Drainage design

WAHPETON, N.D. -- All right, so you're installing tile drainage to improve yields on your farm. Now you might want to think about adding tools for drainage water management, said Gary Sands, an associate professor and engineer from the University...

Drainage structure
Gary Sands of the University of Minnesota, demonstrates how panels are removed in a controlled drainage structure for field drainage systems. The structures are just coming into Minnesota and the Dakotas and work well and affordable for flatter farming areas like the Red River Valley, to manage water tables at times when water retention is desired. (Mikkel Pates, Agweek)

WAHPETON, N.D. -- All right, so you're installing tile drainage to improve yields on your farm.

Now you might want to think about adding tools for drainage water management, said Gary Sands, an associate professor and engineer from the University of Minnesota-St. Paul, who spoke Feb. 22 in Wahpeton at one of the drainage design workshops organized by the extension services at North Dakota State University, South Dakota State University and the University of Minnesota.

"This is kind of an add-on practice to a traditional way of doing subsurface drainage, or tile drainage," Sands said.

It is essentially a box, separating intake and out-flow tiles. The box has a set of panels or boards in the middle, which can be inserted or removed to essentially raise the water table level -- often to conserve moisture, or even to keep more nitrogen in the soil profile. Inserting the boards causes the water table to rise on the inflow side.

The technique is about 40 years old. It was pioneered in North Carolina and used in coastal plains soils. It came to the Midwest about 15 years ago, but interest has grown in the past five years.


"We're on the bubble right now," Sands said. "We're at the point where many of the systems are being designed with this practice in mind. We don't have a great deal of implementation of the practice." He knows a handful of Minnesota farmers who are using the practice, but more adoption is taking place in Iowa, Indiana, Illinois and other states.

The practice is a natural for the Red River Valley, Sands said. "When your fields are relatively flat, you don't need very many of these structures," he said. "Sometimes only one if a field is quite flat." The box structures range in price from $500 to $2,000 each, depending on the size. "The larger the tile, the larger the structure is going to be," he says.

A farmer might wish to scale back from full drainage during the times of the year when he doesn't need it. For example, the farmers need complete drainage in the spring and fall when they are in the fields and need good, trafficable soil. "But in the middle of the growing season, where we're not out there with machinery, and we could use a little extra water, we could use these structures to reduce the amount of drainage," Sands said. "Similarly, in the off-season, once we're finished in the fall, before we go into the fields in the spring, we don't need to have a water table down at the depth of the tile. We can even have a shallower water table at those times of the year."

Sands said he doesn't think the practice will have a positive or negative impact on flooding, but notes there is an opportunity to capture water in the soil profile in the spring, should there be available pore space in the soil, and not let it leave the field.

Hot drainage topic

Tom Scherer, an NDSU extension agricultural engineer who specializes in irrigation and drainage issues, is one of a team of experts who first organized tile drainage design workshops -- a cooperative project between NDSU and the University of Minnesota. The workshops started in 1998 in Crookston, Minn., but more consistent interest has grown in the past decade, and spread into South Dakota in the past few years.

The workshops are two, two-day repeated events, each with a 50-person capacity. The leaders walk through five design processes with special topics on new technology and safety placed between. "We could have probably had 70 in each of these," Scherer said, noting that some that couldn't get into sessions in the Dakotas will be attending a Mankato, Minn., session.

About half of the attendees are looking at how to do tiling on their own, but contractors and vendors also attend.


In Wahpeton, they talked about sources for soil information. In the Red River Valley there is LIDAR (light imaging detecting and ranging) topographical data available on computers.

No one knows exactly how much tiling activity is going on in the Red River Valley. In 1998, there was one tile plow at Brooks, Minn., Scherer said. Ellingson Drainage came in 2000 for the first time. Today, Ellingson has seven or eight plows, two other companies have three or four plows each. Other contractors are working in the area and numerous farmers have bought plows. "About the only way you could do it accurately is poll the guys who make the tile to see how many thousand feet they've sold," he said.

Scherer said he's heard of some cases where farmers who started installing their own tile did it improperly, possibly getting their information word-of-mouth. One of those basics, for example, is to start tiling at the outlet.

A bigger mistake, is failing to be safe.

Dying for drainage?

Jim Walker, from New Prague, Minn., is business and safety manager for Barnett Bros. Inc. in Kilkenny, Minn., midway between Fairibault and Mankato. He spoke about safety issues on behalf of the Minnesota Land Improvement Contractors Association.

What is the biggest mistake farmers make?

"They feel they're invincible," Walker said. "They haven't taken any safety training. They're starting to do this tiling on their own, so they feel they can purchase this tiling machine on their own." He said farmers are basically safe people but also entrepreneurial "risk-takers," temperamentally.


Walker said a typical mistake is a lack of care at the start of a project. A tiling project starts with a main line installation, which is done with an excavator, not a tile plow. "They generally aren't familiar enough with soil types to bench (slope) the soil back sufficiently," to ensure that it doesn't cave in on whoever is going to be down in the trench," Walker said.

Another mistake is that they think a shallow trench -- say five feet deep -- doesn't create any danger, so there isn't any need to bench it back, or slope it. "But the gentleman bends over to make a connection and now he is below the top of the soil, creating that vulnerability," Walker said. Four years ago a man was killed in Le Sueur County.

Farmers tend not to make people wear brightly-colored safety vests, which help prevent machine operators from hitting them. Most don't realize the damage cell-crushing soil can have on people who are even partially buried but rescued, and they need to be prepared to warn emergency workers who may not be familiar with that type of accident.

Another common danger is failing to put the spoil bank, or excavated material, far enough away from the edge of the trench, so that chunks can't tumble in.

Just this past January, a 20-year-old South Dakota State University student home for a weekend on a farm near Lakefield, Minn., was in a trench repairing a main line on a field drain next to a county highway. The victim and an uncle were at the bottom of the trench, the father was on top with a backhoe. The young man bent over to pick up a "T" to make a connection, and the trench caved in and killed him through suffocation and crushing, even though it was only five feet deep. In Walker's demonstration, he notes that a cubic foot of soil weighs 3,000 pounds and has as much mass as some pickup trucks.

One perennial issue discussed in the hallways at the event was about whether tile drainage affects flooding in the Red River Valley.

More research might help, Scherer said. There has been lots of research from April to November, but there is less information about how flows in this area are affected by weather factors -- a killing frost, precipitation, spring thaw timing. "We don't have a very good idea of when they flow, what do they respond to, the timing, because it's all dependent on when do we get snow, when does it thaw, when does the tile start flowing," Scherer says.

With this year's mild temperatures, some farmers in the Brookings, S.D., area were installing tile in early February, Scherer said, chuckling. "There's no frost. How strange is that?"

Mikkel Pates is an agricultural journalist, creating print, online and television stories for Agweek magazine and Agweek TV.
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