Soils play a crucial role in sustaining agro-system productivity and providing numerous ecosystem services essential for sustainable land and water management. The management of both soil and water resources is a primary socio-economic concern that requires a detailed understanding of the physical and biological processes occurring within the soil–plant–atmosphere continuum. However, measuring soil state variables and hydraulic parameters is often challenging due to the complex, nonlinear physical, chemical, and biological interactions that simultaneously control the transfer of heat and mass (water and solutes). Infiltration experiments have been proposed as a simple means to estimate soil hydraulic properties, but their effectiveness is limited by spatio-temporal variability across scales. High-resolution measurements of soil state variables, both in space and time, are therefore essential to adequately describe and analyze soil hydraulic properties and to understand flow processes, including phenomena such as preferential flows.

The session focuses on the principles, methods, and applications of various techniques and their associated mathematical frameworks for monitoring key soil variables, estimating soil hydraulic properties, and accounting for preferential flows. Specific topics include, but are not limited to:

• Multiple measurement techniques and modelling approaches for determining state variables of soil;
• Innovative soil-water measurements techniques for linking the interactions of soil with plant and atmosphere compartments;
• Laboratory and field infiltration techniques from a wide variety of devices;
• Understanding the effect of physical processes and geochemical processes on the dynamics of macropore-fracture and preferential flows across scales;
• Understanding the contribution of preferential flow to flow and mass transport in the vadose zone;
• New or revisited numerical and analytical models to account for physical, chemical and biological interactions in the soil-water flow models (multiple-porosity, permeability, hydrophobicity, clogging, shrinking-swelling, or biofilm development);
• Use of pedotransfer functions based on limited available in-situ measurements to estimate parameters that describe soil hydro-physical and thermal characteristics;
• Multi-data source methodologies also in combination with modelling for assessing the soil physics dynamics at different temporal and spatial scales.