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\hypersetup{pdftitle={Function and Nutrient Status of Sulphur in Oil Palm in Indonesia},pdfauthor={Jóska Gerendás, Chris Donough, Thomas Oberthür},pdfsubject={Tropentag 2011: Abstract},pdfkeywords={Fertilisation, Indonesia, nutrient status, oil palm, sulphur},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{Function and Nutrient Status of Sulphur in Oil Palm in Indonesia\footnote{\textbf{Contact Address:} Jóska Gerendás, K+S Kali GmbH, Agricultural Advisory, Bertha-von-Suttner-Straße 7, 34131 ~Kassel, Germany, \mbox{e-mail}: \email{joska.gerendas@kali-gmbh.com}}\\[0.8ex]}}
\normalsize{\textsc{Jóska Gerendás$^{1}$, Chris Donough$^{2}$, Thomas Oberthür$^{2}$}}
\end{center}
\begin{itemize*}
\item[]{\small{\textit{$^{1}$K+S Kali GmbH, Agricultural Advisory, Germany}}}
\item[]{\small{\textit{$^{2}$International Plant Nutrition Institute (IPNI), Southeast Asia Program, Malaysia}}}
\end{itemize*}
\index[author]{Gerendás, Jóska}
\index[author]{Donough, Chris}
\index[author]{Oberthür, Thomas}
\begin{center}
\vspace{1.1cm}
\textbf{Abstract}
\begin{abstract}
\normalsize{
Sulphur (S) is indispensable for plant growth as S is a constituent of proteins, co"=factors and in the form of sulphate esters a structural component of membranes. In recent decades the use of more concentrated straight and multi"=nutrient fertilisers has led to a reduced S input from fertilisers in many regions of the world. Other important S inputs for agro"=ecosystems, organic fertilisers and depositions from industrial pollution, are either of limited significance or not available.



In oil palm (OP) S has not been considered in nutrient management to any large extent, and in Indonesia S-free fertiliser regimes, consisting of urea, rock phosphate, KCl and dolomite, are frequently used. In addition, S losses by leaching are naturally high in the humid tropics suitable for OP cultivation. Hence, there is a potential risk of S supply being insufficient, but data that allow assessing the S status were not available. In the course of a BMP (Best Management Practise) project initiated by IPNI SEA in July 2006 comprising of 30 commercial"=size blocks in six locations in Sumatra and Kalimantan (three sites each) the leaf nutrient status was assessed by analyses of frond \#17.



A decline in the S status of the blocks receiving a typical fertiliser management (estate practise) was apparent at all six sites. In 2009 average leaf S levels of only \mbox{0.13\,\%} (range: 0.11 "= 14\,\%}) were observed. It is argued that published critical S value (\mbox{0.20\,\%}) might be inflated. Therefore, the N/S ratio, frequently considered a more reliable indicator of the S status, was also evaluated. On average a ratio of 19/1 (range: 16.8 "= 22.8 to 1) was obtained, strongly suggesting a S deficiency situation. Assuming a critical N/S ratio of 15/1 and a critical and adequate N concentration of 2.3 and 2.5\,\%, respectively, adjusted critical S concentrations of 0.15 and 0.17\,\% may be proposed. The S status of oil palm reported here is even below these adjsuted critical levels. Experiments are currently being initiated to (1)~re"=evaluate the critical S concentration and (2)~assess the yield response to S supply at commercial block scale.



}

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\end{abstract}
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\noindent \textbf{Keywords:} Fertilisation, Indonesia, nutrient status, oil palm, sulphur
\index[key]{Fertilisation}
\index[key]{Indonesia}
\index[key]{Nutrient!status}
\index[key]{Oil palm}
\index[key]{Sulphur}
\end{document}