Title : Assessment of the apparent electrical conductivity in soils of a dried lake in Greece using an electromagnetic induction sensor
The high percentages of salinity in a cultivated area can be seen through visual observations which through the systematic mapping of the field in terms of salinity can give us quantitative information but which are not kept constant throughout the crops due to the change of the growth of plants, the existence of surface salts but also the increase of the content of deeper soil horizons in salts due to irrigation. To date, the electrical conductivity of soil is determined by time-consuming laboratory methods, requires infrastructure and materials that make them expensive and often not representative as they depend on the size of the samples taken during soil sampling, how to prepare the soil sample, as well as by the method of analysis. The present work focuses on the study of soil properties of a dried lake and their correlation with the inductive electromagnetic spectrum which according to other researchers can provide accurate estimates of soil salinity at a field scale. Electromagnetic induction offers the ability to collect large volumes of information and data relatively easily, fast, and most importantly for repeated use. Studies have shown that changes in electrical conductivity can be produced by changes in electrical induction from soil minerals. The specific electrical conductivity can be increased by the corresponding increase of the soluble salts of the groundwater and the temperature. The object of the study is the investigation and spatial distribution of soil properties of the soil focusing on the closest estimate of apparent electrical conductivity by electromagnetic induction. The present work was carried out around the dried lake Agoulinitsa, which is located at a short distance from the mouth of the river Alfeios, in Western Greece. For this reason, fieldwork was carried out in a field of 30 acres of industrial tomato cultivation where a precision sampling of 81 soil samples in the shape of a grid at three depths was carried out (a total of 243 samples). The methodologies followed for the assessment of the soil properties of the samples collected from the field in terms of their physicochemical properties are analysed and maps of the spatial distribution of soil properties are presented. In addition, extensive reference is made to the methodology followed for precision sampling, through the SoilSYS system which enables the user to accurately record the sampling process and transfer it to the laboratory for further analysis. Finally, the specific electrical conductivity is assessed using the Profiler EMP-400 electromagnetic induction sensor which can easily and quickly record electromagnetic frequency measurements in the field. This sensor has a range of frequencies, from which the user can select each time depending on the type of application in the field. Frequencies at 6000, 9000 and 12000 kHz were selected for this application. With the help of a linear statistical regression model, correlations of the electromagnetic spectrum data with the soil properties were made. The results showed statistically significant correlations at the frequency of 12000 kHz for the ground depth of 30 cm.