2002 Volume 56 Issue 5 Pages 393-401
For the improvement and restoration of soil saturated with salt, it is important to investigate the vertical and horizontal distribution of salt accumulation in a wide area. Under the conventional methods of soil sampling, the soil layer below groundwater level could not be measured. In this paper, a prototype sensor based on Edlefsen's 4-electrode method was developed in order to enable to measure vertical distribution of the electric conductivity. From experimental results in the laboratory as well as the experimental field in Northeastern Thailand, the following results were obtained.
1) From the results of calibration using an NaCl solution and the experiment in saturated soil, it was found that the prototype sensor could be used as an electric conductivity sensor by calibrating the measurement value.
2) Conventionally, it had been considered that electric conductivity was uniform in the vertical direction below groundwater, but the result in laboratory experiments with a controlled groundwater level showed the difference in electric conductivity at every soil layer
3) The experimental results in saline soil in Northeast Thailand indicate that the prototype sensor enables to measure the extent of salt accumulation at various depths.
