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Published February 25, 2013, 09:47 AM

Setting things straight on soils

The Red River Valley has a diverse soil profile.

By: Kristine Larson, Agweek

Soils in the Red River Valley region are unique, and the salts are not going away.

Diving into the formation of the area, Grand Forks County in the northern Red River Valley in North Dakota, sits above a natural artesian discharge area. This was formed in the Dakota Sandstone Formation, which is what gives us our continuous natural salt elements. On top of that, the area sits in a former glaciated area that turned into a massive lake as the last glacier receded.

We are all guilty of throwing around the term “salinity” to describe what we see as salts. This is not always accurate, however, because we actually have three different soil characteristics, each with its own name, that have the potential to affect crops.

Soil types

Saline soils contain high amounts of soluble salts such as calcium and magnesium. That means the salts are easily dissolved in water and may be moved through the profile. Sodic soils contain high amounts of sodium. Sodium does not dissolve as some of the other elements do. Then, to spice things up, we can have saline-sodic soils, which are high in both salts and sodium. There are separate tests to determine salinity and sodicity, and it is important to know which of these we have. A person must request the specific tests to determine the difference. Alkalinity relates to the pH in the soil. Soils that have a pH greater than 7 are considered basic or alkaline. Alkalinity affects soil structure and results in poor infiltration.

So which of these soil characteristics are present in the valley? All three. Our management practices have played a major role in a rising water table. These natural salts are brought to the surface by this increased water table. They are left on the surface when there is no longer a channel for them to travel back through the profile. When evaporation takes place, the water goes into the air, and the salts are left shining on the soil surface. Tilling exposes the salts that are just below the surface, while also closing off pore spaces that allow water to infiltrate into the soil, and thus restricting salt movement.

Salt issues

Drain tiling has become the newest fad to hit the region, but this is not going to solve our salt issues. Tiling carries only soluble salts away from one area, only to be deposited somewhere else. Tiling also carries away other soluble materials such as fertilizers, which end up in ditches, rivers, and lakes. Do you notice the vegetation changes in the ditches? This vegetation is a visual clue that you are losing fertilizer (and dollars) from your field. If there is sodium in the soil, it will remain there even if the field is tiled. Sodium causes clay soils to clump together, clogging tile and leaving systems virtually ineffective.

Applying new management techniques such as no-till, crop rotations and cover crops allows us to mimic nature. Different root structures help break through the hardpans and feed the microbe population. Their roots create channels that allow water and salts to infiltrate into the soil profile. Continuous vegetation helps build organic matter to increase water holding capacity and water usage.

We can curse the salts and water and try to fight them, but history shows us that nature always wins.

We need to learn to work with nature instead of against it. It is possible if we just give it a chance.

Editor’s Note: Larson is the watershed coordinator for the Grand Forks County (N.D.) Soil Conservation District.

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