Spatial Variability of Salts in Kamphaeng Saen soil Series

Abstract

               Most soil properties show spatial relationships. This is useful for interpolation. Employing the geostatistical technique, analysis of semi-vriograms will establish the spatial relationships, while ordinary kriging ia the algorithm for interpolation. The area of study was a rectangular plot of 120 ha around a reservoir in the experimental field of Kasetsart University at Kamphaeng Saen. The soil was Kamphaeng Saen. The soil was Kamphaeng Saen soil series (Typic Haplustalfs). Sampling pints were the intersection of 100x100 m² grid for a total of 127 points. Soil sampling included the top layer of 0-5 cm and the lower layer of 25-30 cm at two periods: during April and November of 1989. Soil properties under study were electrical conductivity of soil saturation extract (ECe), practical sodium adsorption ratio (SARp) and pH soil:water solution of 1:1                                                  Semi-variograms of the three properties were spherical functions, with sills about equal the ordinary variance. The ranges were around 300 m for ECe and SARp, and 500 m for pH. Interpolation was by punctual kriging at the 10x10 m² scale, giving a total of 12,831 points. Estimated and actual data were displayed in maps of isopleth. The results showed that there were only 3 locations that ECe was higher than 4 dS/m, indication saline soil condition. These were the southern rim of the reservoir, middle and the top right-hand corner of the plot. Since most of the soluble salts were predominantly calcium and magnesium, sodium hazard was limited in only two locations. The areas in the southern rim of the reservoir and in the top right-hand corner contained few patches with SaRp > 13 mol^0.5/m^1.5, indicating a saline-sodic soil. The pH of the area was mainly in the range of 6–8. With kriging, the distribution patterns of salt can be demonstrated with much more details.