For most of us, May proved to be not only as windy as a politician, but also as dry as low-fat popcorn. The combination of dry topsoil and high winds made for some gray days on the prairies. Dusty sloughs and dropping water tables meant hauling water for cattle and even household use. Is it a return to the dirty thirties?
Most of us have heard the grim stories of the dirty decade. Even the 1988 experience is still fresh in many producers' minds. Yet despite these dismal reminders, soil erosion continues to plague our industry (Figures 1- 4). As one producer put it "I don't know how I'm going to get all my seeding done. I've got land from Saskatchewan, Alberta, and Montana!"
What would the skies have looked like this spring if all the land continued to be farmed using dirty-thirties style tillage? Thankfully the reduced tillage movement has begun to catch on. In 2002 over 70 % of the seeded acres in Saskatchewan were seeded using reduced tillage, 40% of which was low disturbance.
In 1994, soil researchers John Doran and Timothy Parkin described the topsoil as "the thin layer covering the earth's surface which represents the difference between survival and extinction for most terrestrial life". In Saskatchewan, it has taken 10,000 years for our present soils to develop. What a shame to leave this precious resource vulnerable to erosion events such as wind and water!
Research at Lethbridge found topsoil losses as high as 30 tonnes/ha during a seven hour-long erosion event (60 km/hr winds on a clay loam textured soil). While the biggest concern with such damage may be the difficulty to establish a crop, there are other costs as well. Ditches may need cleaning out, fence lines may need to be rebuilt - this is all in addition to the actual loss in organic matter and nutrients, and the damage to soil structure. Further, once soils erode, there is a tendency for them to easily do so again. In general, there is a loss in soil productivity.
An erosion loss of even one inch of topsoil is equivalent to over 150 tonnes of soil per acre. In the black soil zone that would include approximately 7 tonnes of organic matter, 400 kilograms of nitrogen, 300 kilograms of phosphorus, and 3 tonnes of potassium lost per acre. That's a loss of $1500.00 per acre just in nutrients and that does not even include the value of the carbon stored in the organic matter. Most would agree the value of our topsoil makes it worth saving.
Some may argue this example was an extreme event; damage to this extent has never occurred before. "If we get normal conditions next year we will be all right." But it is important to realize that normal conditions are made up of average conditions combined with extremes.
For example, at the Waseca, SK Climate Station, 2001 was the driest year since 1937 (Table 1). 2001 was also the 3rd warmest of the last 95 years. In fact from October1, 2000 to June 14, 2002 there has only been 55 % of normal precipitation. Normal precipitation for this region is 397 mm per year.
Although the area has been fortunate in the last 50 years, having relatively stable precipitation each year, earlier in the century extremes were the norm. For instance there was only 45 % and 53 % of normal precipitation during the two-year periods 1917-1918 and 1928-1929, respectively. On the other hand, 14 of the past 95 years have seen more than 125 % of normal precipitation, compared to 13 years with less than 75% of normal precipitation. Such historical data emphasizes that "normal year" statistics actually include many years of abnormal and extreme conditions - conditions in which producers must maintain soil quality and attempt to grow a crop.
Another item that can be gleaned from the long-term climate data at Waseca is the warming trend: over one degree Celsius in the mean annual temperature. To put that in perspective during the last glacial age mean annual temperature was only about five degrees Celsius cooler than it is today. This emphasizes the need to use as many moisture conservation methods as possible. Research shows crops use moisture more efficiently to produce grain in a direct seeding system, and therefore greater yield is possible for each inch of water Mother Nature is willing to impart.
Weather extremes have always and will continue to be part of the agriculture business. It is tough on the nerves, but it needn't be so tough on our primary resource, the soil. It is crucial to plan with these extremes in mind so neither our spirits and nor our soil are gone with the wind.
Figure 1: Ditch filled with topsoil from wind erosion in 2002.
Figure 2: Ditch filled with topsoil from wind erosion in 2002.
Figure 3: Standing stubble filled with adjacent fields topsoil.
Figure 4: Ditch and bush filled with topsoil (2002)
Scroll down for TABLE 1
Table 1: Waseca Climate Station data from 1907 to 2001 (Data courtesy of Jim Maxwell).