Evaluation of Soil Variability in Northwest Florida Using Geostatistics
1988
Ovalles, F. A. | Collins, M. E. (Mary Elizabeth)
The objectives of this research were to (i) investigate the use of geostatistics in studying the spatial variation of previously statistically selected soil properties in northwest Florida; (ii) have a better interpretation of how the variability in the selected soil properties is related to a physiographic region; and (iii) determine areas where sampling density should be increased. Two sets of data from 151 pedons in a 380- by 100-km irregular grid were used. The sets of data were composed of (i) sand, clay, and organic carbon (OC) contents on a weighted average basis; and (ii) A horizon clay and OC contents. Direction-independent and direction-dependent semivariograms were calculated and observed semivariograms indicated drift in the data. Therefore, residuals were used to compute new semivariances. Drift was reduced, but local trends still remained. Semivariograms of sand, clay, and OC contents were anisotropic. Organic carbon content semivariograms exhibited a pure nugget effect indicating a large point-to-point variation at short distances and an absence of spatial correlation at the sampling scale used. Kriged data and standard error diagrams of soil properties were related to the five physiographic regions in northwest Florida. The variability shown by these diagrams may be a consequence of the different topography, geology, and management of the area. Reliability (kriged) diagrams were helpful in locating areas of large standard error, such as the northeast edge of the Dougherty Karst physiographic region, that require an increase in sampling intensity to improve the precision of the estimates.
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