By Dorthea Grégoire
We’ve all seen the black snow in the ditches after strong winter winds. We know what it means; top soil has blown out of the adjacent field. But who cares? Well, to be honest everyone should. Whether you’re the farmer who owns the field, the next-door neighbour, or anyone else; we all should care because in the end it’s costing each and every one of us more than you’d ever expect.
Gusts of wind from 25-50 kmph are strong enough to move unprotected soil. When the wind starts blowing, it picks up soil particles and drops them along the way. These dropped particles collide with the ground and dislodge more soil particles creating a chain reaction that sends clouds of soil into the air. Eventually soil is lost; in some situations, “soil to the entire depth of tillage has been lost” states Agriculture and Agri-Food Canada. Taking a quick look at the soil-laden ditches alongside some fields seems to give us a good idea that the soil is blowing away. But how much has been lost? Dave Franzen, NDSU Extension Soil Specialist, estimates that at least TEN (10) TIMES the amount of soil that is left in the ditch has been taken up by the wind and carried distances up to 100km away. This soil is permanently lost; completely irrecoverable to the field from which it came. The amount of soil in a field is finite and will not regenerate without changes to existing management practices.
When our forefathers settled in the Red River Valley and southern Manitoba, they proudly and tirelessly worked putting the plough to the soil to bring it into production for the first time. In those days the crisp, black fields were a source of pride and showed the hard work that had gone into the farm. When the “Dirty Thirties” arrived there was very little left to protect the soils. Fields had been left vulnerable and the wind took away soil by the ton. Fortunately, farmers are by far some of the most resourceful innovators and masters of adaptive management when it comes to their farm. Today, although localized windstorms continue to displace soils from black earth fields, technologies have changed and so have agricultural approaches. Producers now see the inherent and economic value held within their soils and many have changed their management practices to ensure their soil stays in place. Unfortunately, not everyone has jumped on the soil-saving band wagon and the communal cost that individual field management decisions are having on public goods like infrastructure and water are becoming very apparent.
The erosion of topsoil from fields and its subsequent deposition into nearby drains, ditches and waterways creates a cascade of problems for both the producer and for those using and maintaining local infrastructure. The topsoil that ends up in ditches reduces the flow capacity of these drainage systems resulting in increased back flooding during times of peak flow. This back flooding affects all nearby landowners regardless of their land management practices. It also affects those who depend on the local drainage network itself, as the drains may end up flooded or undermined by the reduced flow capacities and thus not perform as they should. Furthermore, for every pound of soil that is lost from a field, organic matter that took thousands of years to build up is also lost. Organic matter naturally acts like a sponge. It takes up water and allows the water to sink into the soil rather than running off the fields or drowning out crops. The loss of this organic matter caused by wind erosion drastically decreases our soil’s ability to absorb water. This loss of water absorption results in increased runoff, increased in-field flooding and most importantly means that water is no longer being held for later use by the crops during the hot, dry days of summer. The loss of soil and organic matter from a field contributes to a decline in the health and productivity of that field. To further exasperate this problem, their loss also leads to increased runoff from the field and blocked drains adjacent to those same fields further reducing productivity and in-field health.
The consequences of losing topsoil unfortunately do not end with more runoff and less flow. It also means that valuable nutrients are being lost from the fields and ending up in our drainage system leading to the degradation of our water quality. Nutrients that are blown away with top soil end up in our ditches, drains and waterways and are ultimately being washed downstream. We may not see the impact in our own backyards, but downstream they contribute to the ever growing problems associated with sedimentation, nitrification and algal blooms on major water bodies across the prairies including Lake Winnipeg. When soil stays on the field, biologically available nutrients boost crop productivity and increase yields. When soil is lost to wind erosion nutrients fuel algal blooms and pollute waterways. Again this problem is exasperated as producers attempt to replace the nutrients from the soil by applying fertilizers. Unfortunately, studies have shown this has limited success. In many cases even a doubling of the amount of fertilizer applied to a field cannot make up for the loss in yield caused by eroded top soil and the subsequent loss of nutrients and organic matter (Kapoor and Shaykewich, 1990). This vicious cycle of nutrient loss and replacement only compounds downstream water quality problems, especially when year after year the nutrients applied to the field are continually lost through a constant battle with the wind.
A field that has suffered from severe erosion is a field that requires more inputs, is less economically productive and contributes to environmental degradation. Luckily for everyone involved there is an easy, cost effective solution available immediately … simple changes to in-field management practices. Leave stubble in the fields and planting directly into it when the spring comes. Soybean and grain growers across the prairies are already adopting this method successfully. As a bonus, by not having to till under the stubble, producers are not only preventing future wind erosion but are also saving time and money (it’s not cheap to start up those big cultivators!). This method also helps build up organic matter and increase the soil’s ability to absorb water. When we protect the soil, the need for inputs is reduced and fields become more resilient to seasonal flooding and drought. Having nutrients stay put in-field also means that producers can reduce the time commitments and inputs going into each acre, putting more money in each producer’s pocket and fewer nutrients into our waterways. This simple change also leaves resources for municipalities and the Province to spend on improving local communities rather than maintaining soil-laden ditches. In the past, black earth farming made our province viable but there might be good cause for re-thinking it today.
Agriculture and Agri-Food Canada. (2014-06-09). Wind Erosion. Retrieved from www.agr.gc.ca/eng/science-and-innovation/agricultural-practices/sol-and-land/soil-management/wind-erosion
Franzen, Dave. (2015/05/07). Wake Up Call. Retrieved from https://www.ag.ndsu.edu/cpr/soils/wake-up-call-05-07-15
Kapoor, A. and Shaykewich, C.F. 1990. Simulated soil erosion and crop productivity. Pp. 125–130 in Proc. 33rd. Ann. Mtg. Manitoba Soc. Soil Sci., January 9-10, 1990, Winnipeg, MB.
Orginal Article Found at: https://www.manitobawatersheds.org/news/black-earth