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How to Snap Slacker Soils Into Shape
Farmers huddled around Keith Anderson, a North Dakota National Resources Conservation Service soil survey leader, who stood in a soil pit at a North Dakota State University (NDSU) soil health field day. Anderson dissected the various layers of a high-clay sodic soil.
When moist, these soils form a greasy mix that can sink a tractor up to its proverbial axles. When dry, these soils harden like concrete and can nix a crop’s ability to absorb water and nutrients due to reduced water infiltration.
After some silent seconds, one farmer finally asked what they all were thinking: “So, what do you do with this crap?”
Maybe you’ve had a problem field like this – one that just never measures up to the rest of your farm. On one hand, subpar yields drag down the rest of the farm. On the other hand, the cost of snapping such a field in shape to glean higher yields might not be worth the cost.
Examples include sodic and saline soils. Sodic soils impact about 10% of North Dakota’s agricultural land. Meanwhile, 1.2 million acres in the Red River Valley of North Dakota and Minnesota are classified as saline.
Saline soils are high in salts derived from ancient sedimentary rocks. Heavy rainfall prompts these salts to rise to the surface, due to a rising water table.
Salts that cause salinity don’t plague sodic soils. Instead, these soils have high amounts of sodium relative to calcium and magnesium on their exchange sites. When this happens, swelling and dispersion cause disorder of clay and organic matter. These soils then have low productivity and poor soil health.
Both soil conditions have been aggravated by two decades of rampant rainfall in the 1990s and 2000s in areas like eastern North Dakota.
Salts and sodium have likely always existed in these soils, says Tom DeSutter, an NDSU soil scientist. The native prairie grasses kept this in check, though, by properly cycling water and nutrients.
“Then annual crops came along and made it worse,” DeSutter says.
“With sodic soils, you are pretty limited in what you can do,” says Chandra Langseth, an NDSU Extension agent in Richland County in southeastern North Dakota.
Tiling doesn’t help. Cases have existed where tile spacings as tight as 20 feet didn’t help sodic soils. “These soils never drained well to begin with,” says DeSutter.
Sodic soils also tend to be interspersed in fields among better soils.
“This causes trafficability issues,” says DeSutter. “Those pockets cause you to spend two to three hours getting unstuck.”
NDSU trials with alfalfa used as a nurse crop plus soil amendments like gypsum can improve soil water movement. Gypsum provides calcium and helps maintain the soils’ electrical conductivity (EC) above the level needed for flocculation. This allows for good water movement and root growth, says DeSutter.
Soil amendments can be expensive. If all else fails, alfalfa can work as a main crop for several years. Sunflowers – another deep-rooted crop – are another option, says Langseth.
The news is better for saline soils. Before you begin to remedy them, though, a soil check with an EC meter can reveal if the soil is saline. The higher the EC, the higher the salt content. Most labs define a soil as saline if the EC has a reading of 4 decisiemens per meter (the metric used in determining EC) or more.
Some crops, though, are more sensitive to salt. “For rotations with soybeans, an EC of 2 is where we need to manage the soil to keep salts in check,” says Abbey Wick, an NDSU Extension soil health specialist. “You need to shift your brain from production to remediation for those saline parts of the field where crops fail year after year.”
Managing these soils is akin to wicking up water via a dry sponge.
“The more that water goes to the surface, the more salinity you have,” says Frank Casey, an NDSU soil physicist.
Tiling can help. So can cover crops. “In some cases where cover crops are not planted, the soil can be pure white,” says Langseth.
Still, it’s difficult to sort through the plethora of many different cover crop combinations out there.
Confused? Don’t be. Effectiveness exists in simplicity, says Wick. In southeastern North Dakota, Wick and area farmers have managed salinity with a cover crop mix of 40 pounds per acre of barley, 2 pounds per acre of radishes and 40 pounds pounds per acre of cereal rye.
“Each one serves a purpose,” she says. “Barley is the most salt-tolerant cover crop we have. Radishes can open up the soil for drainage, and cereal rye will overwinter to use moisture in the springtime when these areas are typically wet.”
To make this mix economical, Wick advises planting it only on localized salt patches, since this crop will not be harvested.
No-till also is an option, since it boosts soil aggregation. This helps improve water infiltration that pushes salts down in the soil.
That’s been the direction Terry Wehlander, who farms with his brother Kevin, cousin Steve, and uncle Don near Milnor, North Dakota, have taken on saline soils.
“The deeper we worked the ground, the worse the salts got,” he says. The no-till they’ve used in the past five years has helped.
Cover Crops and Soil Health: YieldQuest
bring on barley
No-till hasn’t been enough, though. The Wehlanders chose salt-tolerant barley as a cash crop to remedy those soils and snap them in shape for row crops again.
“We hadn’t raised barley in 21 years,” he says. “We figured if we broke even on that field, we were getting better soil health.”
One knock against barley is that it’s not economically competitive with corn and soybeans. Much depends, though, on yields and whether it makes the malting barley grade.
When they planted the barley in 2014, yields ranged from 65 to 100 bushels per acre. A plus on the 100-bushel field was that it made malting grade, with a price of $5.25 per bushel.
Expenses were minimal, with the biggest adjustment occurring with fertility. Barley needs adequate nitrogen (N) for good yields. However, excess N can trigger excessive protein and small kernel size that can cause brewers to reject barley for malting. Excess N also leads to lodging and boosts severity of head blight and severity in certain years, note NDSU soil scientists.
The Wehlanders had good results with applying a starter fertilizer at planting before topdressing 20 gallons per acre of 28% N.
After barley, they seeded a cover crop before going back to corn the next year.
Problem soils like these will never bust the bins like a deep, rich silt loam soil. In the cases of soils like saline ones, though, steps exist for you to manage them. It just takes time.
“It’s often a 10-year process,” says Casey. “The soil doesn’t fix itself overnight.”
By Gil Gullickson