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\hypersetup{pdftitle={Green Manure Cover Crops for Reduced Input Dependency in Maize Systems under Conservation Agriculture},pdfauthor={Blessing Mhlanga, Stephanie Cheesman, Christian Thierfelder},pdfsubject={Tropentag 2016: Abstract},pdfkeywords={Herbicide, mineral fertiliser, nitrogen, rotations, weed species diversity},pdfpagemode=None,colorlinks=true}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, September 18-21, 2016, Vienna, Austria}}\\[1ex] \Large{``Solidarity in a competing world ---\\fair use of resources''\\[2ex]}}
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\Large{\textbf{Green Manure Cover Crops for Reduced Input Dependency in Maize Systems under Conservation Agriculture\footnote{\textbf{Contact Address:} Blessing Mhlanga, University of Zimbabwe, Dept. of Crop Science, P.O. Box MP 163, Mount Pleasant, Harare, Zimbabwe, \mbox{e-mail}: \email{blessing.mhlangah@gmail.com}}\\[0.8ex]}}
\normalsize{\textsc{Blessing Mhlanga$^{1}$, Stephanie Cheesman$^{2}$, Christian Thierfelder$^{3}$}}
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\begin{itemize*}
\item[]{\small{\textit{$^{1}$University of Zimbabwe, Dept. of Crop Science, Zimbabwe}}}
\item[]{\small{\textit{$^{2}$ETH Zurich, Inst. for Agricultural Sciences, Plant Nutrition, Switzerland}}}
\item[]{\small{\textit{$^{3}$CIAT-TSBF and CIMMYT, Conservation Agriculture, Zimbabwe}}}
\end{itemize*}
\index[author]{Mhlanga, Blessing}
\index[author]{Cheesman, Stephanie}
\index[author]{Thierfelder, Christian}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
An increasing number of smallholder farmers in sub-Saharan Africa are confronted with poor soil fertility and land degradation on their farms, negatively affecting crop productivity. Conservation agriculture (CA); based on three principles: (i) minimum soil disturbance, (ii) crop residue retention, and (iii) plant diversification; has been reported to improve crop productivity while curbing land degradation. Shifts in weed species composition and nitrogen (N) immobilisation have been reported with the adoption of CA. Further, there is competition for the use of maize residues between ground cover and livestock feed. Under CA, weed and N management can be improved by the use of herbicides and mineral fertilisers respectively. However, these are expensive and in some cases inaccessible to smallholder farmers who are often resource constrained. This calls for the need to identify cheaper and more accessible alternatives. The use of green manure cover crops (GMCC) either as rotational or intercrops with maize and the retention of their residues has been shown to have suppressive effects on weeds and if leguminous, can aid to N supplementation. We evaluated the effect of rotating maize with nine different GMCC on weed species composition, supplementary biomass production, ground cover, N supplementation and maize productivity. The effects of the GMCC on the succeeding maize were compared with maize monocropping that received N top dressing. Experiments were set over seven years at four sites with contrasting soil types and depths in Zimbabwe. Substantial decreases in weed density of 218 to 76 weeds m$^{-2}$ occurred in the maize"=cowpea rotation. Common rattle pod gave biomass yields as high as 12 t ha$^{-1}$ (dry mass) resulting in contact ground cover as high as \mbox{96\,\%}. Maize yields after leguminous GMCC were comparable to the monocrop, with maize after jack bean attaining \mbox{61\,\%} more yield suggesting that GMCC could be an alternative for mineral top dressing N. In conclusion, rotating maize with cover crops can reduce the need for expensive inputs like herbicides and fertilisers if land is sufficient. However, no cover crop could offer all benefits, hence this calls for identification of niches and a suitable cover crop for that niche.}

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\noindent \textbf{Keywords:} Herbicide, mineral fertiliser, nitrogen, rotations, weed species diversity
\index[key]{Herbicide}
\index[key]{Mineral fertilizer}
\index[key]{Nitrogen}
\index[key]{Rotations}
\index[key]{Weed species diversity}
\end{document}
