NDSU soil science team tackles saline, sodic soils

FARGO, N.D. -- A new state specialist unveiled North Dakota State University's new Soil Health and Land Management Initiative at the Northern Ag Expo in Fargo, N.D., Nov. 27 and 28.

Abbey Wick, an assistant professor of soil science and an extension specialist at NDSU's main campus in Fargo, asked her audience how many had problems with saline or sodic soils. Nearly every farmer raised his or her hand in a room of about 200 farmers and consultants.

This was no big surprise because NDSU soil specialists say 90 percent of producers in the state have some amount of reduced productivity because of salinity.

The loss of that productivity is especially vexing in years of high-priced soybeans. Agricultural practices are changing with tile drainage being installed, conservation reserve program land coming into row crop production, and years of wet conditions bringing the salts to the surface.

Wick is one of the new faces of the initiative -- an unprecedented effort to get a handle on the soil health problems. In one of the first public presentations on the program, Wick explained the impact of a $2.1 million biennial appropriation by the North Dakota Legislature. Initially, it has financed the hiring of six scientists -- three in extension and three in research across support staff. The scientists were hired within a few months of each other.

Health and profit

The scientist team will work collaboratively on projects designed to study the physical, chemical and biological properties of soil and offer advice to farmers. The idea is to maintain ecological integrity while still producing a profit, Wick said.

Scientists know a lot about soil fertility. "But the biological functions in soil we don't know a lot about," Wick said. "That includes the bacteria, the fungi, earthworms, organic matter."

One key issue is to get farmers and others to distinguish between salinity and sodicity.

Both are salt deposits from the parent material that are naturally in the soils. "Some salts can be added through fertilizer applications but the majority of what we're experiencing is from the parent material and the weathering of it," Wick said. "Those salts dissolve in water and are carried throughout the soil profile in the water."

Capillary action causes the salts to come to the surface.

The smaller spaces between soil particles increase the capillary action. Salts accumulate in the soil if the evaporation exceeds rainfall levels. The water will evaporate, but the salts stay behind. Conversely, a flush of rain water can push the salts down and with reduced evaporation, they'd stay down there.

"Plants go into 'drought stress' when they're salt-affected," Wick said. "Their roots aren't able to take up water with the salts in them." Some crops, such as wheat and barley, are less affected by salt than crops such as corn and soybeans.

Sodicity is an entirely different chemistry issue than salinity and only soil testing can distinguish the two. In sodic soils, the sodium salts are outweighing the calcium or magnesium-type salts. The only way to verify it is through lab testing.

Salts not the same

"You can't treat salinity and sodicity the same," Wick told her audience. "You may have salinity and sodicity existing at the same time, but once that salinity is leached -- the calcium and magnesium salts, they leach first -- then the sodium sticks behind and attaches to the clays and you may have a sodicity problem."

Farmers can cope with salt issues by using deep-rooting cover crops to lower water tables, or interceptor crops to keep water from seeping from ditches into adjacent fields.

In some cases, farmers have used tile drainage to help reduce their saline salts, only to realize that they've knocked the salt content out of balance and are facing sodicity problems.

One farmer told Wick some farmers leave kochia weeds on salty spots on the theory that it "sucks the salts out."

Wick said kochia is tolerant to salt, yes, but don't remove the salts. The kochia weeds may draw the water table down, but creates a bigger issue of kochia resistance to Roundup (glyphosate) herbicide.

One thing is for sure, Wick said. "It took 30 years for these salts to develop in these soils, and it's a slow process to fix it."

For information and updates about the program, go to Facebook.com/soil health.