Analyzing Denitrification in Saturated Riparian Buffers.

Soil microbial denitrification, the reduction of ionic nitrate to a gaseous medium (nitrous oxide and dinitrogen gas) via microbial processes, typically varies both spatially and temporally. This microbial process requires organic carbon, nitrate, and anaerobic conditions. All three of these criteria are met in a saturated riparian buffer, SRB. A SRB is a relatively new nitrate removal technique that intercepts subterranean tile drainage networks from agricultural fields, and forces the tile water to seep through organically rich soils adjacent to waterways. The water level in these buffers is controlled through a control box and lateral tile. For this study, we examined the denitrification rate of three central Iowa SRBs receiving water drained from fields planted in corn in soybeans, by using the acetylene inhibition method for soil cores. We found that these denitrification rates varied greatly, and that the identification of the limitations for the rates were crucial to under the success of the nitrate removal rates for each SRB. We therefore conducted a series of denitrification potential analyses to determine which factor, carbon or nitrate, was most limiting. The results from this study were variable, but provided insight into the mechanism of denitrification in these SRBs.