Congreves: Developing a Soil Health Assessment Protocol for Saskatchewan producers - Phase I
Date: April 2021
Term: 3 years
Status: Completed
Researcher(s): Kate Congreves, Athena Wu, University of Saskatchewan
SaskCanola Investment: $37,820
Total Project Cost: $181,701
Funding Partners: SWDC, WGRF, Agriculture Development Fund
Project Summary
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.
Maintaining and building soil health is an essential component of long-term sustainable agriculture. A healthy soil will produce higher crop yields under favorable weather conditions, have a strong capacity to withstand extreme weather events, and reduce nutrient losses. Monitoring and tracking the soil health status over time will aid in identifying soil constraints, and in adapting management practices for sustained soil functioning. To do this, 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. Pre-existing comprehensive soil health tests such as Cornell University’s Comprehensive Assessment of Soil Health (CASH) is widely used by farmers and researchers to estimate soil health status and improve soil health. However, CASH is not always suitable for regions where soil is different from the northeast US soils used to develop the scoring system; when CASH was used in the southeast US, it showed a lack of consistent responses. Therefore, it is critical to develop and use a regionally adapted soil health test to gain the most meaningful interpretation of soil health and function. 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—one that integrates biological, physical, and chemical indicators, transforms soil attribute values into meaningful scores, and uses a relevant weighting system to calculate the overall Saskatchewan Soil Health Score (SSHS) ranging from 0% (poor) to 100% (optimal).
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 (Figure 1) were representative of Saskatchewan’s soil zones and common crop rotations, including sites that were previously cropped with wheat, canola, barley, chickpea, lentil, field pea, soybean, potato, and green manure. Various soil chemical, physical, and biological attributes were measured (Table 1). Scoring functions were developed based on the data distribution for each attribute. Once the scores were computed for each soil attribute, predictive models were also developed based on the relationship between the soil attribute measurement and score. The individual soil health scores were then combined into a single overall soil health score using a weighted average approach. A weighted average assigns greater weight to soil attributes that explain a greater variation in the data set and can be more accurate than a simple average.
Figure 1. Soil sampling locations across Saskatchewan.
Table 1. Different scoring functions as assigned to each soil attribute.
The soil health scores were developed in relation to the individual soil attribute measurements (Table 1) 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, and median of overall SSHS was 60.17, 65.68, 62.92, 61.02% in Gray, Black, Dark Brown, and Brown soil zone, respectively. A correlation study revealed a positive relationship between soil health scores and cereal yields in certain years (as collected from the past 10 years—reported from the same rural municipalities where the soil samples were collected). The correlation appeared to be stronger during dry years. Thus, researchers recommend further study to explore this linkage at a finer scale.
In conclusion, a new Saskatchewan Soil Health Testing Protocol and Scoring system was developed; this forms the foundation of a promising tool for Saskatchewan producers who are interested in tracking soil health and using the results to inform management practices.
Acknowledgement:
Funding was provided by the Saskatchewan Ministry of Agriculture (Agriculture Development Fund), Western Grains Research Foundation (WGRF), Saskatchewan Canola Development Commission (SaskCanola), and the Saskatchewan Wheat Development Commission (SaskWheat).
Note:
A second phase of the project began in 2020 (CARP ADF 2020.286 Phase Ⅱ) with project funding provided by SaskCanola and SaskWheat. Phase Ⅱ of this project aims to further refine the Saskatchewan Soil Health Protocol by including various soil zones to provide soil zone-specific scores, to incorporate advanced soil biological indicators, and develop a user-friendly online tool that can transform a farmer’s routine soil test data into a soil health score.
Full Report PDF: Developing a soil health assessment protocol for Saskatchewan producers Phase I