Developing a soil health assessment protocol for Saskatchewan producers (Phase 1)

Key Result

Researchers developed a Saskatchewan soil health assessment protocol and scoring functions, providing the foundation for tools to transform a farmer’s routine soil test data into a Saskatchewan Soil Health Score. These scores can track soil health status over time, and can measure the effect of farm management on soil health status.

Project Summary

Overview

Soil health is an essential component of long-term sustainable agriculture. Even though soil health attributes have been identified and various soil health testing protocols have been developed around the world, no standardized science-based soil health test is available to producers 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.

Athena Wu, research technician with Kate Congreves, collects soil samples in the field.

In fall 2018, researchers collected soil samples (0-15, 15-30, and 30-60 cm depths) from 55 arable fields across Saskatchewan along with a couple of native prairie samples to compare. Soil health scores were developed in relation to the individual soil attribute measurements along with predictive models.

  • For the 0-15 cm soil depth, 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 soil depth of 15-30 cm, attributes with 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 carbon and nitrogen indices, including SOC, AC, TN, TC and soil protein, produced the highest weighting factors.

The average Saskatchewan Soil Health Score (SSHS) is 56.97 per cent for the 0-15 cm soil depth, 63.88 per cent for 15-30 cm, and 64.33 per cent for 30-60 cm. The overall SSHS for the 0-60 cm ranged from 41.24 to 77.05 per cent. The highest score belonged to the native prairie soil. The overall SSHS for the 0-60 cm depth did not differ across soil zones.

For the most part, canola and cereal crop yields were not well correlated to the SSHS, although the correlation appeared to be stronger during dry years, particularly for cereals.

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 track soil health status over time and provide scientific information needed to inform and adjust  management plans.
  • 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.
  • 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.

Soil health improvement takes time. Saskatchewan soils hold great potential for carbon sequestration and storage (as Brian McConkey et al. have demonstrated), but changes in soil organic matter or total carbon may only be detected in the long-term – five to 10 years, or more. Soil organic matter is a crucial metric for soil health, but it is difficult to interpret in the short-term.