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\hypersetup{pdftitle={Arbuscular Mycorrhizal Fungi Increase the Abundance of Ammonia"=Oxidising Bacteria, but Suppress N$_{2}$O Emissions after Fertilisation},pdfauthor={Nikola Teutscherová, Eduardo Vazquez, Jacobo Arango, Ashly Arevalo, Marta Benito, Mirjam Pulleman},pdfsubject={Tropentag 2018: Abstract},pdfkeywords={Arbuscular mycorrhizal fungi, brachiaria, N2O emissions, nitrification, urea },pdfpagemode=None,colorlinks=true}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, September 17-19, 2018, Ghent}}\\[1ex] \Large{``Global food security and food safety:\\The role of universities''\\[2ex]}}
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\Large{\textbf{Arbuscular Mycorrhizal Fungi Increase the Abundance of Ammonia"=Oxidising Bacteria, but Suppress N$_{2}$O Emissions after Fertilisation\footnote{\textbf{Contact Address:} Nikola Teutscherová, Technical University of Madrid, School of Agricultural, Food and Biosystems Engineering, Dept. of Agricultural Production, Av. Puerta de Hierro, 2, 28040~Madrid, Spain, \mbox{e-mail}: \email{n.teutscherova@gmail.com}}\\[0.8ex]}}
\normalsize{\textsc{Nikola Teutscherová$^{1}$, Eduardo Vazquez$^{1}$, Jacobo Arango$^{2}$, Ashly Arevalo$^{2}$, Marta Benito$^{1}$, Mirjam Pulleman$^{3}$}}
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\begin{itemize*}
\item[]{\small{\textit{$^{1}$Technical University of Madrid, Dept. of Agricultural Production, Spain}}}
\item[]{\small{\textit{$^{2}$International Center for Tropical Agriculture (CIAT), Colombia}}}
\item[]{\small{\textit{$^{3}$Wageningen University and Research, The Netherlands}}}
\end{itemize*}
\index[author]{Teutscherová, Nikola}
\index[author]{Vazquez, Eduardo}
\index[author]{Arango, Jacobo}
\index[author]{Arevalo, Ashly}
\index[author]{Benito, Marta}
\index[author]{Pulleman, Mirjam}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\small{
The potential of the symbiosis between plants and arbuscular mycorrhizal fungi (AMF) to reduce greenhouse gas emissions from soil is gaining scientific attention in the last years. Given the relatively high nitrogen (N) requirements of the AMF and their generally positive effect on host plant growth, AMF may reduce the availability of mineral N that would otherwise be subject to nitrification, which is associated with N$_{2}$O emissions. We investigated the impact of AMF on the growth of tropical grass \textit{Brachiaria decumbens} Stapf. and N$_{2}$O released after urea application. To detect the role of nitrification in N$_{2}$O emissions we used the nitrification inhibitor dicyandiamide (DCD). A mesocosm study (106 days) with two AMF treatments (with and without AMF) and three fertilisation treatments (control, urea and urea+DCD) was set up and plant growth, soil   properties and N$_{2}$O emissions were measured for two weeks after fertiliser application. Without DCD, the production of N$_{2}$O was significantly increased by urea, suggesting that inhibition of nitrification can mitigate N$_{2}$O emissions. The cumulative emissions of N$_{2}$O after urea application were reduced by \mbox{46\,\%} in the presence of AMF when compared to non-AMF pots. Nevertheless, the abundance of ammonia"=oxidising bacteria (AOB) was increased by urea and AMF, while plant growth was reduced by the AMF presence. The increased root:shoot ratio of the biomass in AMF- pots suggests competition for N between AMF and plants. In this study, we demonstrated that immobilisation of N by AMF may significantly reduce N$_{2}$O emissions, at least in the short"=term, even when plant growth is reduced. Furthermore, the inverse relationship found between (higher) AOB abundance and (lower) nitrification rates suggests that changes in the activity of AOB, rather than abundance, may be indicative of the impact of the mycorrhizal symbiosis on N cycling in tropical grasslands. Alternatively, the difference between N$_{2}$O emissions from AMF and non-AMF pots may (partly) be explained by increased reduction of N$_{2}$O in the presence of AMF. Longer"=term studies are needed to verify whether the observed effects of AMF on N$_{2}$O emissions and/or plant growth persist or are limited to initial immobilisation of N by AMF in N-limited systems.}

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\end{abstract}
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\noindent \textbf{Keywords:} Arbuscular mycorrhizal fungi, \textit{Brachiaria}, N$_{2}$O emissions, nitrification, urea
\index[key]{Arbuscular mycorrhizal fungi}
\index[key]{Brachiaria@\textit{Brachiaria}}
\index[key]{N$_{2}$O emissions}
\index[key]{Nitrification}
\index[key]{Urea}
\end{document}
