Soil moisture extremes over the last few years have caused soil salinity patches to expand in many fields.
“Salinity is a water problem, not a salt problem,” stresses Marla Riekman, soil management specialist with Manitoba Agriculture and Rural Development, in the video below.
While kochia, foxtail barley, and other saline-tolerant weeds are often the symptoms, the root cause of salinity is water movement, she explains. As water moves upward through capillaries in the soil, it can bring salts with it — moving as far as five or six feet above the water table in clay loam soils, she notes.
When dry weather follows wet conditions, evaporation rates exceed the downward movement of water from rain infiltrating the soil. This also results in salts being left behind at the surface, Riekman says. And tillage can make this worse, as it boosts evaporation.
A soil test can be helpful in determining how severe the salinity problem is – mainly for deciding which crop may tolerate it, but she points out this info won’t be found on the results from a regular field soil test, as saline patches are usually avoided because they’re not representative of an entire field.
After diagnosing the problem and its severity, she recommends seeding a forage to help increase water infiltration and use up water before it evaporates to reduce salts at the soil surface. Alfalfa is a common choice, with a moderate tolerance for salinity, while wheatgrass has a high tolerance for more severe situations.
Unfortunately, the years when a salinity problem is most severe are also when it’s the hardest to fix.
“If we’re only thinking about the salinity this year because it’s really bad and we want to establish something and deal with the problem because we’re seeing it in front of us, those years, if you’re trying to establish alfalfa or some kind of forage, are usually the dry years when it’s really hard to establish,” she notes, pointing out it’s best to take a pro-active approach to addressing salinity during wetter years.
Tile drainage also boosts water infiltration, but it requires enough rain to create that downward movement.
For roadside salinity or saline patches that show up adjacent to ditches or sloughs, Riekman suggests seeding strips of deep-rooted, water-loving forages to intercept water before it reaches areas showing the symptoms of salinity.
One of the main symptom weeds itself — kochia — can also be managed to address a salinity problem by mowing it and keeping it in a vegetative stage, using up water and drawing down the water table, notes Riekman. In light of recent feed shortages, it can also be baled, provided it is cut before it produces seed.
Riekman joined us at CropConnect in Winnipeg to discuss strategies for dealing with soil salinity: