First National Report on Soil Salinity Across Paraguay

Abstract

Assessing soil salinity on a national scale provides crucial information on soil fertility. Our objective was to map soil salinity in Paraguay at the topsoil layer (0-30 cm) using indicators such as Electrical Conductivity (EC), pH, and Exchangeable Sodium Percent (ESP). We employed a model with 80 data points for Electrical Conductivity (EC) and 204 points for pH and Exchangeable Sodium Percent (ESP). The statistical model used to map soil salinity properties was the "quantile random forest." For validation and accuracy calculation, we utilized "cross-validation" with all soil sampling sites and a "Random" selection parameter. To ensure result consistency, we repeated the validation five times, calculating the average of the results. Uncertainty was estimated using "predUncertain-quantile random forest," implemented in the R programming language. In general, Paraguayan soils at a depth of 0 to 30 cm exhibit low salt levels, with the soils in the Paraguayan Chaco region showing higher levels. Two primary factors contribute to soil salinity in Paraguay: natural factors, such as a dry climate, high temperatures, and high evapotranspiration, and secondary factors, including soil parent material with alluvial deposits and groundwater with significant salt content. It’s worth noting that actual salinity values, both in Paraguayan Chaco and the eastern region, might surpass those mentioned in this study due to limited available data and the spatial resolution of the map. This study represents the first effort to develop a soil salinity map of Paraguay, providing the initial national baseline for the development of salinity/sodicity monitoring frameworks. It can be instrumental in addressing regional gaps in salinity/sodicity within South America.