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\hypersetup{pdftitle={Crop Rotation Effects on Different Weed Species Appearance},pdfauthor={Leila Alimoradi, Mohammad Hasan Rashed Mohassel, Hamid Reza Khazaee, Amir Ahmadian Yazdi},pdfsubject={Tropentag 2010: Abstract},pdfkeywords={Crop rotation , pCA, Weed population},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{Crop Rotation Effects on Different Weed Species Appearance\footnote{\textbf{Contact Address:} Leila Alimoradi, Islamic Azad University - Mashhad Branch, Department of Agronomy, Azadi Square, 91775-1163~Mashhad, Iran, \mbox{e-mail}: \email{lealimoradi@yahoo.com}}\\[0.8ex]}}
\normalsize{\textsc{Leila Alimoradi$^{1}$, Mohammad Hasan Rashed Mohassel$^{2}$, Hamid Reza Khazaee$^{3}$, Amir Ahmadian Yazdi$^{4}$}}
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\begin{itemize*}
\item[]{\small{\textit{$^{1}$Islamic Azad University - Mashhad Branch, Department of Agronomy, Iran}}}
\item[]{\small{\textit{$^{2}$Ferdowsi University of Mashhad, College of Agriculture, Department of Agronomy, Iran}}}
\item[]{\small{\textit{$^{3}$Ferdowsi University of Mashhad, College of Agriculture, Department of Agronomy, Iran}}}
\item[]{\small{\textit{$^{4}$Agriculture and Natural Resources Research Center, Plant Protection, Iran}}}
\end{itemize*}
\index[author]{Alimoradi, Leila}
\index[author]{Rashed Mohassel, Mohammad Hasan}
\index[author]{Khazaee, Hamid Reza}
\index[author]{Ahmadian Yazdi, Amir}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
Crop rotation is a planned sequence of crops growing in the same field year after year. Rotating crops adds diversity to the cropping system, increasing the sustainability of the system. Crop rotation is the key to both soil improvement and effective weed control. The rotation can include specific crops to control problem weeds in particular fields. Crops suffer the most from weeds that share similar growth patterns. Planting a wide variety of crops with varied characteristics reduces the likelihood that specific weed species will become adapted to the system and become problematic. When diverse crops are used in a rotation, weed germination and growth cycles are disrupted by variations in cultural practices associated with each crop such as tillage, planting dates, crop competition, etc. In order to evaluate the weed species response to different crop type and crop rotations, an experiment was conducted to investigate the weed population during 2 years growing seasons. In this experiment, crops were: corn, sugar beet, cumin, cicer, onion, hey, barley and fallow. The fields that were sown sugar beet, cumin, cicer, onion in the first year, were planted barely in the second year and other fields were planted the same crops. Species such as nightshade (Solanum nigrum L.), garden purslan (Portulaca oleracea L.), red root pigweed (Amaranthus retroflexux L.) had more correlation with corn. Dandelion (Taraxacum officinale L.) and dodder (Cuscuta campestris L.) were seen more in hey fields. The effects of crop rotation on weed species appearance and density showed that creeping oxalis (Oxalis corniculata L.), shepherd's purs (Capsella bursa"=pastoris L.) and Persian speed weel (Veronica persica poir.) had correlation with onion"=barley rotation. Indian mallow (Abutilon teophrasti Medic) and creeping oxalis were seen more in sugar beet"=barley rotation.  PCA weed population analysis was shown that there was relation between crop rotation and weed community.}

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\end{abstract}
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\noindent \textbf{Keywords:} Crop rotation , pCA, Weed population
\index[key]{Crop!rotation }
\index[key]{PCA}
\index[key]{Weed population}
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