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NDSU graduate students examine local sodium-affected soils


That white, powder-like substance you’ve noticed in recent years in some North Dakota ditches and fields is salt. And it’s more and more on the minds of agricultural producers.

“Our wet, climatic cycle since 1993 has really had a significant impact on salt migration in landscapes,” explained David Hopkins, associate professor of soil science. “Part of the reason we are seeing more salts is as the groundwater rose regionally, salts moved both vertically and laterally. Previously, the salts were in the sub-soils, sequestered by long-term soil genesis.”

Growers keep a vigilant eye on their fields because salinity or sodicity can hamper plant growth. It causes crops to appear water-stressed because a high salt content can prevent their ability to absorb water from the soil. Sodium salts can also cause clay dispersion, which impairs soil physical condition and reduces hydraulic conductivity.

“A change in salinity is a complicated, long-term process that is important to watch,” said Hopkins, who wants his graduate students to have a first-hand look at the issue.

From September through November, a group of students taking a Soils 644 class called Soil Genesis and Survey, did a variety of tests on farmland near Casselton, N.D. They examined a heavy clay, sodium-affected soil called Nahon, which can be found on about 100,000 acres in North Dakota and South Dakota.

“We went to look at salinity and sodicity on their own merits from a soil classification perspective, and then we learned the producers were considering tile drainage,” Hopkins said. “So, our opportunity to evaluate deep-soil chemistry had even more significance than typically.”

The students investigated soil chemistry, utilizing a Veris Technologies cart to test for soil electrical conductivity. They conducted surveys, studied the morphology of the soil, took both shallow and deep salinity readings and performed laboratory analysis. “It was an opportunity for graduate students to be outdoors, in the field. It was a hands-on experience, rather than writing a paper,” said Hopkins, who plans to publish results with the students, specifically in the popular press and available to area producers.

“I embraced the opportunity to get out and get field experience,” said graduate student Leif Sande. “It was an awesome opportunity, especially if the work we did can actually be used and applied. Field experience and working on an actual project proved extremely valuable.”

Hopkins has some general advice for farmers who are considering a field drainage plan. “Salts are not created equal, and it is important to test subsoil chemistry in the region where the tile would be placed. If sodium levels are too high, dispersion processes may occur over time that can reduce flow to the tile,” Hopkins said. “Some relatively simple soil tests can indicate what the chemistry is.”

For more information, contact Hopkins at


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North Dakota State University
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Last Updated: Thursday, August 08, 2013 8:33:23 AM