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\hypersetup{pdftitle={Monitoring Soil Organic Carbon and its Relation with Other Soil Properties in Mt Kenya Region},pdfauthor={Evans Mutuma, Erika Michéli, Vince Lang', Ádám Csorba , Judit Nagy},pdfsubject={Tropentag 2016: Abstract},pdfkeywords={Cation exchange capacity, environmental predictors, exchangeable bases, extractable phosphorus, soil organic carbon, total nitrogen},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{Monitoring Soil Organic Carbon and its Relation with Other Soil Properties in Mt Kenya Region\footnote{\textbf{Contact Address:} Evans Mutuma, Kenya Agricultural and Livestock Research Organization, Natural Resource Management, 14733, 00800~Nairobi, Kenya, \mbox{e-mail}: \email{mutumaeva@yahoo.com}}\\[0.8ex]}}
\normalsize{\textsc{Evans Mutuma$^{1}$, Erika Michéli$^{2}$, Vince Lang'$^{2}$, Ádám Csorba $^{2}$, Judit Nagy$^{2}$}}
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\begin{itemize*}
\item[]{\small{\textit{$^{1}$Kenya Agricultural and Livestock Research Organization, Natural Resource Management, Kenya}}}
\item[]{\small{\textit{$^{2}$Szent Istvan University, Soil Science and Agricultural Chemistry, Hungary}}}
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\index[author]{Mutuma, Evans}
\index[author]{Michéli, Erika}
\index[author]{Lang', Vince}
\index[author]{Csorba , Ádám}
\index[author]{Nagy, Judit}
\begin{center}
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\textbf{Abstract}
\begin{abstract}
\normalsize{




Strongly weathered tropical soils rely largely on the organic fraction for there inherent soil fertility. However, detailed information about this dynamic soil functional property and its relation with other soil properties is limited in the study area. This is partly because soil sampling and analysis involves extensive fieldwork and laboratory techniques that are cost inefficient and time consuming. Conditioned Latin Hypercube sampling (cLHS) was used to reduce sample size, sampling bias and to preserve natural distribution of environmental predictors. Digital Elevation Model (Aster DEM; resolution \mbox{30\,m}) was used to extract terrain attributes; Landsat 8 satellite images for Natural Difference Vegetation Index (NDVI) and soil terrain database for Kenya (KENSOTER 1:1M). The result was a sampling design that represented a true feature space.  Reflectance spectra of the Mid-Infrared (4000--400 cm\textsuperscript{-1}) were recorded for 269 samples in seven soil reference groups.  Principal Component Analysis (PCA) cautioned multicolinearity, allowing for the selection of calibration set (n=30) using Kennard stone algorithm in KNIME analytics platform. Thermal Scientific Flash 2000 analyzer was used for SOC and total nitrogen analysis. Mehlich-3 extraction method was used for analysis of available Phosphorus (Ext P) and exchangeable bases (Exc). The Cation Exchange Capacity (CEC) by ammonium acetate method. These measurements were calibrated to first derivative spectra of 269 soil samples using random forest regression. Good predictions were achieved for SOC (R$^{2}$ = 0.76) with root mean square error of prediction (RMSE=1.64). The excellent prediction of N (R$^{2}$=0.81 and RMSE= 0.09) might be due to its high correlation with SOC (r=0.93). Mass of SOC in the soil was 14.2 times higher that of N explaining the low absorbance values for N as compared to C. Correlations between SOC, the Exc bases and pH are as follows(Ext $p = 0.275$, Exc Al=0.65, Exc Ca =0.449 Exc Na= -0.814, Exc K= -0.174 and Exc Mg=-0.458) all significant at P$\leq$0.05. The range of \% SOC was \mbox{0.5\,\%} and \mbox{5\,\%} in the agricultural fields with \mbox{77.32\,\%} below the threshold of \mbox{2.4\,\%}. Our results indicate serious soil degradation and the urgent need for organic carbon replenishment projects to enhance agricultural productivity.}

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\end{abstract}
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\noindent \textbf{Keywords:} Cation exchange capacity, environmental predictors, exchangeable bases, extractable phosphorus, soil organic carbon, total nitrogen
\index[key]{Cation Exchange Capacity}
\index[key]{Conditioned Latin hypercube sampling}
\index[key]{Environmental!predictors}
\index[key]{Exchangeable Bases}
\index[key]{Extractable Phosphorus}
\index[key]{Mid-Infrared spectroscopy}
\index[key]{Soil!Organic Carbon}
\index[key]{Total Nitrogen}
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