Indiana has some of the highest concentrations of nutrients in streams in the United States
Indiana is located in the Corn Belt region. The rich soils and flat lands in this region make it an ideal location to grow row crops, such as corn and soy beans. The production of row crops requires large additions of fertilizer, either synthetic or manure, to improve yields. Large amounts of nutrients are added to Indiana agricultural fields each year, which allows the production of massive quantities of food crops.
One of the downsides to Indiana’s robust agricultural production is the unintentional transport of excess nutrients to streams and groundwater. The addition of tile drains to improve crop yields provides a transport pathway to streams for dissolved nutrients, especially nitrate. The highest concentrations of nitrogen in streams typically occur during the winter months when uptake by plants is lowest. Nitrogen concentrations also peak after rain events following application of fertilizers and manure.
Some of the highest nutrient concentrations in the region are found in Indiana streams and rivers, making the state a leading contributor of nutrients to the Gulf of Mexico.
Martin J.D., Crawford, C.G., Frey, J.W., and Hodgkins, G.A., 1996, Water-quality assessment of the White River Basin, Indiana—Analysis of selected information on nutrients, 1980–92. U.S. Geological Survey Water-Resources Investigations Report 96–4192, 91 p.
Notes: Concentrations of nutrients were higher downstream of urban areas than upstream of urban areas. Seasonal variations in nutrient concentrations and the relations of nutrient concentrations to streamflow depended upon the relative contributions of point and non-point sources of nutrients. Commercial fertilizer was the largest source of nitrogen and phosphorus in the White River Basin.
Royer, T.V., Tank, J.L., and David, M.B., 2004, Transport and fate of nitrate in headwater agricultural streams in Illinois. Journal of Environmental Quality, 33, p. 1296-1304.
Notes: A nutrient spiraling model was used to assess denitrification rates and downstream transport. Denitrification rates tended to be high (up to 15 milligrams of Nitrogen per square meter per hour). Most of the nitrate as nitrogen in these headwater sites was transported downstream.
Royer, T.V., David, M.B., and Gentry, L.E., 2006. Timing of riverine export of nitrate and phosphorus from agricultural watersheds in Illinois: Implications for reducing nutrient loading to the Mississippi River. Environmental Science and Technology, 33, p. 1296-1304.
Notes: This study found that nutrient export occurred when discharge was greater than or equal to the median discharge. Extreme discharges — those greater than the 90th percentile — were responsible for more than 50 percent of the nitrate as nitrogen and 80 percent of the phosphorus export. The export occurred annually during a period beginning in mid-January through June.
Baker, N.T., Stone, W.W., Wilson, J.T. and Meyer, M.T., 2006. Occurrence and transport of agricultural chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003-04. U.S. Geological Survey Scientific Investigations Report 2006-5251, 44 p.
Notes: Nutrients such as nitrate that readily dissolve in water are transported into streams primarily through the tiles. Nutrients that bind to soil are transported primarily through overland flow. This research found that because of the clay layer in the glacial till and the widespread use of tile drains, nutrients do not make it to the groundwater.
Baker, N.T., Stone, W.W., Frey, J.W. and Wilson, J.T., 2007. Water and agricultural-chemical transport in a Midwestern, tile-drained, watershed: Implications for conservation practices. U.S. Geological Survey Fact Sheet 2007-3084, 6 p.
Notes: Nitrogen and phosphorus have different pathways into streams. this research found that how nutrients are transported — whether primarily through tiles or overland flow — impacts the effectiveness of agricultural management practices used to reduce runoff into streams.
Robertson, D.M., Schwarz, G.E., Saad, D.A., and Alexander, R.B., 2009. Incorporating uncertainty into the ranking of SPARROW model nutrient yields from Mississippi/Atchafalaya River basin watersheds. Journal of the American Water Resources Association, v. 45, n. 2, p. 534-549.
Notes: This study found that Indiana streams have some of the highest nutrient yields draining into the Mississippi River Basin.
Alexander, R.B., Smith, R.A., Schwarz, G.E., Boyer, E.W., Nolan, J.V., and Brakebill, J.W., 2008. Differences in phosphorus and nitrogen delivery to the Gulf of Mexico from the Mississippi River Basin. Environmental Science and Technology, v. 42, n. 3, p. 822-830.
Notes: This study found that Indiana streams are a major contributor of nutrients delivered to the Gulf of Mexico.
Vanni, M.J., W.H. Renwick, J.L. Headworth, J.D. Auch, and Schaus, M.H., 2001. Dissolved and particulate nutrient flux from three adjacent agricultural watersheds: A five-year study. Biogeochemistry, 54:85-114.
Notes: Fluxes of dissolved and particulate nitrogen (N) and phosphorus (P) from three adjacent watersheds in southeast Indiana and southwest Ohio were studied over five years. Annual fluxes of dissolved N and P varied by two times among watersheds, but patterns were not related to watershed side. Most N was transported as nitrate. Most export of nutrients occurred during storm flow.