Spatial Variability of Some Soil Properties: A Case Study of The Lower Seyhan River Basin in Turkey

Abstract

The aim of this study was to evaluate the performance of a closed drainage system in one area of the Lower Seyhan river basin in Cukurova, Turkey by measuring spatial variations in soil characteristics. Seven parallel transects which had a 150 m length were selected at 5 m intervals within the study area, and 104 soil samples were collected and analysed for soil pH, electrical conductivity (EC), exchangeable sodium (Na) content and exchangeable sodium percentages (ESP). Results were subjected to inverse distance weighting (IDW) interpolation. EC, pH and ESP estimates obtained from IDW interpolation were compatible with the results of soil analysis. Cross validation was performed to determine the accuracy of the interpolation technique. Interpolation of EC values showed a high mean error in 120-150 cm depth (9.010%), which was attributed to poor drainage conditions. Minimum sample number, maximum sample number, maximum radius and power were found to have an influence on the accuracy of IDW interpolation. ESP, exchangeable Na, EC values were generally low for shallow soil horizons, with values increasing with increases in depth. Data sets were analyzed with two-way ANOVA (the factors were six pipe regions (1-6) and five soil depths (30, 60, 90, 120, 150 cm)) and means compared with Duncan's multiple range test. It was found that the efficiency of drainage pipe, in regions 1, 2, 3 and 4 can diminish rather than the other pipe regions.