Impacts of Reduced Tillage on Soil Health in Saskatchewan

Event

The historical use of tillage and summerfallow practices to control weeds in Saskatchewan had adverse impacts on soil health in the province. It also contributed to soil erosion by wind and water. The commercialization of genetically modified
(GM) canola in the late 1990s transformed weed control, with farmers switching from frequent tillage and summerfallow to control weeds to continuous cropping systems that rely on herbicides to control weeds. Continuous cropping systems also require greater fertilizer use, as fertilizer was never applied to summerfallow fields. Research finds that a rise in continuous cropping systems implementing zero-tillage or minimum-tillage practices occurred alongside increases in farmer-reported soil organic matter (SOM) levels by 41% between 1990 and 2024.

 Significance

Soil health is a multi-facetted factor, which can include wet aggregate stability, soil pH, electronic conductivity, cation exchange capacity, bioavailable nutrients, soil active carbon dioxide, soil protein, pore-size diversity, water storage, aggregation, and nitrous oxide production, among others. One important contributor to productivity SOM, as it improves both physical and chemical properties of the soil. Benefits of increased SOM include improved soil fertility, water movement, soil structure stability, and erosion resistance. Improvements in soil properties, such as water-holding capacity and improved microbial activity, contribute to improvements in crop yield. Reduced tillage helps to increase soil particulate
aggregation and decrease the rate of decomposition, reducing the release of SOM from soils. The increase in crop residue levels returning to the soil with the removal of summerfallow contributes to improved SOM levels.

 Analysis

A survey of Saskatchewan farmers collected data from three time periods (1991-1994, 2004-2006, and 2016-2024), across all three major soil zones, finding reduced tillage passes and a reduction in the number of summerfallow fields. Across the province, the average number of annual tillage passes decreased from 1.7 between 1991-1994 to 0.4 between 2020-2024. The greatest difference was seen in the period between 1991-1994 and 2004-2006, with a decrease in average annual tillage applications of 62%. Relatedly, the average percentage of fields within the sample that were summerfallowed each year decreased by 91%, from 15% of fields between 1991-1994 to just 1.4% from 2020-2024, with 81% of this decrease occurring between 1991-1994 and 2004-2005.
Both reductions in tillage passes and summerfallow practices on Saskatchewan agricultural soils have contributed to increases in overall SOM levels. Between the first ten years of soil sample results obtained (1990-1999) and the last ten years (2015-2024), the average percent of reported SOM in the soil increased from 3.33 to 4.71, an increase of 41%. Looking specifically at the survey time periods, average reported SOM levels increased by 19% between 1991-1994 and 2004-2006 compared to 26% over the most recent 20 years.
A corresponding increase in yields of the most commonly grown crops in Saskatchewan, wheat and canola, was seen in the survey sample data over the same period. Between 1991-1994, wheat yields reported by participants averaged 34.6 bushels per acre (bu/ac), increasing by 47% to 50.7 bu/ac from 2020-2024. Similarly, canola yields increased from 27 bu/ac on average from 1991-1994 to 40.4 bu/ac between 2020-2024, an increase of 50%. The observed increase in yields cannot be credited to any single factor, but rather is a result of the system of agricultural innovations over the study period, as well as variable precipitation between crop years. These innovations include improved crop genetics as well as improvements in pesticide and fertilizer technologies. Innovations in implements have also contributed to the increase in yields, such as the ability to use variable rate applications for fertilizer across a field based on nutrient requirements.
Fertilizer use has increased regarding pounds applied per acre of cropland between the 1990-1994 and 2016-2019 data sets. This has contributed to corresponding crop yield increases. Analysis revealed that for every 1% increase in fertilizer application, there is a corresponding 0.87% increase in crop yield.

 Conclusion

The adoption of GM herbicide tolerant (GMHT) cropping systems has allowed farmers to achieve effective and economical weed control without the need for soil disturbance. The results of this analysis reveal that the continuous innovation and technological advancements in Prairie agriculture are improving the environmental footprint, in terms of soil health, in a tangible way. Based on 30 years of GMHT crop production in Saskatchewan, this technology has contributed to Saskatchewan farmers being among the most sustainable farmers in the world.

The research article this is based on can be found by clicking here.

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