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Tile Drainage (07/26/18)

Over the last decade or so, tile drainage has become more common in North Dakota and Northwest Minnesota.

Tile Drainage

Over the last decade or so, tile drainage has become more common in North Dakota and Northwest Minnesota. The adoption of this subsurface drainage technology in the region is partly due to increased heavy rainfall events since 1993, higher input cost, and therefore higher risk in farming. Tile drainage tends to increase crop yield and reduces yield variability from season to season. Another benefit of tile drainage is that it allows soils to warm-up and dry out faster in the spring. Fields with intermittent wet spots will dry out more uniformly. Spring field operations on tiled fields will most likely be possible at an earlier date than fields without tile drainage.

In the spring of this year, some farmers were unable to plant their crops in a timely fashion due to the wet conditions. Heavy rainfall in certain parts of North Dakota also prevented crop management to take place at the most appropriate time. Increased annual rainfall also has caused salinity to become a problem in many fields due to rising water tables. Saline areas are often observed as large unproductive areas due to the increase in salt concentration in the soil profile, especially near road ditches. If there is an appropriate outlet (ditch or stream), tile drainage is a management practice that can control and reduce salinity in wet soils.

Tile drainage is useful in many soil textures. Tile installation in sandier soils is typically deep and widely spaced, but may need sock filters around the pipe to prevent soil particles from entering the tile. Clay soils can also be drained but require tile to be placed shallower and closer together. In a Fargo clay, a common tile design might be at a depth of 3 feet with a spacing of 40 feet, whereas tile spacing for an Ulen fine sandy loam would be around 100 feet and 4 feet deep. Soils, where shrinking/swelling clays or peat predominate, or sodicity is present, may need special designs with regard to tile drainage. Fields with a minimum slope can still be subsurface drained if minimum grades of 0.05 to 0.1% are maintained for tile laterals. A tile line at 0.1% grade has 1 foot of fall per thousand feet.

In many parts of the US, a typical tile drainage system has an outlet where water can drain freely (by gravity) into a surface ditch. With limited slope or fields that do not allow for a gravity outlet, pumped outlets are useful if a surface waterway exists to discharge the drainage water (photo 1). A pumped outlet or "lift station" provides the lift required to get the drainage water from the elevation of the tile, to the ground surface and into the receiving waterway. Pumped outlets may require electricity (photo 2) and installation will add to the initial investment and operation/maintenance costs of the drainage system. However, pumps have proven to be economically feasible in many situations. A pumped outlet station includes sump, pump, and discharge pipe. Important design features include size and shape of sump and capacity of the pump.

Self-installation is an option; however, the most important benefits of using a tile installer is experience and familiarity with design procedures and standards of tile drainage systems. Depth, grade, pipe size, and field layout are all extremely important in the tile drainage design and will determine the quality and performance of your system. Tile not properly installed may not work as anticipated. It usually takes time to design a system, obtain permits and materials. Fall and early winter, until the ground freezes, are usually good times to install tile.

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 Hans Kandel

Extension Agronomist Broadleaf Crops

Tom Scherer

 NDSU Extension Engineer

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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