Continuous Cropping and GM Crops Improve Soil Health

Innovations often completely transform systems of production. The invention of production lines transformed automobile manufacturing. The innovation of cellphones transformed people’s ability to communicate. Similarly, the innovation of genetically modified (GM) canola in the Canadian Prairies transformed crop production systems. Transitioning to Continuous Cropping and Reduced Tillage Practices The ability to efficiently control weeds through herbicide applications rather than through tillage transformed crop production. Historically, the use of tillage was the leading form of weed control, with many fields producing a crop one year only to be tilled numerous times the following year as part of the practice of summerfallowing. Summerfallowing is when a field is not seeded to a crop and tilled multiple times through the spring, summer and fall to prevent weeds from growing and going to seed. The number of tillage passes would depend on the amount of rainfall during a growing season. The greater the amount of rain, the greater the number of tillage passes. The commercialization of GM canola in the late 1990s transformed in-crop weed control. Farmers could plant herbicide tolerant canola into weedy fields, spray the crop post-germination and receive efficient control of weeds, especially weeds that can be difficult to control such as thistles and wild oats. As the adoption of GM canola grew, farmers consistently experienced superior weed control through continuous cropping practices, removing the vast majority of summerfallow acres and tillage passes. Between the periods of 1991-1994 and 2004-2006, the use of tillage decreased 62%. By the 2020-2024 period only 1.4% of Saskatchewan crop acres included summerfallow. Changes in SOM Levels The frequent use of tillage and summerfallow practices resulted in lower levels of soil organic matter (SOM). Historically, Saskatchewan SOM levels ranged from 5.16% and 5.57% in 1889 at Maple Creek, to 12.74% in 1891 and 13.54% in 1897 at Saltcoats, and 13.27% in 1891 and 14.01% in 1897 at Yorkton. Over the course of the 20th century, the levels of SOM consistently declined across the province. Both reductions in tillage passes and summerfallow practices have contributed to increases in overall SOM levels. A survey of Saskatchewan farmers collected data on SOM percentages dating back to 1990. Between the periods of 1990-1999 and 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. The following figure illustrates this increasing trend in the average reported percentage SOM in agricultural soils. Benefits of Higher SOM Levels The farmer survey identified an increase in yields of the most commonly grown crops in Saskatchewan: wheat and canola. During the period of 1991-1994, wheat yields reported by participants averaged 34.6 bushels per acre (bu/ac), rising to 50.7 bu/ac from 2020-2024, an increase of 47%. 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 are 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 such as GM crops, as well as improvements in pesticide and fertilizer technologies. Innovations in implements have also contributed to this, such as with the ability to use variable rate applications for fertilizer across a field, based on nutrient requirements. Greater SOM levels provide additional crop benefits, such as reduced erosion and increased moisture conservation. Increased SOM has dramatically reduced soil erosion by both wind and water. The reduced water erosion prevents fertilizer nutrients and pesticide residues from leaching into watersheds, providing additional environmental benefits. Higher SOM levels and the increased presence of post-harvest residues contribute to providing an insulating layer of material that reduces moisture evaporation rates during period of intense heat. Some environmental activist organizations are spreading false information about the environmental benefits of continuous cropping and the use of herbicides to control weeds rather than the use of tillage. These activists groups publish reports that are not peer-reviewed, often using flawed methodologies to assess data and advocate results that aren’t supported by the data. Our peer-reviewed research quantifies the improvement of soil health following the transition to continuous cropping and chemical weed control systems, soundly refuting the false information spread by activist organizations. To check out the full, open access article titled “Impacts of reduced tillage on soil health in Saskatchewan”, click here Sutherland, C., S. Gleim, and S.J. Smyth. (2026). Impacts of reduced tillage on soil health in Saskatchewan. Environmental Challenges, 24(101613). https://doi.org/10.1016/j.envc.2026.101613