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\hypersetup{pdftitle={Effects of Cultivated \textit{Brachiaria} Grasses on Soil Aggregation and Stability of a Chromic Luvisol in the Semi"=Arid Tropics of Kenya},pdfauthor={Elias Gichangi, Donald Njarui, Sita Ghimire, James Gatheru, kezia Magiroi},pdfsubject={Tropentag 2016: Abstract},pdfkeywords={Macro-aggregates, micro-aggregates, microbial biomass, particulate organic matter, soil organic carbon },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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\begin{center}
\Large{\textbf{Effects of Cultivated \textit{Brachiaria} Grasses on Soil Aggregation and Stability of a Chromic Luvisol in the Semi"=Arid Tropics of Kenya\footnote{\textbf{Contact Address:} Elias Gichangi, Kenya Agricultural and Livestock Research organization (KALRO), Natural Resources, P.O. Box 340-90100, 90100~Machakos, Kenya, \mbox{e-mail}: \email{gichangim@yahoo.com}}\\[0.8ex]}}
\normalsize{\textsc{Elias Gichangi$^{1}$, Donald Njarui$^{2}$, Sita Ghimire$^{3}$, James Gatheru$^{4}$, kezia Magiroi$^{5}$}}
\end{center}
\begin{itemize*}
\item[]{\small{\textit{$^{1}$Kenya Agricultural and Livestock Research organization (KALRO), Natural Resources, Kenya}}}
\item[]{\small{\textit{$^{2}$Kenya Agricultural and Livestock Research Organization, Katumani, Kenya, Animal Production, }}}
\item[]{\small{\textit{$^{3}$Biosciences Eastern and Central Africa - International Livestock Research Institute (BecA-ILRI) Hub, Nairobi, Genomics, }}}
\item[]{\small{\textit{$^{4}$Kenya Agricultural Research Institute (KARI), Socio-Economics, Kenya}}}
\item[]{\small{\textit{$^{5}$Kenya Agricultural and Livestock Research Organization, Kitale, Kenya , Soil Science, Kenya}}}
\end{itemize*}
\index[author]{Gichangi, Elias}
\index[author]{Njarui, Donald}
\index[author]{Ghimire, Sita}
\index[author]{Gatheru, James}
\index[author]{Magiroi, kezia}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
Soil aggregation is among the key short term indicators of soil quality attributed to changes in land management. A study was conducted to investigate the changes in the size distribution and stability of soil aggregates in a structurally unstable sandy loam soil following cultivation of \textit{Brachiaria} grass in semi"=arid region of Kenya. The \textit{Brachiaria} grass cultivars included \textit{Brachiaria decumbens} cv. Basilisk, \textit{B.~brizantha} cvs Marandu, MG4, Piatã and Xaraes, \textit{B.~humidicola} cv. Llanero and \textit{B}. hybrid cv. Mulato II which were compared with two locally cultivated forage grasses (\textit{Chloris gayana} cv. KAT R$^{3}$ and \textit{Pennisetum purpureum} cv. Kakamega 1) and a bare plot (negative check). The grass treatments were evaluated with fertilisers application (\mbox{40\,kg} P applied at sowing and \mbox{50\,kg} N ha$^{-1}$ in each wet season) and with no fertiliser applications. Aggregate size fractions ($>$2000, 250--2000, 53--250 and 53 $\mu$m) were isolated using the wet sieving method. Aggregation based on the proportion of small macro"=aggregates (250--2000 $\mu$m) increased in soils cultivated with all grass types compared to the bare plots control and was greatest in soils under \textit{B}. hybrid cv. Mulato II. Aggregate stability in terms of mean weight diameter (MWD) differed among the grasses and was highest in soils under cv. Mulato II and cv. Marandu with mean weight diameters of 4.49 and 4.31 mm, respectively. Changes in small macro"=aggregates fraction was positively correlated with particulate organic matter (POM) (r=0.9104, $p = 0.001$), microbial biomass carbon (MBC) (r=0.5474, $p = 0.01$), soil organic carbon (SOC) (r=0.3654, $p = 0.05$) and root biomass (r=0.4977, $p = 0.01$). This indicated that the binding agents were important in the aggregation of soils cultivated with \textit{Brachiaria} grasses. 







}

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\end{abstract}
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\noindent \textbf{Keywords:} Macro"=aggregates, micro"=aggregates, microbial biomass, particulate organic matter, soil organic carbon 
\index[key]{Macro"=aggregates}
\index[key]{Micro"=aggregates}
\index[key]{Microbial biomass}
\index[key]{Particulate organic matter}
\index[key]{Soil!organic carbon }
\end{document}
