How to Deal With Saline and Sodic Soils
Rain makes grain. Yet, too much rain can be too much of a good thing. In eastern North Dakota, northeastern South Dakota, and western Minnesota, rampant rainfall over the past couple of decades has unveiled sodic and saline soils that aren’t conducive to growing crops.
“In the last 25 years, North Dakota has seen a rise in water and a change in its hydrology,” says Frank Casey, a NDSU soil physicist who directs the NDSU School of Natural Resource Sciences.
This has spurred both saline and sodic soils in the region. Sodic soils impact about 10% of North Dakota’s agricultural land. Meanwhile, 1.2 million acres in the Red River Valley are classified as slightly saline. Soybeans are particularly sensitive to these soils, as crop losses of $57 million annually occur in this region.
There are steps farmers can take to help manage these soils in many cases, but it takes time. “It’s often a 10-year project,” Casey says. The soil doesn’t fix itself overnight.”
North Dakota Soil Health Program
In North Dakota, there’s a soil health research program that focuses on management options for salt-affected soils, effective use of conservation tillage and cover crops, soil health evaluation, and soil’s relationship to crop disease pest pressure and economic parameters. These projects are linked to the Soil health And Agriculture Research Extension (SHARE) Farm in Mooreton, North Dakota. There’s a quarter of land, owned by cooperating farmer Ken Johnson, that is extensively soil sampled, and various tillage strategies are tried out on tiled and nontiled saline and nonsaline soils.
Last week, NDSU and the University of Minnesota sponsored a soil health tour in southeastern North Dakota. Here’s some of what they found.
Saline and Sodic Soils
Saline and sodic soils are often lumped together, but they differ.
Sodic soils have high amounts of sodium relative to calcium and magnesium on their exchange sites. When this happens, swelling and dispersion cause disorder of clay and organic matter. These soils then have low productivity and poor soil health.
“With sodic soils, you are pretty limited in what you can do,” says Chandra Langseth, an NDSU research and Extension technician.
Many sodic soils aren’t helped by drainage tile. Cases have existed with pattern tiling on 20-foot spacings on sodic soils, and it didn’t help. “These soils never drained well to begin with,” says Tom DeSutter, an NDSU soil scientist.
Certain soil amendments are available, although expensive. A deep-rooted crop like alfalfa is also an alternative.
Still, options are limited. “Sodic soils are a beast to deal with,” says Langseth.
Better News for Saline Soils
These soils are high in salts derived from ancient sedimentary rocks. Prolific precipitation prompts these salts to rise to the surface due to a rising water table.
These soils can be fixed, but it is a multiyear process.
“You need to shift your brain from production to remediation for those saline areas,” says Abbey Wick, NDSU Extension soil health specialist.
Successfully managing saline soils means successfully managing excess water. Managing these soils is akin to wicking water via a dry sponge. “The more water goes to the surface, the more salinity that you have,” Casey says.
One tool is a cover crop. Tiling is another option. Steps such as no-tilling fields can increase soil aggregation, another step in slowing salinity.
“It’s a lot like making chili,” says Aaron Daigh, an NDSU soil scientist. “Drainage is like adding beans to the chili. But maybe other things like no-till and cover crops are the peppers and the meat. It is putting several things together, where you can speed things up if you want to get there a little faster.”
Cover Crop Choices
There are all kinds of different cover crop combinations that can be planted. Effectiveness exists in simplicity, says Wick. In southeastern North Dakota, Wick and area farmers there have found a good mix of 40 pounds per acre of cereal rye and 5 pounds per acre of radish interseeded around V6 to V10 in corn this year. A week later, they were starting to germinate within the corn rows.
“Both are predictable,” he says. “The radishes die during the winter, and Roundup smokes the cereal rye.”