See more from this Session: Symposium--Mitigation of Greenhouse Gas Emissions In Managed Systems
Monday, October 17, 2011: 2:00 PM
Henry Gonzalez Convention Center, Room 207A, Concourse Level
Soil microbes dominate processes that regulate soil trace gas emissions and soil C and N dynamics. Intensive management in agroecosystems provides unique opportunities to assess the effectiveness of microbial manipulations to enhance soil C retention and reduce trace gas emissions. While reduced tillage can be conducive to the development of the soil microbial community with fungal dominance and facilitation of soil C retention, direct inhibition of nitrifying bacteria has been shown to effectively reduce N2O emission and enhance soil N retention. However, it is unclear whether and how inhibition of nitrification affects soil C dynamics. Inhibition of nitrification would increase soil NH4 and alter plant C allocation to roots and mycorrhizal fungi, potentially affecting organic C inputs to soil and microbial activities. Using wheat as a model plant, we conducted both field and microcosm experiments examining the impact of a nitrification inhibitor (dicyandiamide, DCD) on soil microbes and organic residue decomposition under both ambient and elevated CO2. Our preliminary results from the microcosm experiment showed that elevated CO2, but not the nitrification inhibitor, significantly increased mycorrhizal colonization of roots. Inhibition of nitrification appeared to increase soil N retention, but did not affect plant N uptake. The impact of the nitrification inhibitor on residue decomposition and organic C dynamics in soil is being examined.