Hormone loads exported by a tile-drained agroecosystem receiving animal wastes

Little is known regarding hormone export from tile-drained agricultural fields despite the widespread presence of tile drains in the Midwestern United States. By intensively measuring water flow rates and hormone concentrations in four subsurface tile drains and three receiving ditches at a working Midwest farm, hormone fluxes and loads from the tile-drained fields were quantified. Before and during the 17-month study period (January 2009 - May 2010), the associated farm fields received various animal waste applications (beef, dairy, poultry, sheep, and swine). Hormones monitored included the estrogens17β- and 17α-estradiol, estrone, and estriol; the natural androgens testosterone, and androstenedione; and the synthetic androgens 17β- and 17α-trenbolone, and trendione. Hormone loads measured in the ditches for three drainage areas during the entire 17-month study period were in ranges of 16-58mg/ha for total estrogens, 6.8-19mg/ha for natural androgens, and 4.2-44mg/ha for synthetic androgens. Because higher hormone concentrations generally occurred during discrete periods of increased flow, high flow rates often were associated with a disproportionately high hormone flux. For example, 80% of total estrogens and natural androgens exported into the ditches occurred during only 9-26% of the study period, coinciding with the most significant storm events. In addition, hormone fluxes were highest during storm events that occurred shortly after animal waste applications. Therefore, to effectively reduce hormone loads exported to downstream aquatic ecosystems in the absence of any application reduction, the short periods during which high-flow events occur must be targeted.