The dust bowl of the 1930s conjures up images of heartache, hardship and economic disaster. Could it happen again? Research conducted by Thomas Fox, Thomas Barchyn and Chris Hugenholtz at the University of Lethbridge shows that soil conservation efforts implemented by farmers in the 1990s have significantly reduced the risk of another Dirty Thirties.
The research looked at the frequency of airborne dust between 1961 and 2006 from seven weather stations across the Prairies, and correlated the data to changes in farm management, such as the increase in direct seeding and reduction of summerfallow.
“It is quite difficult to measure changes on a landscape basis, but we were able to show a correlation between changes in dust frequency and wind erosion potential with farming practices,” explains Hugenholtz.
The researchers analyzed Environment Canada’s Historical Weather database from Edmonton, Red Deer, Calgary, Saskatoon, Regina, Brandon and Winnipeg over the 45-year period. They assessed airborne dust records and developed a climatic wind erosion potential equation to standardize the environmental conditions that were conducive to wind erosion events. This environmental data was compared to Agricultural Census farm practices data from Statistics Canada at 5-year intervals from 1976 to 2006.
Two practices linked to reducing wind erosion potential include the adoption of direct seeding and reduction of summerfallow. With direct seeding, pre-seeding tillage is reduced and seed is placed into the soil through standing stubble. This reduces the exposure of the soil to wind erosion.
Summerfallow is the practice of leaving the land unseeded for one year in order to replenish the soil moisture. Tillage during the summerfallow year can leave the soil more exposed to wind erosion, so the reduction of summerfallow acres will reduce the potential for dust events.
Summerfallow data was available from 1976 to 2006, while direct seeding data were available from 1991 to 2006, but extrapolated back to 1976 using data from the United States.
By comparing the changes in farming practices that helped protect the soil against wind erosion, the researchers were able to develop a correlation between fewer dust events and farm practices.
“Climate does play a role in setting up the potential for wind erosion, but it is mostly the actions of humans on the landscape that determine whether wind erosion will be a factor,” says Hugenholtz.
The Environment Canada data showed that the frequency of blowing dust dropped between 1961 and 2006, as did the climatic potential for wind erosion. However the biggest declines came after 1990, when the practices of direct seeding and zero tillage became widely adopted.
Changing farming practices
In 1991, the use of direct seeding was approximately 10 percent of the area under cultivation, but by 2006, direct seeding accounted for over 60 percent of seeded acreage in Saskatchewan. From 1991 to 2006, the amount of summerfallow declined by 40 percent.
In the publication, The Economic, Agronomic and Environmental Impact of No-Till on the Canadian Prairies, published by the Alberta Reduced Tillage Linkages organization, Figure 1 shows the dramatic rise in zero-tillage as derived from Statistics Canada data. Zero-tillage, like direct seeding, places seed directly in to the soil without any previous tillage. In general, less than 10 percent of the soil is disturbed while seeding.
The report, co-authored by Dr. Mirza N. Baig of Consulting Options in Edmonton, and Peter Gamache, former Team Leader of RTL also in Edmonton, is based on peer-reviewed research, and is one of the legacies left behind by RTL, which ceased operations in August 2009.
Hugenholtz says that the significant reduction in dust events after 1990 are indicative of the Prairie-wide change in farming practices, which reached a threshold where soil conservation efforts had an impact on dust events. At this threshold, dust events became more directly correlated with climatic erosion potential where only the most severe climatic conditions produced dust events.
“Overall, our findings suggest that soil conservation initiatives have had an impact in reducing airborne dust on the Canadian Prairies,” explains Hugenholtz. The complete findings were published in Environmental Research Letters 7 (2012) http://iopscience.iop.org/1748-9326/7/1/014008/article.