MODELING OF APPARENT ELECTRICAL CONDUCTIVITY TO IMPROVE THE ASSESSMENT OF AGRICULTURAL SOIL PROPERTIES

Abstract

The use of nearby electromagnetic induction (EMI) sensors is of great interest in the studies of the physicochemical properties of soils used in agriculture. The objective of this work was to evaluate the efficiency of an EMI sensor in determining the horizontal and vertical distribution of soil properties. It was determined the measurement mode or operation that allows relating the apparent electrical conductivity (ECa) of the soil with the edaphic properties with greater accuracy and the depth distribution of the electrical conductivity (EC) of the soil was determined by implementing the 1D inversion method. The ECa surveys were conducted in the field by EMI at three sites: two along transects (sites 1 and 2) and another in an area of a plot under irrigation (site 3). Correlations between ECa and some soil properties were analyzed, and EC maps were made with the models obtained from 1D inversions in transects. The best orientation mode for the instrument was determined to be horizontal. At site 1, ECa was correlated with nitrate content (r= 0.67) and with laboratory-measured soil EC (ECs) (r= 0.69). On the other hand, at site 2, ECa was correlated with volumetric humidity (r= 0.91). At site 3, a high correlation was observed between ECa and pH (r= 0.88), ECs (r= 0.87), percentage of exchangeable sodium (r= 0.91) and sodium content (r= 0.91). The variability of the ECa explained the content of salts and the degree of sodicity of the soil. The ECa modeling allowed the identification of areas or environments with different ranges in soil properties related to salinization and sodification as a consequence of the application of complementary irrigation.