Abstract

The aim of this research is to evaluate the relationship between the measurement of apparent electrical conductivity of soil and its chemical attributes by electromagnetic induction. Geophysics methods used for soil measurement, with electromagnetic induction technique for measuring apparent electrical conductivity of the soil (EC_a) is important for soil digital mapping, as it determines soil properties, with which EC_a is directly related. The apparent soil electrical conductivity (EC_a) was measured by electromagnetic induction with EM38-DD device (Geonics Ltd) at two depths: Vertical dipole (effective depth of 1.5 m- EC_a-V) and horizontal dipole (effective depth of 0.4 m - EC_a-H) in 6 ha of land located in the Northwest of Spain (Castro de Ribeiras de Lea, Lugo) on several dates. The experimental semivariogram showed that there was a drift for EC_a-V and EC_a-H data. Soil chemical properties were shown in 23/06/2008 following the sample scheme building by ESAP program (40 spots). At the 40 optimized sampling points, the following soil properties were measured at 0.0 to 0.3 m depth: Organic matter (OM), pH in CaCl₂, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), potential acidity (H+Al), sum of the basis (SB), cation exchange capacity (CEC) and percent of base saturation (V%). The moderate negative correlation coefficient was found between Log EC_a-V and organic matter. Both EC_a-H and EC_a-V exhibited comparatively low correlations with the chemical properties of soil.

Key words: EM38-DD, geostatistics, soil management, precision agriculture.