ESTIMATE AND MAPPING SALINITY DISTRIBUTION IN SOME SOILS OF EGYPT BY USING ELECTROMAGNETIC INDUCTION INSTRUMENT

Abstract

Remote sensing techniques such as electromagnetic induction (EMI), and electric resistivity are recently used to study soil salinity, water table depth and soil mineralogy in the field. Electromagnetic induction (EMI) is a useful mean of assessing soil salinity in the large areas, particularly after its calibration on different soils. The aim of this work is to estimate and mapping soil salinity distribution for some soils of Egypt by using EMI 400 instrument. Three Egyptian soil parts were chosen for this study from saline and non-saline calcareous soils in El Nubaria area as well as sandy soils in El Sadat area. EMI 400 instrument was used to predict, record and calculate the salinity in the field using three frequency bands of 14, 15 and 16 KHz for these parts. On the other hand, soil samples were collected from the surface and subsurface layers of these parts for determining salinity in the lab using EC meter apparatus. The correlation between the EMI readings and the lab determined EC values were statistically analyzed and results could be summarized in the following: The statistical analyses indicated that, there are a highly significant correlation coefficients between EMI readings at the three frequency bands and the lab determined ECe values of each layer in all studied parts. The highest correlation coefficients were found with the EMI readings at 15 KHz. Moreover, multi factorial as well as simple regression equations were derived from the statistical analyses to calculate the soil salinity (ECc) from EMI readings in the field. The most suitable equation for calculating soil ECc was that based on instrument readings at frequency band 15KHz alone. Spatial salinity distribution maps were produced and presented for both surface and subsurface layers of the studied parts whether based on lab determined ECe or calculated ECc from EMI instrument readings.