Submitted to: American Chemical Society Symposium Series
Publication Type: Book / Chapter
Publication Acceptance Date: November 18, 2003
Publication Date: April 21, 2004
Citation: Moorman, T.B., Hatfield, J.L., Kanwar, R.S. 2004. Herbicide and nitrate in surface and groundwater: results from the Iowa MSEA. American Chemical Society Symposium Series. In: Nett, M.T., Locke, M.A., Pennington, D.A., editors. Water Quality Assessments in the Mississippi Delta. Danvers, MA: Oxford University Press. p. 235-250.
Interpretive Summary: Pesticides and nutrients have been found in surface water and groundwater. These contaminants present a variety of risk to human health and ecosystem function. This report summarizes research on herbicides and nitrate conducted in central Iowa as part of the Management Systems Evaluation Area (MSEA) research program. The research showed that there was little risk of herbicide leaching to groundwater in central and eastern Iowa. However, subsurface drains (tiles) conducted significant amounts of herbicide and nitrate to streams. Tillage practices had relatively minor effects compared to compared to the presence or absence of subsurface drainage and application rates. This information has increased our knowledge of how agricultural practices affect water quality. Results of this research have helped guide current research that seeks to reduce nitrate losses into the Mississippi watershed. Thus, the information has impacted scientists and producers.
The Iowa Management System Evaluation Area (MSEA) program sponsored multidisciplinary research at plot, field and watershed scales. Water monitoring studies targeting herbicide and nitrate transport were conducted in different hydrogeologic settings. In central and northeast Iowa, herbicides were transported from fields in runoff and in subsurface drainage water. Herbicides leached to groundwater, but concentrations generally remain below the MCL. Relative losses of different herbicides are related to their persistence paterns in soil and soil permeability. In contrast to herbicides, nitrate concentrations in stream water often exceed the MCL and losses are controlled by sursurface drainage. Nitrate losses are affected by fertilization, mineralization of soil nitrogen, and timing of spring rainfall. Tillage affects nitrate loss indirectly, through changes in water infiltration. The MSEA program established broader knowledge about the routes of contaminant entry into surface waters, contaminant sources and effects of selected practices.