Wetter-than-normal soil over much of the Prairies may worsen soil salinity problems this year.
Many growers assume they need to see salt before there is a problem, but Western Canada’s sole public agricultural salinity hydrologist said most damage occurs without an obvious ring around the field.
Harold Steppuhn said more farmers will have salinity problems this year because of higher than average soil moisture last year and this year.
“In agriculture, salinity in soil refers to a state where dissolved minerals are concentrated beyond a point where crops’ roots can make use of them and start to cause damage to the plants,” said Steppuhn, who works at Agriculture Canada’s Semiarid Research Centre in Swift Current, Sask.
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“Salinity can vary greatly in our soils, and over the space of a few metres, we can see it go from a problem to no issue at all.”
Grant McLean, cropping management specialist at Saskatchewan Agriculture, said most farmers might not see any changes this year, but they can expect to see more salinity over the next two or three years as the soil dries out.
“The salts have always been there,” McLean said. “We’ve just been managing for them.”
Changes in water accumulation and movement in the soil can mean that an area that had no problems can suddenly develop one and a spot that had high levels of salinity can become rinsed out and fertile again.
Farmers who haven’t had to worry about salinity in the past should consider how they are going to manage it, said McLean.
“It will be worse in fields where there was nothing to use the water,” he added.
Producers refer to their saline areas as alkali, but Saskatchewan Agriculture says the term is a misnomer. These soils are saline, which means large amounts of dissolved salts have accumulated at the surface and are visible as white patches with little or no plant growth.
They are only the tip of the salinity iceberg. It was ice, or its movement, that originally created the problem for western Canadian farmers.
The salt arrived ahead of the glacial till that is now the basis for much of the grain-growing land in the West.
As inland seas retreated, they left a saline stain on the land.
Glaciers formed during the ice ages and deposited soil on top of the salt.
Several million acres of the 50 million arable cropped acres on the Prairies are affected by salinity that seeps and creeps up from below.
Rigas Karamanos, a researcher and fertilizer specialist with Viterra, said many producers will blame spotty crop yield issues on lack of fertility, insects and disease rather than recognizing a salinity problem.
Electrical conductivity measurements are now commonly used to confirm the presence of salt in the soil. The technology has become more affordable and services have developed in precision agriculture to meet the demand for field mapping and fertilizer prescriptions.
Alex Melnitchouck, a research agronomist with Dynagra in Beiseker, Alta., said recent research in southern Alberta found only a weak correlation between soluble salts in the soil and poor biomass and production in the field.
“Generally salts are associated with lower productivity, but you can’t always rely on it. It might depend on the crop and season and soil,” he said.
Steppuhn said plants that can get a good start in saline soil, just ahead of good rain or irrigation, will often be able to stay ahead of the salt. They will become established and grow well as the water level falls in the soil.
“But if it turns dry and you don’t get that rapid germination, you can find yourself with barren ground, especially with small seeded crops like alfalfa.”
Alfalfa is often used where salinity is a serious problem by breaking the salt-moisture cycle.
“Alfalfa is usually a solution that can bring the land back to productivity,” said Steppuhn.
Soil salinization occurs when the water table is close enough to the soil’s surface to allow a wicking action to carry the salty ground water to the surface dirt.
This distance might need to be two metres or closer, depending on the soil’s texture, but it might not begin at all if sufficient water arrives from irrigation, rain or runoff.
“Salinity is solar powered,” Steppuhn said.
“Evaporation at the surface draws the salts up with the water. If it can dry out the soil, you can stop the cycle and reclaim the land.”
In pothole country, many producers have rings around their sloughs but the water in the slough isn’t salty. Instead, the water in the pothole flows into the water table, where it mixes with salty water. The water then rises up along the hillside slopes and appears like a bathtub ring.
“We are going to see some more of this due to the high water tables in Saskatchewan and Manitoba. The good news is that it will go away again as the levels drop,” said Steppuhn.
“Managing salinity is about managing the water that recharges the ground water.”
Rain and irrigation can rinse salts down, but it can become the conduit to return the minerals to the surface and the root zone unless there is a method of using up that water.
In some cases, reducing the recharge water might be as simple as creating drainage ditches or providing deep tillage to break through a hardpan that is trapping water from flowing down.
“Tiling works for some regions, but it is expensive and you need to have a perennial problem, not one that lasts only a few seasons,” he said.
Crops such as canola, flax, mustard, wheat and oats can be grown in soil with an electrical conductivity rating of four to six to keep the soil moisture down and land productive with annual crops.
Barley and sunflowers are more reliable when it rises to six or eight.
In this range a move to forage crops is required for a long-term solution. Salt tolerant alfalfa’s ability to chase moisture with its roots makes the crop the ideal solar water pump for soil moisture reduction.
Grass becomes the best choice when the electrical conductivity rating increases to eight to 16.
McLean said producers should avoid pulse crops in salt prone soil.
He said growers run the risk of the salt tolerant weed kochia moving into bare fields if pulses don’t establish and water ponds on the surface.
AC Saltlander is one of the toughest of the salt tolerant wheatgrasses bred for prairie conditions and one of the few that are highly palatable for cattle throughout the season.
It isn’t the best adapted plant to saline conditions, but it yields well in areas of the fields where salinity isn’t an issue.
“Because the conditions can vary so much in a short distance, you need crops that perform well in both,” he said.
Agriculture Canada researchers in Swift Current rate new cultivars for their value in prairie conditions.
Some producers plant tall grasses in bands across the fields. They use water and capture snow, which creates a rinsing effect and lowers the overall soil moisture.
A few American varieties of alfalfa were recently shown to be moderately better than existing cultivars, but Steppuhn said producers seeking to plant a longer-term alfalfa rotation into saline land might consider waiting.
“There are some great products in the pipeline, but at some point, you have to start to manage the problem,” he said.
“It’s an investment that can pay off handsomely when it comes to bringing acres into annual crop production. But once you know it is saline, you also know you will always be managing it for salts.”
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