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Research Highlights
North Dakota Research Plot Points to Ways of Managing Soil Salinity

Aerial photo of a North Dakota field with soil salinization and major crop damage except for the square area in the bottom right. Photo: Aaron Daigh

By Carol Brown

The old adage about making lemonade out of lemons could be applied to a North Dakota soybean research project. Aaron Daigh, North Dakota State University (NDSU) associate professor, recently completed a study that could have statewide implications for managing soil salinization tolerance.

The soil scientist and his research group were headed to a farmer’s field to set up research plots for a study and found most of the soybeans were dead or dying from salinity in the soil.

“We knew this field had salts far down in the sub-soil, but the history of the field hadn’t dealt with major salinity issues that had affected the crop,” says Daigh. “Until that year–2018.”

A pilot took aerial photos to confirm the damage. Looking at the photos, he and his team noticed one corner of the field had thriving soybeans where the rest of the field had 70 to 80 percent crop failure. This corner wasn’t in any of the current research plots, which prompted them to find out why the area was doing so well.

“This was an unintended project,” Daigh says. “We wanted to reverse-engineer the field to find why this happened and whether it could be replicated elsewhere. The North Dakota Soybean Council funded the study, which was unlike anything they’d funded before. With most field research projects, we go out and impose a treatment to see what happens. This was the reverse.”

Daigh says the summer of 2018 wasn’t a particularly rainy one. It just rained consistently enough to keep the water table raised throughout the growing season, which pulled the salts up from the ground below.

Because of its geology, North Dakota has salinity issues statewide. As the glaciers moved across the state, they deposited shales in the sediment, which are laden with salts. Because of this, there’s no getting rid of the salts; there is only management, says Daigh.

Soil management makes a difference

“We took soil samples across both areas of the field,” Daigh says. “We were looking to see if there were some set of properties that could help us identify if a field will be more at risk when conditions for salinization occur.”

The team conducted many analyses including soil fertility, biological components, levels of fungi, mycorrhizae, and bacteria. They looked at the physical structure of the soil and ran soil cores through CT scanners, but could not discern from where in the field the soil samples were taken. 

They also had reviewed all the previous projects conducted in that field and found the two areas had been managed differently. Daigh concluded that the only variables between the good and bad field areas were in the differences in soil management.

“That little square had been a research site, which was decommissioned about three years prior,” Daigh says. “The area had small, lateral lines of tile drainage just in that corner. They had also converted that corner into no-till and then later planted cover crops.” 

After that project ended, the tile drains remained, and the farmer returned to tilling the field — except for that little square. Conclusions drawn from this field corner study indicate that the processes taking place on the land do make a difference.

“With this ‘case study,’ we know that tile drainage is a way to keep water levels down, and that’s good if you don’t want the salts coming up,” he says. “We also know that no-till keeps more residue on the surface, which cuts down on evaporation, also keeping the salts from coming up. This combination seems to be the main solution to those salinity issues.”

Daigh says that maybe if the entire field had tile drainage and was no-tilled, the field might have been protected like that little corner and the farmer might not have even known there was a salinity issue. These management practices could be applied to other North Dakota farms and this project may end up being a proverbial cautionary tale. 

“Sometimes things are really working for us in the field and we don’t even know it,” Daigh says. “Sometimes we don’t know what we’ve gained by simply avoiding an issue or a loss.”

To find research related to this Research Highlight, please visit the National Soybean Checkoff Research Database.