Tiling for Salinity

Farmers who question the value of tiling to reduce soil salinity will want to pay attention to research being done on a real farm – not just a small experimental plot.

Last August, researchers installed tile on one half of the 160-acre Soil Health and Agriculture Research Extension (SHARE) Farm near Mooreton, North Dakota. On 40 of the tiled 80 acres, water drains into water-level control structure boxes, a relatively new system that allows producers to raise and lower the water table for improved water management.

The setup provides a unique opportunity to compare soils and yields on land with conventional tile, controlled tile, and no tile, says Ken Johnson, who owns and farms the SHARE Farm along with other property known as the Bagg Bonanza Farm.

"The main issue is salinity," he says. "The field has salt spots that don't grow anything, and they're getting bigger," Johnson says.

With support from the state's soil health initiative, an advisory board requested the tiling project.

"Salinity is a symptom. The problem is a high water table," says Andrew Fraase, consultant with Centrol Drainage of Casselton, North Dakota. Salinity has became a bigger challenge since 1993, when the water tables became extremely high and pushed salts to the surface. It's estimated that 90% of North Dakota's farmers deal with saline soils.

"Tiling is a great tool," Fraase says. "It manages the water table in the field, and by lowering the water table in the field, we can lower the salts accumulated in the root zone causing the salinity issues."

Besides being the first important step, he emphasizes that tiling prepares the way to add other management practices that improve soil health.

Tiling Options
Fraase explains that the tiling process begins with a field assessment to determine what the issues are, to check soil type, and to see if it's a wetland. Any type of soil can benefit from tiling, but modifications may be made. For example, sandy soil might be tiled every 80 feet. Sodic soil can benefit, too, but amendments such as calcium must be added.

The high water table on Johnson's property near the Red River Valley and silty (40% to 50%) clay soil compounds the salinity problem because it holds the water longer in the top 6 inches. Patterned tiling (4-inch laterals flowing into 12-inch main) was installed every 40 feet at a depth of 3 to 4 feet.

To add to research options, the acreage tiled with the water-level control system allows additional water management, Fraase says. Solid main tile (instead of perforated tile) near the boxes holds the water. After excess water has been drained and the crop planted, planks and gates can be placed in the box to stop water from draining and to raise the water level 2 to 3 feet from the surface, closer to the plants.

"Roots have an opportunity to go down and access more water before the water table drops, usually in June and July," Fraase says.

He says the key is to keep the water accessible but not so high it drowns out the roots, which defeats the purpose of tiling. Digging holes or probing the soil will indicate water level and help determine how many planks and gates should be placed in the box to hold the appropriate water level.

Control box installation
The relatively level topography at the SHARE Farm simplified installing the control boxes. A box is needed for every foot of elevation change. Two boxes were installed on the 40-acre site at the cost of about $1,500 per box.

"It's something that I think will slowly pick up in this area, because there are some benefits to it," Fraase says of the control box system. "It will be very interesting to see the yield response."

Bonus benefits
As a soil enthusiast, Fraase says tiling is the first important step to decreasing saline soils and improving overall soil health. By removing excess water, fields are drier, more air pockets exist to warm the soil faster, and producers have the option to switch to no-till or minimum-till farming. This builds organic material in soil and holds more moisture during drought conditions. With something growing on the surface, salt doesn't move up, and roots create channels through the soil for more downward movement. All this helps build soil structure.

So do cover crops. Since keeping something growing is important to avoid salt rising to the surface, Johnson planted a cover crop after tiling. It was planted in 160-foot-wide strips (with 160 feet of no crops in between) across the whole 160 acres. That will allow North Dakota researchers to compare cover crops/no cover crops on tiled and untiled soil.

Fraase says he has seen land that once wouldn't grow anything produce 100-bushel-per-acre corn in the first year after tiling. On some land, though, getting any plants to grow is a big step forward.

"On the SHARE Farm, you'd expect greater and faster return on the investment because you are solving more issues (clay, high water table, and salinity) with one tool," he says.

Tile any time
In 2014, Johnson planted wheat, which was harvested early enough so the field could be tiled in mid-August.

Tiling in late summer when it's the driest is ideal, Fraase says. Producers often plant barley or wheat when they plan to tile. Still, he notes that tile can be installed anytime between planting and freeze-up. Producers have had success tiling in planted corn before it is knee-high. Corn yields in the rows over the tile are often much higher than other areas in the field, Fraase says.
Average cost for tiling is $800 per acre with about a 10-year investment return. While there aren't programs to cover the cost of tiling, NRCS offers funds for control boxes because they are used for water management and can also hold back nitrogen and nutrients that would typically be drained, which is another benefit to tiling.

Johnson intends to plant corn in the spring. Just getting it planted in a timely fashion will be an accomplishment.

Researchers and Johnson are eager to see the improvements tiling makes at SHARE Farm. They recognize it is just one piece of the management puzzle to improve the soil and its productivity over several years of careful planning. Fraase says tiling is an important first piece and a valuable tool.