Quantifying Salt Removal from Tile Drainage in the Red River Valley.

Producers of the Red River Valley face difficult management decisions due to a wet cycle inducing increased soil salinity and inaccessible fields during the spring time melt. Implementation of tile drainage can decrease soil moisture during wet periods and remove excess salts dissolved in the leaching water. Some producers who have installed tile drains in the Red River Valley have not observed these benefits of tile drainage. This study was conducted to quantify salt removal through tile drainage from a Fargo silty clay. Six large (20 cm-diameter by 121 cm-length), undisturbed soil monoliths were harvested from a field near Mooreton, ND. Three of these cores were considered saline and three were considered non-saline. A laboratory experiment was designed to accelerate field conditions of a wet/dry cycle native to North Dakota. Five liters of water was applied to the dry soil and leachate was collected for cation analysis to represent salt removal. Results from the two-time leaching events indicate an estimated 131 leaching events with a 0.25% salt removal required to remove excess cations from a high salinity soil to a low salinity soil status. True remediation of these soils is dependent upon improved crop yield response, and not necessarily the measured cations. Leaching events in the field is dependent upon seasonal rainfall duration, frequency, and precipitation volume. The process of salt removal in these soils may take up to 131 years, but the installation of tile drainage can prevent further accumulation of salts above the tile drain and allow for earlier planting in the spring from the removal of excess moisture through the tile drains.