Tile Drainage and Nutrient Management.

1.0 SW CEU

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In response to the Hypoxia Task Force Action Plan, states within the Mississippi River Basin have developed state level plans for reducing nutrient export to downstream water bodies. In Iowa, the Iowa Nutrient Reduction Strategy was officially released in May 2013. The Nutrient Reduction Strategy is Iowa’s response to the Hypoxia Task Force Action Plan. Consistent with other plans across the upper Midwest subsurface drainage (tile drainage) is an important component for nutrient reduction. To reach the goals of 45% reduction in state level export of nitrogen and phosphorus will require a combination of in-field and edge-of-field practices.  The Nonpoint Source Nutrient Reduction Science Assessment portion of the Iowa Nutrient Reduction Strategy outlined some example scenarios for reaching this goal. First, it would take a combination of practices rather than one single practices. Second, the level of practice implementation is very large.  One example scenario that is commonly discussed is one where it is assumed that all corn acres use the Maximum Return to Nitrogen Rate, 60% of corn-soybean and continuous corn acres have cover crops, 27% of all ag land is treated with a wetland, and 60% of the tile drained acres are treated with a bioreactor. The wetlands and bioreactors would specifically be designed and sited to treat tile drainage water. Thise combination of practice approach is consistent with other state level strategies across the upper Midwest.  This presentation will discuss the range of practices that can be used for nutrient reduction specifically focusing how we can reduce nitrate-N export from the subsurface drained landscapes.