Field experiments were conducted for three years (1989-91) at the research farms of Iowa State University near Ames and Ankeny to evaluate water-table management (WTM) effects on groundwater quality. Water-table depths of 0.3, 0.6, and 0.9 m were maintained in field lysimeters at the Ames site, and variable water-table depths were maintained in a subirrigation field at the Ankeny site. Water samples were collected from various soil depths to analyze NO3-N concentrations in groundwater. Concentration of NO3-N in groundwater changed with WTM practices. The lowest NO3-N concentrations were observed under the shallow water-table depths. NO3-N concentrations in groundwater generally decreased with increased depths and time during the growing season under all WTM practices. Crop yields were higher under water-table depths of 0.6 to 0.9 m than under other water-table depths, and corn yields decreased under shallow water-table depths of 0.2 to 0.3 m. Results of this study indicate that WTM practices can be used to substantially reduce the concentrations of NO3-N in groundwater. Results also strongly support the need for further research with WTM practices for water quality and crop production.
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