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\hypersetup{pdftitle={Analyzing Wheat Yield Constraints in Gorgan with Comparative Performance Analysis (CPA) Method},pdfauthor={Benyamin Torabi, Afshin Soltani, Serolla Galeshi},pdfsubject={Tropentag 2010: Abstract},pdfkeywords={CPA, wheat, yield gap},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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\Large{\textbf{Analyzing Wheat Yield Constraints in Gorgan with Comparative Performance Analysis (CPA) Method\footnote{\textbf{Contact Address:} Benyamin Torabi, Gorgan University of Agricultural Sciences and Natural Resources, Agronomy, Basij Square, 49138-15739~Gorgan, Iran, \mbox{e-mail}: \email{ben_torabi@yahoo.com}}\\[0.8ex]}}
\normalsize{\textsc{Benyamin Torabi, Afshin Soltani, Serolla Galeshi}}
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\begin{itemize*}
\item[]{\small{\textit{Gorgan University of Agricultural Sciences and Natural Resources, Agronomy, Iran}}}
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\index[author]{Torabi, Benyamin}
\index[author]{Soltani, Afshin}
\index[author]{Galeshi, Serolla}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
One of the main problems for crops production in our country is different between actual yield and attainable yield of farmers called yield gap. Thus, identifying yield constraint and yield gap are significant. In order to, this study was conducted in Gorgan. This study was conducted as survey in 5 villages and two years 86/87 and 87/88. In this survey, all of the information about management operations, soil and crop characteristics was recorded and measured (including 200 variables). Then, relationship between variables and yield was considered with CPA method (based on stepwise regrresion). The results showed \unitfrac[2348]{kg}{ha} difference (gap) exsited between actual yield (farmers yield) and attainable yield (the yield that farmers can be had). It was identified rate of potassium before planting, rate of nitrogen fertiliser after planting, leaf area index at anthesis stage, leaf chlorophyll index at anthesis stage, nitrogen uptake by total plant at maturity and length of vegetative growth period were effective in gap creation about \mbox{20\,\%}, \mbox{18\,\%}, \mbox{19\,\%}, \mbox{10\,\%}, \mbox{14\,\%} and \mbox{19\,\%}, respectively. Scrutinies showed leaf area index at anthesis stage, leaf chlorophyll index at anthesis stage and rate of nitrogen uptake by total plant at maturity are under control of nitrogen fertiliser management, also length of vegetative growth period is controlled by planting date. Thus, it was concluded rate of applied potassium, nitrogen nutrition and planting date are responsible of \mbox{20\,\%}, \mbox{61\,\%} and \mbox{19\,\%} of yield gap, respectively; and through optimising of them, yield wheat in Gorgan can be increased about \unitfrac[2348]{kg}{ha}.}

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\noindent \textbf{Keywords:} CPA, wheat, yield gap
\index[key]{CPA}
\index[key]{Wheat}
\index[key]{Yield gap}
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