Enhancing the Saskatchewan Soil Health Assessment Protocol – Phase 2

Project Description

This project builds of the recently completed Saskatchewan Soil Health Assessment Protocol (SSHAP) Phase1 studies funded by Sask Wheat along with other industry funders.

It is necessary to build off this research to expand the soil dataset with the goal of adjusting the SSHAP, so that the output will be soil zone-specific scores. This will be performed by increasing the sample size for each soil zone (Brown, Dark Brown, Black, and Gray soil) and provide zone specific soil health scores to enhance the SSHAP. This project will also incorporate novel biological indicators of soil health and will evaluate the contribution of biological properties including microbial abundance and community structure and enzyme activities to the overall soil health assessment.

Biological indicators may have the greatest utility in these comparisons due to their sensitivity and because the rationale for adopting regenerative agricultural practices is founded on increasing biological diversity. In this research, they will compare the soil health scores from conventional and regenerative-type fields in each soil zone, to determine which soil health attributes point towards early-change and improvement of soil, and how much change might be expected.

Thus, the main goal of this Phase 2 study is to deliver a user-friendly online tool that shows growers the soil health curves and where their sample falls on the soil health scoring curve and to provide recommendations to improve the soil health status over time.

Research Results

Healthy soils form the basis of productive farming systems, and soil health tests can be useful tools to support good management decisions. The concept of soil health recognizes soil as a living and dynamic natural system, a notion that aptly fits in the realm of biology; however, soil health tests are often dominated by indicators of soil fertility and chemistry. Biological indicators of soil health remain understudied and underrepresented in soil health assessments. To address this gap, we evaluated biological indicators of soil health (including organic and total C, total N, mineralized C, extracellular enzyme activity, and phospholipid fatty acid (PLFA) analysis for microbial biomass and adaptation response ratio (ARR)). To do so, 153 soil samples were collected from different fields producing major field crops (cereal, oilseed, pulses), spanning the Black, Dark Brown, and Brown soil zones in Saskatchewan. We assessed whether soil biological indicators could be contextualized by soil classification and measured their responsiveness to different agricultural management practices. Despite the dynamic nature of biological indicators of soil health, we found that soil classification by great group constrained measurements and served as a useful contextualizing factor to adjust scoring functions. Further, we found biological indicators of soil health (namely soil organic C, total N, and P and S enzyme activity) generally improved with more regenerative crop production practices such as cover cropping or organic management. Although other indicators such as CO2 mineralization, N and C cycling enzymes, PLFA and ARR showed fewer differences among crop production practices, all were greater under prairie grassland than cropland soils. These trends were also supported by soil organic matter stoichiometry (N:C, P:C, and S:C) results, suggesting that element to carbon ratios might be useful features for future soil health assessments. As a result of this project, a soil health scoring tool was developed where users can input a soil test result for key biological indicators (i.e., soil organic C, total N, CO2 mineralization, and PLFA microbial biomass), select their soil zone, and then be provided with the resultant soil health ranking and description of the relative soil health status for their sample. This tool will be available on my lab website. We will continue to build on the tool as part of the Saskatchewan Assessment of Soil Health (SASH) framework.