There is a lot of concern regarding climate change and specifically about the effects of global warming and drought in many parts of the world. Many cattle producers in Western Canada were severely affected financially by this past summer’s drought. Our climate is always changing and that will continue.
The climate on the Canadian Prairies during the 20th century has been an anomaly because of the absence of prolonged drought. This is not normal for the Prairies. Since settlement in the early 1900s only one decade, the 1930s, had a prolonged drought. However, 70 years later, a severe but short-term drought in 1999 to 2002 caused a significant reduction in forage and pasture production in the Aspen Parkland of Alberta and Saskatchewan. Many ranchers depended upon the generosity of eastern Canadian farmers for emergency shipments of hay to maintain a part of their breeding herds.
How does this severe short-term drought and the one this past summer compare to previous droughts? Dr. David Sauchyn at the University of Regina has been measuring tree ring growth patterns as an indication of historical changes in weather across Western Canada. His findings and historical data indicate much more variability in precipitation than was seen in the 20th century. The 1790s drought at Fort Edmonton, was so severe water levels on the North Saskatchewan River were too low some years to allow fur-laden canoes to navigate downstream during spring runoff. Sixty-five years later the Palliser Expedition surveyed the Canadian Prairies, from 1857 to 1860, during another drought. Captain John Palliser declared the arid Prairies “forever comparatively useless” for crop agriculture.
Sauchyn’s tree ring data confirms four major droughts from1791 to 1873. In the four centuries, from 1600 to 2000, he says this region has averaged one long-term drought every 50 years.
In future, western Canadian cattle producers need to be better prepared for severe drought conditions. This will require more conservative grazing management practices and greater quantities of stored forages than is the norm today. Range managers will need to be more adaptable in the future in order to survive.
In the past, overgrazing of rangelands by livestock especially during drought caused declines in forage production, and the death of many productive grasses, forbs and sedges which were replaced by unpalatable and low-growing plants.
The principal consideration of any grazing system is to balance livestock needs with the available forage supply through proper stocking rates. This is the number of animals that may safely graze a defined area without degrading soil or vegetation, and allows the grazing land in poor health to improve.
On range the proportion of forage produced during the growing season that may be grazed is generally 40 to 50 per cent, but this varies with the stage of growth, climate, location and plant community. The carry-over is left as protective cover to protect the soil and maintain root and crown vigour, conserve scarce moisture, and provides emergency forage. Infertile Prairie sand-hills, for example, can only endure 30 per cent grazing. Moist soils may survive 50 to 60 per cent utilization. Different plant species have varying tolerance levels due to different plant structures and growth patterns.
Deep roots may help some native grasses grow more forage than some tame grasses under adverse conditions such as drought.
Dr. John Dormaar of the Lethbridge Research Centre points out that “tame grasses have fewer roots than many native grasses because they have been selected to have more top growth and less root mass. During high-rainfall years, a higher proportion of tops as compared to roots is advantageous for higher forage production by tame grasses. However, during a drought, more and deeper roots are needed to extract soil moisture and nutrients from deep in the soil.”
Overgrazing reduces too much leaf matter, reduces root growth and leaf tillering and eventually eliminates the palatable, taller grasses and forbs that normally produce 60-80 per cent of the forage and cover in healthy Prairie grasslands. The taller plants are replaced by low-growing or unpalatable grasses, forbs and sedges that provide only about 25 to 35 per cent of normal forage and cover.
Leaving 40 to 60 per cent of the leaf area at the end of the grazing period is critical for the good health of the major range plants for three reasons. First, the remaining leaf area will allow photosynthesis to continue, permitting plants to survive the stresses of grazing and drought. Second, residual leaf area retains active leaf tissue needed to feed and replenish plant tops and roots after each grazing interval. Third, the residual leaf area provides the energy needed by plant roots to keep them alive.
Remaining leaf tissue after grazing will eventually become litter or dead plant material. Litter contributes to range health in several ways. It keeps the soil cooler, improves water infiltration, prevents erosion, and shades weed seedlings. In the dry, mixed-grass prairie, where the rangeland is being grazed, there is rarely “too much” litter. In contrast, in the higher rainfall areas of the Aspen Parkland, some litter is necessary but too much litter reduces grass tillering and young regrowth. It may smother forage seedlings, and it creates a fire hazard.
The effect of removing plant litter and altering the microclimate is immediate and it can be long lasting. Dr. Walter Willms at Lethbridge, Dr. Paul Jefferson at the Western Beef Development Centre and Dr. Ann Naeth at the University of Alberta all stress that “plant litter moderates the soil environment, and removing too much results in increased soil temperature, increased evaporation, and reduced soil water infiltration which causes the scarce rain during drought to run off rather than soak into the soil.”
They conclude that long-term heavy grazing reduced water infiltration rates and increased soil compaction. Lightly grazed sites had about twice the water infiltration rates compared to very heavily grazed sites in their research findings.
Drought can be managed most effectively by having plans in place to deal with a shortage of both stock water and forage before it occurs. Prairie cattle producers need a plan so they can utilize all their options when the next major drought occurs. Water and forage are the most precious commodities, and their conservation and availability need to be planned in advance.
Grazing grass, shrubs and forbs in
combination, as found in naturally occurring native rangeland, is one means of providing high-quality forage during periods of declining forage production, especially during drought.
Dr. Mike Schellenberg of the Swift Current Research Centre points out that “shrubs have the potential to provide high-protein forage during periods when grasses and forbs are low and have been found to provide more consistent year-round source of nutrients. Under drought conditions the shrubs’ advantages lie with their ability to extract water and minerals from depth.”
Aspen, balsam poplar, willows, western snowberry, silverberry, saskatoon, chokecherry and pin cherry, wild raspberry and wild gooseberry are all available for browsing by livestock. Only balsam poplar, western snowberry, silverberry and some willow species are not preferred browse for livestock during the growing season. During a drought, hungry cattle are known to eat much more western snowberry than when other forages are abundant. Thus grazing cattle can take full advantage of forested rangelands if available for grazing and browsing during drought.
In a drought, stocking rate, season of grazing and animal distribution are even more critical than in wet periods to ensure the survival of rangeland plants and sufficient growth to cover the soil to minimize erosion. Coolseason natural grasslands need to be protected during the vulnerable spring period of growth.
It makes sense to graze soft grasses in spring and summer when they are palatable and nutritious. If left ungrazed, about 60 per cent of the foliage disappears by early fall.
Hard grasses on upland natural grasslands remain palatable in summer, fall and winter so they make good late-summer and fall-winter grazing. A moderate stocking rate, lighter grazing pressure, and a grazing system that allows for periodic deferral of grazing during the vulnerable spring season enables native plants to grow foliage for grazing and reproduce shoots and roots during drought.
After a period of grazing, the residual foliage is critical for several reasons. During the growing season this residual leaf area feeds the range plant tops so they can regrow and tiller, while they recover from grazing. The residue also feeds energy into plant roots enabling them to remain deep underground, collecting both soil moisture and mineral nutrients. By fuelling both top and root growth this residual foliage preserves the life of the forage plants.
Litter also prevents erosion in winter, traps snow and stores energy in stem bases needed for spring regrowth.
Nevertheless, perennial tame pastures are the logical first fields to be grazed in spring, preferably using a complimentary grazing system that defers the use of natural grasslands until later in the grazing season. They need to be grazed using a type of rotational grazing where the first field grazed in the spring in year one is not grazed first in year two. If there is forested rangeland available then graze it from late spring through summer. Then graze the natural grasslands from late summer, fall and winter, grazing where available.
If there are early-summer rains, seed annual cereals, for summer grazing or fall-winter swath grazing.
Perennial cool-season grasses, whether native or tame, have grown most of their foliage for the year by July 15. If the May-June rains have failed, July is the time to ship the herd to a different region where good rains have produced more forage. The alternative is weaning calves early, and selling both calves and part of the cow herd well ahead of the normal fall sales.
Russian wild rye and Altai wild rye, noted for deep roots, are drought-tolerant introduced grasses. Dr. Bruce Coulman at the University of Saskatchewan, found a big difference in these grasses by midsummer. In drought years “they were still green and growing whereas all the other tame grasses had turned brown.” In the Aspen Parkland on black soils, Russian wild rye provided excellent early-spring and late-fall pastures, and allowed an extension of the grazing season. However, on grey wooded soils, Kentucky bluegrass outcompeted the Russian wild rye after two to three years.
Crested wheatgrass can be successfully used for early-spring and late-fall pasture in the Aspen Parkland as well as in the drier areas of the Prairie. It displays a drought-escape tendency, initiating growth early in the spring and then shutting down as soil moisture decreases. It produces seeds earlier and undergoes more rapid leaf senescence than smooth brome grass and western wheatgrass.
Crested wheatgrass stops growing during the hot, dry summers and reinitiates growth in the fall, if soil moisture is available. Thus, crested wheatgrass needs to be grazed in the spring, left to regrow over summer, and grazed last thing in the fall. With fertilizer, crested wheatgrass at the Pathlow Community Pasture Research site near Melfort, Sask., provided grazing for about 10 days to two weeks earlier in the spring and later in the fall than the rest of the tame pasture grass species.
At the Kinsella Research Ranch in northeastern Alberta the native plains rough fescue grew about one-half a crop in the drought of 1999-2002, while smooth brome grass grew very little due to a lack of soil moisture and its lower root mass.
Drought is a fact of life in a Prairie climate. Thus, every range manager must prepare a personal drought management program for his or her property and have it ready to implement when drought occurs. This should include the storage of hay and other feeds in long-term dry storage facilities for emergency use during the next drought.
The question is not if there will be a drought, it is when, how long will it last, and how severe will it be?
The drought in 1999 to 2002 and again this past summer in central Alberta and Saskatchewan was a warning to range and cattle managers to be better prepared for the next long drought. It will happen again!
Water is still the world’s most precious resource. We need it every day.
Duane McCartney is a retired forage beef systems research scientist with Agriculture Canada in Lacombe. Art Bailey is a retired range professor from the University of Alberta.
For more on dealing with drought download the new publication MANAGING THE CANADIAN PRAIRIE RANGELANDS. It summarizes all the current research and is available on