Abstract
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 (ECa) readings are highly location- and soil-specific, so soil properties influencing the measurement of ECa must be clearly understood. From the various calibration results, it appears that regression constants for the relationships between ECa, electrical conductivity of aqueous soil extracts (ECe), texture, yield, etc., are not necessarily transferable from one region to another. The modelling of ECa, soil properties, climate and yield are important for identifying the location to which specific utilizations of ECa technology (e.g., ECa−texture relationships) can be appropriately applied. In general, the determination of absolute levels of ECa 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 ECa is restricted to its application as a covariate or the use of the readings in a relative sense rather than as absolute terms.
Highlights
Fast and accurate detection of within-field variation is essential for the detection and management of the environment
From the various calibration results, it appears that regression constants for the relationships between ECa, electrical conductivity of aqueous soil extracts (ECe ), texture, yield, etc., are not necessarily transferable from one region to another
The objective of this study is to summarize the results of recent measurements and the development of algorithms from ECa measurements obtained with the geophysical sensor EM38
Summary
Fast and accurate detection of within-field variation is essential for the detection and management of the environment. Ltd., Mississauga, ON, Canada), a sensor that delivers dense datasets, can be used to accomplish this goal. The EM38 meter is the most widely used EMI sensor in agriculture [1,2]. Researchers have related EM38-ECa (apparent electrical conductivity—ECa ) to a number of different soil properties either within an individual field or across the entire landscape [3]. The application of EM38 began with the detection of salinity and continued with the determination of clay and water content [2]. Areas of application include the estimation of nutrient levels and other soil chemical and physical properties, soil sampling points, the determination of soil types and their boundaries, the prediction of yield and the delineation of crop management zones.
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