NITRATE-NITROGEN LOSSES FOLLOWING TALLGRASS PRAIRIE RECONSTRUCTION AT A WATERSHED SCALE: UPDATING THE WATER QUALITY RECORD AT THE NEAL SMITH NATIONAL WILDLIFE REFUGE (NSNWR) AFTER 22 YEARS

A large scale effort at tallgrass prairie ecosystem reconstruction was undertaken at the NSNWR in central Iowa beginning 1994. A variety of hydrologic investigations have been undertaken since then to document how ground and surface water systems have responded to conversion from cropland to prairie. One of these efforts has tracked nitrate-nitrogen losses. The first 10 years of record showed a slow decline in nitrate losses, averaging less than 1 mg/L NO3-N decline. This report will update that finding to consider 22 years of record. The headwaters of the watershed have remained in agricultural production, hence differences in upstream and downstream records are being evaluated to infer how effective the prairie reconstruction has been in driving a reduction in N loss.