Wet-dry cycle drives up salinity and cuts yields

Invisible soil salinity affects 22 million acres on the Prairies, cutting yields by a quarter

Saline seeps don’t have to be as serious as this eight-acre one in southern Alberta 
to cause major yield losses, says agronomist Jack Payne.
Reading Time: 3 minutes

Another dry spring could leave producers feeling salty over increased salinity in their soil.

“This year and part of last year, we’ve started to see more salinity showing up,” said Jack Payne, western Prairies regional agronomist with Farmers Edge.

“Saline seeps tend to form more readily after we’ve had a series of wet years followed by dry years. The wet years build up the water table and move the salts, and then when we have dry conditions, we get salts accumulating on the surface.”

Alberta Agriculture and Forestry estimates that at least 1.6 million acres of land in Alberta are affected by visible salinity, said Payne, who spoke at a soil salinity workshop hosted by the Grey Wooded Forage Association.

“If you took all those saline patches we see around the country and put them into one huge consolidated saline seep, it’s about 1-1/2 counties,” he said. “That’s a lot of ground.”

But farmers are also being affected by invisible salinity — “those mildly saline soils that don’t show up with that typical white crusting.”

“When you see a saline area, there’s also an area around it that’s affected by salt that we don’t see,” said Payne.

In the mid-2000s, Agriculture and Agri-Food Canada estimated that 22 million acres across the Prairies are affected by invisible salinity.

“Farmers are losing about $400 million a year due to invisible salinity,” said Payne, adding yield loss estimates in Alberta are around 25 per cent, depending on the crop.

“Invisible salinity is stealing more yield than we think.”

Managing salinity

And soil salinity “creeps up on you.”

“It’s a slow process, and you don’t notice it from one year to the next,” said Payne.

In most cases, a salinity problem in the field is “really a water management problem,” he said.

“We see the symptoms on the soil, but the problem is actually groundwater. Dealing with salinity is actually dealing with groundwater,” he said.

“When we exceed what the soil can hold, it either runs off or it percolates down and picks up the dissolved salts. When the water table gets within two metres of the soil surface, the water starts to come to the surface through evaporation or transpiration, and the salts are left behind.

“What we need to do is do something with that excess water.”

For some types of saline seeps — such as contact seeps or slope-change seeps, where groundwater is forced to flow near the soil surface — vegetative controls can help, said Payne.

“If we want to draw down the water table, we need to grow a crop that uses a lot of water and is deep rooted,” he said. “If I want to dry out the soil and get rid of that extra water, the crop I should grow is alfalfa.”

Alfalfa is a “hog on water,” using about 26 inches of water during the growing season, and depending on the variety, it will root down to three metres deep.

But vegetative controls won’t work on every saline seep, he cautioned.

“Some people question the effectiveness of vegetative controls. They say they don’t work,” he said.

“And they don’t — in some cases. But if you’ve got a contact seep or a slope-change seep, it will work.”

By planting vegetative controls like alfalfa, producers can “stabilize” the land and make it productive again, said Payne.

“If you don’t do anything, it will get worse, but there are things we can do to manage it. We can’t cure it, but we can manage it,” he said.

“Soil salinity is like arthritis. We won’t get rid of it. We just have to manage it.”

About the author

Reporter

Jennifer Blair

Jennifer Blair is a Red Deer-based reporter with a post-secondary education in professional writing and nearly 10 years of experience in corporate communications, policy development, and journalism. She's spent half of her career telling stories about an industry she loves for an audience she admires--the farmers who work every day to build a better agriculture industry in Alberta.

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