In some areas of the field, the soil on Mark Chitley's farm in North Dakota presents a particular problem: Salinity causes chemical reactions that harden soil layers over a long period of time, slow water movement, restrict root penetration, and ultimately reduce crop yields. This phenomenon is called the "Rings of Death".
According to Tom DeSutter, professor of soil science at North Dakota State University (NDSU), salts typically enter the soil from the parent rock (from which soil is formed) and from groundwater. In the northeastern part of the state, salts are formed from shale and rising water from the Dakota Formation aquifer, while in southwestern North Dakota they are formed predominantly from sedimentary materials.
“When there is too much sodium in the soil and an overall low salt content, the clay particles in the soil repel each other,” notes DeSutter. “Under natural conditions, over a long period of time, dispersed clay particles move down the soil profile and create a columnar structure that can be quite difficult for plant roots to penetrate. So the soil is not very productive.”
To address these issues, Cheatley partnered with NDSU Extension to restore soils by incorporating flue gas desulfurization gypsum, a by-product of coal combustion. “The problem is getting worse, and I'm looking forward to seeing gypsum reverse that trend,” Chitley says.
Gypsum is a by-product of coal-fired power plants in western North Dakota. When incorporated into the soil, a series of chemical reactions occur in which calcium "acts as a bridge between soil particles and promotes chemical aggregation," explains Naeem Kalvar, a soil specialist with NDSU Extension, who helps Cheatley restore difficult soils. “This results in improved soil structure, soil porosity and water infiltration.”
The use of gypsum — along with other soil-healing practices such as cover crops, which Chitley will be trialling for the first time this year — is intended to combat solonets, salt marshes and saline soils, as well as improve overall soil health.
These efforts could save the region's farmers millions of dollars, Kalvar said, especially in the most at-risk crops such as soybeans, corn, spring wheat and canola. It will take years for Chitley and his neighbors to see the benefits of the products and methods they are introducing.
On the Chitley farm, Kalvar recommended applying 7 to 10 tons of gypsum per acre. Chitley purchased a Chandler spreader for use in saline areas and purchases gypsum for about $4 a ton from a plant in Stanton, North Dakota. The product has "the consistency of wet flour and does not spread well from conventional fertilizer equipment," Chitley notes.
There are other methods to soften saline soils. Among them, planting perennial salt-tolerant grasses in areas where annual crops simply won't grow. Farmers can save between $82 and $187 per acre, Kalvar said. Although growers must pay upfront for grasses in the first year, they will grow back on their own in subsequent seasons.
“By providing good vegetation cover, perennial grasses will reduce evaporation, while growing roots will help lower the water table and minimize capillary rise,” says Kalvar. “Farmers can cut hay or graze these grasses and can make some income, not just lose money on distressed acres. When cut at the right time, these grasses make good hay."
At the moment, Chitley does not plant perennial grasses. He is focused on evaluating the benefits of gypsum and cover crops while continuing to improve the potential of his farm's soil.