Soil experts, farmers look into saline-sodic soil problems

Farm Forum

NATURAL RESOURCES CONSERVATION SERVICE, Huron, SD — Farmers across South Dakota, especially in the east and the James River Valley, are seeing an increase in salinity and sodic soil problems. Out on the landscape, the white spots on the soil surface without vegetation are identified as saline soils that have high salts, while sodic soils have high sodium levels.

At a July 8, 2014 field day near Pierpont, SD, farm groups hosted experts from the USDA Natural Resources Conservation Service (NRCS), South Dakota State University (SDSU) and about 120 farmers to take a close look at what is happening with water movement within the soils of those problem areas. As part of a Conservation Innovation Grant from NRCS, North Dakota State University and SDSU are exploring salinity and sodicity treatment practices. The universities are tracking soil performance under various management options and researching alternatives such as using amendments to improve infiltration, especially in the affected areas that are tiled. Much of SDSU’s research and the discussions that day where about successes.

How those areas are managed, i.e., crop rotation, use of a no-till system or conventional tillage, tile drainage, etc., affects the productivity. NRCS Conservation Agronomist Jason Miller, Pierre, told the crowd that managing soil moisture or water stored in the soil throughout the year is important to keep the fields productive. The high salinity/sodic problem is caused by a combination of soils that have high salt concentrations deep in the soil profile and then not growing a crop to utilize the majority of soil moisture received throughout the year. “The management made the natural function of water movement in soils quit working properly,” Miller explained. “So, in essence, the water table begins to rise in some areas because the cropping has been changed to an annual crop versus a perennial vegetation. While other areas, it is water coming or nearing the soil surface on a sidehill, or what we call a saline seep. Both occur when the cropping system that is employed does not use enough of the moisture.”

At the field day, Dave Gillen who farms in Aurora County, SD, explained how he is dealing with some of the areas through seeding perennial vegetation to try to get these areas producing again. With corn prices this year, Gillen says his strategy is to get the soil and water movement back working properly so when there is an upswing in corn prices, those areas could potentially be planted again.

“Understanding water movement through those soils and using farming practices that mimic nature to better manage plant available water will speed recovery and get saline or sodic soils producing any return,” Miller explains.

“Just tiling a corn and soybean field to try to move water isn’t the answer because in a salinity/sodic area, the overall soil ecosystem has been damaged and isn’t functioning correctly,” says Miller. “You’ve got to address ‘the whole’ of the situation. Those areas need a perennial crop that will tolerate the salinity/sodicity soil to use the available soil water.”

Conventional tillage systems destroy soil structure and the macropores that are essential for water movement,” explains Miller, “so eliminating tillage will help the soil’s physical, biological and chemical properties. Tillage makes the problem worse because it dries the surface which results in more salts accumulating at the soil surface from the capillary rise of soil water from the distrubed area.

Soil microbes need food. Corn and soybeans are not growing in these areas so there’s no food for the microbes to function. Miller recommends planting a barley or rye at the minimum, but perennial vegetation for a minimum of 3-5 years would be best. Monitoring through soil tests will document the soil health benefits.

“Managing for healthier soils can be complex task with long-term implications. If you’re seeing problems with your soil and production, get help,” says Miller.

Increasing organic matter to get better use of water in those areas can be done by eliminating tillage and keeping living roots growing longer throughout the year. Miller says, “Crops, like corn and soybeans, use water in the soil for a limited time so adding cover crops use more moisture and to feed the soil will help.”

Diversifying crop rotations or other alternatives such as seeding perennial vegetation will also help to bring back proper soil function. An area could also be entered into the Conservation Reserve Program (CRP) under continuous sign-up. NRCS can help farmers determine the best option for these resource concerns.