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\hypersetup{pdftitle={Improving Nitrogen Use Efficiencies in Rice"=Wheat Rotations in Southeastern China},pdfauthor={Maximilian Hofmeier, Yong Han, Ting Lan, Zucong Cai, Marco Roelcke, Rolf Nieder},pdfsubject={Tropentag 2011: Abstract},pdfkeywords={Nitrogen balances, nitrogen fertilisation, nitrogen use efficiency, rice-wheat rotation},pdfpagemode=None,colorlinks=true}
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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{Improving Nitrogen Use Efficiencies in Rice"=Wheat Rotations in Southeastern China\footnote{\textbf{Contact Address:} Maximilian Hofmeier, TU Braunschweig, Institute of Geoecology, Langer Kamp 19c, 38106~Braunschweig, Germany, \mbox{e-mail}: \email{m.hofmeier@tu-bs.de}}\\[0.8ex]}}
\normalsize{\textsc{Maximilian Hofmeier$^{1}$, Yong Han$^{2}$, Ting Lan$^{2}$, Zucong Cai$^{2}$, Marco Roelcke$^{1}$, Rolf Nieder$^{1}$}}
\end{center}
\begin{itemize*}
\item[]{\small{\textit{$^{1}$TU Braunschweig, Institute of Geoecology, Germany}}}
\item[]{\small{\textit{$^{2}$Chinese Academy of Sciences, Nanjing Institute of Soil Science, China}}}
\end{itemize*}
\index[author]{Hofmeier, Maximilian}
\index[author]{Han, Yong}
\index[author]{Lan, Ting}
\index[author]{Cai, Zucong}
\index[author]{Roelcke, Marco}
\index[author]{Nieder, Rolf}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
Excessive use of mineral nitrogen (N) fertiliser is a common practice in rice"=wheat rotations in southeastern China. At the same time the N use efficiencies (NUEs) in this rice"=based cropping system are very low. The consequences are high N losses from arable land to water bodies (surface and ground water) and to the atmosphere. To investigate the scope and scale of reductions in mineral N fertiliser inputs, demonstration field experiments on farmers' field sites were conducted for three consecutive summer rice"=winter wheat double crop rotations in the two counties Yixing and Huai'an in Jiangsu Province from 2008 to 2011. The experimental design was according to the so"=called ``3+x'' approach with three different N fertilisation treatments (``conventional'' (farmers' practice), ``reduced'' (by 25--\mbox{30\,\%}) and zero-N application) and two agronomical (``x'') treatments within each N treatment. Effects on crop growth, crop N nutrition status, mineral N contents in the soil and soil solution as well as grain yields were determined and nitrogen balance sheets were calculated. In spite of the lower N fertilisation rate, no significant differences in crop growth, crop N nutrition status and grain yields were observed in the ``reduced'' N fertilisation treatments compared to the ``conventional'' N treatment in any year and crop over the three"=year period. In contrast, a significant increase in NUEs could be achieved and the calculated N balances showed a clear decrease in nitrogen balance surpluses in the ``reduced'' N fertilisation treatments compared to farmers' practice. To summarise, we could demonstrate that the risk of N losses from arable land can be efficiently decreased by reducing the overall nitrogen fertilisation rate by approx. 25--\mbox{30\,\%} compared to local practice without any decline in grain yields of rice and wheat, and with a distinct increase in NUEs.



}

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\end{abstract}
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\noindent \textbf{Keywords:} Nitrogen balances, nitrogen fertilisation, nitrogen use efficiency, rice"=wheat rotation
\index[key]{Nitrogen!balances}
\index[key]{Nitrogen!fertilization}
\index[key]{Nitrogen!use efficiency}
\index[key]{Rice"=wheat rotation}
\end{document}