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Microbial Soil pH Index (v3.0c, 3.1g)

Microbial pH Index (MpHI) reveals where soil pH limits carbon assimilation and helps assess the effectiveness of pH-altering management strategies for increasing SOC sequestration

This index is an indicator of how much microbial activity is possible for sequestering carbon based on the soil pH conditions. Higher values are indicative of soil pH values that are more favorable for microbial communities to sequester carbon.

To access high-resolution data for your area(s) of interest, contact our team.

High-Level Description

Within SOCSPOT 3.0c and 3.1g, the Microbial pH Index (MpHI) is a dimensionless gridded data product that captures how soil pH impacts soil microbial activity across space. Version 3.0c extends across rangelands and croplands within the Continental US (CONUS, 'c'), while 3.1g goes beyond to include a global extent. This product leverages understanding from contemporary studies of microbial communities responses to varying soil pH alongside the highest quality and spatial resolution geospatial data inputs to generate a global map of MpHI.

Use Cases

Knowing values of MpHI enables customers to:

  • Gauge where soil pH may be limiting carbon assimilation relative to soil temperature or moisture, thereby enabling them to understand whether particular management strategies to alter pH would be efficacious for increasing SOC sequestration.

Technical Specifications

  • Native Resolution: 100-250m
  • Spatial Extent: 3.0c = CONUS, 3.1g = Global
  • Domain: Croplands and/or rangelands
  • Units: Dimensionless (0-10)
  • Inputs: Soil pH
  • Temporal Frequency & Range: 2021

Algorithm Theoretical Basis

The algorithms for the Microbial pH Index (MpHI) are based on empirical equations derived from hundreds of observations across multiple studies spanning forests, grasslands, and agricultural lands across the globe. The index captures the relationship between soil pH and both soil microbial activity and abundance as found in empirical peer-reviewed literature. As such, values reflect the parabolic response curve of microbial communities across the range of possible soil pH.

Model Assumptions & Constraints

A number of assumptions and methodological choices are important to consider when using MpHI.

  • We only account for spatial variability in soil pH, and assume that temporal variability in soil pH is negligible relative to the spatial variance.

Known Issues

Temporal variability in soil pH is not accounted for due to lack of data availability.

What’s New?

Within the frameworks of SOCSPOT 3.0c and 3.1g, updates include:

  • SOCSPOT 3.0c and 3.1g are based on an improved relationship between microbial activity and soil pH that includes the most recent peer-reviewed literature.
  • Within SOCSPOT 3.1g, the extent has gone beyond CONUS to include global coverage.
  • Within SOCSPOT 3.1g, the source of soil pH has changed from SoilGrids+ to SoilGrids v2.0, which also resulted in a change in the input resolution.

Data Partners, Providers, and References

SoilGrids +: Poggio, L., de Sousa, L.M., Batjes, N.H., et al. 2021. SoilGrids 2.0: Producing soil information for the globe with quantified spatial uncertainty. SOIL, 7(1), 217–240. DOI: 10.5194/soil-7-217-2021

Accessing Data

Contact our team to request high-resolution data for your area(s) of interest.