Assessing salinity and sodicity of irrigated soils using apparent electrical conductivity in the Pampean region

Abstract

In the Pampean region, the groundwater mostly used for supplementary irrigation is sodium bicarbonate, which poses a potential risk to soil salinity and sodicity. It is therefore necessary to carry out a monitoring of the soil quality. The use of electromagnetic sensors is an interesting alternative for this purpose. These instruments measure the apparent electrical conductivity of a volume of soil (ECap), which has been shown to be related to many properties. The aim of this work was to evaluate the effectiveness of ECap in monitoring and mapping the properties of a non-saline soil in irrigated agriculture. Plots, including irrigated and rainfed areas, were surveyed with an electromagnetic sensor to measure ECap. Soil samples were taken to establish relationships. The edaphic properties that correlated better with ECap were precisely those related to salinization and sodification, such as electrical soil conductivity (ECs), pH and exchangeable sodium percentage (ESP), which are usually affected by irrigation. Even in some plots, the most conductive zones were distributed over the irrigated area with high values of these variables. The predictive models of these soil properties based on the ECap had good fittings. Moreover, in one of the plots, the maps obtained from predictions agreed with the maps interpolated from the soil samples. Thus, ECap can be considered as a good predictor of the variability of soil properties related to the impact of supplemental irrigation on non-saline soil. Geophysical exploration allows rapid and non-invasive monitoring of soil salinity and sodicity to improve irrigation management practices.