Douaik A., Van Meirvenne M. and Tóth T., 2004. Spatio-temporal kriging of soil 
salinity rescaled from bulk soil electrical conductivity. In: Sánhez-Vila, 
Carrera J. & Gómez-Hernández J. (Eds.) geoENV IV-Geostatistics for Environmental 
Applications, Kluwer Academic Publishers, Dordrecht, pp. 413-424. ISBN: 1-4020-
2007-4.

Our spatial data consist of  413 measurements of the apparent electrical 
conductivity (ECa) obtained with electrical probes in the east of Hungary. 
Additionally, a limited subset of the locations (15 to 20) was sampled for 
laboratory analysis of soil electrical conductivity of 1:2.5 soil:water 
suspension (EC2.5), a simple proxy for the electrical conductivity of soil 
saturation extract (ECe). The latter formed our calibration data set. This 
procedure was repeated 17 times between November 1994 and December 2000 yielding 
a large spatio-temporal database. The first step was to rescale EC2.5 from ECa, 
based on the calibration data sets, using classical and spatial regression 
models. The residuals of the ordinary least squares model were tested for the 
absence of spatial dependence using the Moran`s I test. This hypothesis was 
accepted, the EC2.5 was rescaled using the classical regression model. The next 
step was to identify the structure of the variability of the rescaled EC2.5 by 
computing and modeling the spatial, the temporal, and the spatio-temporal 
covariograms. Finally, soil salinity maps were produced for the study area and 
for any time instant using spatio-temporal kriging. The estimates were more 
precise compared to the ones obtained using only the spatial covariogram 
computed and modeled separately for each time instant.