WILLISTON, N.D. - A common dryland practice has led to a common problem in the Oil Patch of western North Dakota - the saline seep.
The Williston Research Extension Center is taking a closer look at seeps and examining the best ways to address them.
Saline seeps are areas where the power of evaporation, which can reach as far as 6 feet below the surface of the soil, is pulling salts up from the ground water, sterilizing patches of land. From a distance, seeps look like snow in summer, but they are a salty crust that sterilizes the land and prevents things from growing. They are a remnant of the wheat-fallow approach to dryland farming, once fairly common, and still in use by some producers today. In the fallow year, no crop is grown in an attempt to accrue water for a subsequent crop. But the accumulating rain water from that area feeds the groundwater table, raising it too near the surface in some places. In dry, summer months, evaporation can then pull salts from that groundwater, depositing them on the surface.
The first signs of this happening out in a field may be stunted or dying trees in a nearby shelter belt, or wet spots that persist two or three days longer in the field. These are the places where tractors tend to bog down or cut deep ruts.
Later, when the spot dries, occasional salt crystals may be visible, sparkling here and there in the sun.
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Rank wheat or barley growth, sometimes accompanied with lodging in an area that had been normal, may be the best and last crop where the saline seep is about to finally appear. The next time, the crop may not survive at all, or do very poorly. Kochia might persist in the spot for a year or so, followed by foxtail barley infestations, and then nothing. Nothing at all grows. When the ground is wet, it may seem darker than usual, but when ground dry, there is the tell-tale patch of snow in summer. A saline seep has arrived.
In some countries, saline seeps have been approached with tile or mole drain systems, which intercept water before it can feed the groundwater, but that isn't the right approach in the semi-arid western North Dakota. There's not enough water to flush salts out of the soil, and, even if there was, where would all that salt ultimately go?
Most likely, to a neighbor's field, where it causes problems for them instead.
Agronomic approaches are better in semi-arid land. This approach uses deep-rooted plants to use up water in a defined watershed, and keep it from feeding the groundwater in a problem area.
The latter approach to saline seeps is the subject of a reclamation study being conducted at the Williston Research Extension Center by cropping specialist Clair Keene. The research center has had a seep that had been gradually increasing in size for 20 or so years. In the last five, however, the increase was substantial enough to worry the farm manager.
Keene began her study with a set of simple monitoring wells - plastic PVC pipes - to get a handle on what area is charging up and feeding the seep. Now she is looking at which varieties of salt-tolerant alfalfa will work best to address the problem in a multi-year variety trial.
Her study hit the spotlight at a recent Field Day for pipeline reclamation. Seeps are pertinent to oilfield efforts because things like well pads remove plants from an area's watershed, and this can potentially contribute to rising groundwater levels.
Keene acknowledges an alfalfa management system would be quite a change for a producer growing mostly annuals. They'd need different equipment to bale hay if they didn't happen to have a neighbor wanting it for their livestock.
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That could seem pretty silly, but it could still be the best choice for returning the land to high productivity in the shortest timeframe, and it is fairly low cost and low rent.
Alfalfa is a perennial crop that, once established, doesn't need much in the way of herbicides or fertilizer. Being a legume, it fixes nitrogen, which can ultimately enrich the soil for subsequent grain crops once the seep is under control.
Another benefit to using alfalfa is its long lifespan - up to seven years. It won't need replanting, and because it's a perennial, it can be out there growing during early spring and late fall, catching as much water as possible in the wetter periods of the growing season. It is also deep-rooted, and can reach as far as 20 feet down.
Once a seep is addressed, an area might then be returned to annual crops, but using a more intensive cropping system instead of fallow, to ensure water is no longer feeding groundwater in a shallow area.
An intensive cropping system replaces the fallow year with a cash crop like peas. Even better, add some safflower or sunflower to the rotation. The three-crop rotation can help prevent diseases and pests, as well as manage the watershed to eliminate future seeps.
Alfalfa isn't the only option, of course, to address a seep. There are perennial grasses with high salt tolerance such as AC Saltlander and Garrison Creeping Foxtail, which may be useful in areas with really high salt concentrations.
Plans for addressing a seep can be customized, Keene says, but the big thing to realize is that a producer cannot just manage the "problem" spot. The entire watershed has to be considered when developing a plan.
"The seep itself is like the tip of the iceberg. It's the visible part," Keene said. "But to deal with it and make it go away you have to manage the whole recharge area."
