Effects of Various Soil Amendments on Subsurface Water Quality at the ISU Farm

Starting in 2003, a series of field studies were conducted in conjunction with researchers from Illinois State University (ISU) at the ISU Farm north of Lexington, IL. Three sites for monitoring subsurface water quality beneath row crops receiving various soil amendments were established at or near the ISU Farm. The first site was a series of small experimental plots located on the northern edge of farm property just west of road 2550E, which were amended with various fertilizers, including compost (at two application rates), swine manure slurry, separated swine manure effluent, and synthetic fertilizer (urea). A zero-rate control plot was also initiated. The swine that produced the manure used in these studies were dosed with chlortetracycline prior to the 2004 applications and for every year afterward. A common practice in the livestock industry is to provide sub-therapeutic doses of antibiotics to prevent disease outbreaks and increase growth rates (Mason et al., 2009). Tetracyclines are one of the most commonly used families of antibiotics for these purposes. The second site covered a larger area of privately owned fields to the north of the ISU Farm, which were amended with materials from the farm. Amendments included compost, manure slurry, and separated swine manure effluent. The third site was located on the northern section of ISU Farm property to the east of road 2550E. Narrowly spaced tile drains were installed at this site for the application of separated effluent via subsurface irrigation. The goal of all studies was to determine if the various soil amendments were affecting subsurface water quality. Monitoring wells were installed in up-gradient and down-gradient locations to monitor changes in shallow groundwater quality. Lysimeters were installed at the first and third sites beneath fields where various soil amendments were applied, as well as at a control location at site one. A summary of soil amendment and monitoring activities for all three sites is shown in Table 1. In addition to the field studies, a series of flow-through soil column experiments were conducted to help understand nitrogen dynamics, especially changes in nitrate isotopes.