"I used to think that it would take a long time to fix soil salinity problem,s but it seems like we can make some real progress quickly with cover crops," says Abbey Wick, North Dakota State University Extension soil health specialist.

Cover crops do several things that help reduce soil salt levels:

When water table is too high, they use up water and draw down the water table. Excess water rising to the soil surface carries salt with it.

When it rains, water follows the channels created by the cover crop roots in the soil. As rain water moves into the soil in dissolves salts, which flow deeper into the soil.

When it's hot, cover crops slows the rate of evaporation from the soil. The faster water evaporates from the soil surface, the more water is drawn to surface. As water rises in the soil, it dissolves the salt it comes in contact with and moves it closer to the surface.

Cover crops also add organic matter to the soil. That gives microbes in the soil more to feed on, which increases their population and in turns makes more nutrients available to plants.

"It's a cycle that builds on itself once it gets going," Wick says.

Dave and Paul Mueller, who farm near Cummings, N.D., are hoping Wick is right. They turned over 20 acres to Wick to use as part of a network of saline soil demonstration project that covers about 250 acres from Grand Forks to Wahpeton, N.D. Hardly anything but wheat, barley and sunflowers – three of the more salt-tolerant crop species – can be grown on affected the tract, and those crops are performing poorly.

"The field has a high quality soil," Dave Mueller says, "but the salt is ruining it."

Wick estimates that farmers in the southern Red River Valley are seeing yield drags on 20% of the land they farm from salt. In the northern Red River Valley, the figure is 30-35%. More than 90% of all North Dakota farmers report some yield losses due to saline areas in the field, she says.

Wick's Soil Health team, the local county extension agent and the Muellers planted three different cover crop mixes with variations of cereal rye, radish, turnip, forage pea, crimson clover, sorghum/sudangrass and dwarf essex rapeseed on the land after the wheat was harvested. They plan plant to corn or soybeans in the overwintering cereal rye next year.

"We're pretty nervous about how it will turn out, especially if we try to grow soybeans," Paul Mueller. "Soybeans have not done well at all here."

Lot to learn
Wick says there is a lot to learn about managing cover crops.

Tillage, weed control and time management are all challenges.

You need a high residue planter or air seeder to plant cover crop quickly and economically, but I have also seen farmers successfully plant cover crops with the equipment they have available, she says.

The earlier you can plant a cover crop the better. It works okay after wheat, but even better after winter wheat because winter wheat is typically harvested earlier than spring wheat. The extra time increase the chance of getting a good catch on the cover crop and the longer a cover crop can grow before it dies in late fall the bigger and deeper the roots will go into the soil. Wick and other farmers she is working with are experimenting with seeding cover crops into corn and soybeans in the summer.

Using cover crops in combination with tile drainage may be a good idea on some soils, Wick says. Tile would intercept a rising water table while a cover crop would add organic matter to the soil and help create channels to move salt near the surface deeper into the soil. The combination of tiling and cover crops may work better than either one alone.

Given what's known now about cover crops, Wick recommends using them first on parts of fields where you notice salt levels are starting to reduce yields. You might be able to turn those areas around quickly. Then you can tackle areas where nothing but weeds like kochia grow.

"That may give you the most bang for the buck," she says.