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Crops and saline soils

Plant something, but choose carefully

Some crops are a little more salt tol­erant — like canola shown above as well as alfalfa, corn, oats and wheat — and you will probably not see sig­nificant yield loss until you hit a conductivity number of about two mS/cm, says Lyle Cowell with Nutrien Ag Solutions.

When it comes to planting most annual cash crops on saline land, Lyle Cowell does not mince words: stop.

“When a cattle farm has a cow that is no longer productive, that cattle farmer will not continue to try to breed that cow. It will be culled,” says the agronomist with Nutrien Ag Solutions in Saskatchewan.

But some grain farmers do not apply that same logic to saline areas, says Cowell, who spoke at Ag in Motion Discovery Plus last summer.

“We often try to farm every acre on every farm even if the acre is losing money. We have some canola or wheat that doesn’t make money because it’s simply on unproductive land.”

But simply removing saline areas from annual crop production isn’t sufficient — it still needs to be managed. For one thing, salinity can spread; it’s essential to plant something in order to keep the water table low and help prevent further salinization. For another, saline areas are a haven for mobile weeds like kochia.

Finally, if you don’t plant something you could be losing money; most saline-tolerant crops are perennials — frequently forages that can eventually be baled and sold.

The first thing you need to know is just how saturated your saline areas are so you know what to plant there. Producers should get a baseline soil test done, making sure salinity is measured in the process, says Brianna Lummerding, also an agronomist with Nutrien Ag Solutions who spoke at the presentation.

“Could it support a more salt-tolerant crop such as a barley or is the salinity high enough that you may only be able to use salt-tolerant forages?”

It’s important to stop planting annual cash crops on saline land. Rather, manage those areas with a saline-tolerant crop (e.g. barley) or forages, which could earn you money.

Source: Nutrien Ag Solutions.

How to read your soil test

Soil salinity is measured in electrical conductivity using a 1:1 ratio of soil (in the case of the Nutrien Ag Solutions’ research, loam) to water. It’s expressed here in milliSiemens per centimetre (mS/cm).

“Certain crops are going to be more sensitive to salinity,” says Cowell.

“With crops like red clover, flax, peas, beans and lentils, the yield is going to start to decline at a conductivity level of about one mS/cm. Some crops are a little bit more tolerant — alfalfa, canola, corn, oats and wheat will probably not see significant yield loss until you hit a conductivity number of about two mS/cm.”

Barley is kind of a wild card among annual crops because it can be grown in soils measured between 1.9 and 3.6 mS/cm — about the point where you start seeing serious yield reductions for most annuals. For irrigation farmers, sugar beets are another crop that can be grown within this salinity range.

However, don’t expect malt-quality barley at that level of salinity, says Cowell. “You will probably have thinner, higher-protein barley in those saline areas.”

If you have a measurement of four mS/cm on a 1:1 soil-to-water ratio, you’re looking at planting forages exclusively on that patch, and only certain forages at that, says Cowell. Examples of perennials you can plant between 3.7 to 7.2 mS/cm include tall wheatgrass and Altai wild ryegrass. Meanwhile, Russian wild ryegrass, tall wheatgrass and AC Saltlander green wheatgrass can withstand salinity levels of 7.2 and above.

Don’t trust your eyes alone

Some might wonder why this test is necessary, especially considering how visible high salinity can be on the soil surface.

However, some low — but potentially destructive — underground salinity content cannot be detected with the naked eye. Cowell says you will probably not see salts visible on the soil surface until there’s an mS/cm of two, which already exceeds the point where most annual crops will start seeing yield losses.

“For example, once you have a salinity measurement of over two, your wheat yields are going to be significantly reduced, probably 30 to 50 per cent,” he says.

For irrigation farmers, sugar beets are another crop that can be grown in soils measuring between 1.9 and 3.6 mS/cm. photo: iStock/Getty Images

The mobility of salts presents another reason not to trust your eyes when assessing salinity levels.

“Salinity can stare you right in the face, but there can be salts right on the soil surface that do not always appear and may come and go through the year,” says Cowell.

“In the spring the salts may be dissolved; maybe moved a little bit into the soil or melting snow or run-off and you may not see them on the surface. Even through the summer you get a few rains and they will be dissolved and moved a little bit below the soil surface. During a bit of a dry spell they will move back upward, then you will see those white salts right on the soil surface.”

Be patient

Once you’ve made a decision on what to plant, Lummerding recommends seeding in the fall if possible. Realize, though, that it will not be a short-term solution for salinity.

“This isn’t a ‘one year and we can grow an annual crop on there again (scenario),’” she says. “This needs to be seen as more of a three- to five-year investment.

“You’re going to need to be patient. You’re probably going to be able to get some cuts of hay and bales in the meantime and are going to get where you’re having some sort of profitability.”

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