Establishing perennial forages is one of the top recommended methods to manage saline soils for the long term
Growing up on a mixed farm in southern Alberta, Alan Iwaasa was no stranger to the costly headaches that saline soils could create.
“There were certain land bases that just were poor,” Iwaasa recalls. “For a period of time, there was a lot of effort that was looking at levelling your land and putting in drainage tiles, putting in ditches in which to carry the runoff.”
These efforts often didn’t tackle the greater issues at play or lead to sustained improvements, he says. “It was very expensive, and in actuality it was very difficult to solve some of those long-term soil conditions.”
As a grazing research scientist at the Agriculture and Agri-Food Canada Research and Development Centre at Swift Current, Sask., soil salinity is a particular area of interest for Iwaasa. He estimates five to 10 million acres on the Canadian Prairies are affected by slight to severe salinity, depending on the year’s moisture.
“Sometimes in certain years when we have lots of moisture and salts get driven down from the soil profile, then it doesn’t seem to be a concern,” says Iwaasa. However, dry conditions after years of sufficient moisture lead to dissolved salts rising in the already-high water table, decreasing the availability of water needed for crops to grow.
In addition to poor crop production, saline soils can be identified by a white crust on the soil surface and the presence of saline-tolerant weeds, such as foxtail barley, kochia or Russian thistle. These areas can vary in size and are often in lower spots.
Experts agree there are no easy short-term solutions for saline soils and instead they need to be managed on an ongoing basis. “Soil salinity is actually more of a water problem than a soil problem,” says Shannon Friesen, crops extension specialist with Saskatchewan Agriculture.
“All we can really do is try to manage it to actually bring those salt levels down,” says Friesen. “If you do suspect that you have some saline issues in the soil, we always recommend, of course, doing the soil test for that so you have a better gauge of exactly what your levels are.”
Long-term salinity issues can be managed with practices that help intercept the groundwater. Establishing perennial forages, especially saline-tolerant varieties, help prevent weeds from spreading into any annual crops.
“I really feel that if there is an opportunity in which you can place a perennial, something that’s going to continue growing in that location and lower that water table or intercept that water so that the salinity issues don’t rise to the surface, that that is one of the best solutions,” says Iwaasa.
“We have struggled in the past to find forages that could survive, could maintain in those slight-to-moderate to even moderate-to-severe salinity issues, and some of those forages were plants that just grew there that animals actually didn’t really like to eat or couldn’t really be best suited for haying practice.”
AC Saltlander shows promise
Today, more promising saline-tolerant forage varieties are available, and Iwaasa and his team have conducted extensive research on AC Saltlander, a saline-tolerant green wheatgrass. One of these studies found that seeding at a rate of five or 10 lbs. per acre resulted in “no real difference in the overall forage biomass production,” says Iwaasa. Based on the results, however, he recommends a seeding rate of five lbs. per acre for slight to moderate saline areas, while areas affected with moderate to severe salinity can benefit from 10 lbs. per acre to ensure a successful yield.
Another study explored a variety of best management practices for establishing AC Saltlander at two locations, Swift Current and Outlook, Sask. This compared seeding rates of five and 10 lbs. per acre, conventional and direct seeding methods and seeding in spring or fall. It also included two salinity ranges, slight to moderate and moderate to severe.
Seeding rate results were very similar. With more moisture and irrigation used at the Outlook site, the five lbs. per acre seeding rate performed consistently across seeding methods and time of year. Dry conditions at the Swift Current site, however, resulted in greater success with conventional seeding compared to direct seeding, with less weed competition.
They also found that mixtures with AC Saltlander and other saline-tolerant grasses, such as slender wheatgrass, establish successfully and perform well in areas of slight to moderate salinity. While the other grass may phase out over time, the AC Saltlander would persist and provide benefits, which provides opportunities for areas of higher salinity, Iwaasa says. “Then it’s able to…move into eventually some of those more moderate to severe saline areas.”
Once a perennial forage is well established and growing in an area affected by salinity, he adds, “then we have to make sure that we don’t be tempted to rip it up and try to plant some sort of annual species into it that doesn’t have the salinity tolerance of any of these potential perennial grass species.”
As stands tend to diminish after five years, Iwaasa says more research is needed on increasing AC Saltlander’s longevity on benefits related to its weed-suppression ability and on how it would perform in a mixture with a legume.
Salinity may vary in small area
At Langham, Sask.’s Discovery Farm site, the home of Ag in Motion, applied research lead Blake Weiseth is heading up an ongoing field-scale study on establishing saline-tolerant perennial forages on saline soils. This study, which began last spring in partnership with Ducks Unlimited Canada and Nutrien Ag Solutions, compares three different treatments: AC Saltlander; Halo alfalfa; and a proprietary mix, Saline Master Blend, from Proven Seed, another partner in the study.
The study will examine differences in productivity each year for at least five years, Weiseth says, as well as the impact of salt levels in the surface soils over time.
While the first year of the study focused on gathering observations, and data collection will begin this year, Weiseth says one of the most interesting initial observations was how the level of salinity varied across the two-acre study site.
“The site is quite level topography, it’s in a relatively small area, so you might expect the salinity would be sustained across the entire area, but in fact it isn’t. It ranges quite drastically,” he says.
“Some of the soil test results that we collected show some of the areas really could be rated as not saline all the way up to moderately to severely saline, based on the electrical conductivity values that we measured.”
This observation showed him “the importance of taking a soil sample really to understand the extent of the area that you’re dealing with, and then how you can use maybe new techniques like variable rate input applications or seeding techniques to address that.”
For those who want to seed an annual crop in saline areas, choosing the right crop will depend on the level of salinity. For slightly saline soils, Friesen says pulse crops, and some oilseeds, such as canola, will still do very well in moderate salinity. Barley is one of the most saline-tolerant crops, she says, though it depends on the variety.
“We always want it to be the best variety that’s adapted to your soil and to your field and your area,” says Friesen, noting that farming saline areas separately can also be advantageous. “Certainly things like continuous cropping, ensuring that you have the right crop for the right field, certainly goes a long way.”
Friesen explains that producers may find annual crops “on the fringe of that saline area” don’t produce as well. “What you may be doing is continuing to put more fertilizer, more inputs into those areas to try to get them to grow, but those areas really aren’t meant for those crops.”
In this case, she suggests seeding a saline-tolerant crop in the most severe parts of a saline area, then leaving a one- to two-metre buffer zone between that and the regular crop. “This, of course, would help you keep those areas separate, but then you are not also adding additional salt through fertilizer, and you’re also hopefully seeing a benefit from those crops.”