Recommended Measurements for Scaling Soil Health Assessment

Overview

Healthy soil is the foundation for regenerative, climate-smart agriculture. Measuring management-induced changes in soil health can provide insight into farmers’ progress at establishing more regenerative systems and guide place-based selection of practice changes that promote enhanced ecosystem processes and services.

To identify effective and widely applicable measurements of soil health, the Soil Health Institute (SHI) conducted a 3-year, $6.5-million project that evaluated over 30 soil health indicators at 124 long-term agricultural research sites across North America where conventional systems were compared with regenerative soil health systems. Sites were selected to enable statistical assessment of each soil measurement across a continental range in climates, soils, cropping systems, and management practices to identify a minimal suite of measurements that are cost-effective, interpretable, and responsive to soil health promoting practices.

Based on these results, SHI recommends three measurements to be widely applied across North America (and likely beyond). Those measurements include:

  1. soil organic carbon concentration
  2. carbon mineralization potential
  3. aggregate stability
Measurement Method Reflected Outcome
Organic Carbon Concentration Dry combustion. For calcareous soil: Total C – Inorganic C
  • Nutrient cycling and retention
  • Stable and distinct soil structure
  • Available water holding capacity
Carbon Mineralization Potential 24-hr CO2 burst resulting from rewetting air dried, sieved soil
  • Carbon and nutrient cycling capacity
  • Strongly related to microbial biomass and activity
Aggregate Stability 10-min change in slaking via image analysis
  • Resistance to wind and water erosion
  • Soil water infiltration and storage
  • Stable soil structure

While these three metrics provide a minimum suite of widely applicable measurements for assessing soil health, additional measurements may be included depending on the landowner’s or researcher’s objectives. For example, adding soil texture to this list of measurements allows us to calculate a soil’s available water holding capacity. We can then show a farmer how much more water they can store by increasing their organic carbon and improving soil health. Because management does not change soil texture (sand, silt, and clay), it only needs to be measured once.

Together, these three indicators and predicted available water holding capacity can inform stakeholders on how soil health management practices affect soil’s ability to support biomass production; store, filter, and transform nutrients and water; host biodiversity; and regulate C pools. This minimal suite of soil health indicators is expected to increase the number of stakeholders capable of quantitatively testing and monitoring their soil, which in turn may increase adoption of management practices that result in healthier soils.

Learn more about our recommended measurements for scaling soil health.

Resources

Peer-Reviewed Publications and Summaries

Peer-reviewed publications detailing our research efforts to identify a minimum suite of recommended measurements are linked below along with brief interpretive summaries that distill the key findings from each study.
  • Introducing the North American project to evaluate soil health measurements

  • Carbon-sensitive pedotransfer functions for plant available water

  • Linking soil microbial community structure to potential carbon mineralization: A continental scale assessment of reduced tillage

  • An evaluation of carbon indicators of soil health in long-term agricultural experiments

  • Selecting soil hydraulic properties as indicators of soil health: Measurement response to management and site characteristics

  • Evaluation of aggregate stability methods for soil health

Standard Measurement Methods

Here we share laboratory SOPs (Standard Operation Procedures) that SHI uses to communicate needs with commercial soil testing labs.
  • Soil Health Sampling Standard Operating Procedure

  • Soil Total Carbon and Nitrogen by Dry Combustion Standard Operating Procedure

  • Soil Inorganic Carbon by Modified Pressure Calcimeter

  • Wet Aggregate Stability by Image Quantification Standard Operating Procedure

  • Potential Carbon Mineralization Standard Operating Procedure

  • Particle Size Analysis by Hydrometer Standard Operating Procedure

  • Predicting Available Water Holding Capacity

Additional Resources


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Funders


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