The Application of EM38: Determination of Soil Parameters, Selection of Soil Sampling Points and Use in Agriculture...

Fast and accurate assessment of within-field variation is essential for detecting field-wide heterogeneity and contributing to improvements in the management of agricultural lands. The goal of this paper is to provide an overview of field scale characterization by electromagnetic induction, firstly with a focus on the applications of EM38 to salinity, soil texture, water content and soil water turnover, soil types and boundaries, nutrients and N-turnover and soil sampling designs. Furthermore, results concerning special applications in agriculture, horticulture and archaeology are included. In addition to these investigations, this survey also presents a wide range of practical methods for use. Secondly, the effectiveness of conductivity readings for a specific target in a specific locality is determined by the intensity at which soil factors influence these values in relationship to the desired information. The interpretation and utility of apparent electrical conductivity (EC_a) readings are highly location- and soil-specific, so soil properties influencing the measurement of EC_a must be clearly understood. From the various calibration results, it appears that regression constants for the relationships between EC_a, electrical conductivity of aqueous soil extracts (EC_e), texture, yield, etc., are not necessarily transferable from one region to another. The modelling of EC_a, soil properties, climate and yield are important for identifying the location to which specific utilizations of EC_a technology (e.g., EC_a-texture relationships) can be appropriately applied. In general, the determination of absolute levels of EC_a is frequently not possible, but it appears to be quite a robust method to detect relative differences, both spatially and temporally. Often, the use of EC_a is restricted to its application as a covariate or the use of the readings in a relative sense rather than as absolute terms.