Soil particle size distribution using the integral suspension pressure method (ISP) and gamma-ray spectrometry techniques for soil texture mapping.

Understanding the role of soil texture in soil-water management amid climate change is crucial for sustainable agriculture as it influences water availability, nutrient dynamics, erosion control, carbon sequestration, and overall soil health. Therefore, having soil texture mapping is an important decision tool for establishing sustainable resource management.

In this study, we present findings from soil sampling conducted in 2023 and a decade earlier from Hydrological Open-Air Laboratory (HOAL) in Petzenkirchen, Lower Austria. The PARIO system was used to analyse soil particle distribution utilising the Integral Suspension Pressure (ISP) method. This method utilizes the stokes’ law to calculate the particle size distribution based on changes in suspension pressure and temperature. The change of suspension pressure as well the temperature is measured at 10- seconds intervals following the chemical and physical dispersion, along with the pretreatment of soil samples involving the removal of organic matter, soluble salts and determination of sample dry weight.

The analysis of soil texture from the 2023 soil sampling, conducted using the PARIO system, revealed a predominant silty clay loam structure, with a particle distribution of 9% sand, 56% silt, and 35% clay, aligning closely with results from a decade prior. Concurrently, we utilized Gamma-Ray Sensor (GRS) technology to measure the spatial activity concentrations (Bq.kg^-1) of ⁴⁰K (potassium), ²³⁸U (uranium), and ²³²Th (thorium) over more 20 points across the fields. The aim was to correlate these radionuclide concentrations with soil texture data using a Python-based correlation model. Preliminary results showed the best correlation between ⁴⁰K radionuclide concentrations versus clay (R² = 0.8) and silt (R² = 0.7) and ²³⁸U versus silt (R²= 0.7). Thus, spatial monitoring of ⁴⁰K and ²³⁸U with mobile GRS can be used for spatial determination of clay and silt. Nevertheless, further analysis is essential to compare and validate these results with a more extensive dataset encompassing additional soil texture data.

These preliminary results demonstrate the potential of monitoring ⁴⁰K and ²³⁸U concentrations by a portable gamma sensor for soil texture mapping in agricultural land. Further analysis and validation are required to verify the robustness of this model.