126-4 Overwinter Changes in Denitrification and N2 O-Producing Microorganisms in an Agricultural Soil with Different N Sources.

See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: The Role of Soil Management in Influencing Nitrous Oxide Emissions and Microbial Processes
Monday, October 22, 2012: 1:50 PM
Duke Energy Convention Center, Room 204, Level 2
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Enrico Tatti1, Sophie Wertz1, Claudia Goyer1, Bernie Zebarth1, David Burton2, Martin Chantigny3 and Martin Filion4, (1)Potato Research Centre, Agriculture Agri-Food Canada, Fredericton, NB, Canada
(2)Environmental Sciences, Nova Scotia Agricultural College, Truro, NS, Canada
(3)Agriculture and Agri-Food Canada, Quebec, QC, Canada
(4)Université de Moncton, Moncton, NB, Canada
Soil nitrogen (N) processes and changes in related microbial communities have been extensively studied during the growing season. However, there is a scarcity of information on N cycle processes and microbial communities in agricultural soils during winter. It is possible that different N sources such as inorganic fertilizer or manure could influence soil denitrifier and nitrifier abundance and structure thus changing N cycle processes during winter. We evaluated changes in nitrifiers and denitrifiers abundance and composition and in denitrification and N2O emissions during the winter period in soils with spring application of NO3NH4, cattle manure or poultry manure. Soil samples were collected from a sandy loam (Saint-Augustin-de-Desmaures, Qc, Canada) during two consecutive winters (2009-2010 and 2010-2011) in November (end of cropping season), December (freeze-thaw cycles), January (moderate snow cover, frozen soil), March (deep snow cover, progressive soil warming) and April (early spring after thaw period).  Seasonal variations, but not different N fertilizer sources, had the largest impact on the greenhouse gas N2O emission, and denitrification rates that were higher during January and March for two consecutive winters. Nitrifier and denitrifier abundances responded to seasonal changes and N fertilizer sources only in the winter of 2010-2011. Abundance of nitrifiers (nxrA, archaeal amoA) and denitrifiers (nirK, nirS and nosZ) increased in March and April compared with other sampling dates. Nitrifier abundance (nxrA) was greater in soil with cattle manure application, while denitrifiers (nirK and nosZ) were more abundant in poultry manure treated soil compared with other N fertilizer treatments. Bacterial and archaeal amoA, nxrA, nirK, nirS and nosZ showed different composition between sampling times and different N treatments in the two monitored winters, suggesting that changes in environmental conditions overtime and N fertilizer sources both influenced these communities. Our findings demonstrate that N2O emission and denitrification rates and denitrifier and nitrifier abundance and composition are controlled by different factors in agricultural field during winter. The decoupling between N2O emissions and denitrification and the community composition of N2O-producing microorganisms suggests a functional redundancy of nitrifiers and denitrifiers during the winter months.
See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: The Role of Soil Management in Influencing Nitrous Oxide Emissions and Microbial Processes