An assessment of the accuracy of soil map of Kwara state, Nigeria.

Abstract

The variability of particle size fraction, pH, organic matter, total nitrogen, available phosphorus, exchangeable Ca, Mg, Na, exchangeable acidity, effective cation exchange capacity (CEC), base saturation, extractable Fe, Mn and Zn contents within and among the three major soil mapping units delineated in Kwara State, on the Federal Department of Agricultural Land Resources (FDALR) soil map of Nigeria was examined using some statistical measures. Sand content was the least variable (Cv=10.96-15.63%), while available phosphorus was the most Variable (CV=23.91%-181.05%) property. Except for Wilk's criterion (L), all the statistical tools used (coefficient of variation (CV), intra-class correlation coefficient (PI), Relative variance (RV), and the compliment of RV (I-RV) showed that the individual mapping units are heterogeneous. The F-ratio indicated that three mapping units were significantly different for17 out of 18 properties studied. If the usefulness of a soil map is judged by the precision with which it can predict soil conditions at any point of interest within the area covered by the map, the soil map evaluated here may not be practically accurate and its utility is limited.

Nigerian Journal of Soil Science Vol. 17 2007: pp. 16-23