Saturated Riparian Buffer in Situ and Potential Denitrification.

Saturated riparian buffers were developed as a way of removing nitrate from tile drainage water before the nitrate is exported to adjacent streams. These buffers intercept tile drainage water via a control box with stoplogs, and divert the water into tile laid parallel to the field and stream edge. The intercepted water is allowed to slowly seep through organically rich soil (Coland clay loam) to the stream via hydraulic head. This situation is potentially optimal for microbial denitrification to occur. Both in situ and potential denitrification rates for three saturated buffers in central Iowa were analyzed in this study. Soil cores were taken down to a meter once a month for two years. These cores were divided into 20 centimeter sections that were processed according to the acetylene inhibition technique. The results indicated that the saturated buffers studied have an in situ denitrification rate between 0.02 and 77.9 mg N₂O-N m^-3 hr^-1. Further, according to the denitrification potential experiment, the studied buffers could potentially treat a larger nitrate load via larger tile water nitrate concentrations. Therefore, carbon by itself did not significantly limit the amount of denitrification. The buffers in this study were considered optimal for experimental saturated buffer sites. Further research is needed to develop a ground-truthing metric for siting future successful saturated buffers. The denitrification potential experiments done in this study may be a step towards this goal.