Abstract
The apparent soil electrical conductivity (ECa) was continuously recorded in three successive dates using electromagnetic induction in horizontal (ECa-H) and vertical (ECa-V) dipole modes at a 6 ha plot located in Northwestern Spain. One of the ECa data sets was used to devise an optimized sampling scheme consisting of 40 points. Soil was sampled at the 0.0–0.3 m depth, in these 40 points, and analyzed for sand, silt, and clay content; gravimetric water content; and electrical conductivity of saturated soil paste. Coefficients of correlation between ECa and gravimetric soil water content (0.685 for ECa-V and 0.649 for ECa-H) were higher than those between ECa and clay content (ranging from 0.197 to 0.495, when different ECa recording dates were taken into account). Ordinary and universal kriging have been used to assess the patterns of spatial variability of the ECa data sets recorded at successive dates and the analyzed soil properties. Ordinary and universal cokriging methods have improved the estimation of gravimetric soil water content using the data of ECa as secondary variable with respect to the use of ordinary kriging.
Highlights
The quality of soil data collection for precision agriculture has a very important influence, since it has been found that acquisition of exhaustive information in this phase supports the use of geospatial technologies for the estimation of soil spatial variability and later on assists in the determination of “management units.” for assessing the soil spatial variability, a large number of samples are generally needed, which considerably increases costs of sampling and analysis
It is verified that the apparent electrical conductivity of the soil (ECa) measurement with the horizontal dipole (ECa-H) has lower CV than the measurements with the vertical dipole (ECa-V)
The values of the electrical conductivity of the saturation paste extract of the soil (ECe) are higher than the values of ECa-V and electromagnetic induction in horizontal (ECa-H); this fact is because electrical conductivity of soil saturated extracts (ECe) is a parameter that depends on the content of anions and cations in the soil solution; the water content is homogeneous in all samples, because the sample is saturated with water, and the soil apparent electric conductivity values measured with the equipment
Summary
The quality of soil data collection for precision agriculture has a very important influence, since it has been found that acquisition of exhaustive information in this phase supports the use of geospatial technologies for the estimation of soil spatial variability and later on assists in the determination of “management units.” for assessing the soil spatial variability, a large number of samples are generally needed, which considerably increases costs of sampling and analysis. The quality of soil data collection for precision agriculture has a very important influence, since it has been found that acquisition of exhaustive information in this phase supports the use of geospatial technologies for the estimation of soil spatial variability and later on assists in the determination of “management units.”. The measurement of apparent soil electrical conductivity (ECa) allows the collection of information on the field and on the spatial distribution of other properties that are correlated. In accordance with Corwin and Rhoades [1] the main methods for the measurement of soil ECa are contact and electromagnetic induction. The use of ECa for soil classification allows recognition and delimitation of the physical, chemical, and biological soil properties that play an important role
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