PS 64-71
Arbuscular mycorrhizal fungi markedly reduce N2O emissions from an organic soil

Friday, August 15, 2014
Exhibit Hall, Sacramento Convention Center
Xuelin Zhang, Plant pathology, North Carolina State University, Raleigh, NC 27695, USA, Raleigh, NC
Shuijin Hu, Plant Pathology, North Carolina State University, Raleigh, NC
Cong Tu, Department of Plant Pathology, North Carolina State University, Raleigh, NC
S. Chris Reberg-Horton, Department of Crop Science, North Carolina State University, Raleigh, NC
Yunpeng Qiu, Plant pathology, North Carolina State University, Raleigh, NC 27695, USA, Raleigh, NC
Background/Question/Methods

Arbuscular mycorrhizal fungi (AMF) form symbiotic associations with over 80% of terrestrial plants. Recent studies showed that AMF can enhance plant N uptake and consequently alter N2O emissions. They may reduce N2O emissions through reducing soil NO3- for denitrification or increase N2O emissions through supplying labile C for denitrifying microbes. However, few experiments have so far assessed the relative effect of AMF removal of N and AMF supply of labile C. We conducted a microcosm experiment to assess the effect of AMF on N2O emissions in two soils with different sources and quantity of N inputs. We employed a nylon mesh (20 um) to allow AMF hyphae but not fine roots to penetrate through so that AMF effects can be quantified.

Results/Conclusions

AMF significantly reduced N2O emissions by 25% and 44% in an organic soil with low and high organic N inputs, respectively. In contrast, AMF had only marginal or no effect on N2O emissions in the conventional soil with synthetic N (urea) inputs. Also, AMF did not stimulate N2O emissions in spite of high NO3- in soil, indicating that the effect of AMF through C supply to denitrifying microbes was negligible. Together, our results suggest that AMF removal of mineral N (likely NH4+) dominates their effects on N2O emissions.