Anthropogenic activities have altered the global cycle of nitrogen substantially. Land use and nitrogen-based fertilizer inputs are known to influence groundwater nitrate levels and nitrous oxide gas fluxes from soil ecosystems. However, little is known about the relationship between these gas fluxes, the denitrification potential of the microbial community (i.e. presence of denitrification genes), and nitrogen inputs in relation to land use in semiarid ecosystems. Thus, the objective of this study was to determine denitrification potential at five sites with different land uses (i.e. grazed-grassland, cropland, urban, wetland, sub-irrigated), and varying nitrate and water inputs. Soil collected from the different sites was incubated at varying water potentials (dry, field capacity, and saturated), and potassium nitrate was added to all treatments, except the dry treatment group. During the incubation, nitrous oxide gas fluxes were measured and at the end the soil was analyzed for presence of microbial genes involved in denitrification (narG, nirS/K, norB, and nosZ genes).
Results/Conclusions
Gene presence differed for all land uses, with the grazed-grassland site showing lowest percent frequency for all genes. Preliminary analyses indicate the addition of nitrate and water conditions result in variations in nitrous oxide gas fluxes, but there were no common patterns across land uses. Further data analysis will provide a better understanding of the dynamics between biotic and abiotic variables influencing denitrification in semiarid ecosystems.