ASSESSMENT OF SOME KRIGING METHODS FOR MAPPING THE SOIL ELECTRICAL CONDUCTIVITY: CASE STUDY OF SOUTHEASTERN COAST OF CASPIAN SEA OF IRAN

This study assessed kriging methods for mapping soil electrical conductivity (EC) in Southeastern, Coastal region of the Caspian Sea of Iran. The coordinates of the study area were Longitude=47.975896177 Latitude=36.995353646224 and Longitude=48.209973627223 Latitude=37.241702530966 which covered approximately 500 km2 of land area. The average maximum and minimum temperatures are 22.3 ºC and 13 ºC, respectively. Sampling points were selected from seven (7) rows each containing 20 points (where 4 points had been lost from the last row). The soils were sampled from 136 locations at 0-20 cm deep in order to measure soil EC. Soil EC maps showing unique management zones due to EC results were created using ordinary kriging, universal kriging, log-normal kriging and inverse distance weighting (IDW) using ArcGIS software version 10.4.1 GS+ v 5.1 and SPSS v 16. Results indicated that log-normal kriging was the most accurate method for predicting and mapping soil EC. All four statistical methods suggest that the lowest soil salinity occurred in the Southeastern region and the highest EC was recorded in the Northwestern of the study area. Furthermore, the lowest soil EC was observed in agricultural activities involved soil tillage and soil draining, which are far from the present shoreline.