8. Spatial Variability of Soil Salinization as Judged from the Comparison of Soil Maps and Remote Sensing Materials for Different Years in Uzbekistan

Quantitative assessments of the temporal variability in soil salinity are discussed in this chapter. Currently such assessments are based on the comparison of point-size data for several years (regular observations and sampling in the same point) or on the comparison of soil salinization maps developed in different years. Both methods have drawbacks. In the case of point-size data, it is difficult to extrapolate them on large territories. In the case of comparison of two soil maps obtained in different times, the problem of temporal extrapolation of the data arises. We estimated the dynamics of soil salinization on the basis of remote sensing materials with ground-truth calibration for the territory of the Usman Yusupov farm in the Golodnaya Steppe of Uzbekistan. Remote sensing materials on this territory were obtained for years 1983, 1985, 1986, 1988, 1989, 1990, 2000, and 2008. On their basis, eight separate soil salinity maps were developed for the area of 80 km². A comparison between them made it possible to develop a series of the maps of soil salinization dynamics. Separation of the areas with a stable soil salinity status upon the comparison of the maps for different years proved to be very informative. Such areas comprised no more than 1.5% of the farm area for the whole period (25 years) and about 25% of the farm area for two consecutive years. Quantitative data on soil salinization dynamics made it possible to outline certain drawbacks in soil reclamation procedures and to suggest the ways of their optimization.