Metric Development Process

Throughout 2023, in partnership with the Soil Health Institute the SISC Metric Technical Advisory Committee (MTAC) and outside specialty crop soil health experts, put the Soil Health Institute’s (SHI) three leading soil health indicators (Organic Carbon Concentration, Aggregate Stability and Carbon Mineralization Potential) through the SISC metric development process.  The goal of this work was to put SHI’s three leading soil health indicators through a specialty crop (perennial and annual) lens to see if they held up for specialty crop’s and specialty crop cropping systems.  
 

SHI did extensive work to arrive at their recommended three leading soil health indicators. SHI’s three metrics provide a minimum suite of widely applicable measurements for assessing soil health.  Because the vast majority of SHI’s work was done in commodity crops, SISC wanted to run that work through a specialty crop specific process to see if those same three indicators true as the top three indicators for measuring soil health for specialty crops.

 

Which SHI Indicators Did SISC Align With?

Through detailed review the SISC MTAC and specialty crop soil experts came to a clear recommendation that SISC align with two of the three SHI indicators.  This work was presented to the SISC Coordinating Council (CC) in late 2023, at which time the SISC CC approved SISC’s alignment with SHI’s indicators: Organic Carbon Concentration and Aggregate Stability as the best overarching metrics to measure soil health for specialty crops.

 

Why Not Carbon Mineralization Potential?

SISC did not align with the third SHI indicator, Carbon Mineralization Potential.  Carbon Mineralization Potential measures health of biological activity via the soil respiration rates of microbes in the soil.  The reason why this metric was ruled out by SISC for specialty crops is that in arid and semi-arid environments where irrigation is applied, higher respiration rates could indicate either a healthy biological activity in the soil OR a stressed activity in the soil.  Because of this, SISC did not find this metric a useful way to measure soil health for specialty crops.  SHI developed this indicator through research largely focused on row crops across N America.

 

SISC came to this conclusion with the SHI team, and recommended that SHI work with soil scientists from UC Davis to better understand/resolve this outstanding issue.

 

Unfortunately, there is not currently another simple universal way to measure the health of biological activity in the soil for arid and semi-arid environments. SISC is staying abreast of work being done in CA on this exact issue.  Once such a metric is better understood and agreed upon for all environments, including arid and semi-arid, SISC will revisit such a metric. 

 

Outcome and Conclusion

In conclusion, SISC is now aligned with two SHI Soil Health Indicators, Organic Carbon Concentration and Aggregate Stability as the minimum suite of widely applicable measurements for assessing soil health for all specialty crop cropping systems.

 

How Does A Grower Use These Metrics?

Organic Carbon Concentration requires taking a soil sample and sending it to a lab.  Be sure to take the soil sample at the same point in time (in the calendar year as well as the cropping cycle) each year to allow for best comparisons over time.

 

Aggregate Stability can be measured by anyone with the slakes app, which was developed by SHI.  Slakes mobile app is available for download from the App Store or Google Play.  It can also be sent into a lab with the Organic Carbon Concentration sample. Either option works.

 

For soil sampling, SISC is also aligned with SHI’s protocol for collecting soil samples for Organic Carbon Concentration and Aggregate Stability. Important Note:  SHI’s protocol documents are not limited to the two SISC Soil Health metrics.  When using SHI protocol documents, please only follow appropriate and needed protocol for Organic Carbon Concentration and Aggregate Stability.  You can disregard any directions regarding bulk density and Carbon Mineralization Potential within these guidance documents.

 

SISC is alligned with SHI's Soil Sampling Protocal: https://soilhealthinstitute.org/app/uploads/2022/06/SOP_SoilSampling-v1.1.pdf. 

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SISC is also aligned with SHI’s protocol for labs, see Standard Measurement Procedures:

https://soilhealthinstitute.org/our-work/initiatives/measurements/#resources for lab testing protocol for these two soil health metrics.

 

Key to using these metrics to measure Soil Health is sampling in the same way at the same point of the year/cropping cycle each year.  That allows a grower to see if their management changes are improving their soil health outcomes. 

 

If you have any questions or comments, please contact us: info@stewardshipindex.org

 

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