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United States Department of Agriculture

Agricultural Research Service

Research Project: ASSESSING CONSERVATION EFFECTS ON WATER QUANTITY AND QUALITY AT FIELD AND WATERSHED SCALES

Location: National Soil Erosion Research Lab

Title: Surface runoff and tile drainage transport of phosphorus in the Midwestern United States

Authors
item Smith, Douglas
item King, Kevin
item Johnson, L -
item Francesconi, Wendy
item Richards, P -
item Baker, D -
item Sharpley, A -

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2014
Publication Date: July 3, 2014
Citation: Smith, D.R., King, K.W., Johnson, L., Francesconi, W., Richards, P., Baker, D., Sharpley, A.N. 2014. Surface runoff and tile drainage transport of phosphorus in the Midwestern United States. Journal of Environmental Quality. DOI:10.2134/jeq2014.04.0176.

Interpretive Summary: The Midwestern US has some of the most productive agricultural soils in the world. Given the climate, much of the region would not be able to support agriculture without drainage, as the high water table would potentially damage crops and not allow machinery to be in the fields at critical times. While drainage is designed to remove excess water as quickly as possible, it can also remove agrochemicals, including phosphorus rapidly. This paper is intended to provide a context for the importance of tile drainage for P transport in the Midwestern US. Fields in the St. Joseph River watershed in northeast Indiana have been monitored for surface and tile discharge since 2008. While the traditional concept of tile drainage has been that of moving slowly to the tile because it has to move through the soil, peak volume of water flowing through tile occured at the same time as peak surface runoff. This suggests a strong surface connection through large pores in the soil, called maropores. Tile discharge accounted for approximately half of the soluble and total phosphorus lost from fields. Soluble phosphorus and total phosphorus loads often exceed the loadings from the Maumee River on an acre for acre basis. As researchers, policy makers and farmers search for treatments to reduce P loading to surface waters, such as Lake Erie, the present work highlights that treating surface runoff may not provide sufficient treatment to reach a goals that have been established to minimize algal blooms.

Technical Abstract: The Midwestern US offers some of the most productive agricultural soils in the world. Given the cool humid climate, much of the region would not be able to support agriculture without drainage, as the high water table would potentially damage crops and not allow machinery to be in the fields at critical times. While drainage is designed to remove excess water as quickly as possible, it can also remove agrochemicals, including phosphorus rapidly. This paper is intended to provide a context for the importance of tile drainage for P transport in the Midwestern US. Fields in the St. Joseph River watershed in northeast Indiana have been monitored for surface and tile discharge since 2008. While the traditional concept of tile drainage has been that of removing matrix flow, peak tile discharge occurs at the same time as peak surface runoff, suggesting a strong surface connection through macropore flow. Tile discharge accounted for 49% of soluble P and 48% of total P exiting monitored fields. Soluble P and total P loads often exceed the aerial loadings from the Maumee River, where algal blooms have been a pervasive problem for the last ten years. As researchers, policy makers and farmers search for treatments to reduce P loading to surface waters, the present work highlights that treating surface runoff may not provide sufficient treatment to reach a goal of 41% reduction in P loading, as has been set for Lake Erie.

Last Modified: 8/27/2014
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