169-1 Composition of N Gases Produced in Riparian Buffers: The Role of Artificial Drainage.

Poster Number 2404

See more from this Division: S11 Soils & Environmental Quality
See more from this Session: Not for Export: Contaminant Issues in Agricultural Drainage: III
Monday, October 22, 2012
Duke Energy Convention Center, Exhibit Hall AB, Level 1
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Lori Bebinger and Pierre-Andre Jacinthe, Earth Sciences, Indiana University and Purdue University - Indianapolis, Indianapolis, IN

The US Corn Belt is a leading contributor to nitrate (NO3-) enrichment and the so-called dead-zone in the Gulf of Mexico. Located at the interface between agricultural fields and surface water bodies, riparian buffers have shown great capacity to remove NO3- from agricultural runoff, and thus reduce fertilizer N export to streams. N removal is achieved primarily via denitrification, a process whereby riparian soil microbes convert NO3- into nitrous oxide (N2O) and dinitrogen (N2). However, from an air quality standpoint, a low N2O production relative to N2 (mole fraction of N2O) would be preferred because N2O contributes to the greenhouse effect and depletion of the ozone layer. With the hypothesis that frequent water saturation is favorable to the reduction of N2O into N2 (thus a low N2O mole fraction), a study was conducted to identify controlling factors of N2O mole fraction across various riparian buffers [well-drained (WD), poorly-drained (PD), and tile-drained (TD) sites] in Central Indiana. The relative production of N2O and N2 was measured in the laboratory using the acetylene (C2H2) block technique. In the absence of C2H2, there was no difference in N2O production rate among the sites. However, in the presence of C2H2, N2O production at PD (30 g N2O kg-1 soil h-1) was much higher than at the WD site (8.42 g N2O kg-1 soil h-1). Conversely, the N2O mole fraction at PD (0.11) was lower than at WD (0.28). These results are consistent with the greater soil moisture, and higher total soil organic C at PD compared to WD. In our on-going studies, we examine the impact of tile drainage on the depth distribution of denitrification, N2O-reductase and hydrogenase activity in artificially-drained riparian buffers.

See more from this Division: S11 Soils & Environmental Quality
See more from this Session: Not for Export: Contaminant Issues in Agricultural Drainage: III
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