such as impaired resilience to extreme weather, and water and air quality. The Soil Renaissance Measurement Working Group, convened by the Noble Foundation and the Farm Foundation, included farmers, as well as representatives of agri-businesses, government (local, state and federal), non-government (NGO), university, and other partners. It should be noted that this new emphasis on soil resources actually represents a return to the roots of the Noble Foundation which focused its early efforts on educating and encouraging southern Oklahoma farmers and ranchers to practice land stewardship and resource conservation, including the use of soil testing.
Desired outcomes include improved health of our global soil resources such that they are:
1) not being eroded by wind, water, or tillage at rates exceeding their local regeneration capacity;
2) productive for their site-specific use (i.e., crop, tree, fruit, vegetable, vine, fiber, fuel, pasture, or range production);
3) capable of regulating and partitioning soil water (i.e., allowing rapid infiltration, storing large amounts of water in the root zone for use by the plants, and recharging ground water);
4) providing a suitable habitat for soil microorganisms and soil fauna (e.g., earthworms, arthropods, fungi, bacteria, etc.) that efficiently cycle and facilitate access to nutrients, help control pests and pathogens, promote plant growth, and cycle carbon captured into the soil through photosynthesis, and otherwise enhance physical, chemical, and biological properties and processes;
5) effective filters and buffers for anthropogenic and other materials added to them;
6) an efficient source/sink for essential plant nutrients such as N and P, so that those nutrients can be more efficiently cycled rather than lost to water or air resources; and
7) capable of providing a wide variety of goods and services needed to meet the needs of a rising population in a sustainable manner.
Soil Health Management needs to begin by identifying the characteristics of a healthy soil, assessing current soil conditions against that standard, and determining the greatest vulnerabilities. Remediation, restoration and maintenance practices need to be chosen and implemented based on measured soil conditions, as well as soil type, climate, and cropping system considerations, and need to be monitored for positive response, and adjusted accordingly.
The specific characteristics of a healthy soil (Harris et al., 1996) are goal or use dependent, because soils have both inherent (determined by the basic soil forming factors) and dynamic (influenced by current and recent management) properties. For essentially all uses except as a building material, a healthy soil will provide functions 1, 3, 4, and 5 above.
For productivity of food, feed, fiber, flowers or fuel, a “healthy soil” should also support high yields by providing optimum conditions with respect to the following:
• aeration, water storage and drainage;
• storage and facilitation of access to all essential nutrients in a form that is readily available to the plant species being grown;
• cycling of nutrients such as N and P efficiently and at times that are phenologically appropriate so that excesses vulnerable to leaching, drainage, or being transported through surface runoff to surface or groundwater resources do not accumulate within the soil profile; and
• support of sufficient biological diversity so that nutrient needs, pests, pathogens, and diseases affecting desirable plant species can be managed with minimal external input costs.
A Tiered Approach to Measuring Soil Health
The Soil Renaissance Measurement Working Group found commonality in embracing a tiered approach to development and expansion of soil health measurement. There was a sense of urgency that needed to 1) embrace current soil heath testing efforts that are “directionally correct,” but 2) acknowledge and respect the desire for robust research and development for increased regionally specific applicability, thus requiring version-designation and careful science-based articulation of current benefits as well as limitations of available assessments.
Thus the working group decided that a standard but simplified set of measures, representing all three categories of soil processes (physical, biological, chemical; Tier 1) needed to be broadly available immediately as a ‘conversation starter’ between any ag service provider and producer. This Tier 1 set will be able to be provided with a relatively short set of talking points on key soil health concepts. Additional more comprehensive soil health testing and cropping system assessment (Tier 2) which is currently available but has limited regionally-specific validation and calibration will be available at limited locations, and will be expanded and standardized as research and development of appropriate interpretations and recommendations progresses.
Tier 1. Version 1.0: Standardized soil health measures should be easy and relatively inexpensive to measure or to calculate from readily available information sources, and should include, at a minimum:
• Standard soil test (nutrients and pH). Justification: easily available through private and public labs; starts the conversation with familiar concepts regarding managing identified constraints
• Organic matter. Justification: readily available from most labs, used to discuss importance of water storage, pore space, soil hardness, interactions of biological, chemical, and physical processes.
• Aggregate stability. Justification: easily measured, visually and conceptually impactful indicator of physical soil health that producers can easily relate to; used to discuss infiltration, runoff, erosion, ‘housing’ for organisms; also biological processes
• Respiration. Justification: easily and inexpensively measured, conceptually impactful indicator of important biological processes in soil
• Solar utilization. Justification: the percent of time in a year when plants are actively growing and thus feeding soil life is easy and free to calculate, and stimulates discussion about management options.
• Amount of N fertilizer applied per yield. Justification: generally easy and free to calculate, stimulates discussion about biological N contributions and use efficiency
Deeper insights into current soil health status and how to enhance soil health to promote greater profitability, resilience, and environmental conservation will require more comprehensive soil health assessment (Tier 2) and management planning based on recommended practices that are appropriate to the region and cropping system. Diverse currently available tools contribute to this process and will be improved through continued research and development.
Tier 2, Version 1.0: Supplementary to the ‘conversation starter’ Tier 1 measures, additional tools /assessments/measures may be used. These should be chosen as needed and applicable for more comprehensive soil health management planning, to further diagnose soil health constraints and inform management changes. Special focus should be put on those indicators known to be most directly related to visually identified resource concerns or farm attributes that most significantly impact annual farm profitability. These could include:
• Active carbon
• Water and/or weak acid extractable C and N fractions
• Quantity of nitrogen in the active pool of organic matter
• Available water capacity
• Water infiltration rates;
• Compaction measurements
• Levels of enzymes indicative of the presence, level of activity, and resilience of microorganisms known to deliver microbial biocontrol services.
• Pathogen bioassays
• Soil macro- or micro-nutrient balances and/or concentrations
• Additional indicators
Further calculations and farm characteristics to integrate in decision making:
• The crops or plants growing in a field during a calendar year;
• Crop yields and/or pasture production;
• Quantities of nitrogen and other nutrients from off the farm applied to each field; and
• Quantity of N carried over from the previous production season;
• Rates of manure, compost, and organic amendment applications, levels of N in these inputs, and N in irrigation water when applicable;
Current publically available Tools/Packages which should be used with acknowledgement of need for regional adjustments that need to be made:
• Cornell Soil Health Assessment
• Soil Health Nutrient Tool (Haney Test)
• Soil Management Assessment Framework
• Additional offerings at other private and public labs
Critical factors that will drive selection and adoption of soil health indicators are:
• responsiveness of indicator to soil management
• ease of sampling
• economically viable cost of soil analytical work
• repeatability of analysis
• ability to interpret results in ways that inform economically and environmentally beneficial actions that enhance soil health for a given location, farm, and cropping system
Research needs identified by the Soil Renaissance Measurement Working Group to support a robust national soil health measurement platform include:
• Regional interpretation of indicator values and calibration of relative scoring and/or outcome-based scoring;
• Calibration of new nutrient recommendation tools that incorporate biological and physical processes to show outcomes, yields and nutrient response;
• Soil health management recommendations informed by soil health measures that are locally- and cropping-system-appropriate
• Research which embraces an “open access” concept.
Harris, R. F., Karlen, D. L. and Mulla, D. J. A conceptual framework for assessment and management of soil quality and health. p. 61-82. In Doran, J. W. and Jones, A. J. (eds.) Methods for assessing soil quality. Special Publication No. 49, Soil Science Soc. Am., Inc., Madison, WI. 1996. (Special Publication)