Developing a soil health assessment protocol for Saskatchewan producers Phase Ⅰ

Researcher: Dr. Kate Congreves and Athena Wu, Department of Plant Sciences, University of Saskatchewan

Project Code: CARP ADF 2017.151

Final Report: April 2021

Summary: Maintaining and building soil health is an essential component of long-term sustainable agriculture. Farmers and researchers need appropriate tools and methods for assessing and interpreting the health status of their soils. Even though soil health attributes have been identified and various soil health testing protocols have been developed around the world, there is no standardized science-based soil health test available to producers for use with soils in Saskatchewan and the Prairie provinces. The objective of this research is to develop a new Saskatchewan Soil Health Assessment Protocol (SSHAP) tailored to Saskatchewan's semi-arid climate and major soil zones.

In fall 2018, soil samples (0-15, 15-30, and 30-60 cm depths) were collected from 55 arable fields across Saskatchewan along with a couple native prairie samples to compare. The sampling sites were representative of Saskatchewan's soil zones and common crop rotations. Various soil chemical, physical, and biological attributes were measured.

The soil health scores were developed in relation to the individual soil attribute measurements along with the predictive models of best fit. For the 0-15 cm soil depth, the attributes with the greatest weight and therefore the most influence on the soil health score include Phosphorus (P), Total Carbon (TC), Active Carbon (AC), Soil Organic Carbon (SOC), Total Nitrogen (TN), and Nitrous Oxide (N2O). For the deeper soil depth of 15-30, the attributes that have the most influence on the soil health score are: TC, SOC, Field Capacity (FC), P, TN, and Wet Aggregate Stability (WAS). For the 30-60 cm depth SOC, FC, Manganese (Mn), TN, Zinc (Zn), and TC have the greatest influence. Overall, soil C and N indices including SOC, AC, TN, TC, and soil protein produced the highest weighting factors. The average SSHS is 56.97%, 63.88 and 64.33% in soil depths of 0-15 cm, 15-30 cm, and 30-60 cm, respectively. The overall SSHS for the 0-60 cm ranged from 41.24 to 77.05% - the highest score belonging to the native prairie soil. The overall SSHS for the 0-60 cm depth did not differ across soil zones. A correlation study revealed a positive relationship between soil health scores and cereal yields in certain years. The correlation appeared to be stronger during dry years.

Key Messages:
- A Saskatchewan Soil Health Assessment Protocol and Scoring Functions were successfully developed. This provides the foundation for developing tools that are capable of transforming a farmer's routine soil test data into a Saskatchewan Soil Health Score.
- Saskatchewan Soil Health Scores can be used to monitor and track soil health status over time and provide scientific information needed to inform and adjust management plans aimed at improving soil health and functioning.
- Research results showed that soil Carbon (C) and Nitrogen (N)-indices primarily drive soil health differences, and therefore indicate that management decisions aimed at improving C and N sequestration will also improve soil health scores.
- A positive relationship was revealed when testing the linkage between soil health and crop productivity which means healthier soils may help safeguard crop yields during sub-optimal dry growing conditions. Further research is warranted to confirm the observed apparent relationship between soil health and yield during dry years.

Click the links below to download a short version of the report, the full detailed long version of the report, or the related Canola Digest PDF.

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