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\hypersetup{pdftitle={Does Combined Appliction of Crop Residues and Inorganic Fertiliser Lower Emisiosn of N$_{2}$O from Soil?},pdfauthor={Kwame Agyei Frimpong, Elizabeth M. Baggs},pdfsubject={Tropentag 2010: Abstract},pdfkeywords={Crop residues, inorganic fertiliser, nitrous oxide, stable isotopes, tropical soil},pdfpagemode=None,colorlinks=true}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, September 14-16, 2010, Zurich}}\\[1ex] \Large{``World Food System  ---\\A Contribution from Europe''\\[2ex]}}
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\begin{center}
\Large{\textbf{Does Combined Appliction of Crop Residues and Inorganic Fertiliser Lower Emisiosn of N$_{2}$O from Soil?\footnote{\textbf{Contact Address:} Kwame Agyei Frimpong, University of Aberdeen, Institute of Biological and Environmental Sciences, Cruickshank Building, AB24 3UU~Aberdeen, United Kingdom, \mbox{e-mail}: \email{k.frimpong@abdn.ac.uk}}\\[0.8ex]}}
\normalsize{\textsc{Kwame Agyei Frimpong, Elizabeth M. Baggs}}
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\begin{itemize*}
\item[]{\small{\textit{University of Aberdeen, Institute of Biological and Environmental Sciences, United Kingdom}}}
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\index[author]{Frimpong, Kwame Agyei}
\index[author]{Baggs, Elizabeth M.}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
Emissions of N$_{2}$O were measured following addition of $^{15}$N-labelled residues of \textit{Vigna unguiculata} (cowpea), \textit{Mucuna pruriens} and \textit{Leucaena leucocephala}) to a Ferric Luvisol from Ghana at a rate of 100 mg N kg$^{-1}$ soil under controlled environment conditions. Residues were also applied in different ratio combinations with inorganic N fertiliser, each combination applied at a total rate of 100 mg N kg$^{-1}$ soil. N$_{2}$O emissions were increased after addition of residues, and further increased with combined applications of residues and inorganic N fertiliser. However, $^{15}$N-N$_{2}$O production was low and short"=lived in all treatments, suggesting that most of the measured N$_{2}$O-N was derived from the applied fertiliser or native soil mineral N pools. There was no consistent trend in magnitude of emissions with increasing proportion of inorganic fertiliser in the application. The positive interactive effect between residue- and fertiliser-N sources was most pronounced in the 25:75 Leucena:fertiliser treatment where 22.5 g N$_{2}$O-N m$^{-2}$ kg biomass$^{-1}$ was emitted over 30 days. N$_{2}$O (loge) emission over the 30 day experiment from all residue amended treatments was positively correlated with residue C:N ratio (r=0.63; $p < 0.05$), and negatively correlated with residue polyphenol content (r=-0.59; $p < 0.05$), polyphenol:N ratio (r=-0.61; $p < 0.05$) and (lignin+polyphenol):N ratio (r=-0.61; $p < 0.05$), indicating the role of residue chemical composition, or quality, in regulating emissions even when combined with inorganic fertiliser. Under our controlled experimental conditions the 75:25 residue: fertiliser ratio appeared to offer the best compromise between release of N and management of N$_{2}$O emission, but the positive interactive effect even in this treatment means that it is unlikely that combined applications of residues and inorganic fertiliser can lower N$_{2}$O emissions, unless the residue is of very low quality promoting strong immobilisation of soil mineral N. 







}

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\noindent \textbf{Keywords:} Crop residues, inorganic fertiliser, nitrous oxide, stable isotopes, tropical soil
\index[key]{Crop!residues}
\index[key]{Inorganic fertilizer}
\index[key]{Nitrous oxide}
\index[key]{Stable isotopes}
\index[key]{Tropical soil}
\end{document}