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Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/25/2018 Publication Date: 12/24/2018 Citation: Maul, J.E., Cavigelli, M.A., Emche, S.E., Vinyard, B.T., Buyer, J.S. 2019. Cropping system history and crop rotation phase drive the abundance of soil denitrification genes nirK, nirS and nosZ in conventional and organic grain agroecosystems. Agriculture, Ecosystems and Environment. 273:95-106. https://doi.org/10.1016/j.agee.2018.11.022. DOI: https://doi.org/10.1016/j.agee.2018.11.022 Interpretive Summary: Globally, nitrous oxide (N2O) is a greenhouse gas that is 300X more potent than carbon dioxide (CO2) in terms of global warming potential (GWP). This greenhouse gas is produced mainly by soil, gut and aquatic microorganisms. Soils are a significant source of N2O but the mechanisms that underlie the regulation of greenhouse gas production by soil are only partially understood. In this study we focus on measuring abundance and diversity of the soil microbial genes that are responsible for denitrification and N2O production. By analyzing the change in gene abundance and community composition (diversity) of these genes within the soil microbial community we may better understand some of the key drivers of agricultural greenhouse gas emissions. This research tries to make in-roads into solving issues related to fertility management in farming systems that lead to greenhouse gas emission and what role the soil microbial community has in fertility management. This research will help modelers improve environmental greenhouse gas emission models and help policy makers make more accuarate assessments of the impact of agroecosystems. Technical Abstract: Dissimilatory denitrification is an important pathway of the global nitrogen cycle that conserves energy within ecosystems and returns biologically “fixed” inorganic nitrogen (NO3, NH4) back to the atmosphere as dinitrogen (N2) or intermediate products of the pathway.* Primarily this pathway is linked to bioenergetic electron transport phosphorylation with NO3, NO and N20 and O2 acting as successive terminal electron acceptors in anaerobic conditions in lieu of O2. This is primarily a microbially driven process and is carried out by nitrate reductase (nar), nitrite reductase (nirK and nirS), nitrogen oxide reductase (nor) and nitrous oxide reductase (nosZ) (Zumft, 1997). Here we report results from a study in which we have shown that the abundance of the nirK and nosZ metagenome changes in these agroecosystems over the course of a season and farming system type (organic, conventional till or no-till) influences the phylogenetic structure of the microbial community. Based on multivariate analysis community clone library sequence similarity of nirK and nosZ we were able to determine that the similarity among the microbes that harbor the nirK gene are affected primarily by time of season and secondarily by whether the system is conventional or organic. Whereas analysis of the nosZ metagenomic clone library shows that microbial community compositional similarity is primarily driven by the type of farming system and secondarily by whether the system is conventional or organic. |
