Switching from forages to soybeans is one way to see if you’ve got saline soil, but it’s not the method Marla Riekman recommends.
The provincial land management specialist told producers attending Manitoba Ag Days that testing is the only surefire way to learn what kind of salinity you have on your farm, although there are provincial maps and surveys that can help point you in the right direction.
“When I hear people in the valley say, I’ve never seen salinity before… I think it’s really that they’ve never grown so many soybeans before,” said Riekman.
While most forage crops are salt tolerant, pulses and soybeans are not.
“Soybeans are tolerant for a very, very short period of time then that tolerance plummets; corn isn’t far behind,” she said, adding that if farmers are thinking about expanding corn or soybean acres, they should test to see if their land is well suited to those crops before making any big changes.
In cases where crusty white salt appears on soil surface, salinity is obvious, said the specialist. But in most cases the signs of salinity are much more subtle.
“It might be little patches of foxtail barley along the edges and around potholes,” she said, adding that kochia is another indicator of salinity.
However, there is an upside to seeing those weeds in a salty patch of soil because they do suck up water and help control the water table, something Riekman said is key to managing salinity.
“When you think about salinity, I want you to be thinking about water,” she said. “Think about where your water table is, because that’s what’s driving salinity. That salt is coming up to the surface from below… that’s the reason we’re seeing a lot of salinity right now, because we’ve seen that water table come to the surface.”
As water evaporates, more salty water is brought to the surface, wicking more salt to the top layer of soil. Planting salt-tolerant crops such as alfalfa or sunflowers helps to control water levels and also works to prevent salt from accumulating.
“Typically, salinity isn’t seen in wet years, it’s driven by the wet years, but it’s not seen when it’s wet,” she said. “The reason is that when the water is flowing around it is diluted.”
It’s when that water sticks around and evaporates that the real problems begin. Tile drainage can help manage some salinity, but it isn’t a silver bullet, said Riekman. Tile drainage is only effective in the right type of soil and where there is a proper drainage system in which to channel excess water.
Increasing the amount of organic matter in your soil can also reduce salinity, as can cutting back on tillage. What won’t help are applications of any anti-salt solutions or scraping fields.
“What happens if you scrape the salt off? It will come right back, it’s coming up from below,” said Riekman. “Soil salinity isn’t something we can fix. I wish I could come out to every one of your farms and fix all of your salinity. I can’t do that. But I can work with you to manage it.”