Tile drainage has become popular in areas where soils have poor internal drainage because it helps to convert land that would otherwise be too wet to consistently farm into highly productive cropland. While the benefits of tile drainage are improved traffic-ability and increased crop yields, the practice also delivers nitrates and phosphorus to stream systems which have a detrimental impact on water quality.
One strategy that can be used to reduce nitrates in tile drainage water is drainage water management. With drainage water management, water level control structures are included as a part of the tile drainage system, and these structures are used to manipulate water levels at different times during the year. The greatest nitrate removal benefits occur when water levels are maintained in the biologically active zone during the growing season where nitrates can be converted to nitrogen gas by denitrifying bacteria.
A properly managed system can also increase crop yields by conserving water in the soil profile for crops to utilize. When is drainage water management a good fit for a new or an existing tile drainage system? Generally, drainage water management is unfeasible on land slopes greater than about one percent. It may be possible to retrofit existing tile installations with water level control structures depending on how the tile layout fits with the field topography.
Tile systems utilizing drainage water management do not require closer tile spacing, but tile layout should be aligned with the field’s contours as much as possible in order to provide the most complete coverage and consistent water levels across the field. State and Federal funds are available for assistance in planning and installing these type of systems. Retrofits can also be added in some situations to implement subsurface irrigation in feasible locations.
Contact the Yellow Medicine Soil and Water Conservation District (SWCD) office in Clarkfield to find out more information about our programs, or call the office at (320) 669-4442 ext. 3. Our website also has a lot of information on all of our programs and services. Visit www.yellowmedicineswcd.org to learn more and stay up to date on all Yellow Medicine SWCD has to offer and what we are working on. You can also like us on Facebook!