No real fix to soil salinity but options exist

With more than five million acres at risk to salinity in Western Canada, farmers could do a better job of managing their acres, say some advisers.

“It’s a very big deal,” said Lyle Cowell, manager of agronomic services at Nutrien Ag Solutions in northeast Saskatchewan.

He and colleague Brianna Lummerding discussed salinity during a presentation at Ag in Motion Discovery Plus July 21-26, which was held as an online event following the cancellation of the Ag in Motion outdoor farm show due to COVID-19.

They said prairie producers too often farm every acre, even if that acre is losing money.

“Saline land is probably the biggest culprit in Western Canada when it comes to unproductive land. Saline land is just rarely a money maker when it comes to annual crops,” said Cowell.

Added Lummerding: “We need to stop spending money on those saline areas and we want to move the money into the productive areas of the field.”

While there are many factors in soils that can limit yield — acidity, flooding, poor fertility, compaction, drought — salinity has the biggest impact on a lot of acres and crops because it’s difficult to fix. It can also grow.

With a high concentration of soluble salts in water, salinity is “just too much of a good thing.” Its severity is contingent upon the growth stage of whatever crop is being grown.

A good practice is to first have a baseline soil test completed with the salinity measurement, which will determine if the land can support a more salt-tolerant crop.

Using a one-to-one ratio of soil and water to measure salinity, most labs will start to consider a soil saline at about two millisiemens per centimetre.

However, crops like red clover, flax, peas, beans, and lentils are more sensitive to salinity and their yield will decline at a conductivity level of about one mS/cm.

More tolerant crops like alfalfa, canola, corn, oats and wheat will probably not see a significant yield loss until reaching a conductivity number of about two mS/cm.

“For example, once you’re over a salinity measurement of two, wheat yields are going to be significantly reduced probably 30 to 50 percent. That’s when you’re actually starting to see some salts on the soil surface, but you can have yield losses on crops at a lower salinity,” Cowell said.

Saline soils with a conductivity of more than four mS/cm in a one-to-one water to salt ratio will only grow certain forages.

Red clover and timothy hay are intolerant of salinity, whereas Russian wildrye, tall wheatgrass, and especially saltlander green wheatgrass can be successfully grown in very saline soils.

Germination is a critical phase for the success of a crop because mature plants will tolerate more salinity.

“This is then an even bigger topic with annual cropping because you’re trying to get that crop to germinate in those saline areas every year. Whereas if you can establish a perennial forage there, then you’ve gotten past that stage,” he said.

Often overlooked is the degree that salinity can vary from year to year, which hinges on movement of the water table.

“The frequency of success of annual cropping can become very low in even slightly saline soils. So keeping those salts downwards, keeping the water table lower and therefore the salts lower in the soil profile is really the key to being able to see the crop and be able to have some sort of crop there on an annual basis,” Cowell said.

Subsurface drainage assists to leach out salts and create more productive land, however there are limits to its effectiveness depending on topography.

Another choice is establishing forages that can get the water table lower: crested wheatgrass, tall wheatgrass, green wheatgrass, wild rye.

Allowing weeds and forage species to grow together will help bring salt levels down below the rooting zone while preventing the soil surface from staying black. Mowing instead of spraying also lets them cohabitate.

“Actually a lot of salt tolerant forages are pretty competitive with species such as foxtail barley,” said Lummerding.

Saline areas are often wet in spring, making it difficult to seed salt tolerant forages.

It’s not a short-term solution for salinity, however one way is to fall dormancy plant, which gives forages time and ability to establish.

While soil salinity will never get fixed, one way is plant forages late in the fall, which gives choices available to improve profitability but producers will also need to grow tolerance.

“This is not a one year and we can grow an annual crop on there again. This needs to be seen as more of a three to five-year investment, but you’re probably going to get some cuts potentially for hay and bales in there in the meantime. And you will get there; where you’re going to end up having some sort of profitability,” she said.

“We just really need to be patient and allow something to establish and get that subsoil water to move lower.”

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