SPATIAL VARIABILITY OF SOIL MOISTURE AND ELECTRICAL CONDUCTIVITY IN AN ALLUVIAL VALLEY USING GEOPHYSICAL TECHNIQUES

Abstract

The methods of electromagnetic induction in precision agriculture have high potential in applications aimed at studying the spatial variability of soil salinity and moisture. The objective of this paper was to verify the performance of EM38^® in an alluvial valley in the semiarid region for the purpose of application for precision agriculture, and to evaluate the dynamics and spatial dependence of soil moisture and electrical conductivity at different depths along the profile. The study area is located in the municipality of Parnamirim, Pernambuco State, on the Advanced Campus of Irrigated Agriculture in Parnamirim from the Federal Rural University of Pernambuco. Two regular meshes were adopted, one of 10 x 10 m for measuring the apparent soil electrical conductivity (ECa) estimated with the EM38^® device and another of 20 x 10 m for soil sampling, to determine soil moisture, salinity, silt and clay contents in the 0-0.3 m, 0.3-0.6 m and 0.6-0.9 m layers. Direct and indirect information was used in geostatistical analysis, construction of semivariograms and map kriging. The Degree of Spatial Dependence of the evaluated attributes varied from strong to moderate. Higher soil moisture in the deepest layer was found, whereas the highest ECa was found in the 0.3-0.6 m layer. The EM38^® proved to be efficient in estimating the soil electrical conductivity, and enabled the validation of a previously calibrated regression model for the same area, in a period of soil water restriction.