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\hypersetup{pdftitle={Horizontal Nutrient Flows and Balances in Irrigated Urban Gardens of Khartoum, Sudan},pdfauthor={Sahar Babiker Abdalla, Jens Gebauer, Martina Predotova, Andreas Buerkert},pdfsubject={Tropentag 2011: Abstract},pdfkeywords={Gerif soils, nutrient fluxes, sediment deposits, soil nutrient status},pdfpagemode=None,colorlinks=true}
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\begin{document}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, October 5-7, 2011, Bonn}}\\[1ex] \Large{``Development on the margin''\\[2ex]}}
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\begin{center}
\Large{\textbf{Horizontal Nutrient Flows and Balances in Irrigated Urban Gardens of Khartoum, Sudan\footnote{\textbf{Contact Address:} Andreas Buerkert, University of Kassel, Organic Plant Production and Agroecosystems Research in the Tropics and Subtropics, Steinstraße 19, 37213~Witzenhausen, Germany, \mbox{e-mail}: \email{tropcrops@uni-kassel.de}}\\[0.8ex]}}
\normalsize{\textsc{Sahar Babiker Abdalla, Jens Gebauer, Martina Predotova, Andreas Buerkert}}
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\begin{itemize*}
\item[]{\small{\textit{University of Kassel, Organic Plant Production and Agroecosystems Research in the Tropics and Subtropics, Germany}}}
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\index[author]{Abdalla, Sahar Babiker}
\index[author]{Gebauer, Jens}
\index[author]{Predotova, Martina}
\index[author]{Buerkert, Andreas}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
The role of urban and peri"=urban agriculture (UPA) for the supply of fresh vegetables, fruits and meat for local markets is well"=known. The periodically flooded Gerif soils on the River Nile banks in the core of Khartoum city harbour vegetable gardens that supply perishable leafy vegetables with a short life cycle. In an effort to assess their sustainability and possible negative environmental externalities we used a horizontal balance approach (total outputs minus inputs for N, P, K and C) to determine the nutrient use efficiency of four intensively cropped UPA gardens. Two of the gardens were located in downstream lowlands (L1 \& L2) and the other two belonged to the upstream highlands (H1 \& H2). Deposits of river sediments were estimated to contribute 752, 994, 389 and \mbox{189\,kg} N ha$^{-1}$, 5, 8, 2 and \mbox{1.1\,kg} P ha$^{-1}$, 7, 6.5, 4 and \mbox{1\,kg} K ha$^{-1}$ and 6\,943, 9\,691, 2\,760 and 1\,116\,kg C ha$^{-1}$ for gardens L1, L2, H1 and H2, respectively. Taking into account management related fluxes, yielded positive horizontal balances for N and C and negative balances of P and K. These were estimated at 1\,553, 1\,508, 969 and \mbox{745\,kg} N ha$^{-1}$ yr$^{-1}$, 19\,410, 17\,772, 9\,949 and 3\,201\,kg C ha$^{-1}$ yr$^{-1}$, -4, -29, -36 and \mbox{-0.9\,kg} P ha$^{-1}$ yr$^{-1}$ and -8,055, -6,181, -4,886 and \mbox{-450\,kg} K ha$^{-1}$ yr$^{-1}$ for garden L1, L2, H1 and H2, respectively. While the River Nile floods contribute significantly to soil fertility maintenance, the negative P and K balances call for a better integration of UPA gardening with livestock husbandry and the regular addition of animal manure in these cropping systems.  }

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\noindent \textbf{Keywords:} Gerif soils, nutrient fluxes, sediment deposits, soil nutrient status
\index[key]{Gerif soils}
\index[key]{Nutrient!fluxes}
\index[key]{Sediment deposits}
\index[key]{Soil!nutrient status}
\end{document}